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Showing new listings for Friday, 22 November 2024
- [1] arXiv:2411.13593 [pdf, other]
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Title: On quantum models for opinion and voting intention pollsFrançois Dubois (LMSSC)Comments: arXiv admin note: substantial text overlap with arXiv:2411.10041Journal-ref: seventh international Quantum Interaction conference, Universit{\'e} de Leicester, Jul 2013, Leicester, United Kingdom. pp.286-295Subjects: Physics and Society (physics.soc-ph)
In this contribution, we construct a connection between two quantum voting models presented previously. We propose to try to determine the result of a vote from associated given opinion polls. We introduce a density operator relative to the family of all candidates to a particular election. From an hypothesis of proportionality between a family of coefficients which characterize the density matrix and the probabilities of vote for all the candidates, we propose a numerical method for the entire determination of the density operator. This approach is a direct consequence of the Perron-Frobenius theorem for irreductible positive matrices. We applyour algorithm to synthetic data and to operational results issued from the French presidential election of April 2012.
- [2] arXiv:2411.13596 [pdf, other]
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Title: End-to-End Multi-Track Reconstruction using Graph Neural Networks at Belle IILea Reuter, Giacomo De Pietro, Slavomira Stefkova, Torben Ferber, Valerio Bertacchi, Giulia Casarosa, Luigi Corona, Patrick Ecker, Alexander Glazov, Yubo Han, Martina Laurenza, Thomas Lueck, Ludovico Massaccesi, Suryanarayan Mondal, Bianca Scavino, Stefano Spataro, Christian Wessel, Laura ZaniSubjects: Instrumentation and Detectors (physics.ins-det); High Energy Physics - Experiment (hep-ex); Data Analysis, Statistics and Probability (physics.data-an)
We present the study of an end-to-end multi-track reconstruction algorithm for the central drift chamber of the Belle II experiment at the SuperKEKB collider using Graph Neural Networks for an unknown number of particles. The algorithm uses detector hits as inputs without pre-filtering to simultaneously predict the number of track candidates in an event and and their kinematic properties. In a second step, we cluster detector hits for each track candidate to pass to a track fitting algorithm. Using a realistic full detector simulation including beam-induced backgrounds and detector noise taken from actual collision data, we find significant improvements in track finding efficiencies for tracks in a variety of different event topologies compared to the existing baseline algorithm used in Belle II. For events with a hypothetical long-lived massive particle with a mass in the GeV-range decaying uniformly along its flight direction into two charged particles, the GNN achieves a combined track finding and fitting efficiency of 85.4% with a fake rate of 2.5%, compared to 52.2% and 4.1% for the baseline algorithm. This is the first end-to-end multi-track machine learning algorithm for a drift chamber detector that has been utilized in a realistic particle physics environment.
- [3] arXiv:2411.13600 [pdf, other]
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Title: The Laboratory of Mechanics and Acoustics in Marseilles (France): from the first world war to the present daySabine Meunier (LMA), Dominique Habault (LMA), Emmanuel Friot (LMA), Philippe Lasaygues (O&I), Hervé Moulinec (LMA), Christophe Vergez (LMA)Journal-ref: Acoustique&Techniques, 2024, 100, pp.41-44Subjects: History and Philosophy of Physics (physics.hist-ph)
The Laboratory of Mechanics and Acoustics in Marseilles (France) was created in 1941, under the name of Centre de Recherches Scientifiques, Industrielles et Maritimes (CRSIM). But it was actually issued from the French Naval Research Center created in Toulon by the French Navy to work on submarine detection during World War I. LMA is therefore the result of a long and quite amazing story with several moves and even more name changes. It benefited from all these events and is today established in a new campus with large facilities specially designed for its latest research activities. This article presents the story in some details, summarize the evolution of the research domains through all these years and finally gives a description of the LMA today.
- [4] arXiv:2411.13618 [pdf, other]
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Title: 100 years of plastic -- using the past to guide the futureSubjects: Physics and Society (physics.soc-ph)
Robust and credible material flow data are required to support the ongoing efforts to reconcile the economic and social benefits of plastics with their human and environmental health impacts. This study presents a global, but regionalized, life cycle material flow analysis (MFA) of all plastic polymers and applications for the period 1950-2020. It also illustrates how this dataset can be used to generate possible scenarios for the next 30 years. The historical account documents how the relentless growth of plastic production and use has consistently outpaced waste management systems worldwide and currently generates on the order of 60 Mt of mismanaged plastic waste annually. The scenarios show that robust interventions are needed to avoid annual plastic waste mismanagement from doubling by 2050.
- [5] arXiv:2411.13621 [pdf, html, other]
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Title: Underestimation of Hubble constant error bars: a historical analysisComments: 9 pages, accepted to be published in the conference proceedings of the session "Current Status of the H_0 and growth tensions: theoretical models and model-independent constraints" within 17th Marcel Grossmann Meeting (Pescara, Italy, July 7th-12th 2024). arXiv admin note: substantial text overlap with arXiv:2210.07078Subjects: History and Philosophy of Physics (physics.hist-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
An analysis of a historical compilation of Hubble-Lemaître constant values ($H_0$: 163 data points measured between 1976 and 2019) assuming the standard cosmological model gives a $\chi^2$ value of the dispersion with respect to the weighted average of 580, much larger than the number of points, which has an associated probability that is very low. This means that Hubble tensions were always present in the literature, due either to the underestimation of statistical error bars associated with the observed parameter measurements, or to the fact that systematic errors were not properly taken into account in many of the measurements.
The fact that the underestimation of error bars for $H_0$ is so common might explain the apparent 4.4-sigma discrepancy by Riess et al. As a matter of fact, more recent precise $H_0$ measurements with JWST data by Freedman et al. using standard candles in galaxies find there is no tension with CMBR data, possibly indicating that previously Riess et al. had underestimated their errors.
Here we have carried out a recalibration of the probabilities. The tension of 4.4-$\sigma $, estimated between the local Cepheid-supernova distance ladder and cosmic microwave background (CMB) data, is indeed a 2.1-$\sigma $ tension in equivalent terms of a normal distribution, with an associated probability $P$ = 0.036 (1 in 28). This can be increased to an equivalent tension of 2.5-$\sigma $ in the worst cases of claimed 6-$\sigma $ tension, which may in any case happen as a random statistical fluctuation.
If Hubble tensions were always present in the literature, and present day tensions are not more important than previous ones, why, then, is there so much noise and commotion surrounding Hubble tension after 2019? It is suggested here that this obeys a sociological phenomenon of ``groupthink''. - [6] arXiv:2411.13685 [pdf, html, other]
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Title: Using AI Large Language Models for Grading in Education: A Hands-On Test for PhysicsComments: 16 pages + appendicesSubjects: Physics Education (physics.ed-ph)
Grading assessments is time-consuming and prone to human bias. Students may experience delays in receiving feedback that may not be tailored to their expectations or needs. Harnessing AI in education can be effective for grading undergraduate physics problems, enhancing the efficiency of undergraduate-level physics learning and teaching, and helping students understand concepts with the help of a constantly available tutor. This report devises a simple empirical procedure to investigate and quantify how well large language model (LLM) based AI chatbots can grade solutions to undergraduate physics problems in Classical Mechanics, Electromagnetic Theory and Quantum Mechanics, comparing humans against AI grading. The following LLMs were tested: Gemini 1.5 Pro, GPT-4, GPT-4o and Claude 3.5 Sonnet. The results show AI grading is prone to mathematical errors and hallucinations, which render it less effective than human grading, but when given a mark scheme, there is substantial improvement in grading quality, which becomes closer to the level of human performance - promising for future AI implementation. Evidence indicates that the grading ability of LLM is correlated with its problem-solving ability. Through unsupervised clustering, it is shown that Classical Mechanics problems may be graded differently from other topics. The method developed can be applied to investigate AI grading performance in other STEM fields.
- [7] arXiv:2411.13703 [pdf, html, other]
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Title: High-Fidelity Optical Monitoring of Laser Powder Bed Fusion via Aperture Division MultiplexingSubjects: Optics (physics.optics)
Qualification of high-performance metal components produced by laser powder bed fusion (LPBF) must identify process-induced porous defects that reduce ductility and nucleate fatigue cracking. Detecting such defects via optical monitoring of LPBF provides a path towards in-process quality control without downstream testing such as by computed tomography. However, integration of in-process sensing with LPBF is hampered by geometric and optical complications and, as a result, it has yet to be proven that the finest pores that limit component fatigue life can be resolved via in situ data. We present aperture division multiplexing (ADM) as a method for simultaneously focusing the process laser and providing unobstructed optical access for high-fidelity process monitoring using a common optic. Construction of an ADM optic of achieving imaging at 50 micron spatial resolution in the mid-wave infrared is described, and this optic is demonstrated on a production-representative LPBF testbed. High-speed infrared video data are correlated to micro-CT measurement of pores as fine as 4.3 microns, through multiple process signatures, establishing the promise of ADM for qualification of LPBF component fatigue performance.
- [8] arXiv:2411.13715 [pdf, html, other]
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Title: SimPhony: A Device-Circuit-Architecture Cross-Layer Modeling and Simulation Framework for Heterogeneous Electronic-Photonic AI SystemComments: 7-pageSubjects: Optics (physics.optics); Artificial Intelligence (cs.AI); Hardware Architecture (cs.AR); Emerging Technologies (cs.ET); Machine Learning (cs.LG)
Electronic-photonic integrated circuits (EPICs) offer transformative potential for next-generation high-performance AI but require interdisciplinary advances across devices, circuits, architecture, and design automation. The complexity of hybrid systems makes it challenging even for domain experts to understand distinct behaviors and interactions across design stack. The lack of a flexible, accurate, fast, and easy-to-use EPIC AI system simulation framework significantly limits the exploration of hardware innovations and system evaluations on common benchmarks. To address this gap, we propose SimPhony, a cross-layer modeling and simulation framework for heterogeneous electronic-photonic AI systems. SimPhony offers a platform that enables (1) generic, extensible hardware topology representation that supports heterogeneous multi-core architectures with diverse photonic tensor core designs; (2) optics-specific dataflow modeling with unique multi-dimensional parallelism and reuse beyond spatial/temporal dimensions; (3) data-aware energy modeling with realistic device responses, layout-aware area estimation, link budget analysis, and bandwidth-adaptive memory modeling; and (4) seamless integration with model training framework for hardware/software co-simulation. By providing a unified, versatile, and high-fidelity simulation platform, SimPhony enables researchers to innovate and evaluate EPIC AI hardware across multiple domains, facilitating the next leap in emerging AI hardware. We open-source our codes at this https URL
- [9] arXiv:2411.13719 [pdf, other]
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Title: Persistent but weak magnetic field at Moon's midlife revealed by Chang'e-5 basaltShuhui Cai, Huafeng Qin, Huapei Wang, Chenglong Deng, Saihong Yang, Ya Xu, Chi Zhang, Xu Tang, Lixin Gu, Xiaoguang Li, Zhongshan Shen, Min Zhang, Kuang He, Kaixian Qi, Yunchang Fan, Liang Dong, Yifei Hou, Pingyuan Shi, Shuangchi Liu, Fei Su, Yi Chen, Qiuli Li, Jinhua Li, Ross N. Mitchell, Huaiyu He, Chunlai Li, Yongxin Pan, Rixiang ZhuSubjects: Geophysics (physics.geo-ph)
The evolution of the lunar magnetic field can reveal the Moon's interior structure, thermal history, and surface environment. The mid-to-late stage evolution of the lunar magnetic field is poorly constrained, and thus the existence of a long-lived lunar dynamo remains controversial. The Chang'e-5 mission returned the heretofore youngest mare basalts from Oceanus Procellarum uniquely positioned at mid-latitude. We recovered weak paleointensities of 2-4 uT from the Chang'e-5 basalt clasts at 2 billion years ago, attestting to the longevity of a lunar dynamo until at least the Moon's midlife. This paleomagnetic result implies the existence of thermal convection in the lunar deep interior at the lunar mid-stage which may have supplied mantle heat flux for the young volcanism.
- [10] arXiv:2411.13725 [pdf, html, other]
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Title: Renormalization of States and Quasiparticles in Many-body DownfoldingSubjects: Computational Physics (physics.comp-ph); Materials Science (cond-mat.mtrl-sci)
We explore the principles of many-body Hamiltonian complexity reduction via downfolding on an effective low-dimensional representation. We present a unique measure of fidelity between the effective (reduced-rank) description and the full many-body treatment for arbitrary (i.e., ground and excited) states. When the entire problem is mapped on a system of interacting quasiparticles [npj Computational Materials 9 (1), 126, 2023], the effective Hamiltonians can faithfully reproduce the physics only when a clear energy scale separation exists between the subsystems and its environment. We also demonstrate that it is necessary to include quasiparticle renormalization at distinct energy scales, capturing the distinct interaction between subsystems and their surrounding environments. Numerical results from simple, exactly solvable models highlight the limitations and strengths of this approach, particularly for ground and low-lying excited states. This work lays the groundwork for applying dynamical downfolding techniques to problems concerned with (quantum) interfaces.
- [11] arXiv:2411.13734 [pdf, html, other]
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Title: uRWELL detector developments at Jefferson Lab for high luminosity experimentsComments: * 6 figures * 6 pages excluding the abstract and the bibliographySubjects: Instrumentation and Detectors (physics.ins-det)
One of the future plans at Jefferson Lab is running electron scattering experiments with large acceptance detectors at luminosities $> 10^{37}cm^{-2}s^{-1}$. These experiments allow the measurements of the Double Deeply Virtual Compton Scattering (DDVCS) reaction, an important physics process in the formalism of Generalized Parton Distributions, which has never been measured because of its small cross-section. The luminosity upgrade of CLAS12 or the SOLID detector makes Jefferson Lab a unique place to measure DDVCS. One of the important components of these high luminosity detectors is a tracking system that can withstand high rates of $\approx 1MHz/cm^{2}$. The recently developed Micro-Resistive Well (uRWELL) detector technology is a promising option for such a tracking detector by combining good position resolutions, low material budget with simple mechanical construction, and low production costs. In this proceeding, we will discuss recent developments and studies with uRWELL detectors at Jefferson Lab for future upgrades of the CLAS12 detector to study the DDVCS reaction.
- [12] arXiv:2411.13741 [pdf, html, other]
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Title: Spatial prisoner's dilemma optimally played in small-world networksComments: 4 figuresJournal-ref: Physics Letters A, 313, 55-61 (2003)Subjects: Physics and Society (physics.soc-ph)
Cooperation is commonly found in ecological and social systems even when it apparently seems that individuals can benefit from selfish behavior. We investigate how cooperation emerges with the spatial prisoner's dilemma played in a class of networks ranging from regular lattices to random networks. We find that, among these networks, small-world topology is the optimal structure when we take into account the speed at which cooperative behavior propagates. Our results may explain why the small-world properties are self-organized in real networks.
- [13] arXiv:2411.13747 [pdf, html, other]
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Title: Interfacial Water Polarization: A Critical Force for Graphene-based Electrochemical InterfacesSubjects: Chemical Physics (physics.chem-ph)
Water molecules predominantly act as solvents in electrochemical systems and are often modeled as a passive dielectric medium. In this work, we use molecular dynamics simulations and theoretical analysis to revisit this conventional view. We reveal that the interfacial polarized water overscreens the electrostatic potential between ions and the surface beyond being a passive dielectric medium. This overscreening enables the interfacial water to dominate the electric potential spatial distribution, inverting the electrode surface potential polarity and dominating the capacitance. A model is then developed to incorporate this critical interfacial water polarization.
- [14] arXiv:2411.13803 [pdf, other]
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Title: 3D-architected gratings for polarization-sensitive, nature-inspired structural colorComments: 10 pages, 5 figuresSubjects: Optics (physics.optics); Applied Physics (physics.app-ph)
Structural coloration, a color-generation mechanism often found in nature, arises from light-matter interactions such as diffraction, interference and scattering, with micro- and nanostructured elements. Herein, we systematically study anisotropic, 3D-architected grating structures with polarization-tunable optical properties, inspired by the vivid blue of Morpho butterfly wings. Using two-photon lithography, we fabricate multilayered gratings, varying parameters such as height (through scanning speed and laser power), periodicity, and number of layers. In transmission, significant color transitions from blue to brown were identified when varying structural parameters and incident light polarization conditions (azimuthal angle and ellipticity). Based on thin film diffraction efficiency theory in the Raman-Nath regime, optical characterization results are analytically explained, evaluating the impact of each parameter variation. Overall, these findings contribute to technological implementations of polarization-sensitive, 3D-architected gratings for structural color applications.
- [15] arXiv:2411.13815 [pdf, html, other]
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Title: FLRNet: A Deep Learning Method for Regressive Reconstruction of Flow Field From Limited Sensor MeasurementsSubjects: Fluid Dynamics (physics.flu-dyn); Machine Learning (cs.LG)
Many applications in computational and experimental fluid mechanics require effective methods for reconstructing the flow fields from limited sensor data. However, this task remains a significant challenge because the measurement operator, which provides the punctual sensor measurement for a given state of the flow field, is often ill-conditioned and non-invertible. This issue impedes the feasibility of identifying the forward map, theoretically the inverse of the measurement operator, for field reconstruction purposes. While data-driven methods are available, their generalizability across different flow conditions (\textit{e.g.,} different Reynold numbers) remains questioned. Moreover, they frequently face the problem of spectral bias, which leads to smooth and blurry reconstructed fields, thereby decreasing the accuracy of reconstruction. We introduce FLRNet, a deep learning method for flow field reconstruction from sparse sensor measurements. FLRNet employs an variational autoencoder with Fourier feature layers and incorporates an extra perceptual loss term during training to learn a rich, low-dimensional latent representation of the flow field. The learned latent representation is then correlated to the sensor measurement using a fully connected (dense) network. We validated the reconstruction capability and the generalizability of FLRNet under various fluid flow conditions and sensor configurations, including different sensor counts and sensor layouts. Numerical experiments show that in all tested scenarios, FLRNet consistently outperformed other baselines, delivering the most accurate reconstructed flow field and being the most robust to noise.
- [16] arXiv:2411.13832 [pdf, html, other]
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Title: Smartphone tristimulus colorimetry for skin-tone analysis at common pulse oximetry anatomical sitesComments: 29 pages, 6 figures, 3 supplemental figuresSubjects: Medical Physics (physics.med-ph); Optics (physics.optics)
Significance: Smartphones hold great potential in point-of-care settings due to their accessibility and computational capabilities. This is critical as clinicians increasingly seek to quantify skin-tone, a characteristic which has been shown to impact the accuracy of pulse oximetry readings, particularly for dark skin tones, and hence, disproportionately affect patient outcomes. Aim: This study presents a smartphone-based imaging technique for determining individual typology angle (ITA) and compares these results to those obtained using an industry-standard tristimulus colorimeter, particularly for the finger, a common site for pulse oximetry measurements. Approach: We employ a smartphone-based imaging method to extract ITA values from four volunteers with diverse skin-tones. The study provides recommendations for minimizing errors caused by ambient light scattering, which can affect skin-tone readings. Results: The smartphone-based ITA (SITA) measurements with camera flash disabled and minimal ambient lighting correlates well with the industry-standard colorimeter without the need for auxiliary adapters and complex calibration. The method presented enables wide-field ITA mapping for skin-tone quantification that is accessible to clinicians. Conclusions: Our findings demonstrate that smartphone-based imaging provides an effective alternative for assessing skin-tone in clinical settings. The reduced complexity of the approach presented makes it highly accessible to the clinical community and others interested in carrying out pulse oximetry across a diversity of skin-tones in a manner that standardizes skin-tone assessment.
- [17] arXiv:2411.13850 [pdf, html, other]
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Title: ALKPU: an active learning method for the DeePMD model with Kalman filterSubjects: Computational Physics (physics.comp-ph)
Neural network force field models such as DeePMD have enabled highly efficient large-scale molecular dynamics simulations with ab initio accuracy. However, building such models heavily depends on the training data obtained by costly electronic structure calculations, thereby it is crucial to carefully select and label the most representative configurations during model training to improve both extrapolation capability and training efficiency. To address this challenge, based on the Kalman filter theory we propose the Kalman Prediction Uncertainty (KPU) to quantify uncertainty of the model's prediction. With KPU we design the Active Learning by KPU (ALKPU) method, which can efficiently select representative configurations that should be labelled during model training. We prove that ALKPU locally leads to the fastest reduction of model's uncertainty, which reveals its rationality as a general active learning method. We test the ALKPU method using various physical system simulations and demonstrate that it can efficiently coverage the system's configuration space. Our work demonstrates the benefits of ALKPU as a novel active learning method, enhancing training efficiency and reducing computational resource demands.
- [18] arXiv:2411.13866 [pdf, html, other]
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Title: A Phase-Space Electronic Hamiltonian for Molecules in a Static Magnetic Field I: Conservation of Total Pseudomomentum and Angular MomentumSubjects: Chemical Physics (physics.chem-ph)
We develop a phase-space electronic structure theory of molecules in magnetic fields. For a system of electrons in a magnetic field with vector potential $\bf{A}(\hat{\bf{r}})$, the usual Born-Oppenheimer Hamiltonian is the sum of the nuclear kinetic energy and the electronic Hamiltonian, $\frac{(\bf{P} - q\bf{A}(\bf{X}) )^2}{2M} + \hat{H}_{e}(\bf{X})$ (where $q$ is a nuclear charge). To include the effects of coupled nuclear-electron motion in the presence of magnetic field, we propose that the proper phase-space electronic structure Hamiltonian will be of the form $\frac{(\bf{P} - q^{\textit{eff}}\bf{A}(\bf{X}) - e\hat{\bf{\Gamma}})^2}{2M} + \hat{H}_{e}(\bf{X})$. Here, $q^{\textit{eff}}$ represents the {\em screened} nuclear charges and the $\hat{\bf{\Gamma}}$ term captures the local pseudomomentum of the electrons. This form reproduces exactly the energy levels for a hydrogen atom in a magnetic field; moreover, single-surface dynamics along the eigenstates is guaranteed to conserve both the total pseudomomentum as well as the total angular momentum in the direction of the magnetic field. This Hamiltonian form can be immediately implemented within modern electronic structure packages (where the electronic orbitals will now depend on nuclear position ($\bf{X}$) and nuclear momentum ($\bf{P}$)). One can expect to find novel beyond Born-Oppenheimer magnetic field effects for strong enough fields and/or nonadiabatic systems.
- [19] arXiv:2411.13879 [pdf, html, other]
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Title: A Phase-Space Electronic Hamiltonian for Molecules in a Static Magnetic Field II: Quantum Chemistry Calculations with Gauge Invariant Atomic OrbitalsSubjects: Chemical Physics (physics.chem-ph)
In a companion paper, we have developed a phase-space electronic structure theory of molecules in magnetic fields, whereby the electronic energy levels arise from diagonalizing a phase-space Hamiltonian $\hat H_{PS}(\bf{X},\bf{\Pi})$ that depends parametrically on nuclear position and momentum. The resulting eigenvalues are translationally invariant; moreover, if the magnetic field is in the $z-$direction, then the eigenvalues are also invariant to rotations around the $z-$direction. However, like all Hamiltonians in a magnetic field, the theory has a gauge degree of freedom (corresponding to the position of the magnetic origin in the vector potential), and requires either $(i)$ formally, a complete set of electronic states or $(ii)$ in practice, gauge invariant atomic orbitals (GIAOs) in order to realize such translational and rotational invariance. Here we describe how to implement a phase-space electronic Hamiltonian using GIAOs within a practical electronic structure package (in our case, Q-Chem). We further show that novel phenomena can be observed with finite $\bf{B}-$fields, including minimum energy structures with $\bf{\Pi}_{min} \ne 0$, indicating non-zero electronic motion in the ground-state.
- [20] arXiv:2411.13889 [pdf, html, other]
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Title: The SABRE South Technical Design Report Executive SummaryE. Barberio, T. Baroncelli, V. U. Bashu, L. J. Bignell, I. Bolognino, G. Brooks, S.S. Chun, F. Dastgiri, A. R. Duffy, M. B. Froehlich, T. Fruth, G. Fu, G. C. Hill, R. S. James, K. Janssens, S. Kapoor, G. J. Lane, K. T. Leaver, P. McGee, L. J. McKie, P. C. McNamara, J. McKenzie, W. J. D. Melbourne, M. Mews, G. Milana, L. J. Milligan, J. Mould, K. J. Rule, F. Scutti, Z. Slavkovská, O. Stanley, A. E. Stuchbery, B. Suerfu, G. N. Taylor, D. Tempra, T. Tunningly, P. Urquijo, A. G. Williams, Y. Xing, M. J. ZurowskiSubjects: Instrumentation and Detectors (physics.ins-det); High Energy Physics - Experiment (hep-ex)
In this Technical Design Report (TDR) we describe the SABRE South detector to be built at the Stawell Underground Physics Laboratory (SUPL). The SABRE South detector is designed to test the long-standing DAMA/LIBRA signal of an annually modulating rate consistent with dark matter by using the same target material. SABRE South uses seven ultra-high purity NaI(Tl) crystals (with a total target mass of either 35 kg or 50 kg), hermetically sealed in copper enclosures that are suspended within a liquid scintillator active veto. High quantum efficiency and low background Hamamatsu R11065 photomultiplier tubes are directly coupled to both ends of the crystal, and enclosed with the crystal in an oxygen free high thermal conductivity copper enclosure. The active veto system consists of 11.6 kL of linear alkylbenzene (LAB) doped with a mixture of fluorophores and contained in a steel vessel, which is instrumented with at least 18 Hamamatsu R5912 photomultipliers. The active veto tags key radiogenic backgrounds intrinsic to the crystals, such as ${^{40}}$K, and is expected to suppress the total background by 27% in the 1-6 keV region of interest. In addition to the liquid scintillator veto, a muon veto is positioned above the detector shielding. This muon veto consists of eight EJ-200 scintillator modules, with Hamamatsu R13089 photomultipliers coupled to both ends. With an expected total background of 0.72 cpd/kg/keV, SABRE South can test the DAMA/LIBRA signal with 5$\sigma$ discovery or 3$\sigma$ exclusion after two years of data taking.
- [21] arXiv:2411.13893 [pdf, html, other]
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Title: Simulating squirmers with smoothed particle dynamicsComments: 32 pages, 14 figuresSubjects: Fluid Dynamics (physics.flu-dyn); Soft Condensed Matter (cond-mat.soft)
Microswimmers play an important role in shaping the world around us. The squirmer is a simple model for microswimmer whose cilia oscillations on its spherical surface induce an effective slip velocity to propel itself. The rapid development of computational fluid dynamics methods has markedly enhanced our capacity to study the behavior of squirmers in aqueous environments. Nevertheless, a unified methodology that can fully address the complexity of fluid-solid coupling at multiple scales and interface tracking for multiphase flows remains elusive, posing an outstanding challenge to the field. To this end, we investigate the potential of the smoothed particle dynamics (SPD) method as an alternative approach for simulating squirmers. The Lagrangian nature of the method allows it to effectively address the aforementioned difficulty. By introducing a novel treatment of the boundary condition and assigning appropriate slip velocities to the boundary particles, the SPD-squirmer model is able to accurately represent a range of microswimmer types including pushers, neutral swimmers, and pullers. We systematically validate the steady-state velocity of the squirmer, the resulting flow field, its hydrodynamic interactions with the surrounding environment, and the mutual collision of two squirmers. In the presence of Brownian motion, the model is also able to correctly calculate the velocity and angular velocity autocorrelation functions at the mesoscale. Finally, we simulate a squirmer within a multiphase flow by considering a droplet that encloses a squirmer and imposing a surface tension between the two flow phases. We find that the squirmer within the droplet exhibits different motion types.
- [22] arXiv:2411.13930 [pdf, html, other]
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Title: Nonlinear dynamics in an artificial feedback spin maserComments: 6 pages,5 figuresSubjects: Atomic Physics (physics.atom-ph)
Spin masers with optical detection and artificial feedback are widely used in fundamental and practical applications. However, a full picture of the maser dynamics is still absent. By solving the feedback driven Bloch equations, we simulated the dynamics of an ideal spin maser in a broad parameter space. Rich nonlinear dynamics including high order harmonics generation, nonperiodic spin oscillations and frequency comb were revealed when the artificial feedback interaction exceeds the normal spin-field interaction. We also propose a pulse feedback spin maser protocol, which constructs an ultralow field magnetic frequency comb and could be useful in precision atomic magnetometers in searching for spin-dependent exotic interactions.
- [23] arXiv:2411.13986 [pdf, html, other]
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Title: On the applicability of CCSD(T) for dispersion interactions in large conjugated systemsSubjects: Chemical Physics (physics.chem-ph)
In light of the recent discrepancies reported between fixed node diffusion Monte Carlo and local natural orbital coupled cluster with single, double and perturbative triples (CCSD(T)) methodologies for non-covalent interactions in large molecular systems [Al-Hamdani et al., Nat. Comm., 2021, 12, 3927], the applicability of CCSD(T) is assessed using a model framework. The use of the Pariser-Parr-Pople (PPP) model for studying large molecules is critically examined and is shown to recover both bandgap closure as system size increases and long range dispersive behavior of r^-6 with increasing separation between monomers, in corollary with real systems. Using the PPP model, coupled cluster methodologies, CCSDTQ and CCSDT(Q), are then used to benchmark CCSDT and CCSD(T) methodologies for non-covalent interactions in large one- and two-dimensional molecular systems up to the dibenzocoronene dimer. We show that CCSD(T) demonstrates no signs of overestimating the interaction energy for these systems. Furthermore, by examining the Hartree-Fock HOMO-LUMO gap of these large molecules, the perturbative treatment of the triples contribution in CCSD(T) is not expected to cause problems for accurately capturing the interaction energy for system sizes up to at least circumcoronene.
- [24] arXiv:2411.13992 [pdf, html, other]
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Title: The efficient implementation of transport velocity formulationComments: 33 pages and 17 figuresSubjects: Fluid Dynamics (physics.flu-dyn)
The standard smoothed particle hydrodynamics (SPH) method suffers from tensile instability, resulting in particle clumping and void regions under negative pressure conditions. In this study, we extend the transport-velocity formulation of Adami et al. (2013) \cite{adami2013transport} in the weakly-compressible SPH (WCSPH) framework to address this long-standing issue. Rather than relying on background pressure, our modified and improved transport-velocity correction scales directly to the smoothing length, making it suitable for variable-resolution flows. Additionally, we introduce a limiter to the new formulation to prevent overcorrection, especially for flow with small velocities. These modifications enhance the general applicability of the transport velocity in fluid dynamics. Numerical tests involving low-velocity and variable-resolution cases demonstrate that the new formulation offers a general and accurate solution for multi-physics SPH simulations.
- [25] arXiv:2411.14048 [pdf, html, other]
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Title: Generating optical angular momentum through wavefront curvatureSubjects: Optics (physics.optics)
Recent developments in the understanding of optical angular momentum have resulted in many demonstrations of unusual optical phenomena, such as optical beams with orbital angular momentum and transverse spinning light. Here we detail novel contributions to spin and orbital angular momentum generated by the gradient of wavefront curvature that becomes relevant in strongly focused beams of light. While circularly polarized beams are shown to develop helicity-dependent transverse spin, a linearly polarized Gaussian beam produces longitudinal spin and orbital angular momenta in the focal region, even if lacking both of these before focusing. Analytical treatment of a nonparaxial electromagnetic field, validated with vectorial diffraction modelling, shows that the terms related to higher orders of a paraxial parameter are responsible for the appearance of non-trivial angular momenta. The obtained dependences relate these quantities to the gradient of the wavefront curvature, showing how it can be used as a novel degree of freedom for applications in optical manipulation and light-matter interactions at subwavelength scales, enabling angular momentum transfer even from a simple Gaussian beam with linear polarization.
- [26] arXiv:2411.14060 [pdf, other]
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Title: Tunable Nanostructuring for van der Waals MaterialsGleb Tselikov, Anton Minnekhanov, Georgy Ermolaev, Gleb Tikhonowski, Ivan Kazantsev, Dmitry Dyubo, Daria Panova, Daniil Tselikov, Anton Popov, Arslan Mazitov, Sergei Smirnov, Fedor Lipilin, Umer Ahsan, Nikita Orekhov, Ivan Kruglov, Alexander Syuy, Andrei Kabashin, Boris Chichkov, Zdenek Sofer, Aleksey Arsenin, Kostya Novoselov, Valentyn VolkovComments: 24 pages, 6 figuresSubjects: Applied Physics (physics.app-ph); Materials Science (cond-mat.mtrl-sci); Optics (physics.optics)
Van der Waals (vdW) materials are becoming increasingly popular in scientific and industrial applications because of their unique mixture of record electronic, optical, and mechanical properties. However, nanostructuring of vdW materials is still in its infancy and strongly depends on the specific vdW crystal. As a result, the universal self-assembled technology of vdW materials nanostructuring opens vast technological prospects. This work demonstrates an express and universal synthesis method of vdW nanoparticles with well-defined geometry using femtosecond laser ablation and fragmentation. The disarming simplicity of the technique allows us to create nanoparticles from over 50 vdW precursor materials covering transition metal chalcogenides, MXenes, and other vdW materials. Obtained nanoparticles manifest perfectly defined crystalline structures and diverse shapes, from nanospheres to nanocubes and nanotetrahedrons. Thus, our work provides a new paradigm for vdW nanostructuring with a vast potential of tunability for size, shape, and materials specific to the particular application.
- [27] arXiv:2411.14069 [pdf, html, other]
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Title: Characterization of Supersonic Jet and Shock Wave with High-Resolution Quantitative Schlieren ImagingComments: 16 pages, 13 figuresSubjects: Optics (physics.optics); Fluid Dynamics (physics.flu-dyn)
This paper presents an enhanced optical configuration for a single-pass quantitative Schlieren imaging system that achieves an optical resolution of approximately 4.6 micrometers. The modified setup decouples sensitivity from resolution, enabling independent optimization of these critical parameters. Using this high-resolution system, we conduct quantitative analyses of supersonic jets emitted from sub-millimeter nozzles into the atmosphere and investigate shock waves induced by knife blades interacting with these jets in a vacuum environment. The fine resolution allows for detailed visualization of shock wave structures and accurate measurement of density gradients. We demonstrate the system's effectiveness by examining the density gradient profile along the shock diamonds and mapping density profiles across shock waves. These density profiles are analyzed for their relevance in laser-plasma applications, including laser wakefield acceleration and the Analog Black Hole Evaporation via Laser (AnaBHEL) experiment. Our findings indicate that this system can help determine key parameters such as peak density, plateau length, and shock wave thickness-essential for optimizing electron acceleration and achieving specific plasma density profiles. This high-resolution quantitative Schlieren imaging technique thus serves as a valuable tool for exploring complex fluid dynamics and supporting advancements in laser-plasma physics research.
- [28] arXiv:2411.14071 [pdf, html, other]
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Title: Evidence of potential thermospheric overcooling during the May 2024 geomagnetic superstormComments: 16 pages, 8 figuresSubjects: Space Physics (physics.space-ph)
During intense geomagnetic storms, the rapid and significant production of NO followed by its associated infrared radiative emission in lower thermosphere contributes crucially to the energetics of the upper atmosphere. This makes NO infrared radiative cooling a very important phenomenon which needs to be considered for accurate density forecasting in thermosphere. This study reports the investigation of variations in thermospheric density, and NO radiative cooling during the recent geomagnetic superstorm of May 2024. A very rare post-storm thermospheric density depletion of about -23% on May 12 was observed by Swarm-C in northern hemisphere in comparison to the prestorm condition on May 9. This overcooling was observed despite the continuous enhancement in solar EUV (24-36 nm) flux throughout the event. The thermospheric NO infrared radiative emission in the recovery phase of the storm seems to be the plausible cause for this observed post-storm density depletion. The TIMED/SABER observed thermospheric density between 105 and 110 km altitude shows an enhancement during this thermospheric overcooling. Our analysis also suggests an all time high thermospheric NO radiative cooling flux up to 11.84 ergs/cm2/sec during May 2024 geomagnetic superstorm, which has also been compared with famous Halloween storms of October 2003.
- [29] arXiv:2411.14099 [pdf, html, other]
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Title: Asymmetric Opinion Formation of Emotional Eccitable AgentsComments: 21 pages, 18 figures. This paper extends the bounded confidence model by incorporating emotion-driven bound tuning, multibody interactions, and synchronization dynamics. Previously submitted to the Conference on Complex Systems 2021 and 2022, and Complex Networks 2021Subjects: Physics and Society (physics.soc-ph)
The bounded confidence model represents a widely adopted framework for modeling opinion dynamics wherein actors have a continuous-valued opinion and interact and approach their positions in the opinion space only if their opinions are within a specified confidence threshold. Here, we propose a novel framework where the confidence bound is determined by a decreasing function of their emotional arousal, an additional independent variable distinct from the opinion value. Additionally, our framework accounts for agents' ability to broadcast messages, with interactions influencing the timing of each other's message emissions. Our findings underscore the significant role of synchronization in shaping consensus formation. Furthermore, we demonstrate that variable confidence intervals alter the impact of step length when navigating the opinion space, leading to deviations from observations in the traditional Deffuant model.
- [30] arXiv:2411.14101 [pdf, other]
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Title: Low-Contrast BIC Metasurfaces with Quality Factors Exceeding 100,000Comments: 20 pages, 4 main figures + 4 supporting figuresSubjects: Optics (physics.optics); Applied Physics (physics.app-ph)
Dielectric metasurfaces operating at quasi-bound states in the continuum (qBICs) can achieve exceptionally high radiative quality ($\textit{Q}$) factors by introducing small asymmetries into their unit cells. However, fabrication imperfections often impose major limitations on the experimentally observed $\textit{Q}$ factors. In this study, we experimentally demonstrate BIC metasurfaces with a record-high $\textit{Q}$ factor of 101,486 under normal excitation of light in the telecom wavelength range achieved by employing low-contrast silicon pairs. Our findings show that such ultrahigh-$\textit{Q}$ factors can be attained by leveraging both the high radiative $\textit{Q}$ factors of higher-order qBIC modes and reduced scattering losses in shallow-etched designs. Additionally, we demonstrate stable sub-picometer-level wavelength fluctuations in water, with a limit of detection of $10^{-5}$ for environmental refractive index changes. The proposed approach can be extended to BIC metasurfaces with many other configurations and operating wavelengths for ultrahigh-$\textit{Q}$ applications in both fundamental physics and advanced devices.
- [31] arXiv:2411.14104 [pdf, html, other]
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Title: A comprehensive study of the Spin-Hall effect of tightly focused linearly polarized light through a stratified medium in optical tweezersComments: 10 pages, 7 figuresSubjects: Optics (physics.optics)
The optical Spin-Hall effect originates from the interaction between the spin angular momentum (SAM) and extrinsic orbital angular momentum (OAM) of light, leading to mutual interrelations between the polarization and trajectory of light in case of non-paraxial fields. Here, we extensively study the SHE and the resultant Spin-Hall shifts (SHS) in optical tweezers (OT) by varying the numerical aperture of objective lenses, and the refractive index (RI) stratification of the trapping medium. Indeed, we obtain much larger values of the SHS for particular combinations of NA and stratification compared to the sub-wavelength orders typically reported. We also observe that the longitudinal component of the spin angular momentum (SAM) density - which is responsible for the spin of birefringent particles in optical tweezers - changes more-or-less monotonically with the lens numerical aperture, except around values of the latter where the angle subtended by the focused light equals the critical angle for a particular RI interface. Our results may find applications in designing experiments for tuning the SHS and SAM induced due to SOI to generate exotic optomechanics of trapped particles in optical tweezers.
- [32] arXiv:2411.14106 [pdf, html, other]
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Title: Adjoint-based online learning of two-layer quasi-geostrophic baroclinic turbulenceComments: 25 pages, 1 table, 8 figuresSubjects: Atmospheric and Oceanic Physics (physics.ao-ph); Machine Learning (cs.LG); Fluid Dynamics (physics.flu-dyn)
For reasons of computational constraint, most global ocean circulation models used for Earth System Modeling still rely on parameterizations of sub-grid processes, and limitations in these parameterizations affect the modeled ocean circulation and impact on predictive skill. An increasingly popular approach is to leverage machine learning approaches for parameterizations, regressing for a map between the resolved state and missing feedbacks in a fluid system as a supervised learning task. However, the learning is often performed in an `offline' fashion, without involving the underlying fluid dynamical model during the training stage. Here, we explore the `online' approach that involves the fluid dynamical model during the training stage for the learning of baroclinic turbulence and its parameterization, with reference to ocean eddy parameterization. Two online approaches are considered: a full adjoint-based online approach, related to traditional adjoint optimization approaches that require a `differentiable' dynamical model, and an approximately online approach that approximates the adjoint calculation and does not require a differentiable dynamical model. The online approaches are found to be generally more skillful and numerically stable than offline approaches. Others details relating to online training, such as window size, machine learning model set up and designs of the loss functions are detailed to aid in further explorations of the online training methodology for Earth System Modeling.
- [33] arXiv:2411.14116 [pdf, other]
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Title: Equivalent slip length of flow around a super-hydrophobic cylinderSubjects: Fluid Dynamics (physics.flu-dyn)
In this research, a two-dimensional numerical simulation is conducted to determine the equivalent wall slip length for flow around a circular cylinder featuring a super-hydrophobic surface. The super-hydrophobic surface is modeled as an alternating distribution of slip and no-slip conditions along the cylinder's surface. The smallest unit of this alternating pattern is referred to as a monomer. The study takes into account the Reynolds number and two critical dimensionless parameters: the gas fraction (GF) and the ratio l/a. GF indicates the proportion of the slip length relative to the total length of the monomer, while l/a denotes the ratio of the monomer length (l) to the cylinder's radius (a). The ranges considered for the Reynolds number, GF, and l/a are from 0.2 to 180, 0.1 to 0.99, and $\pi$/80 to $\pi$/5, respectively. A dimensionless number, the Knudsen number (Kn), is introduced to measure the ratio between the equivalent slip length ($\lambda$) and the cylinder's diameter (D). By equating the integral wall friction resistance on the cylinder surface, a quantitative relationship between the equivalent Kn and the parameters (Re, GF, l/a) is established. A meticulous comparison of flow parameters between the equivalent slip length model and the slip-no-slip scenario reveals that the slip length model is an effective approximation for the slip-no-slip alternating model.
- [34] arXiv:2411.14122 [pdf, html, other]
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Title: From underground natural gas to hydrogen storage in fractured reservoir rock : comparing relative permeabilities for hydrogen versus methane and nitrogenSojwal Manoorkar, Gülce Kalyoncu Pakkaner, Hamdi Omar, Soetkin Barbaix, Dominique Ceursters, Maxime Lathinis, Stefanie Van Offenwert, Tom BultreysComments: 58 pages, 24 figuresSubjects: Fluid Dynamics (physics.flu-dyn)
Underground hydrogen storage in saline aquifers is a potential solution for seasonal renewable energy storage. Among potential storage sites, facilities used for underground natural gas storage have advantages, including well-characterized cyclical injection-withdrawal behavior and partially reusable infrastructure. However, the differences between hydrogen-brine and natural gas-brine flow, particularly through fractures in the reservoir and the sealing caprock, remain unclear due to the complexity of two-phase flow. Therefore, we investigate fracture relative permeability for hydrogen versus methane (natural gas) and nitrogen (commonly used in laboratories). Steady-state relative permeability experiments were conducted at 10 MPa on fractured carbonate rock from the Loenhout natural gas storage in Belgium, where gas flows through {\textmu}m-to-mm scale fractures. Our results reveal that the hydrogen exhibits similar relative permeability curves to methane, but both are significantly lower than those measured for nitrogen. This implies that nitrogen cannot reliably serve as a proxy for hydrogen at typical reservoir pressures. The low relative permeabilities for hydrogen and methane indicate strong fluid phase interference, which traditional relative permeability models fail to capture. This is supported by our observation of periodic pressure fluctuations associated with intermittent fluid connectivity for hydrogen and methane. In conclusion, our findings suggest that the fundamental flow properties of fractured rocks are complex but relatively similar for hydrogen and natural gas. This is an important insight for predictive modeling of the conversion of Loenhout and similar natural gas storage facilities, which is crucial to evaluate their hydrogen storage efficiency and integrity.
- [35] arXiv:2411.14134 [pdf, html, other]
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Title: Simulating Nonadiabatic Dynamics in Benzophenone: Tracing Internal Conversion Through Photoelectron SpectraSubjects: Chemical Physics (physics.chem-ph)
Benzophenone serves as a prototype chromophore for studying the photochemistry of aromatic ketones, with applications ranging from biochemistry to organic light-emitting diodes. In particular, its intersystem crossing from the first singlet excited state to triplet states has been extensively studied, but experimental or theoretical studies on the preceding internal conversion within the singlet manifold are very rare. This relaxation mechanism is particularly important because direct population transfer of the first singlet excited state from the ground state is inefficient due to its low oscillator strength. In this work, we aim to fill this gap by employing mixed quantum classical and full quantum dynamics simulations and time-resolved photoelectron spectroscopy for gas-phase benzophenone and meta-methyl benzophenone. Our results show that nonadiabatic relaxation via conical intersections leads to a linear increase in the population of the first singlet excited state. This population transfer due to conical intersections can be directly detected by a bifurcation of the photoelectron signal. In addition, we are able to clarify the role of the third singlet excited state degenerate to the second excited state - a topic that remains largely unexplored in the existing literature on benzophenone.
- [36] arXiv:2411.14159 [pdf, html, other]
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Title: Predicting rigidity and connectivity percolation in disordered particulate networks using graph neural networksComments: 8 pages, 5 figure files plus a supplementary material PDFSubjects: Computational Physics (physics.comp-ph)
Graph neural networks can accurately predict the chemical properties of many molecular systems, but their suitability for large, macromolecular assemblies such as gels is unknown. Here, graph neural networks were trained and optimised for two large-scale classification problems: the rigidity of a molecular network, and the connectivity percolation status which is non-trivial to determine for systems with periodic boundaries. Models trained on lattice systems were found to achieve accuracies >95% for rigidity classification, with slightly lower scores for connectivity percolation due to the inherent class imbalance in the data. Dynamically generated off-lattice networks achieved consistently lower accuracies overall due to the correlated nature of the network geometry that was absent in the lattices. An open source tool is provided allowing usage of the highest-scoring trained models, and directions for future improved tools to surmount the challenges limiting accuracy in certain situations are discussed.
- [37] arXiv:2411.14180 [pdf, html, other]
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Title: Unveiling Ultrafast Spin-Valley Dynamics and Phonon-Mediated Charge Transfer in MoSe$_{2}$/WSe$_{2}$ HeterostructuresJulian Wagner, Robin Bernhardt, Lukas Rieland, Omar Abdul-Aziz, Qiuyang Li, Xiaoyang Zhu, Stefano Dal Conte, Giulio Cerullo, Paul H. M. van Loosdrecht, Hamoon HedayatSubjects: Applied Physics (physics.app-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
We use helicity-resolved ultrafast transient absorption spectroscopy to study spin-valley polarization dynamics in a vertically stacked MoSe$_{2}$/WSe$_{2}$ heterostructure. The experimental findings reveal details of interlayer charge transfer on ultrafast timescales, showing that the spin-valley polarized state of photoexcited carriers is conserved during the charge transfer and formation of interlayer excitons. Our results confirm that phonon scattering mediates the interlayer charge transfer process, while a high phonon population at elevated temperatures causes a significant decrease in spin-valley selective charge transfer. Moreover, the experimental findings demonstrate the possibility that interlayer excitons and their spin-valley polarization can be probed in the optical response of intralayer excitons. These findings pave the way for ultrafast detection, control, and manipulation of spin-valley polarized excitons in transition metal dichalcogenide-based 2D heterostructures.
- [38] arXiv:2411.14182 [pdf, html, other]
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Title: Enhanced receiver function imaging of crustal structures using symmetric autoencodersComments: 26 pages, 10 figures, submitted to Geophysical Journal InternationalSubjects: Geophysics (physics.geo-ph)
Receiver-function (RF) is a crustal imaging technique that entails deconvolving the radial or transverse component with the vertical component seismogram. Analysis of the variations of RFs along backazimuth and slowness is the key in determining the geometry and anisotropic properties of the crustal layers. Nonetheless, pseudorandom nuisance effects, influenced by the unknown earthquake source signature and seismic noise, are produced by the deconvolution process and obstruct precise comparisons of RFs across different backazimuths. Various methods such as weighted stacking, sparsity-induced transform and supervised denoising neural-network have been developed to reduce the nuisance effects. However, the common assumption of the nuisance effects as random Gaussian proves inadequate. Supervised denoising neural-network struggles to generalize effectively in intricate tectonic environments like subduction zones. In this study, we take an unsupervised approach where a network-based representation of a group of RFs with similar raypaths, enables disentanglement of the coherent crustal effects from the RF-specific nuisance effects. The representation learning task is performed using symmetric autoencoders (SymAE). SymAE effectively generates virtual RFs that capture coherent crustal effects and mitigate nuisance effects. Applied to synthetic RFs with real data-derived nuisances, our method exceeds bin-wise and phase-weighted stacking in quality and accuracy. Using real Cascadia Subduction Zone data, it enhances RFs and aids in interpreting a dual-layer subducting slab. We also provided sanity checks to verify the accuracy of the network-derived virtual RFs. One major advantage of our method is its ability to utilize all available earthquakes, irrespective of their signal quality, thereby enhancing reproducibility and enabling automation in RF analysis.
- [39] arXiv:2411.14183 [pdf, html, other]
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Title: Origin and Limits of Invariant Warming Patterns in Climate ModelsComments: To be submitted to J ClimSubjects: Atmospheric and Oceanic Physics (physics.ao-ph)
Climate models exhibit an approximately invariant surface warming pattern in typical end-of-century projections. This observation has been used extensively in climate impact assessments for fast calculations of local temperature anomalies, with a linear procedure known as pattern scaling. At the same time, emerging research has also shown that time-varying warming patterns are necessary to explain the time evolution of effective climate sensitivity in coupled models, a mechanism that is known as the pattern effect and that seemingly challenges the pattern scaling understanding. Here we present a simple theory based on local energy balance arguments to reconcile this apparent contradiction. Specifically, we show that the pattern invariance is an inherent feature of exponential forcing, linear feedbacks, a constant forcing pattern and diffusive dynamics. These conditions are approximately met in most CMIP6 Shared Socioeconomic Pathways (SSP), except in the Arctic where nonlinear feedbacks are important and in regions where aerosols considerably alter the forcing pattern. In idealized experiments where concentrations of CO2 are abruptly increased, such as those used to study the pattern effect, the warming pattern can change considerably over time because of spatially inhomogeneous ocean heat uptake, even in the absence of nonlinear feedbacks. Our results illustrate why typical future projections are amenable to pattern scaling, and provide a plausible explanation of why more complicated approaches, such as nonlinear emulators, have only shown marginal improvements in accuracy over simple linear calculations.
- [40] arXiv:2411.14192 [pdf, html, other]
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Title: Learning Pore-scale Multi-phase Flow from Experimental Data with Graph Neural NetworkComments: Accpeted for Machine Learning and the Physical Sciences Workshop at the 38th conference on Neural Information Processing Systems (NeurIPS 2024)Subjects: Fluid Dynamics (physics.flu-dyn); Machine Learning (cs.LG)
Understanding the process of multiphase fluid flow through porous media is crucial for many climate change mitigation technologies, including CO$_2$ geological storage, hydrogen storage, and fuel cells. However, current numerical models are often incapable of accurately capturing the complex pore-scale physics observed in experiments. In this study, we address this challenge using a graph neural network-based approach and directly learn pore-scale fluid flow using micro-CT experimental data. We propose a Long-Short-Edge MeshGraphNet (LSE-MGN) that predicts the state of each node in the pore space at each time step. During inference, given an initial state, the model can autoregressively predict the evolution of the multiphase flow process over time. This approach successfully captures the physics from the high-resolution experimental data while maintaining computational efficiency, providing a promising direction for accurate and efficient pore-scale modeling of complex multiphase fluid flow dynamics.
- [41] arXiv:2411.14196 [pdf, html, other]
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Title: Uncertainty Quantification in Working Memory via Moment Neural NetworksComments: Code released: this https URLSubjects: Biological Physics (physics.bio-ph); Neural and Evolutionary Computing (cs.NE); Applications (stat.AP)
Humans possess a finely tuned sense of uncertainty that helps anticipate potential errors, vital for adaptive behavior and survival. However, the underlying neural mechanisms remain unclear. This study applies moment neural networks (MNNs) to explore the neural mechanism of uncertainty quantification in working memory (WM). The MNN captures nonlinear coupling of the first two moments in spiking neural networks (SNNs), identifying firing covariance as a key indicator of uncertainty in encoded information. Trained on a WM task, the model demonstrates coding precision and uncertainty quantification comparable to human performance. Analysis reveals a link between the probabilistic and sampling-based coding for uncertainty representation. Transferring the MNN's weights to an SNN replicates these results. Furthermore, the study provides testable predictions demonstrating how noise and heterogeneity enhance WM performance, highlighting their beneficial role rather than being mere biological byproducts. These findings offer insights into how the brain effectively manages uncertainty with exceptional accuracy.
- [42] arXiv:2411.14211 [pdf, html, other]
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Title: Fluid flow channeling and mass transport with discontinuous porosity distributionComments: 12 pages, 9 figuresSubjects: Geophysics (physics.geo-ph); Fluid Dynamics (physics.flu-dyn)
The flow of fluids within porous rocks is an important process with numerous applications in Earth sciences. Modeling the compaction-driven fluid flow requires the solution of coupled nonlinear partial differential equations that account for the fluid flow and the solid deformation within the porous medium. Despite the nonlinear relation of porosity and permeability that is commonly encountered, natural data show evidence of channelized fluid flow in rocks that have an overall layered structure. Layers of different rock types routinely have discontinuous hydraulic and mechanical properties. We present numerical results obtained by a novel space-time method which can handle discontinuous initial porosity (and permeability) distributions. The space-time method enables a straightforward coupling to models of mass transport for trace elements. Our results show the influence of different kinds of layering in the development of fluid-rich channels and mass transport.
- [43] arXiv:2411.14282 [pdf, html, other]
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Title: Singlet Fission in Carotenoid Dimers -- The Role of the Exchange and Dipolar InteractionsSubjects: Chemical Physics (physics.chem-ph)
A theory of singlet fission in carotenoid dimers is presented which aims to explain the mechanism behind the creation of two uncorrelated triplets. Following the initial photoexcitation of a carotenoid chain to a "bright" $n^1B_u^+$ state, there is ultrafast internal conversion to the intrachain "dark" $1^1B_u^-$ triplet-pair state. This strongly exchanged-coupled state evolves into a pair of triplets on separate chains and spin-decoheres to form a pair of single, unentangled triplets, corresponding to complete singlet fission. The simulated EPR spectra for lycopene dimers shows a distinct spectral signal due to the residual exchange coupling between the triplet-pairs on seperate carotenoid chains.
- [44] arXiv:2411.14286 [pdf, html, other]
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Title: Direct Numerical Simulations of K-type transition in a flat-plate boundary layer with supercritical fluidsComments: To appear in the Proceedings of the 10th IUTAM Symposium on Laminar-Turbulent Transition (Nagano, 2024)Subjects: Fluid Dynamics (physics.flu-dyn)
We investigate the controlled K-type breakdown of a flat-plate boundary-layer with highly non-ideal supercritical fluid at a reduced pressure of $p_{r,\infty}=1.10$. Direct numerical simulations are performed at a Mach number of $M_\infty=0.2$ for one subcritical (liquid-like regime) temperature profile and one strongly-stratified transcritical (pseudo-boiling) temperature profile with slightly heated wall. In the subcritical case, the formation of aligned $\Lambda$-vortices is delayed compared to the reference ideal-gas case of Sayadi et al. (J. Fluid Mech., vol. 724, 2013, pp. 480-509), with steady longitudinal modes dominating the late-transitional stage. When the wall temperature exceeds the pseudo-boiling temperature, streak secondary instabilities lead to the simultaneous development of additional hairpin vortices and near-wall streaky structures near the legs of the primary aligned $\Lambda$-vortices. Nonetheless, transition to turbulence is not violent and is significantly delayed compared to the subcritical regime.
- [45] arXiv:2411.14294 [pdf, html, other]
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Title: Enhanced Collisional Losses from a Magnetic Mirror Using the Lenard-Bernstein Collision OperatorComments: 21 pages, 4 figures, 3 tables, submitted to journal of plasma physicsSubjects: Plasma Physics (physics.plasm-ph)
Collisions play a crucial role in governing particle and energy transport in plasmas confined in a magnetic mirror trap. Modern gyrokinetic codes are used to model transport in magnetic mirrors, but some of these codes utilize approximate model collision operators. This study focuses on a Pastukhov-style method of images calculation of particle and energy confinement times using a Lenard-Bernstein model collision operator. Prior work on parallel particle and energy balances used a different Fokker-Planck plasma collision operator and the method needs to be extended in non-trivial ways to study the Lenard-Bernstein operator. To assess the effectiveness of our approach, we compare our results with a modern finite element solver. Our findings reveal that the particle confinement time scales like $a \exp(a^2)$ using the Lenard-Bernstein operator, in contrast to the more accurate scaling that the Coulomb collision operator would yield $a^2 \exp(a^2)$, where $a^2$ is approximately proportional to the ambipolar potential. We propose that codes modeling collisional losses in a magnetic mirrors utilizing the Lenard-Bernstein or Dougherty collision operator scale their collision frequency of any electrostatically confined species. This study illuminates the intricate role the collision operator plays in the Pastukhov-style method of images calculation of collisional confinement.
- [46] arXiv:2411.14309 [pdf, html, other]
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Title: Inverse-Designed Tapers for Compact Conversion Between Single-Mode and Wide WaveguidesComments: 4 pages, 3 figuresSubjects: Optics (physics.optics)
Waveguide tapers are critical components for leveraging the benefits of both single-mode and wide waveguides. Adiabatic tapers are typically hundreds of microns in length, dramatically limiting density and scalability. We reenvision the taper design process in an inverse-design paradigm, introducing the novel L-taper. We present a novel approach to inverse-designed tapers where the input and output waveguides are rotated 90 degrees with respect to each other. The resultant design has an order-of-magnitude smaller footprint, and the design process is compatible with a variety of fabrication processes. We demonstrate an L-taper designed on 220 nm silicon-on-insulator that converts a 0.5 micron waveguide to a 12 micron waveguide with -0.38 dB transmission and 40 nm 1-dB bandwidth. The footprint is 16 micron by 6 micron, representing a 12x smaller footprint than a linear taper with the same transmission.
- [47] arXiv:2411.14324 [pdf, html, other]
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Title: Platinum Black for stray-light mitigation on high-aspect-ratio micromechanical cantileverSubjects: Optics (physics.optics); Materials Science (cond-mat.mtrl-sci)
Microscopic devices are widely used in optomechanical experiments at the cutting-edge of precision experimental physics. Such devices often need to have high electrical conductivity but low reflectivity at optical wavelengths, which can be competing requirements for many commonly available coatings. In this manuscript, we present a technique to electroplate platinum with a highly convoluted surface on a $475\,\mathrm{\mu m } \, \times 500\,\mathrm{\mu m } \, \times 10\,\mathrm{\mu m }$ Silicon/Gold cantilever, preserving its electrical conductivity but reducing its reflectivity in the $0.3 - 1\,\mathrm{\mu m}$ range by a factor of $100$ or greater. The fact that the deposition can be done post-fabrication without damaging delicate structures makes this technique of interest to a potentially large range of experimental applications.
- [48] arXiv:2411.14335 [pdf, html, other]
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Title: Distribution of plastics of various sizes and densities in the global ocean from a 3D Eulerian modelComments: 22 pages, 13 figures. Results are presented at the APS-DFD 77th annual meetingSubjects: Atmospheric and Oceanic Physics (physics.ao-ph)
We develop a 3D Eulerian model to study the transport and distribution of microplastics in the global ocean. Among other benefits that will be discussed in the paper, one unique feature of our model is that it takes into consideration the effect of properties of particles (size and density, the former for the first time) to their vertical terminal velocity. With ocean current velocity taken from ECCOv4r4, a dataset generated from a data-assimilated MITgcm reanalysis, our model is integrated for 26 years for particles of different properties with their stationary patterns studied. We find that only low-density particles with sufficient size (e.g. density $900kg/m^3$ with size $\gtrsim 10 \mu m$) aggregate in the five subtropical gyres observed in previous studies. In contrast, particles of smaller size ($\sim 1 \mu m$), irrespective of their density, behave like neutrally buoyant particles with a weaker pattern on the surface and a deeper penetration into depth (up to about 1km deep). In addition, we observe seasonal variations of floating particle concentration on the ocean surface, which reasonably agree with the satellite observation by Cyclone Global Navigation Satellite System (CYGNSS) in terms of the phase of the variation. We find that the seasonal variation of the surface particle concentration correlates well with the variation of the mixing layer (ML) depth globally, due to an almost uniform vertical distribution of particles in the ML with total amount of particles conserved.
- [49] arXiv:2411.14378 [pdf, other]
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Title: CoNFiLD-inlet: Synthetic Turbulence Inflow Using Generative Latent Diffusion Models with Neural FieldsComments: 27 pages, 10 figuresSubjects: Fluid Dynamics (physics.flu-dyn); Machine Learning (cs.LG)
Eddy-resolving turbulence simulations require stochastic inflow conditions that accurately replicate the complex, multi-scale structures of turbulence. Traditional recycling-based methods rely on computationally expensive precursor simulations, while existing synthetic inflow generators often fail to reproduce realistic coherent structures of turbulence. Recent advances in deep learning (DL) have opened new possibilities for inflow turbulence generation, yet many DL-based methods rely on deterministic, autoregressive frameworks prone to error accumulation, resulting in poor robustness for long-term predictions. In this work, we present CoNFiLD-inlet, a novel DL-based inflow turbulence generator that integrates diffusion models with a conditional neural field (CNF)-encoded latent space to produce realistic, stochastic inflow turbulence. By parameterizing inflow conditions using Reynolds numbers, CoNFiLD-inlet generalizes effectively across a wide range of Reynolds numbers ($Re_\tau$ between $10^3$ and $10^4$) without requiring retraining or parameter tuning. Comprehensive validation through a priori and a posteriori tests in Direct Numerical Simulation (DNS) and Wall-Modeled Large Eddy Simulation (WMLES) demonstrates its high fidelity, robustness, and scalability, positioning it as an efficient and versatile solution for inflow turbulence synthesis.
- [50] arXiv:2411.14407 [pdf, other]
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Title: Exploring Methods for Integrating and Augmenting Multimodal Data to Improve Prognostic Accuracy in Imbalanced Datasets for Intraoperative Aneurysm OcclusionParisa Naghdi, Mohammad Mahdi Shiraz Bhurwani, Ahmad Rahmatpour, Parmita Mondal, Michael Udin, Kyle A Williams, Swetadri Vasan Setlur Nagesh, Ciprian N IonitaComments: 6 pagesSubjects: Medical Physics (physics.med-ph)
This study evaluates a multimodal machine learning framework for predicting treatment outcomes in intracranial aneurysms (IAs). Combining angiographic parametric imaging (API), patient biomarkers, and disease morphology, the framework aims to enhance prognostic accuracy. Data from 340 patients were analyzed, with separate deep neural networks processing quantitative and categorical data. These networks' pre decision layers were concatenated and inputted into a final predictive network. Various data augmentation strategies, including Synthetic Minority Oversampling Technique for Nominal and Continuous data (SMOTE NC), addressed dataset imbalances. Performance metrics, evaluated through Monte Carlo cross validation, showed significant improvements with augmentation, particularly in intermediate fusion models. This study validates the framework's efficacy in accurately predicting IA treatment outcomes, demonstrating that data augmentation techniques can substantially enhance model performance.
- [51] arXiv:2411.14410 [pdf, html, other]
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Title: Engineering spectro-temporal light states with physics-trained deep learningComments: Welcome to place your commentsSubjects: Optics (physics.optics); Pattern Formation and Solitons (nlin.PS); Classical Physics (physics.class-ph); Quantum Physics (quant-ph)
Frequency synthesis and spectro-temporal control of optical wave packets are central to ultrafast science, with supercontinuum (SC) generation standing as one remarkable example. Through passive manipulation, femtosecond (fs) pulses from nJ-level lasers can be transformed into octave-spanning spectra, supporting few-cycle pulse outputs when coupled with external pulse compressors. While strategies such as machine learning have been applied to control the SC's central wavelength and bandwidth, their success has been limited by the nonlinearities and strong sensitivity to measurement noise. Here, we propose and demonstrate how a physics-trained convolutional neural network (P-CNN) can circumvent such challenges, showing few-fold speedups over the direct approaches. We highlight three key advancements enabled by the P-CNN approach: (i) on-demand control over spectral features of SC, (ii) direct generation of sub-3-cycle pulses from the highly nonlinear fiber, and (iii) the production of high-order solitons, capturing distinct "breather" dynamics in both spectral and temporal domains. This approach heralds a new era of arbitrary spectro-temporal state engineering, with transformative implications for ultrafast and quantum science.
- [52] arXiv:2411.14426 [pdf, html, other]
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Title: Quantum States Imaging of Magnetic Field Contours based on Autler-Townes Effect in Yb AtomsSubjects: Atomic Physics (physics.atom-ph); Quantum Physics (quant-ph)
An inter-combination transition in Yb enables a novel approach for rapidly imaging magnetic field variations with excellent spatial and temporal resolution and accuracy. This quantum imaging magnetometer reveals "dark stripes" that are contours of constant magnetic field visible by eye or capturable by standard cameras. These dark lines result from a combination of Autler-Townes splitting and the spatial Hanle effect in the $^{1}S_{0} - ^{3}P_{1}$ transition of Yb when driven by multiple strong coherent laser fields (carrier and AM/FM modulation sidebands of a single-mode 556 nm laser). We show good agreement between experimental data and our theoretical model for the closed, 4-level Zeeman shifted V-system and demonstrate scalar and vector magnetic fields measurements at video frame rates over spatial dimensions of 5 cm (expandable to $>$ 1 m) with 0.1 mm resolution. Additionally, the $^{1}S_{0} - ^{3}P_{1}$ transition allows for $\sim\mu$s response time and a large dynamic range ($\mu$T to many Ts).
New submissions (showing 52 of 52 entries)
- [53] arXiv:2411.13561 (cross-list from math.NA) [pdf, html, other]
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Title: Model discovery on the fly using continuous data assimilationSubjects: Numerical Analysis (math.NA); Dynamical Systems (math.DS); Data Analysis, Statistics and Probability (physics.data-an)
We review an algorithm developed for parameter estimation within the Continuous Data Assimilation (CDA) approach. We present an alternative derivation for the algorithm presented in a paper by Carlson, Hudson, and Larios (CHL, 2021). This derivation relies on the same assumptions as the previous derivation but frames the problem as a finite dimensional root-finding problem. Within the approach we develop, the algorithm developed in (CHL, 2021) is simply a realization of Newton's method. We then consider implementing other derivative based optimization algorithms; we show that the Levenberg Maqrquardt algorithm has similar performance to the CHL algorithm in the single parameter estimation case and generalizes much better to fitting multiple parameters. We then implement these methods in three example systems: the Lorenz '63 model, the two-layer Lorenz '96 model, and the Kuramoto-Sivashinsky equation.
- [54] arXiv:2411.13569 (cross-list from math.NA) [pdf, html, other]
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Title: Unconditionally stable symplectic integrators for the Navier-Stokes equations and other dissipative systemsSutthikiat Sungkeetanon, Joseph S. Gaglione, Robert L. Chapman, Tyler M. Kelly, Howard A. Cushman, Blakeley H. Odom, Bryan MacGavin, Gafar A. Elamin, Nathan J. Washuta, Jonathan E. Crosmer, Adam C. DeVoria, John W. SandersComments: 18 pages, 7 figuresSubjects: Numerical Analysis (math.NA); Dynamical Systems (math.DS); Fluid Dynamics (physics.flu-dyn)
Symplectic integrators offer vastly superior performance over traditional numerical techniques for conservative dynamical systems, but their application to \emph{dissipative} systems is inherently difficult due to dissipative systems' lack of symplectic structure. Leveraging the intrinsic variational structure of higher-order dynamics, this paper presents a general technique for applying existing symplectic integration schemes to dissipative systems, with particular emphasis on viscous fluids modeled by the Navier-Stokes equations. Two very simple such schemes are developed here. Not only are these schemes unconditionally stable for dissipative systems, they also outperform traditional methods with a similar degree of complexity in terms of accuracy for a given time step. For example, in the case of viscous flow between two infinite, flat plates, one of the schemes developed here is found to outperform both the implicit Euler method and the explicit fourth-order Runge-Kutta method in predicting the velocity profile. To the authors' knowledge, this is the very first time that a symplectic integration scheme has been applied successfully to the Navier-Stokes equations. We interpret the present success as direct empirical validation of the canonical Hamiltonian formulation of the Navier-Stokes problem recently published by Sanders~\emph{et al.} More sophisticated symplectic integration schemes are expected to exhibit even greater performance. It is hoped that these results will lead to improved numerical methods in computational fluid dynamics.
- [55] arXiv:2411.13630 (cross-list from q-bio.MN) [pdf, html, other]
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Title: Competitive binding of Activator-Repressor in Stochastic Gene ExpressionComments: 34 pages,47 figuresSubjects: Molecular Networks (q-bio.MN); Biological Physics (physics.bio-ph)
Regulation of gene expression is the consequence of interactions between the promoter of the gene and the transcription factors (TFs). In this paper, we explore the features of a genetic network where the TFs (activators and repressors) bind the promoter in a competitive way. We develop an analytical theory that offers detailed reaction kinetics of the competitive activator-repressor system which could be the powerful tools for extensive study and analysis of the genetic circuit in future research. Moreover, the theoretical approach helps us to find a most probable set of parameter values which was unavailable in experiments. We study the noisy behaviour of the circuit and compare the profile with the network where the activator and repressor bind the promoter non-competitively. We further notice that, due to the effect of transcriptional reinitiation in the presence of the activator and repressor molecules, there exits some anomalous characteristic features in the mean expressions and noise profiles. We find that, in presence of the reinitiation the noise in transcriptional level remains low while it is higher in translational level than the noise when the reinitiation is absent. In addition, it is possible to reduce the noise further below the Poissonian level in competitive circuit than the non-competitive one with the help of some noise reducing parameters.
- [56] arXiv:2411.13661 (cross-list from quant-ph) [pdf, html, other]
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Title: Non-Bloch self-energy of dissipative interacting fermionsComments: 7+5 pages, 3+1 figuresSubjects: Quantum Physics (quant-ph); Quantum Gases (cond-mat.quant-gas); Strongly Correlated Electrons (cond-mat.str-el); Optics (physics.optics)
The non-Hermitian skin effect describes the phenomenon of exponential localization of single-particle eigenstates near the boundary of the system. We explore its generalization to the many-body regime by investigating interacting fermions in open quantum systems. Therein, the elementary excitations from the ``vacuum'' (steady state) are given by two types of dissipative quasi-particles composed of single-fermion operators. We perturbatively calculate the self-energy of these quasi-particles in the presence of interactions, and utilize the non-Bloch band theory to develop an exact integral formula, which is further simplified by imposing complex momentum conservation. The formula allows calculating the Liouvillian gap modified by interactions with high precision, as demonstrated by comparison to numerical results. Furthermore, our results show that interactions can even enhance the non-reciprocity of fermion hoppings, contrary to the conventional viewpoint from the Pauli exclusion principle. Our formulation provides a quantitative tool for investigating dissipative interacting fermions with non-Hermitian skin effect, and generalizes the Fermi liquid theory to open quantum systems in the context of diagrammatic perturbation theory.
- [57] arXiv:2411.13680 (cross-list from q-bio.QM) [pdf, html, other]
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Title: Long-term predictive models for mosquito borne diseases: a narrative reviewSubjects: Quantitative Methods (q-bio.QM); Dynamical Systems (math.DS); Biological Physics (physics.bio-ph)
In face of climate change and increasing urbanization, the predictive mosquito-borne diseases (MBD) transmission models require constant updates. Thus, is urgent to comprehend the driving forces of this non stationary behavior, observed through spatial and incidence expansion. We observed that temperature is a critical driver in predictive models for MBD transmission, also being consistently used in multiple reviewed papers with considerable incidence predictive capacity. Rainfall, however, have more subtle importance as moderate precipitation creates breeding sites for mosquitoes, but excessive rainfall can reduce larvae populations. We highlight the frequent use of mechanistic models, particularly those that integrate temperature-dependent biological parameters of disease transmission in incidence proxies as the Vectorial Capacity (VC) and temperature-based basic reproduction number $R_0(t)$, for example. These models show the importance of climate variables, but the socio-demographic factors are often not considered. This gap is a significant opportunity for future research to incorporate socio-demographic data into long-term predictive models for more comprehensive and reliable forecasts. With this survey, we outline the most promising paths to be followed by long-term MBD transmission research and highlighting the potential facing challenges. Thus, we offer a valuable foundation for enhancing disease forecasting models and supporting more effective public health interventions, specially in the long term.
- [58] arXiv:2411.13695 (cross-list from cond-mat.mes-hall) [pdf, other]
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Title: Robust coherent dynamics of homogeneously limited anisotropic excitons in two-dimensional layered ReS2Rup Kumar Chowdhury, Md Samiul Islam, Marie Barthelemy, Nicolas Beyer, Lorry Engel, Jean-Sebastien Pelle, Mircea Rastei, Alberto Barsella, Francois FrasSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Optics (physics.optics); Quantum Physics (quant-ph)
The discovery of in-plane anisotropic excitons in two-dimensional layered semiconductors enables state-of-the-art nanophotonic applications. A fundamental yet unknown parameter of these quasiparticles is the coherence time (T_2 ), which governs the quantum dephasing timescale, over which the coherent superposition of excitons can be maintained and manipulated. Here, we report the direct measurement of T_2 within the sub-picosecond range, along with multiple population decay timescales (T_1 ) at resonance for anisotropic excitons in pristine layered rhenium disulfide (ReS2). We observe a notable weak dependence on layer thickness for T_2 , and a quasi-independence for T_1 . The excitonic coherence in few-layer ReS2 exhibits exceptional robustness against optical density and temperature compared to other two-dimensional semiconductors, enabling quantum features even at room temperature. No photon echo fingerprints were observed in pristine ReS2, highlighting the homogeneous character of the anisotropic excitonic transitions and a particularly low level of disorder in exfoliated flakes. Lastly, our results for mono- to bulk-like ReS2 support a direct gap band structure regardless their layer thickness, addressing the ongoing discussion about its nature.
- [59] arXiv:2411.13739 (cross-list from quant-ph) [pdf, html, other]
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Title: Conditional t-independent spectral gap for random quantum circuits and implications for t-design depthsComments: 53 pages, 6 figuresSubjects: Quantum Physics (quant-ph); Computational Physics (physics.comp-ph)
A fundamental question is understanding the rate at which random quantum circuits converge to the Haar measure. One quantity which is important in establishing this rate is the spectral gap of a random quantum ensemble. In this work we establish a new bound on the spectral gap of the t-th moment of a one-dimensional brickwork architecture on N qudits. This bound is independent of both t and N, provided t does not exceed the qudit dimension q. We also show that the bound is nearly optimal. The improved spectral gaps gives large improvements to the constant factors in known results on the approximate t-design depths of the 1D brickwork, of generic circuit architectures, and of specially-constructed architectures which scramble in depth O(log N). We moreover show that the spectral gap gives the dominant epsilon-dependence of the t-design depth at small epsilon. Our spectral gap bound is obtained by bounding the N-site 1D brickwork architecture by the spectra of 3-site operators. We then exploit a block-triangular hierarchy and a global symmetry in these operators in order to efficiently bound them. The technical methods used are a qualitatively different approach for bounding spectral gaps and and have little in common with previous techniques.
- [60] arXiv:2411.13771 (cross-list from cs.CY) [pdf, other]
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Title: Deciphering Urban Morphogenesis: A Morphospace ApproachComments: 20 pages, 8 figuresSubjects: Computers and Society (cs.CY); Social and Information Networks (cs.SI); Physics and Society (physics.soc-ph)
Cities emerged independently across different world regions and historical periods, raising fundamental questions: How did the first urban settlements develop? What social and spatial conditions enabled their emergence? Are these processes universal or context-dependent? Moreover, what distinguishes cities from other human settlements? This paper investigates the drivers of city creation through a hybrid approach that integrates urban theory with the biological concept of morphospace (the space of all possible configurations) and archaeological evidence. It examines the transition from sedentary hunter-gatherer communities to urban societies, identifying key forces such as defence, social hierarchy formation, population scale, and work specialization, culminating in increasingly complex divisions of labour as a central driver of urbanization. Morphogenesis is conceptualised as a trajectory across morphospace, shaped by structure-seeking selection processes that balance density, permeability, and information as critical dimensions. The study highlights the non-ergodic nature of urban morphogenesis, where configurations are progressively selected based on their fitness to support the diversifying interactions between mutually dependent agents. The morphospace framework effectively distinguishes between theoretical spatial configurations, non-urban and proto-urban settlements, and contemporary cities. This analysis supports the proposition that cities emerge and evolve as solutions balancing density, permeability, and informational organization, enabling them to support increasingly complex societal functions.
- [61] arXiv:2411.13772 (cross-list from math.NA) [pdf, html, other]
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Title: A Characteristic Mapping Method with Source Terms: Applications to Ideal MagnetohydrodynamicsComments: The preprint has not been revised yet!Subjects: Numerical Analysis (math.NA); Computational Physics (physics.comp-ph); Fluid Dynamics (physics.flu-dyn); Plasma Physics (physics.plasm-ph)
This work introduces a generalized characteristic mapping method designed to handle non-linear advection with source terms. The semi-Lagrangian approach advances the flow map, incorporating the source term via the Duhamel integral. We derive a recursive formula for the time decomposition of the map and the source term integral, enhancing computational efficiency. Benchmark computations are presented for a test case with an exact solution and for two-dimensional ideal incompressible magnetohydrodynamics (MHD). Results demonstrate third-order accuracy in both space and time. The submap decomposition method achieves exceptionally high resolution, as illustrated by zooming into fine-scale current sheets. An error estimate is performed and suggests third order convergence in space and time.
- [62] arXiv:2411.13776 (cross-list from hep-ex) [pdf, html, other]
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Title: Maximizing Quantum Enhancement in Axion Dark Matter ExperimentsChao-Lin Kuo, Chelsea L. Bartram, Aaron S. Chou, Taj A. Dyson, Noah A. Kurinsky, Gray Rybka, Osmond Wen, Matthew O. Withers, Andrew K. Yi, Cheng ZhangSubjects: High Energy Physics - Experiment (hep-ex); Instrumentation and Detectors (physics.ins-det)
We provide a comprehensive comparison of linear amplifiers and microwave photon-counters in axion dark matter experiments. The study is done assuming a range of realistic operating conditions and detector parameters, over the frequency range between 1--30 GHz. As expected, photon counters are found to be advantageous under low background, at high frequencies ($\nu>$ 5 GHz), {\em if} they can be implemented with robust wide-frequency tuning or a very low dark count rate. Additional noteworthy observations emerging from this study include: (1) an expanded applicability of off-resonance photon background reduction, including the single-quadrature state squeezing, for scan rate enhancements; (2) a much broader appeal for operating the haloscope resonators in the over-coupling regime, up to $\beta\sim 10$; (3) the need for a detailed investigation into the cryogenic and electromagnetic conditions inside haloscope cavities to lower the photon temperature for future experiments; (4) the necessity to develop a distributed network of coupling ports in high-volume axion haloscopes to utilize these potential gains in the scan rate.
- [63] arXiv:2411.13838 (cross-list from math.AP) [pdf, html, other]
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Title: Mathematical Analysis of Regularity, Bifurcations, and Turbulence in Fluid Dynamics via Sobolev, Besov, and Triebel-Lizorkin SpacesComments: 27 pagesSubjects: Analysis of PDEs (math.AP); Fluid Dynamics (physics.flu-dyn)
This article presents a comprehensive mathematical framework for the study of regularity, bifurcations, and turbulence in fluid dynamics, leveraging the power of Sobolev and Besov function spaces. We delve into the detailed definitions, properties, and notations of these spaces, illustrating their relevance in the context of partial differential equations governing fluid flow. The work emphasizes the intricate connections between Sobolev, Besov, and Triebel-Lizorkin spaces, highlighting their interplay in the analysis of fluid systems. We propose new regularity criteria for solutions to the Navier-Stokes equations, based on the interaction of low and high-frequency modes in turbulent regimes. These criteria offer a novel perspective on the conditions under which singularities may form, providing critical insights into the structure of turbulent flows. The article further explores the applications of these function spaces to the analysis of bifurcations in fluid systems, offering a deeper understanding of the mechanisms that lead to complex flow phenomena such as turbulence. Through the development of rigorous theorems and proofs, the paper aims to bridge the gap between abstract mathematical theory and practical fluid dynamics. In particular, the results contribute to ongoing efforts in solving the Navier-Stokes existence and smoothness problem, a key challenge in the field, and have potential implications for the Millennium Prize Problem. The conclusion underscores the significance of these findings, offering a pathway for future research in the analysis of fluid behavior at both small and large scales.
- [64] arXiv:2411.13881 (cross-list from cs.LG) [pdf, html, other]
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Title: Exploring applications of topological data analysis in stock index movement predictionComments: 20 pages, 10 figuresSubjects: Machine Learning (cs.LG); Data Analysis, Statistics and Probability (physics.data-an)
Topological Data Analysis (TDA) has recently gained significant attention in the field of financial prediction. However, the choice of point cloud construction methods, topological feature representations, and classification models has a substantial impact on prediction results. This paper addresses the classification problem of stock index movement. First, we construct point clouds for stock indices using three different methods. Next, we apply TDA to extract topological structures from the point clouds. Four distinct topological features are computed to represent the patterns in the data, and 15 combinations of these features are enumerated and input into six different machine learning models. We evaluate the predictive performance of various TDA configurations by conducting index movement classification tasks on datasets such as CSI, DAX, HSI and FTSE providing insights into the efficiency of different TDA setups.
- [65] arXiv:2411.13915 (cross-list from hep-ex) [pdf, html, other]
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Title: An accurate solar axions ray-tracing response of BabyIAXOS. Ahyoune, K. Altenmueller, I. Antolin, S. Basso, P. Brun, F. R. Candon, J. F. Castel, S. Cebrian, D. Chouhan, R. Della Ceca, M. Cervera-Cortes, V. Chernov, M. M. Civitani, C. Cogollos, E. Costa, V. Cotroneo, T. Dafni, A. Derbin, K. Desch, M. C. Diaz-Martin, A. Diaz-Morcillo, D. Diez-Ibanez, C. Diez Pardos, M. Dinter, B. Doebrich, I. Drachnev, A. Dudarev, A. Ezquerro, S. Fabiani, E. Ferrer-Ribas, F. Finelli, I. Fleck, J. Galan, G. Galanti, M. Galaverni, J. A. Garcia, J. M. Garcia-Barcelo, L. Gastaldo, M. Giannotti, A. Giganon, C. Goblin, N. Goyal, Y. Gu, L. Hagge, L. Helary, D. Hengstler, D. Heuchel, S. Hoof, R. Iglesias-Marzoa, F. J. Iguaz, C. Iniguez, I. G. Irastorza, K. Jakovcic, D. Kaefer, J. Kaminski, S. Karstensen, M. Law, A. Lindner, M. Loidl, C. Loiseau, G. Lopez-Alegre, A. Lozano-Guerrero, B. Lubsandorzhiev, G. Luzon, I. Manthos, C. Margalejo, A. Marin-Franch, J. Marques, F. Marutzky, C. Menneglier, M. Mentink, S. Mertens, J. Miralda-Escude, H. Mirallas, F. Muleri, V. Muratova, J. R. Navarro-Madrid, X. F. Navick, K. Nikolopoulos, A. Notari, A. Nozik, L. Obis, A. Ortiz-de-Solorzano, T. O'Shea, J. von Oy, G. Pareschi, T. Papaevangelou, K. Perez, O. Perez, E. Picatoste, M. J. Pivovaroff, J. Porron, M. J. Puyuelo, A. Quintana, J. Redondo, D. Reuther, A. Ringwald, M. Rodrigues, A. Rubini, S. Rueda-TeruelComments: 36 pages, 18 figures, 4 tables, Submitted to JHEPSubjects: High Energy Physics - Experiment (hep-ex); Instrumentation and Methods for Astrophysics (astro-ph.IM); Solar and Stellar Astrophysics (astro-ph.SR); Computational Physics (physics.comp-ph); Data Analysis, Statistics and Probability (physics.data-an)
BabyIAXO is the intermediate stage of the International Axion Observatory (IAXO) to be hosted at DESY. Its primary goal is the detection of solar axions following the axion helioscope technique. Axions are converted into photons in a large magnet that is pointing to the sun. The resulting X-rays are focused by appropriate X-ray optics and detected by sensitive low-background detectors placed at the focal spot. The aim of this article is to provide an accurate quantitative description of the different components (such as the magnet, optics, and X-ray detectors) involved in the detection of axions. Our efforts have focused on developing robust and integrated software tools to model these helioscope components, enabling future assessments of modifications or upgrades to any part of the IAXO axion helioscope and evaluating the potential impact on the experiment's sensitivity. In this manuscript, we demonstrate the application of these tools by presenting a precise signal calculation and response analysis of BabyIAXO's sensitivity to the axion-photon coupling. Though focusing on the Primakoff solar flux component, our virtual helioscope model can be used to test different production mechanisms, allowing for direct comparisons within a unified framework.
- [66] arXiv:2411.13925 (cross-list from astro-ph.SR) [pdf, html, other]
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Title: Nonlinear internal waves breaking in stellar radiation zones. Parametrisation for the transport of angular momentum: bridging geophysical to stellar fluid dynamicsComments: 9 pages, 1 figure, accepted for publication in Astronomy & AstrophysicsSubjects: Solar and Stellar Astrophysics (astro-ph.SR); Earth and Planetary Astrophysics (astro-ph.EP); Atmospheric and Oceanic Physics (physics.ao-ph)
Internal gravity waves (hereafter IGWs) are one of the mechanisms that can play a key role to redistribute efficiently angular momentum in stars along their evolution. The study of IGWs is thus of major importance since space-based asteroseismology reveals a transport of angular momentum in stars, which is stronger by two orders of magnitude than the one predicted by stellar models ignoring their action or those of magnetic fields. IGWs trigger angular momentum transport when they are damped by heat or viscous diffusion, when they meet a critical layer or when they break. Theoretical prescriptions have been derived for the transport of angular momentum induced by IGWs because of their radiative and viscous dampings and of the critical layers they encounter along their propagation. However, none has been proposed for the transport triggered by their nonlinear breaking. In this work, we aim to derive such a physical and robust prescription, which can be implemented in stellar structure and evolution codes. We adapt an analytical saturation model, which has been developed for IGWs nonlinear convective breaking in the Earth atmosphere and has been successfully compared to in-situ measurements in the stratosphere, to the case of deep spherical stellar interiors. In a first step, we neglect the modification of IGWs by the Coriolis acceleration and the Lorentz force, which are discussed and taken into account in a second step. We derive a complete semi-analytical prescription for the transport of angular momentum by IGWs, which takes into account both their radiative damping and their potential nonlinear breaking because of their convective and vertical shear instabilities. This allows us to bring the physical prescription for the interactions between IGWs and the differential rotation to the same level of realism that the one used in global circulation models for the atmosphere.
- [67] arXiv:2411.13936 (cross-list from nlin.PS) [pdf, html, other]
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Title: Formation of nonlinear modes in one-dimensional quasiperiodic lattices with a mobility edgeComments: 13 pages, 7 figures; accepted for Phys. Rev. ASubjects: Pattern Formation and Solitons (nlin.PS); Quantum Gases (cond-mat.quant-gas); Optics (physics.optics)
We investigate the formation of steady states in one-dimensional Bose-Einstein condensates of repulsively interacting ultracold atoms loaded into a quasiperiodic potential created by two incommensurate periodic lattices. We study the transformations between linear and nonlinear modes and describe the general patterns that govern the birth of nonlinear modes emerging in spectral gaps near band edges. We show that nonlinear modes in a symmetric potential undergo both symmetry-breaking pitchfork bifurcations and saddle-node bifurcations, mimicking the prototypical behaviors of symmetric and asymmetric double-well potentials. The properties of the nonlinear modes differ for bifurcations occurring below and above the mobility edge. In the generic case, when the quasiperiodic potential consists of two incommensurate lattices with a nonzero phase shift between them, the formation of localized modes in the spectral gaps occurs through a cascade of saddle-node bifurcations. Because of the analogy between the Gross-Pitaevskii equation and the nonlinear Schrödinger equation, our results can also be applied to optical modes guided by quasiperiodic photonic lattices.
- [68] arXiv:2411.13943 (cross-list from quant-ph) [pdf, other]
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Title: Independent Optical Frequency Combs Powered 546 km Field Test of Twin-Field Quantum Key DistributionLai Zhou, Jinping Lin, Chengfang Ge, Yuanbin Fan, Zhiliang Yuan, Hao Dong, Yang Liu, Di Ma, Jiu-Peng Chen, Cong Jiang, Xiang-Bin Wang, Li-Xing You, Qiang Zhang, Jian-Wei PanComments: To appear in Physical Review AppliedSubjects: Quantum Physics (quant-ph); Applied Physics (physics.app-ph); Optics (physics.optics)
Owing to its repeater-like rate-loss scaling, twin-field quantum key distribution (TF-QKD) has repeatedly exhibited in laboratory its superiority for secure communication over record fiber lengths. Field trials pose a new set of challenges however, which must be addressed before the technology's roll-out into real-world. Here, we verify in field the viability of using independent optical frequency combs -- installed at sites separated by a straight-line distance of 300~km -- to achieve a versatile TF-QKD setup that has no need for optical frequency dissemination and thus enables an open and network-friendly fiber configuration. Over 546 and 603 km symmetric links, we record a finite-size secure key rate (SKR) of 0.53~bit/s and an asymptotic SKR of 0.12 bit/s, respectively. Of practical importance, the setup is demonstrated to support 44~km fiber asymmetry in the 452 km link. Our work marks an important step towards incorporation of long-haul fiber links into large quantum networks.
- [69] arXiv:2411.13956 (cross-list from cond-mat.mes-hall) [pdf, html, other]
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Title: Hybrid dielectrophoretic-optical trap for microparticles in aqueous suspensionCarlos D. Gonzalez-Gomez, Jose Garcia-Guirado, Romain Quidant, Felix Carrique, Emilio Ruiz-Reina, Raul A. Rica-AlarconSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Applied Physics (physics.app-ph)
We demonstrate that a set of microfabricated electrodes can be coupled to a commercial optical tweezers device, implementing a hybrid electro-optical trap with multiple functionalities to manipulate micro/nanoparticles in suspension. Our design allows us to simultaneously trap tens of particles in a single potential well generated in the low electric field region of the electrode arrangement, taking advantage of negative dielectrophoresis. Together with the optical tweezers, we show that the hybrid scheme allows enhanced manipulation capabilities, including controlled loading and accumulation in the dielectrophoretic trap from the optical tweezers, selectivity, and tracking of the individual trajectories of trapped particles.
- [70] arXiv:2411.13957 (cross-list from math.NA) [pdf, html, other]
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Title: Variational Multiscale Evolve and Filter Strategies for Convection-Dominated FlowsSubjects: Numerical Analysis (math.NA); Fluid Dynamics (physics.flu-dyn)
The evolve-filter (EF) model is a filter-based numerical stabilization for under-resolved convection-dominated flows. EF is a simple, modular, and effective strategy for both full-order models (FOMs) and reduced-order models (ROMs). It is well-known, however, that when the filter radius is too large, EF can be overdiffusive and yield inaccurate results. To alleviate this, EF is usually supplemented with a relaxation step. The relaxation parameter, however, is very sensitive with respect to the model parameters. In this paper, we propose a novel strategy to alleviate the EF overdiffusivity for a large filter radius. Specifically, we leverage the variational multiscale (VMS) framework to separate the large resolved scales from the small resolved scales in the evolved velocity, and we use the filtered small scales to correct the large scales. Furthermore, in the new VMS-EF strategy, we use two different ways to decompose the evolved velocity: the VMS Evolve-Filter-Filter-Correct (VMS-EFFC) and the VMS Evolve-Postprocess-Filter-Correct (VMS-EPFC) algorithms. The new VMS-based algorithms yield significantly more accurate results than the standard EF in both the FOM and the ROM simulations of a flow past a cylinder at Reynolds number Re = 1000.
- [71] arXiv:2411.14061 (cross-list from cond-mat.mtrl-sci) [pdf, other]
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Title: One-step Synthesis of Cubic Gauche Polymeric Nitrogen with High Yield Just by HeatingComments: 7 pages, 4 figuresSubjects: Materials Science (cond-mat.mtrl-sci); Chemical Physics (physics.chem-ph)
A high-efficient one-step synthesis of cubic gauche polymeric nitrogen was developed just by thermal treatment of KN3 powders. The Raman and infrared spectra confirm the formation of polymeric nitrogen networks. Thermogravimetric differential scanning calorimeter measurements show that the content of cubic gauche polymeric nitrogen is as high as 1.5 wt% with high thermal stability, which is the highest content value so far.
- [72] arXiv:2411.14073 (cross-list from cs.CL) [pdf, html, other]
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Title: Meaning at the Planck scale? Contextualized word embeddings for doing history, philosophy, and sociology of scienceComments: 18 pages, 7 figures (1 in the Supplement)Subjects: Computation and Language (cs.CL); History and Philosophy of Physics (physics.hist-ph)
This paper explores the potential of contextualized word embeddings (CWEs) as a new tool in the history, philosophy, and sociology of science (HPSS) for studying contextual and evolving meanings of scientific concepts. Using the term "Planck" as a test case, I evaluate five BERT-based models with varying degrees of domain-specific pretraining, including my custom model Astro-HEP-BERT, trained on the Astro-HEP Corpus, a dataset containing 21.84 million paragraphs from 600,000 articles in astrophysics and high-energy physics. For this analysis, I compiled two labeled datasets: (1) the Astro-HEP-Planck Corpus, consisting of 2,900 labeled occurrences of "Planck" sampled from 1,500 paragraphs in the Astro-HEP Corpus, and (2) a physics-related Wikipedia dataset comprising 1,186 labeled occurrences of "Planck" across 885 paragraphs. Results demonstrate that the domain-adapted models outperform the general-purpose ones in disambiguating the target term, predicting its known meanings, and generating high-quality sense clusters, as measured by a novel purity indicator I developed. Additionally, this approach reveals semantic shifts in the target term over three decades in the unlabeled Astro-HEP Corpus, highlighting the emergence of the Planck space mission as a dominant sense. The study underscores the importance of domain-specific pretraining for analyzing scientific language and demonstrates the cost-effectiveness of adapting pretrained models for HPSS research. By offering a scalable and transferable method for modeling the meanings of scientific concepts, CWEs open up new avenues for investigating the socio-historical dynamics of scientific discourses.
- [73] arXiv:2411.14075 (cross-list from cond-mat.mes-hall) [pdf, html, other]
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Title: Photon drag at the junction between metal and 2d semiconductorSubjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Optics (physics.optics)
Photon drag represents a mechanism of photocurrent generation wherein the electromagnetic (EM) field momentum is transferred directly to the charge carriers. It is believed to be small by the virtue of low photon momentum compared to the typical momenta of the charge carriers. Here, we show that photon drag becomes particularly strong at the junctions between metals and 2d materials, wherein highly non-uniform local EM fields are generated upon diffraction. To this end, we combine an exact theory of diffraction at 'metal-2d material' junctions with microscopic transport theory of photon drag, and derive the functional dependences of the respective photovoltage on the parameters of EM field and 2d system. The voltage responsivity appears inversely proportional to the electromagnetic frequency $\omega$, the sheet density of charge, and a dimensionless momentum transfer coefficient $\alpha$ which depends only on 2d conductivity in units of light speed $\eta = 2\pi \sigma/c$ and light polarization. For $p$-polarized incident light, the momentum transfer coefficient appears finite even for vanishingly small 2d conductivity $\eta$, which is a consequence of dynamic lightning rod effect. For $s$-polarized incident light, the momentum transfer coefficient scales as $\eta \ln \eta^{-1}$, which stems from long-range dipole radiation of a linear junction. A simple estimate shows that the ratio of thermoelectric and photon drag photovoltages at the junction for $p$-polarization is roughly $\omega\tau_\varepsilon$, where $\tau_\varepsilon$ is the energy relaxation time, while for $s$-polarization the photon drag always dominates over the thermoelectric effect.
- [74] arXiv:2411.14089 (cross-list from gr-qc) [pdf, html, other]
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Title: Is there any Trinity of Gravity, to start with?Comments: 11 pages; prepared for Proceedings of 11th Mathematical Physics Meeting, September 2024 in Belgrade, SerbiaSubjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th); Mathematical Physics (math-ph); History and Philosophy of Physics (physics.hist-ph)
In recent years, it has been rather fashionable to talk about geometric trinity of gravity. The main idea is that one can formally present the gravity equations in different terms, those of either torsion or nonmetricity instead of curvature. It starts from a very erroneous claim that the Levi-Civita connection, and therefore the (pseudo-)Riemannian geometry itself, are nothing but an arbitrary choice. The point is that, as long as we admit the need of having a metric for describing gravity, the standard approach does not involve any additional independent geometric structures on top of that. At the same time, any other metric-affine model does go for genuinely new stuff. In particular, the celebrated teleparallel framework introduces a notion of yet another parallel transport which is flat. It gives us curious new ways of modifying gravity, even though very often quite problematic. However, in GR-equivalent models, we only get a new language for describing the same physics, in terms of absolutely unobservable and unpredictable geometrical inventions. For sure, one can always safely create novel constructions which do not influence the physical equations of motion, but in itself it does not make much sense and blatantly goes against the Occam's razor.
- [75] arXiv:2411.14220 (cross-list from cond-mat.mtrl-sci) [pdf, other]
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Title: Self-passivation Causes the Different Fermi Level Pinning between Metal-Si and Metal-Ge ContactsComments: 20 pages, 10 figuresSubjects: Materials Science (cond-mat.mtrl-sci); Computational Physics (physics.comp-ph)
Metal-Ge contacts possess much stronger Fermi level pinning (FLP) than metal-Si contacts, which is commonly believed to be due to Ge having a narrower bandgap and higher permittivity in the context of FLP caused by metal-induced gap states. Here, we show that both Ge and Si have a similar FLP strength if they adopt an identical interface chemical bonding configuration at the contact interface by performing first-principles calculations: Si and Ge have FLP factors of 0.16 and 0.11, respectively, if they adopt the same reconstructed bonding configuration and have FLP factors of 0.05 and 0, respectively, if they adopt the same non-reconstructed bonding configuration. We illustrate that Ge prefers the latter configuration at the contact interface, which has denser dangling-bond-induced surface states, and Si prefers the latter one, which has a self-passivation effect for reducing the dangling bond-induced interface states, to reproduce the experimental data. By revealing the significance of dangling bond-induced interface gap states on FLP, these findings shed new light on lowering the contact resistance for developing future Si CMOS technology.
- [76] arXiv:2411.14229 (cross-list from cond-mat.mtrl-sci) [pdf, other]
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Title: Thermal emission of hydrogenated amorphous silicon microspheres in the mid-infraredComments: 9 pages, 6 figuresSubjects: Materials Science (cond-mat.mtrl-sci); Optics (physics.optics)
Hydrogenated amorphous silicon microspheres feature a pronounced phononic peak around 2000 cm-1 when they are thermally excited by means of a blue laser. This phononic signature corresponds to vibrational modes of silicon-hydrogen bonds and its emitted light can be coupled to Mie modes defined by the spherical cavity. The signal is apparently quite stable at moderate excitation intensities although there appeared some signs pointing to hydrides bonds reconfiguration and even hydrogen emission. Above a certain excitation threshold, a phase change from amorphous to poly-crystalline silicon occurs that preserves the good structural quality of the microspheres.
- [77] arXiv:2411.14259 (cross-list from quant-ph) [pdf, html, other]
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Title: Addressing the Readout Problem in Quantum Differential Equation Algorithms with Quantum Scientific Machine LearningComments: 5 pages, 4 figuresSubjects: Quantum Physics (quant-ph); Disordered Systems and Neural Networks (cond-mat.dis-nn); Fluid Dynamics (physics.flu-dyn)
Quantum differential equation solvers aim to prepare solutions as $n$-qubit quantum states over a fine grid of $O(2^n)$ points, surpassing the linear scaling of classical solvers. However, unlike classically stored vectors of solutions, the readout of exact quantum states poses a bottleneck due to the complexity of tomography. Here, we show that the readout problem can be addressed with quantum learning tools where we focus on distilling the relevant features. Treating outputs of quantum differential equation solvers as quantum data, we demonstrate that low-dimensional output can be extracted using a measurement operator adapted to detect relevant features. We apply this quantum scientific machine learning approach to classify solutions for shock wave detection and turbulence modeling in scenarios where data samples come directly from quantum differential equation solvers. We show that the basis chosen for performing analysis greatly impacts classification accuracy. Our work opens up the area of research where quantum machine learning for quantum datasets is inherently required.
- [78] arXiv:2411.14262 (cross-list from math.NA) [pdf, html, other]
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Title: Accelerating Construction of Non-Intrusive Nonlinear Structural Dynamics Reduced Order Models through HyperreductionSubjects: Numerical Analysis (math.NA); Computational Physics (physics.comp-ph)
We present a novel technique to significantly reduce the offline cost associated to non-intrusive nonlinear tensors identification in reduced order models (ROMs) of geometrically nonlinear, finite elements (FE)-discretized structural dynamics problems. The ROM is obtained by Galerkin-projection of the governing equations on a reduction basis (RB) of Vibration Modes (VMs) and Static Modal Derivatives (SMDs), resulting in reduced internal forces that are cubic polynomial in the reduced coordinates. The unknown coefficients of the nonlinear tensors associated with this polynomial representation are identified using a modified version of Enhanced Enforced Displacement (EED) method which leverages Energy Conserving Sampling and Weighting (ECSW) as hyperreduction technique for efficiency improvement. Specifically, ECSW is employed to accelerate the evaluations of the nonlinear reduced tangent stiffness matrix that are required within EED. Simulation-free training sets of forces for ECSW are obtained from displacements corresponding to quasi-random samples of a nonlinear second order static displacement manifold. The proposed approach is beneficial for the investigation of the dynamic response of structures subjected to acoustic loading, where multiple VMs must be added in the RB, resulting in expensive nonlinear tensor identification. Superiority of the novel method over standard EED is demonstrated on FE models of a shallow curved clamped panel and of a nine-bay aeronautical reinforced panel modelled, using the commercial finite element program Abaqus.
- [79] arXiv:2411.14289 (cross-list from cond-mat.mtrl-sci) [pdf, html, other]
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Title: Octahedral tilt-driven phase transitions in BaZrS3 chalcogenide perovskiteSubjects: Materials Science (cond-mat.mtrl-sci); Chemical Physics (physics.chem-ph)
Chalcogenide perovskites are lead-free materials for potential photovoltaic or thermoelectric applications. BaZrS$_3$ is the most studied member of this family due to its superior thermal and chemical stability, desirable optoelectronic properties, and low thermal conductivity. Phase transitions of the BaZrS$_3$ perovskite are under-explored in literature as most experimental characterization is performed at ambient conditions where the orthorhombic Pnma phase is reported to be stable. In this work, we study the dynamics of BaZrS$_3$ across a range of temperatures and pressures using an accurate machine-learned interatomic potential trained with data from hybrid density functional theory calculations. At 0Pa, we find a first-order phase transition from the orthorhombic to tetragonal I4/mcm phase at 610K, and a second-order transition from the tetragonal to the cubic Pm-3m phase at 880K. The tetragonal phase is stable over a larger temperature range at higher pressures. To confirm the validity of our model we report the static structure factor as a function of temperature and compare our results with published experimental data.
- [80] arXiv:2411.14302 (cross-list from cond-mat.quant-gas) [pdf, html, other]
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Title: Electrodynamics of Vortices in Quasi-2D Scalar Bose-Einstein CondensatesComments: 15 pages, 1 figureSubjects: Quantum Gases (cond-mat.quant-gas); Statistical Mechanics (cond-mat.stat-mech); Mathematical Physics (math-ph); Plasma Physics (physics.plasm-ph); Quantum Physics (quant-ph)
In two spatial dimensions, vortex-vortex interactions approximately vary with the logarithm of the inter-vortex distance, making it possible to describe an ensemble of vortices as a Coulomb gas. We introduce a duality between vortices in a quasi-two-dimensional (quasi-2D) scalar Bose-Einstein condensates (BEC) and effective Maxwell's electrodynamics. Specifically, we address the general scenario of inhomogeneous, time-dependent BEC number density with dissipation or rotation. Starting from the Gross-Pitaevskii equation (GPE), which describes the mean-field dynamics of a quasi-2D scalar BEC without dissipation, we show how to map vortices in a quasi-2D scalar BEC to 2D electrodynamics beyond the point-vortex approximation, even when dissipation is present or in a rotating system. The physical meaning of this duality is discussed.
- [81] arXiv:2411.14313 (cross-list from hep-ex) [pdf, html, other]
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Title: Physics Performance and Detector Requirements at an Asymmetric Higgs FactoryAntoine Laudrain, Ties Behnke, Carl Mikael Berggren, Karsten Buesser, Frank Gaede, Christophe Grojean, Benno List, Jenny List, Jürgen Reuter, Christian SchwanenbergerComments: To be published in PoSSubjects: High Energy Physics - Experiment (hep-ex); Instrumentation and Detectors (physics.ins-det)
The Hybrid Asymmetric Linear Higgs Factory (HALHF) proposes a shorter and cheaper design for a future Higgs factory. It reaches a $\sqrt{s} = 250$ GeV using a 500 GeV electron beam accelerated by an electron-driven plasma wake-field, and a conventionally-accelerated 31 GeV positron beam. Assuming plasma acceleration R&D challenges are solved in a timely manner, the asymmetry of the collisions brings additional challenges regarding the detector and the physics analyses, from forward boosted topologies and beam backgrounds. This contribution will detail the impact of beam parameters on beam-induced backgrounds, and provide a first look at what modification compared to e.g. the ILD can improve the physics performance at such a facility. The studies will be benchmarked against some flagship Higgs Factory analyses for comparison.
- [82] arXiv:2411.14315 (cross-list from math.NA) [pdf, html, other]
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Title: Introducing a Harmonic Balance Navier-Stokes Finite Element Solver to Accelerate Cardiovascular SimulationsSubjects: Numerical Analysis (math.NA); Fluid Dynamics (physics.flu-dyn)
The adoption of cardiovascular simulations for diagnosis and surgical planning on a patient-specific basis requires the development of faster methods than the existing state-of-the-art techniques. To address this need, we leverage the periodic nature of these flows to accurately capture their time-dependence using spectral discretization. Owing to the reduced size of the discrete problem, the resulting approach, known as the harmonic balance method, significantly lowers the solution cost when compared against the conventional time marching methods. This study describes a stabilized finite element implementation of the harmonic balanced method that targets the simulation of physically-stable time-periodic flows. That stabilized method is based on the Galerkin/least-squares formulation that permits stable solution in convection-dominant flows and convenient use of the same interpolation functions for velocity and pressure. We test this solver against its equivalent time marching method using three common physiological cases where blood flow is modeled in a Glenn operation, a cerebral artery, and a left main coronary artery. Using the conventional time marching solver, simulating these cases takes more than ten hours. That cost is reduced by up to two orders of magnitude when the proposed harmonic balance solver is utilized, where a solution is produced in approximately 30 minutes. We show that that solution is in excellent agreement with the conventional solvers when the number of modes is sufficiently large to accurately represent the imposed boundary conditions.
Cross submissions (showing 30 of 30 entries)
- [83] arXiv:1806.07428 (replaced) [pdf, html, other]
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Title: Minimum Quadratic Helicity StatesComments: 15 pages, 3 figuresSubjects: Fluid Dynamics (physics.flu-dyn); Solar and Stellar Astrophysics (astro-ph.SR); Differential Geometry (math.DG)
Building on previous results on the quadratic helicity in magnetohydrodynamics (MHD) we investigate particular minimum helicity states. Those are eigenfunctions of the curl operator and are shown to constitute solutions of the quasi-stationary incompressible ideal MHD equations. We then show that these states have indeed minimum quadratic helicity.
- [84] arXiv:2309.14553 (replaced) [pdf, other]
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Title: Inverse non-linear problem of the long wave run-up on coastAlexei Rybkin, Efim Pelinovsky, Oleksandr Bobrovnikov, Noah Palmer, Ekaterina Pniushkova, Daniel AbramowiczComments: To appear in Journal of Ocean Engineering and Marine EnergySubjects: Fluid Dynamics (physics.flu-dyn); Mathematical Physics (math-ph); Geophysics (physics.geo-ph)
The study of the process of catastrophic tsunami-type waves on the coast makes it possible to determine the destructive force of waves on the coast. In hydrodynamics, the one-dimensional theory of the run-up of non-linear waves on a flat slope has gained great popularity, within which rigorous analytical results have been obtained in the class of non-breaking waves. In general, the result depends on the characteristics of the wave approaching (or generated on) the slope, which is usually not known in the measurements. Here we describe a rigorous method for recovering the initial displacement in a source localised in an inclined power-shaped channel from the characteristics of a moving shoreline. The method uses the generalised Carrier-Greenspan transformation, which allows one-dimensional non-linear shallow-water equations to be reduced to linear ones. The solution is found in terms of Erdélyi-Kober integral operator. Numerical verification of our results is presented for the cases of a parabolic bay and an infinite plane beach.
- [85] arXiv:2402.16807 (replaced) [pdf, html, other]
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Title: An $^{115}$In$^+$-$^{172}$Yb$^+$ Coulomb crystal clock with $2.5\times10^{-18}$ systematic uncertaintyH. N. Hausser, J. Keller, T. Nordmann, N. M. Bhatt, J. Kiethe, H. Liu, I. M. Richter, M. von Boehn, J. Rahm, S. Weyers, E. Benkler, B. Lipphardt, S. Doerscher, K. Stahl, J. Klose, C. Lisdat, M. Filzinger, N. Huntemann, E. Peik, T. E. MehlstäublerComments: 13 pages, 10 figuresSubjects: Atomic Physics (physics.atom-ph); Quantum Physics (quant-ph)
We present a scalable mixed-species Coulomb crystal clock based on the $^1S_0$ $\leftrightarrow$ $^3P_0$ transition in $^{115}$In$^+$. $^{172}$Yb$^+$ ions are co-trapped and used for sympathetic cooling. Reproducible interrogation conditions for mixed-species Coulomb crystals are ensured by a conditional preparation sequence with permutation control. We demonstrate clock operation with a 1In$^+$-3Yb$^+$ crystal, achieving a relative systematic uncertainty of $2.5\times10^{-18}$ and a relative frequency instability of $1.6\times10^{-15}/\sqrt{\tau/1\;\mathrm{s}}$. We report on absolute frequency measurements with an uncertainty of $1.3\times10^{-16}$ and optical frequency comparisons with clocks based on $^{171}$Yb$^+$ (E3) and $^{87}$Sr. With a fractional uncertainty of $4.4\times10^{-18}$, the former is - to our knowledge - the most accurate frequency ratio value reported to date. For the $^{115}$In$^+$/$^{87}$Sr ratio, we improve upon the best previous measurement by more than an order of magnitude. We also demonstrate operation with four $^{115}$In$^+$ clock ions, which reduces the instability to $9.2\times10^{-16}/\sqrt{\tau/1\;\mathrm{s}}$.
- [86] arXiv:2403.05670 (replaced) [pdf, html, other]
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Title: A Spectral Element Enrichment Wall-ModelSubjects: Fluid Dynamics (physics.flu-dyn)
We develop an enrichment wall-model within the spectral element method (SEM) framework for large-eddy simulations of wall-bounded flows. The method augments the polynomial solution in the wall-adjacent elements with an analytical law-of-the-wall enrichment function representing the mean velocity near the wall. In the solution representation, this enrichment function captures the large gradients in the boundary layer, which allows the polynomial modes to represent the turbulent fluctuations. The enriched solution is able to resolve the shear stress at the wall without any modification to the no-slip wall boundary conditions. The performance of the SEM enrichment wall-modeling approach is assessed in turbulent channel flow LES for a range of Reynolds numbers. The results show that the proposed method improves solution accuracy on under-resolved near-wall grids as compared to the traditional shear stress wall-models.
- [87] arXiv:2404.17445 (replaced) [pdf, html, other]
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Title: Metrology of microwave fields based on trap-loss spectroscopy with cold Rydberg atomsRomain Duverger, Alexis Bonnin, Romain Granier, Quentin Marolleau, Cédric Blanchard, Nassim Zahzam, Yannick Bidel, Malo Cadoret, Alexandre Bresson, Sylvain SchwartzComments: 12 pages, 9 figuresSubjects: Atomic Physics (physics.atom-ph); Quantum Physics (quant-ph)
We demonstrate a new approach for the metrology of microwave fields based on the trap-loss-spectroscopy of cold Rydberg atoms in a magneto-optical trap. Compared to state-of-the-art sensors using room-temperature vapors, cold atoms allow longer interaction times, better isolation from the environment and a reduced Doppler effect. Our approach is particularly simple as the detection relies on fluorescence measurements only. Moreover, our signal is well described by a two-level model across a broad measurement range, allowing in principle to reconstruct the amplitude and the frequency of the microwave field simultaneously without the need for an external reference field. We report on a scale factor linearity at the percent level and no noticeable drifts over two hours, paving the way for new applications of cold Rydberg atoms in metrology such as calibrating blackbody shifts in state-of-the-art optical clocks, monitoring the Earth cryosphere from space, measuring the cosmic microwave background or searching for dark matter.
- [88] arXiv:2405.13098 (replaced) [pdf, html, other]
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Title: Do deep neural networks behave like structural glasses?Comments: 17 pages, 18 figuresSubjects: Computational Physics (physics.comp-ph); Disordered Systems and Neural Networks (cond-mat.dis-nn); Statistical Mechanics (cond-mat.stat-mech)
Deep Neural Networks (DNNs) share important similarities with structural glasses. Both have many degrees of freedom, and their dynamics are governed by a high-dimensional, non-convex landscape representing either the loss or energy, respectively. Furthermore, both experience gradient descent dynamics subject to noise. In this work we investigate, by performing quantitative measurements on realistic networks trained on the MNIST and CIFAR-10 datasets, the extent to which this qualitative similarity gives rise to glass-like dynamics in neural networks. We demonstrate the existence of a Topology Trivialisation Transition as well as the previously studied under-to-overparameterised transition analogous to jamming. By training DNNs with overdamped Langevin dynamics in the resulting disordered phases, we do not observe diverging relaxation times at non-zero temperature, nor do we observe any caging effects, in contrast to glass phenomenology. However, the weight overlap function follows a power law in time, with exponent $\approx -0.5$, in agreement with the Mode-Coupling Theory of structural glasses. In addition, the DNN dynamics obey a form of time-temperature superposition. Finally, dynamic heterogeneity and ageing are observed at low temperatures. These results highlight important and surprising points of both difference and agreement between the behaviour of DNNs and structural glasses.
- [89] arXiv:2406.05153 (replaced) [pdf, html, other]
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Title: Integrating Physics of the Problem into Data-Driven Methods to Enhance Elastic Full-Waveform Inversion with Uncertainty QuantificationSubjects: Geophysics (physics.geo-ph); Machine Learning (cs.LG); Numerical Analysis (math.NA)
Full-Waveform Inversion (FWI) is a nonlinear iterative seismic imaging technique that, by reducing the misfit between recorded and predicted seismic waveforms, can produce detailed estimates of subsurface geophysical properties. Nevertheless, the strong nonlinearity of FWI can trap the optimization in local minima. This issue arises due to factors such as improper initial values, the absence of low frequencies in the measurements, noise, and other related considerations. To address this challenge and with the advent of advanced machine-learning techniques, data-driven methods, such as deep learning, have attracted significantly increasing attention in the geophysical community. Furthermore, the elastic wave equation should be included in FWI to represent elastic effects accurately. The intersection of data-driven techniques and elastic scattering theories presents opportunities and challenges. In this paper, by using the knowledge of elastic scattering (physics of the problem) and integrating it with machine learning techniques, we propose methods for the solution of time-harmonic FWI to enhance accuracy compared to pure data-driven and physics-based approaches. Moreover, to address uncertainty quantification, by modifying the structure of the Variational Autoencoder, we introduce a probabilistic deep learning method based on the physics of the problem that enables us to explore the uncertainties of the solution. According to the limited availability of datasets in this field and to assess the performance and accuracy of the proposed methods, we create a comprehensive dataset close to reality and conduct a comparative analysis of the presented approaches to it.
- [90] arXiv:2406.16787 (replaced) [pdf, html, other]
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Title: A Parrondo paradox in susceptible-infectious-susceptible dynamics over periodic temporal networksComments: 10 figuresJournal-ref: Mathematical Biosciences, Volume 378, December 2024, 109336Subjects: Physics and Society (physics.soc-ph); Dynamical Systems (math.DS)
Many social and biological networks periodically change over time with daily, weekly, and other cycles. Thus motivated, we formulate and analyze susceptible-infectious-susceptible (SIS) epidemic models over temporal networks with periodic schedules. More specifically, we assume that the temporal network consists of a cycle of alternately used static networks, each with a given duration. We observe a phenomenon in which two static networks are individually above the epidemic threshold but the alternating network composed of them renders the dynamics below the epidemic threshold, which we refer to as a Parrondo paradox for epidemics. We find that network structure plays an important role in shaping this phenomenon, and we study its dependence on the connectivity between and number of subpopulations in the network. We associate such paradoxical behavior with anti-phase oscillatory dynamics of the number of infectious individuals in different subpopulations.
- [91] arXiv:2406.18488 (replaced) [pdf, html, other]
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Title: Modeling the amplitude and energy decay of a weakly damped harmonic oscillator using the energy dissipation rate and a simple trickComments: The main changes compared to the previous version are: the expansion of section IV and the addition of two new sections, i.e. sections VI and VII. The paper is accepted in European Journal of PhysicsSubjects: Classical Physics (physics.class-ph)
We demonstrate how to derive the exponential decrease of amplitude and an excellent approximation of the energy decay of a weakly damped harmonic oscillator without solving the associated equation of motion and without insight into the analytical form of its solution. This is achieved using a basic understanding of the undamped harmonic oscillator and the connection between the damping force's power and the energy dissipation rate. The trick is adding the energy dissipation rates corresponding to two specific pairs of initial conditions with the same energy. In this way, we obtain a first-order differential equation from which we get the time-dependent amplitude and the energies corresponding to each pair of considered initial conditions. Comparing the results of our model to the exact solutions and energies yielded an excellent agreement. The physical concepts and mathematical techniques we employ are well-known to first-year undergraduates.
- [92] arXiv:2407.05612 (replaced) [pdf, html, other]
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Title: On the locus formed by the maximum heights of an ultra-relativistic projectileComments: 26 pages, 3 figuresSubjects: Classical Physics (physics.class-ph)
We consider the problem of relativistic projectiles in a uniform gravitational force field in an inertial frame. For the first time, we have found the curve that joins the points of maximum height of all trajectories followed by a projectile in the ultra-relativistic limit. The parametric equations of this curve produce an onion-like curve; in fact, it is one of the loops of a lemniscate-type curve. We also verify that the curve is an ellipse in the nonrelativistic approximation. These two limiting results are obtained by following two slightly distinct approaches. In addition, we calculate the nonrelativistic and ultra-relativistic approximations of the trajectory equation and parametric equations of the trajectory as functions of time. We also find the asymptotic behavior of the ultra-relativistic trajectory equations for points that are very distant from the launching point. All limiting cases in the article are studied in detail. Additionally, we discuss various physical issues related to some of our results. The content of the article is appropriate for advanced undergraduate students.
- [93] arXiv:2407.20541 (replaced) [pdf, other]
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Title: Rapid Forecast and Optimization of Geological CO2 Storage in Deep Saline Aquifers: A Data-driven Dynamic Mode Decomposition Model Order Reduction ApproachSubjects: Computational Physics (physics.comp-ph)
Data-driven and non-intrusive DMDc and DMDspc models successfully expedite the reconstruction and forecasting of CO2 fluid flow with acceptable accuracy margins, aiding in the rapid optimization of geological CO2 storage forecast and optimization. DMDc and DMDspc models were trained with weekly, monthly, and yearly simulation pressure and CO2 saturation fields using a commercial simulator. The domain of interest is a large-scale, offshore, highly heterogeneous reservoir model with over 100,000 cells. DMD snapshot reconstruction significantly reduced simulation times from several hours to mere minutes. DMDspc reduced the number of DMD modes for pressure without losing accuracy while sometimes even improving accuracy. Two operation cases were considered: 1. CO2 injection, 2. CO2 injection and water production for pressure maintenance. For pressure, DMDspc achieved a slightly higher than DMDc average error by removing several modes. On the other hand, DMDspc showed limited success in reducing modes for CO2 saturation. The forecast performance of DMD models was evaluated using percent change error, mean absolute error and Pearsons R correlation coefficient metrics. Almost all DMD pressure models managed to successfully forecast pressure fields, while a smaller number of DMD models managed to forecast CO2 saturation. While forecast errors have a considerable range, only DMD models with errors below 5% PCE for pressure or 0.01 MAE for saturation were considered acceptable for geological CO2 storage optimization. Optimized CO2 injection and water production amounts were consistent across selected DMD models and all time scales. The DMDspc-monitored cells approach, which only reconstructs the monitored-during-optimization cells, reduced even further optimization time while providing consistent results with the optimization that used full snapshot reconstruction.
- [94] arXiv:2408.05384 (replaced) [pdf, html, other]
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Title: Nonlinear Propagation of Non-Gaussian UncertaintiesSubjects: Space Physics (physics.space-ph); Symbolic Computation (cs.SC); Probability (math.PR); Chaotic Dynamics (nlin.CD)
This paper presents a novel approach for propagating uncertainties in dynamical systems building on high-order Taylor expansions of the flow and moment-generating functions (MGFs). Unlike prior methods that focus on Gaussian distributions, our approach leverages the relationship between MGFs and distribution moments to extend high-order uncertainty propagation techniques to non-Gaussian scenarios. This significantly broadens the applicability of these methods to a wider range of problems and uncertainty types. High-order moment computations are performed one-off and symbolically, reducing the computational burden of the technique to the calculation of Taylor series coefficients around a nominal trajectory, achieved by efficiently integrating the system's variational equations. Furthermore, the use of the proposed approach in combination with event transition tensors, allows for accurate propagation of uncertainties at specific events, such as the landing surface of a celestial body, the crossing of a predefined Poincaré section, or the trigger of an arbitrary event during the propagation. Via numerical simulations we demonstrate the effectiveness of our method in various astrodynamics applications, including the unperturbed and perturbed two-body problem, and the circular restricted three-body problem, showing that it accurately propagates non-Gaussian uncertainties both at future times and at event manifolds.
- [95] arXiv:2409.19249 (replaced) [pdf, html, other]
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Title: Enhancing the ODMR Signal of Organic Molecular QubitsComments: 11 pages, 5 figures. Some rephrasing was done for better readability and the figure texts have been enlargedSubjects: Chemical Physics (physics.chem-ph); Materials Science (cond-mat.mtrl-sci); Quantum Physics (quant-ph)
In quantum information science and sensing, electron spins are often purified into a specific polarisation through an optical-spin interface, a process known as optically-detected magnetic resonance (ODMR). Diamond-NV centres and transition metals are both excellent platforms for these so-called colour centres, while metal-free molecular analogues are also gaining popularity for their extended polarisation lifetimes, milder environmental impacts, and reduced costs. In our earlier attempt at designing such organic high-spin $\pi$-diradicals, we proposed to spin-polarise by shelving triplet $M_{S}=\pm1$ populations as singlets. This was recently verified by experiments albeit with low ODMR contrasts of $<1\%$ at temperatures above 5 K. In this work, we propose to improve the ODMR signal by moving singlet populations back into the triplet $M_{S}=0$ sublevel, designing a true carbon-based molecular analogue to the NV centre. Our proposal is based upon transition-orbital and group-theoretical analyses of beyond-nearest-neighbour spin-orbit couplings, which are further confirmed by ab initio calculations of a realistic trityl-based radical dimer. Microkinetic analyses point towards high ODMR contrasts of around $30\%$ under experimentally-feasible conditions, a stark improvement from previous works. Finally, in our quest towards ground-state optically-addressable molecular spin qubits, we exemplify how our symmetry-based design avoids Zeeman-induced singlet-triplet mixings, setting the scene for realising electron spin qubit gates.
- [96] arXiv:2410.01496 (replaced) [pdf, html, other]
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Title: Reduced Representations of Rayleigh-B\'enard Flows via AutoencodersComments: 21 pages, 18 figuresSubjects: Fluid Dynamics (physics.flu-dyn)
We analyzed the performance of Convolutional Autoencoders in generating reduced-order representations the temperature field of 2D Rayleigh-Bénard flows at $Pr=1$ and Rayleigh numbers extending from $10^6$ to $10^8$, capturing the range where the flow transitions to turbulence. We present a way of estimating the minimum number of dimensions needed by the Autoencoders to capture all the relevant physical scales of the data that is more apt for highly multiscale flows than previous criteria applied to lower dimensional systems. We compare our architecture with two regularized variants as well as with linear methods, and find that manually fixing the dimension of the latent space produces the best results. We show how the estimated minimum dimension presents a sharp increase around $Ra \sim 10^7$, when the flow starts to transition to turbulence. Furthermore, we show how this dimension does not follow the same scaling as the physically relevant scales, such as the dissipation lengthscale and the thermal boundary layer.
- [97] arXiv:2410.09906 (replaced) [pdf, other]
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Title: Influence of Spatial Dispersion in the Topological Edge States of Magnetized PlasmasComments: 37 pages, 5 figuresSubjects: Optics (physics.optics)
Conventional Chern insulators are two-dimensional periodic structures that support unidirectional edge states at the boundary, while the wave propagation in the bulk regions is forbidden. The number of unidirectional edge states is governed by the gap Chern number, a topological invariant that depends on the global properties of the system over the entire wavevector space. This concept can also be extended to systems with a continuous translational symmetry provided they satisfy a regularization condition for large wavenumbers. Here, we discuss how the spatial dispersion, notably the high-spatial frequency behavior of the material response, critically influences the topological properties, and consequently, the net number of unidirectional edge states. In particular, we show that seemingly small perturbations of a local magnetized plasma can lead to distinct Chern phases and, consequently, markedly different edge state dispersions.
- [98] arXiv:2410.10092 (replaced) [pdf, html, other]
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Title: A Digital and Compact High-Precision Locking System for Pulse Laser Repetition FrequencyComments: Submitted to IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENTSubjects: Optics (physics.optics); Instrumentation and Detectors (physics.ins-det)
This paper proposes a novel approach that employs error amplification and ADC-based dual-mixer time-difference (ADC-based-DMTD) technique for high-precision locking of laser repetition frequency with compact size. This electronic system consists of two main components: a digitized error amplification module (EAM) and an FPGA-based digital frequency locking module (DFLM). The EAM mainly integrates a configurable frequency generator (CFG), a configurable frequency multiplier (CFM) and a mixer to process the laser pulses and a high-stability reference source (e.g., an atomic clock), enabling high-precision locking of pulse lasers operating at different repetition frequencies. By employing frequency multiplication and mixing, the EAM amplifies the laser's frequency error and performs frequency down-conversion, enhancing measurement sensitivity and reducing the hardware requirements of the back-end. The DFLM receives the EAM outputs by using an ADC-based-DMTD method to precisely measure frequency errors, then the digital proportional-integral-derivative (PID) controller provides feedback to achieve accurate frequency locking. Initial testing with a voltage-controlled oscillator (VCO) demonstrated excellent locking performance, achieving an Allan deviation of $9.58 \times 10^{-14}$ at 10 seconds and a standard deviation (STD) of 7.7 \textmu Hz root mean square (RMS) after locking, marking a five-order-of-magnitude stability enhancement. In laboratory experiments with a custom-built femtosecond fiber laser, the system achieved robust locking of the repetition frequency, with a stability improvement from $1.51 \times 10^{-7}$ to $1.12 \times 10^{-12}$ at a 10-second gate time and an STD of 0.43 mHz RMS after locking.
- [99] arXiv:2410.12976 (replaced) [pdf, html, other]
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Title: Kapitza-Inspired Stabilization of Non-Foster Circuits via Time ModulationsComments: 10 pages (7 pages main text, 3 pages supplementary materials), 4 figures; a minor issue in Fig. 3(a) is correctedSubjects: Applied Physics (physics.app-ph); Systems and Control (eess.SY)
With his formal analysis in 1951, the physicist Pyotr Kapitza demonstrated that an inverted pendulum with an externally vibrating base can be stable in its upper position, thus overcoming the force of gravity. Kapitza's work is an example that an originally unstable system can become stable after a minor perturbation of its properties or initial conditions is applied. Inspired by his ideas, we show how non-Foster circuits can be stabilized with the application of external \textit{electrical vibration}, i.e., time modulations. Non-Foster circuits are highly appreciated in the engineering community since their bandwidth characteristics are not limited by passive-circuits bounds. Unfortunately, non-Foster circuits are usually unstable and they must be stabilized prior to operation. Here, we focus on the study of non-Foster $L(t)C$ circuits with time-varying inductors and time-invariant negative capacitors. We find an intrinsic connection between Kapitza's inverted pendulum and non-Foster $L(t)C$ resonators. Moreover, we show how positive time-varying modulations of $L(t)>0$ can overcome and stabilize non-Foster negative capacitances $C<0$. These findings open up an alternative manner of stabilizing electric circuits with the use of time modulations, and lay the groundwork for application of, what we coin \textit{Vibrational Electromagnetics}, in more complex media.
- [100] arXiv:2410.15159 (replaced) [pdf, other]
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Title: Cryogenic W-band Electron Spin Resonance Probehead with an Integral Cryogenic Low Noise AmplifierComments: 29 pages, 11 figuresSubjects: Chemical Physics (physics.chem-ph)
The quest to enhance the sensitivity of electron spin resonance (ESR) is an ongoing challenge. One potential strategy involves increasing the frequency, for instance, moving from Q-band (approximately 35 GHz) to W-band (approximately 94 GHz). However, this shift typically results in higher transmission and switching losses, as well as increased noise in signal amplifiers. In this work, we address these shortcomings by employing a W-band probehead integrated with a cryogenic low-noise amplifier (LNA) and a microresonator. This configuration allows us to position the LNA close to the resonator, thereby amplifying the acquired ESR signal with minimal losses. Furthermore, when operated at cryogenic temperatures, the LNA exhibits unparalleled noise levels that are significantly lower than those of conventional room temperature LNAs. We detail the novel probehead design and provide some experimental results at room temperature as well as cryogenic temperatures for representative paramagnetic samples. We find, for example, that spin sensitivity of ~3*10^5 spins/sqrt(Hz) is achieved for a sample of phosphorus doped 28Si, even for sub-optimal sample geometry with potential improvement to <10^3 spins/sqrt(Hz) in more optimal scenarios.
- [101] arXiv:2410.17889 (replaced) [pdf, html, other]
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Title: Variational MineGAN: A Data-efficient Knowledge Transfer Architecture for Generative AI-assisted Design of Nanophotonic StructuresSubjects: Optics (physics.optics)
Leveraging the power of deep learning to design nanophotonic devices has been an area of active research in recent times, with Generative Adversarial Networks (GANs) being a popular choice alongside autoencoder-based methods. However, both approaches typically require large datasets and significant computational resources, which can outweigh the advantages of saving time and effort. While GANs trained on smaller datasets can experience challenges such as unstable training and mode collapse, fine-tuning pre-trained GANs on these limited datasets often introduces additional problems, such as overfitting and lack of flexibility. This limits the model's ability to generalize, reducing its overall effectiveness. In this study, we present Variational MineGAN, an enhanced version of MineGAN that is less susceptible to overfitting while leveraging pre-trained GANs. This approach ensures a more robust sampling process, improving the model's generalization ability while transferring knowledge to domains with limited data. Experimental results demonstrate a lower Frechet Inception Distance (FID) score of 52.14, along with an increased Inception Score (IS) of 3.59 compared to prior methods. This implies better quality design images, which allow for the exploration of highly efficient designs with desired spectral responses and improved learning of nonlinear relationships between the latent space and the corresponding designs.
- [102] arXiv:2411.09632 (replaced) [pdf, other]
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Title: Leveraging Convolutional Neural Networks for 3D Quantitative Angiography Reconstructions from Sparse Cone Beam CT Projections Utilizing CFD DataAhmad Rahmatpour, Allison Shields, Parmita Mondal, Parisa Naghdi, Michael Udin, Kyle A Williams, Mohammad Mahdi Shiraz Bhurwani, Swetadri Vasan Setlur Nagesh, Ciprian N IonitaSubjects: Medical Physics (physics.med-ph)
This study leverages convolutional neural networks to enhance the temporal resolution of 3D angiography in intracranial aneurysms focusing on the reconstruction of volumetric contrast data from sparse and limited projections. Three patient-specific IA geometries were segmented and converted into stereolithography files to facilitate computational fluid dynamics simulations. These simulations first modeled blood flow under steady conditions with varying inlet velocities: 0.25 m/s, 0.35 m/s, and 0.45 m/s. Subsequently, 3D angiograms were simulated by labeling inlet particles to represent contrast bolus injections over durations of 0.5s, 1.0s, 1.5s, and 2.0s. The angiographic simulations were then used within a simulated cone beam C arm CT system to generate in-silico rotational DSAs, capturing projections every 10 ms over a 220-degree arc at 27 frames per second. From these simulations, both fully sampled (108 projections) and truncated projection datasets were generated the latter using a maximum of 49 projections. High fidelity volumetric images were reconstructed using a Parker weighted Feldkamp Davis Kress algorithm. A modified U Net CNN was subsequently trained on these datasets to reconstruct 3D angiographic volumes from the truncated projections. The network incorporated multiple convolutional layers with ReLU activations and Max pooling, complemented by upsampling and concatenation to preserve spatial detail. Model performance was evaluated using mean squared error (MSE). Evaluating our U net model across the test set yielded a MSE of 0.0001, indicating good agreement with ground truth reconstructions and demonstrating acceptable capabilities in capturing relevant transient angiographic features. This study confirms the feasibility of using CNNs for reconstructing 3D angiographic images from truncated projections.
- [103] arXiv:2411.10916 (replaced) [pdf, html, other]
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Title: The initial acceleration of a buoyant spherical bubble revisitedSubjects: Fluid Dynamics (physics.flu-dyn)
An analytical derivation of the buoyancy-induced initial acceleration of a spherical gas bubble in a host liquid is presented. The theory makes no assumptions further than applying the two-phase incompressible Navier-Stokes equations, showing that neither the classical approach using potential theory nor other simplifying assumptions are needed. The result for the initial bubble acceleration as a function of the gas and liquid densities, classically built on potential theory, is retained. The result is reproduced by detailed numerical simulations. The accelerated, although stagnant state of the bubble induces a pressure distribution on the bubble surface which is different from the result related to the Archimedean principle, emphasizing the importance of the non-equilibrium state for the force acting on the bubble.
- [104] arXiv:2411.11064 (replaced) [pdf, other]
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Title: Optical Tweezers with AC Dielectric Levitation: A Powerful Approach to Microparticle ManipulationHaobing Liu, Rongxin Fu, Zongliang Guo, Menglei Zhao, Gong Li, Fenggang Li, Hang Li, Shuailong ZhangComments: 29 pages,20 figuresSubjects: Optics (physics.optics)
Optical tweezers, with their high precision, dynamic control, and non-invasiveness, are increasingly important in scientific research and applications at the micro and nano scales. However, manipulation by optical tweezers is challenged by adsorption forces, including van der Waals forces, capillary forces, and electrostatic forces, which are present between micro- and nano-objects. Due to the inherent limitations of optical forces imposed by laser power, these adsorption forces are difficult to overcome. Inspired by maglev trains, we propose a multiphysics coupling method that combines dielectrophoretic and optical gradient forces to achieve broad applicability and low-damage micro-nanoscale particle manipulation. We developed a device that introduces electric fields to detach objects from hard substrates using alternating current (AC) dielectric levitation before manipulation with optical tweezers. We utilized micron-sized polystyrene (PS) microspheres as objects and elucidated the levitation mechanism through finite element simulation. For larger particles, such as a 100 {\mu}m PS microparticle and a 200 {\mu}m micro-gear, AC dielectric levitation enabled manipulation by optical tweezers. Also, the better viability of three kinds of cells displayed the low bio-damage of the proposed method. Given its broad applicability and biocompatibility, AC dielectric levitation technology significantly expands the capabilities of optical tweezers, allowing for the manipulation of larger particles and cells. This advancement addresses the limitations of optical tweezers in handling large-scale particles and enhances their versatility in various applications.
- [105] arXiv:2411.12283 (replaced) [pdf, html, other]
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Title: Isospectral reduction of the SSH3 lattice and its bulk-edge correspondenceSubjects: Applied Physics (physics.app-ph)
Here, we propose an isospectral reduction (IR) approach for the mapping of a trimer Su-Schrieffer-Heeger (SSH3) lattice into a simplified two-site model, whose coupling dynamics ingeniously results in a precise bulk-edge correspondence of the original lattice. The isospectrally-reduced model has inter-cell couplings with dynamic response to the eigenstate energy, allowing for the control of topological phase transition by energy. We relate the bulk property of the reduced model to the band topology of the SSH3 lattice, allowing for there distinct topological phases with different number of topological edge state pair. An acoustic SSH3 chain is fabricated for experimental demonstration. The said topological edge state pairs are measured. Our study takes a pivotal step toward the exploration of topology in multiple wave systems, opening up possibilities for advanced control of topological waves.
- [106] arXiv:2411.12381 (replaced) [pdf, other]
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Title: Particle manipulations based on acoustic valley topological rainbow defect-state trappingDecai Wu, Bowei Wu, Tingfeng Ma, Shuanghuizhi Li, Iren Kuznetsova, Ilya Nedospasov, Boyue Su, Teng WangSubjects: Classical Physics (physics.class-ph)
Acoustic microfluidic is an important technology in particle manipulations in biomedical analyses and detections. However, the particle-movement manipulations achieved by the standing surface acoustic wave is suitable for particles in a thin layer of fluids, however it is difficult to manipulate particles in deeper solutions due to the energy loss of surface acoustic waves. The traditional standing bulk wave method can realize the particle manipulation in deep solutions, but it cannot work properly for particle manipulation within a long distance due to the energy loss. In this work, the topological rainbow defect-state trapping is realized, the results show that an effect of point accumulation of acoustic pressure in the waveguide path exists, the position of maximum acoustic pressure can be adjusted flexibly by changing the frequency of the incident acoustic wave, based on which, long-distance movement and capture manipulations of particles in deep solution have been realized. The phenomenon presented in this work can provide a reliable method for manipulations of continuous long-distance particle movement and capture to meet the demand of multiple processing steps in biochemical analyses and detections. The experiment verification results will be presented in the near future.
- [107] arXiv:2411.13361 (replaced) [pdf, html, other]
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Title: Integration of Active Learning and MCMC Sampling for Efficient Bayesian Calibration of Mechanical PropertiesComments: 28 pages, 14 figuresSubjects: Computational Physics (physics.comp-ph); Applications (stat.AP); Machine Learning (stat.ML)
Recent advancements in Markov chain Monte Carlo (MCMC) sampling and surrogate modelling have significantly enhanced the feasibility of Bayesian analysis across engineering fields. However, the selection and integration of surrogate models and cutting-edge MCMC algorithms, often depend on ad-hoc decisions. A systematic assessment of their combined influence on analytical accuracy and efficiency is notably lacking. The present work offers a comprehensive comparative study, employing a scalable case study in computational mechanics focused on the inference of spatially varying material parameters, that sheds light on the impact of methodological choices for surrogate modelling and sampling. We show that a priori training of the surrogate model introduces large errors in the posterior estimation even in low to moderate dimensions. We introduce a simple active learning strategy based on the path of the MCMC algorithm that is superior to all a priori trained models, and determine its training data requirements. We demonstrate that the choice of the MCMC algorithm has only a small influence on the amount of training data but no significant influence on the accuracy of the resulting surrogate model. Further, we show that the accuracy of the posterior estimation largely depends on the surrogate model, but not even a tailored surrogate guarantees convergence of the this http URL, we identify the forward model as the bottleneck in the inference process, not the MCMC algorithm. While related works focus on employing advanced MCMC algorithms, we demonstrate that the training data requirements render the surrogate modelling approach infeasible before the benefits of these gradient-based MCMC algorithms on cheap models can be reaped.
- [108] arXiv:2301.05666 (replaced) [pdf, html, other]
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Title: Beyond MP2 initialization for unitary coupled cluster quantum circuitsSubjects: Quantum Physics (quant-ph); Strongly Correlated Electrons (cond-mat.str-el); Chemical Physics (physics.chem-ph)
The unitary coupled cluster (UCC) ansatz is a promising tool for achieving high-precision results using the variational quantum eigensolver (VQE) algorithm in the NISQ era. However, results on quantum hardware are thus far very limited and simulations have only accessed small system sizes. We advance the state of the art of UCC simulations by utilizing an efficient sparse wavefunction circuit solver and studying systems up to 64 qubits. Here we report results obtained using this solver that demonstrate the power of the UCC ansatz and address pressing questions about optimal initial parameterizations and circuit construction, among others. Our approach enables meaningful benchmarking of the UCC ansatz, a crucial step in assessing the utility of VQE for achieving quantum advantage.
- [109] arXiv:2303.02029 (replaced) [pdf, html, other]
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Title: Topologically invisible defects in chiral mirror latticesAntonin Coutant, Li-Yang Zheng, Vassos Achilleos, Olivier Richoux, Georgios Theocharis, Vincent PagneuxComments: 9+6 pages, 6+5 figures. Few minor corrections and clarifications. Match published versionJournal-ref: Advanced Physics Research 3 no. 4, (2024) 2300102Subjects: Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Classical Physics (physics.class-ph); Optics (physics.optics)
One of the hallmark of topological insulators is having conductivity properties that are unaffected by the possible presence of defects. In this work, we go beyond backscattering immunity and obtain topological invisibility across defects or disorder. Using a combination of chiral and mirror symmetry, the transmission coefficient is guaranteed to be unity. Importantly, but no phase shift is induced making the defect completely invisible. Many lattices possess the chiral-mirror symmetry, and we choose to demonstrate the principle on an hexagonal lattice model with Kekule distortion displaying topological edge waves, and we show analytically and numerically that the transmission across symmetry preserving defects is unity. We then realize this lattice in an acoustic system, and confirm the invisibility with numerical experiments. We foresee that the versatility of our model will trigger new experiments to observe topological invisibility in various wave systems, such as photonics, cold atoms or elastic waves.
- [110] arXiv:2311.00167 (replaced) [pdf, html, other]
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Title: Hierarchical Information-sharing Convolutional Neural Network for the Prediction of Arctic Sea Ice Concentration and VelocitySubjects: Machine Learning (cs.LG); Computer Vision and Pattern Recognition (cs.CV); Atmospheric and Oceanic Physics (physics.ao-ph)
Forecasting sea ice concentration (SIC) and sea ice velocity (SIV) in the Arctic Ocean is of great significance as the Arctic environment has been changed by the recent warming climate. Given that physical sea ice models require high computational costs with complex parameterization, deep learning techniques can effectively replace the physical model and improve the performance of sea ice prediction. This study proposes a novel multi-task fully conventional network architecture named hierarchical information-sharing U-net (HIS-Unet) to predict daily SIC and SIV. Instead of learning SIC and SIV separately at each branch, we allow the SIC and SIV layers to share their information and assist each other's prediction through the weighting attention modules (WAMs). Consequently, our HIS-Unet outperforms other statistical approaches, sea ice physical models, and neural networks without such information-sharing units. The improvement of HIS-Unet is more significant to when and where SIC changes seasonally, which implies that the information sharing between SIC and SIV through WAMs helps learn the dynamic changes of SIC and SIV. The weight values of the WAMs imply that SIC information plays a more critical role in SIV prediction, compared to that of SIV information in SIC prediction, and information sharing is more active in marginal ice zones (e.g., East Greenland and Hudson/Baffin Bays) than in the central Arctic.
- [111] arXiv:2311.04216 (replaced) [pdf, html, other]
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Title: Directly observing replica symmetry breaking in a vector quantum-optical spin glassRonen M. Kroeze, Brendan P. Marsh, David Atri Schuller, Henry S. Hunt, Alexander N. Bourzutschky, Michael Winer, Sarang Gopalakrishnan, Jonathan Keeling, Benjamin L. LevComments: main text 6 pages and 4 figures plus references, supplement 40 pages and 26 figures plus referencesSubjects: Quantum Physics (quant-ph); Disordered Systems and Neural Networks (cond-mat.dis-nn); Quantum Gases (cond-mat.quant-gas); Statistical Mechanics (cond-mat.stat-mech); Atomic Physics (physics.atom-ph)
Spin glasses are quintessential examples of complex matter. Although much about their order remains uncertain, abstract models of them inform, e.g., the classification of combinatorial optimization problems, the magnetic ordering in metals with impurities, and artificial intelligence -- where they form a mathematical basis for neural network computing and brain modeling. We demonstrate the ability of an active quantum gas microscope to realize a spin glass of a novel driven-dissipative and vector form. By microscopically visualizing its glassy spin states, the technique allows us to directly measure replica symmetry breaking and the resulting ultrametric hierarchical structure. Ultrametricity is known to be emergent in models of evolution, protein folding, climate change, and infinite-range equilibrium spin glasses; this work shows it to be directly observable in a physically realized system.
- [112] arXiv:2312.08045 (replaced) [pdf, html, other]
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Title: Theories Without Models: Uncontrolled Idealizations in Particle PhysicsSubjects: High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th); History and Philosophy of Physics (physics.hist-ph)
The perturbative treatment of realistic quantum field theories, such as quantum electrodynamics, requires the use of mathematical idealizations in the approximation series for scattering amplitudes. Such mathematical idealisations are necessary to derive empirically relevant models from the theory. Mathematical idealizations can be either controlled or uncontrolled, depending on whether current scientific knowledge can explain whether the effects of the idealization are negligible or not. Drawing upon negative formal results in asymptotic analysis (failure of Borel summability) and renormalization group theory (failure of asymptotic safety), we argue that the mathematical idealizations applied in perturbative quantum electrodynamics should be understood as uncontrolled. This, in turn, leads to the problematic conclusion that such theories do not have theoretical models in the standard understanding of this term. The existence of unquestionable empirically successful theories without theoretical models has significant implications both for our understanding of the theory-model relationship in physics and the concept of empirical adequacy.
- [113] arXiv:2401.08758 (replaced) [pdf, other]
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Title: DiscoTEX 1.0: Discontinuous collocation and implicit-turned-explicit (IMTEX) integration symplectic, symmetric numerical algorithms with higher order jumps for differential equations I: numerical black hole perturbation theory applicationsComments: 50 pages, 19 figures, 9 tables. Several typos corrected, higher-order results for the computation of energy and angular moment fluxes added. Includes overview of previous numerical methods implemented in the time-domain for the modelling of asymmetric mass ratio inspirals with suitability checks on Table 9. Now first of a series of papers. Comments are welcomeSubjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); Numerical Analysis (math.NA); Computational Physics (physics.comp-ph)
Dirac $\delta-$ distributionally sourced differential equations emerge in many dynamical physical systems from machine learning, finance, neuroscience, and seismology to black hole perturbation theory. These systems lack exact analytical solutions and are thus best tackled numerically. We describe a generic numerical algorithm which constructs discontinuous spatial and temporal discretisations by operating on discontinuous Lagrange and Hermite interpolation formulae, respectively. By solving the distributionally sourced wave equation, possessing analytical solutions, we demonstrate that numerical weak-form solutions can be recovered to high-order accuracy by solving a first-order reduced system of ODEs. The method-of-lines framework is applied to the \texttt{DiscoTEX} algorithm i.e. through \underline{dis}continuous \underline{co}llocation with implicit\underline{-turned-explicit} integration methods which are symmetric and conserve symplectic structure. Furthermore, the main application of the algorithm is proved by calculating the amplitude at any desired location within the numerical grid, including at the position (and at its right and left limit) where the wave- (or wave-like) equation is discontinuous via interpolation using \texttt{DiscoTEX}. This is demonstrated, firstly by solving the wave- (or wave-like) equation and comparing the numerical weak-form solution to the exact solution. We further demonstrate how to reconstruct the gravitational metric perturbations from weak-form numerical solutions of a non-rotating black hole, which do not have known exact analytical solutions, and compare them against state-of-the-art frequency domain results. We conclude by motivating how \texttt{DiscoTEX}, and related numerical algorithms, both open a promising new alternative waveform generation route for modelling highly asymmetric binaries and complement current frequency domain methods.
- [114] arXiv:2401.12213 (replaced) [pdf, html, other]
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Title: Identifying gap-closings in open non-Hermitian systems by Biorthogonal PolarizationComments: typos correctedJournal-ref: J. Appl. Phys. 135, 094402 (2024)Subjects: Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); High Energy Physics - Theory (hep-th); Optics (physics.optics)
We investigate gap-closings in one- and two-dimensional tight-binding models with two bands, containing non-Hermitian hopping terms, and open boundary conditions (OBCs) imposed along one direction. We compare the bulk OBC spectra with the periodic boundary condition (PBC) spectra, pointing out that they do not coincide, which is an intrinsic characteristic of non-Hermitian systems. The non-Hermiticity, thus, results in the failure of the familiar notions of bulk-boundary correspondence found for Hermitian systems. This necessitates the search for topological invariants which can characterize gap-closings in open non-Hermitian systems correctly and unambiguously. We elucidate the behaviour of two possible candidates applicable for one-dimensional slices - (1) the sum of winding numbers for the two bands defined on a generalized Brillouin zone and (2) the biorthogonal polarization (BP). While the former shows jumps/discontinuities for some of the non-Hermitian systems studied here, at points when an edge mode enters the bulk states and becomes delocalized, it does not maintain quantized values in a given topological phase. On the contrary, BP shows jumps at phase transitions, and takes the quantized value of one or zero, which corresponds to whether an actual edge mode exists or whether that mode is delocalized and absorbed within the bulk (not being an edge mode anymore).
- [115] arXiv:2401.16374 (replaced) [pdf, html, other]
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Title: Analytic Model Reveals Local Molecular Polarizability Changes Induced by Collective Strong Coupling in Optical CavitiesSubjects: Quantum Physics (quant-ph); Chemical Physics (physics.chem-ph)
Despite recent numerical evidence, one of the fundamental theoretical mysteries of polaritonic chemistry is how and if collective strong coupling can induce local changes of the electronic structure to modify chemical properties. Here we present non-perturbative analytic results for a model system consisting of an ensemble of $N$ harmonic molecules under vibrational strong coupling (VSC) that alters our present understanding of this fundamental question. By applying the cavity Born-Oppenheimer partitioning on the Pauli-Fierz Hamiltonian in dipole approximation, the dressed many-molecule problem can be solved self-consistently and analytically in the dilute limit. We discover that the electronic molecular polarizabilities are modified even in the case of vanishingly small single-molecule couplings. Consequently, this non-perturbative local polarization mechanism persists even in the large-$N$ limit. In contrast, a perturbative calculation of the polarizabilities leads to a qualitatively erroneous scaling behavior with vanishing effects in the large-$N$ limit. Nevertheless, the exact (self-consistent) polarizabilities can be determined from single-molecule strong coupling simulations instead. Our fundamental theoretical observations demonstrate that hitherto existing collective-scaling arguments are insufficient for polaritonic chemistry and they pave the way for refined single- (or few-) molecule strong-coupling ab-initio simulations of chemical systems under collective strong coupling.
- [116] arXiv:2402.00272 (replaced) [pdf, other]
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Title: Quantum phase transitions and composite excitations of antiferromagnetic spin trimer chains in a magnetic fieldComments: 15+6 pages, 16 figures, to be published in npj Quantum materialsSubjects: Strongly Correlated Electrons (cond-mat.str-el); Computational Physics (physics.comp-ph)
Motivated by recent advancements in theoretical and experimental studies of the high-energy excitations on an antiferromagnetic trimer chain, we numerically investigate the quantum phase transition and composite dynamics in this system by applying a magnetic field. The numerical methods we used include the exact diagonalization, density matrix renormalization group, time-dependent variational principle, and cluster perturbation theory. From calculating the entanglement entropy, we have revealed the phase diagram which includes the XY-I, $1/3$ magnetization plateau, XY-II, and ferromagnetic phases. Both the critical XY-I and XY-II phases are characterized by the conformal field theory with a central charge $c \simeq 1$. By analyzing the dynamic spin structure factor, we elucidate the distinct features of spin dynamics across different phases. In the regime with weak intertrimer interaction, we identify the intermediate-energy and high-energy modes in the XY-I and $1/3$ magnetization plateau phases as internal trimer excitations, corresponding to the propagating of doublons and quartons, respectively. Notably, applying a magnetic field splits the high-energy spectrum into two branches, labeled as the upper quarton and lower quarton. Furthermore, we explore the spin dynamics of a frustrated trimerized model closely related to the quantum magnet \ce{Na_2Cu_3Ge_4O_12}. In the end, we extend our discuss on the possibility of the quarton Bose-Einstein condensation in the trimer systems. Our results are expected to be further verified through the inelastic neutron scattering and resonant inelastic X-ray scattering, and also provide valuable insights for exploring high-energy exotic excitations.
- [117] arXiv:2402.18953 (replaced) [pdf, html, other]
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Title: Noise-Robust Detection of Quantum Phase TransitionsComments: 11 pages, 10 figuresSubjects: Quantum Physics (quant-ph); Materials Science (cond-mat.mtrl-sci); Other Condensed Matter (cond-mat.other); Statistical Mechanics (cond-mat.stat-mech); Computational Physics (physics.comp-ph)
Quantum computing allows for the manipulation of highly correlated states whose properties quickly go beyond the capacity of any classical method to calculate. Thus one natural problem which could lend itself to quantum advantage is the study of ground-states of condensed matter models, and the transitions between them. However, current levels of hardware noise can require extensive application of error-mitigation techniques to achieve reliable computations. In this work, we use several IBM devices to explore a finite-size spin model with multiple `phase-like' regions characterized by distinct ground-state configurations. Using pre-optimized Variational Quantum Eigensolver (VQE) solutions, we demonstrate that in contrast to calculating the energy, where zero-noise extrapolation is required in order to obtain qualitatively accurate yet still unreliable results, calculations of the energy derivative, two-site spin correlation functions, and the fidelity susceptibility yield accurate behavior across multiple regions, even with minimal or no application of error-mitigation approaches. Taken together, these sets of observables could be used to identify level crossings in a simple, noise-robust manner which is agnostic to the method of ground state preparation. This work shows promising potential for near-term application to identifying quantum phase transitions, including avoided crossings and non-adiabatic conical intersections in electronic structure calculations.
- [118] arXiv:2404.08782 (replaced) [pdf, html, other]
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Title: Phase transitions of correlated systems from graph neural networks with quantum embedding techniquesComments: 12 pages, 4 figuresSubjects: Strongly Correlated Electrons (cond-mat.str-el); Materials Science (cond-mat.mtrl-sci); Computational Physics (physics.comp-ph)
Correlated systems represent a class of materials that are difficult to describe through traditional electronic structure methods. The computational demand to simulate the structural dynamics of such systems, with correlation effects considered, is substantial. Here, we investigate the structural dynamics of $f$- and $d$-electron correlated systems by integrating quantum embedding techniques with interatomic potentials derived from graph neural networks. For Cerium, a prototypical correlated $f$-electron system, we use Density Functional Theory with the Gutzwiller approximation to generate training data due to efficiency with which correlations effects are included for large multi-orbital systems. For Nickel Oxide, a prototypical correlated $d$-electron system, advancements in computational capabilities now permit the use of full Dynamical Mean Field Theory to obtain energies and forces. We train neural networks on this data to create a model of the potential energy surface, enabling rapid and effective exploration of structural dynamics. Utilizing these potentials, we delineate transition pathways between the $\alpha$, $\alpha'$, and $\alpha''$ phases of Cerium and predict the melting curve of Nickel Oxide. Our results demonstrate the potential of machine learning potentials to accelerate the study of strongly correlated systems, offering a scalable approach to explore and understand the complex physics governing these materials.
- [119] arXiv:2405.00663 (replaced) [pdf, html, other]
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Title: Quantum cryptographic protocols with dual messaging system via 2D alternate quantum walk of a genuine single-photon entangled stateComments: 13 pages (including appendix), two figures and one table, accepted for publication in Journal of Physics A: Mathematical and Theoretical as a letterJournal-ref: Journal of Physics A: Mathematical and Theoretical (2024)Subjects: Quantum Physics (quant-ph); Disordered Systems and Neural Networks (cond-mat.dis-nn); Cryptography and Security (cs.CR); Quantum Algebra (math.QA); Optics (physics.optics)
A single-photon entangled state (or single-particle entangled state (SPES) in general) can offer a more secure way of encoding and processing quantum information than their multi-photon (or multi-particle) counterparts. The SPES generated via a 2D alternate quantum-walk setup from initially separable states can be either 3-way or 2-way entangled. This letter shows that the generated genuine three-way and nonlocal two-way SPES can be used as cryptographic keys to securely encode two distinct messages simultaneously. We detail the message encryption-decryption steps and show the resilience of the 3-way and 2-way SPES-based cryptographic protocols against eavesdropper attacks like intercept-and-resend and man-in-the-middle. We also detail the experimental realization of these protocols using a single photon, with the three degrees of freedom being OAM, path, and polarization. We have proved that the protocols have unconditional security for quantum communication tasks. The ability to simultaneously encode two distinct messages using the generated SPES showcases the versatility and efficiency of the proposed cryptographic protocol. This capability could significantly improve the throughput of quantum communication systems.
- [120] arXiv:2406.16898 (replaced) [pdf, html, other]
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Title: Detecting kHz gravitons from a neutron star merger with a multi-mode resonant mass detectorComments: 8 + 3 pages, 2 FiguresSubjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th); Instrumentation and Detectors (physics.ins-det); Quantum Physics (quant-ph)
We propose a multi-mode bar consisting of mass elements of decreasing size for the implementation of a gravitational version of the photo-electric effect through the stimulated absorption of up to kHz gravitons from a binary neutron star merger and post-merger. We find that the multi-mode detector has normal modes that retain the coupling strength to the gravitational wave of the largest mass-element, while only having an effective mass comparable to the mass of the smallest element. This allows the normal modes to have graviton absorption rates due to the tonne-scale largest mass, while the single graviton absorption process in the normal mode could be resolved through energy measurements of a mass-element in-principle smaller than pico-gram scale. We argue the feasibility of directly counting gravito-phonons in the bar through energy measurements of the end mass. This improves the transduction of the single-graviton signal, enhancing the feasibility of detecting single gravitons.
- [121] arXiv:2408.03413 (replaced) [pdf, html, other]
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Title: A TVD neural network closure and application to turbulent combustionSubjects: Machine Learning (cs.LG); Computational Engineering, Finance, and Science (cs.CE); Fluid Dynamics (physics.flu-dyn)
Trained neural networks (NN) have attractive features for closing governing equations. There are many methods that are showing promise, but all can fail in cases when small errors consequentially violate physical reality, such as a solution boundedness condition. A NN formulation is introduced to preclude spurious oscillations that violate solution boundedness or positivity. It is embedded in the discretized equations as a machine learning closure and strictly constrained, inspired by total variation diminishing (TVD) methods for hyperbolic conservation laws. The constraint is exactly enforced during gradient-descent training by rescaling the NN parameters, which maps them onto an explicit feasible set. Demonstrations show that the constrained NN closure model usefully recovers linear and nonlinear hyperbolic phenomena and anti-diffusion while enforcing the non-oscillatory property. Finally, the model is applied to subgrid-scale (SGS) modeling of a turbulent reacting flow, for which it suppresses spurious oscillations in scalar fields that otherwise violate the solution boundedness. It outperforms a simple penalization of oscillations in the loss function.
- [122] arXiv:2410.08887 (replaced) [pdf, html, other]
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Title: How Semilocal Are Semilocal Density Functional Approximations? -Tackling Self-Interaction Error in One-Electron SystemsSubjects: Materials Science (cond-mat.mtrl-sci); Chemical Physics (physics.chem-ph)
Self-interaction error (SIE), arising from the imperfect cancellation of the spurious classical Coulomb interaction between an electron and itself, is a persistent challenge in modern density functional approximations. This issue is illustrated using the prototypical one-electron system $H_2^+$. While significant efforts have been made to eliminate SIE through the development of computationally expensive nonlocal density functionals, it is equally important to explore whether SIE can be mitigated within the framework of more efficient semilocal density functionals. In this study, we present a non-empirical meta-generalized gradient approximation (meta-GGA) that incorporates the Laplacian of the electron density. Our results demonstrate that the meta-GGA significantly reduces SIE, yielding a binding energy curve for $H_2^+$ that matches the exact solution at equilibrium and improves across a broad range of bond lengths over those of the Perdew-Burke-Ernzerhof (PBE) and strongly-constrained and appropriately-normed (SCAN) semilocal density functionals. This advancement paves the way for further development within the realm of semilocal approximations.
- [123] arXiv:2411.00262 (replaced) [pdf, html, other]
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Title: Content Aware Analysis of Scholarly Networks: A Case Study on CORD19 DatasetSubjects: Social and Information Networks (cs.SI); Information Retrieval (cs.IR); Physics and Society (physics.soc-ph)
This paper investigates the relationships among key elements of the scientific research network, namely articles, researchers, and journals. We introduce a novel approach to use semantic information through the HITS algorithm-based propagation of topic information in the network. The topic information is derived by using the Named Entity Recognition and Entity Linkage. In our case, MedCAT is used to extract the topics from the CORD19 Dataset, which is a corpus of academic articles about COVID-19 and the coronavirus scientific network. Our approach focuses on the COVID-19 domain, utilizing the CORD-19 dataset to demonstrate the efficacy of integrating topic-related information within the citation framework. Through the application of a hybrid HITS algorithm, we show that incorporating topic data significantly influences article rankings, revealing deeper insights into the structure of the academic community.
- [124] arXiv:2411.04650 (replaced) [pdf, html, other]
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Title: Many-body nonequilibrium dynamics in a self-induced Floquet systemYuechun Jiao, Yu Zhang, Jingxu Bai, Suotang Jia, C. Stuart Adams, Zhengyang Bai, Heng Shen, Jianming ZhaoComments: 6 pages, 4 figuresSubjects: Quantum Physics (quant-ph); Quantum Gases (cond-mat.quant-gas); Atomic Physics (physics.atom-ph)
Floquet systems are periodically driven systems. In this framework, the system Hamiltonian and associated spectra of interest are modified, giving rise to new quantum phases of matter and nonequilibrium dynamics without static counterparts. Here we experimentally demonstrate a self-induced Floquet system in the interacting Rydberg gas. This originates from the photoionization of thermal Rydberg gases in a static magnetic field. Importantly, by leveraging the Rydberg electromagnetically induced transparency spectrum, we probe the nonequilibrium dynamics in the bistable regime and identify the emergence of a discrete time crystalline phase. Our work fills the experimental gap in the understanding the relation of multistability and dissipative discrete time crystalline phase. In this regard, it constitutes a highly controlled platform for exploring exotic nonequilibrium physics in dissipative interacting systems.
- [125] arXiv:2411.13190 (replaced) [pdf, html, other]
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Title: Ab-Initio Approach to Many-Body Quantum Spin DynamicsComments: 12 pages, 9 figuresSubjects: Quantum Physics (quant-ph); Quantum Gases (cond-mat.quant-gas); Atomic Physics (physics.atom-ph); Computational Physics (physics.comp-ph)
A fundamental longstanding problem in studying spin models is the efficient and accurate numerical simulation of the long-time behavior of larger systems. The exponential growth of the Hilbert space and the entanglement accumulation at long times pose major challenges for current methods. To address these issues, we employ the multilayer multiconfiguration time-dependent Hartree (ML-MCTDH) framework to simulate the many-body spin dynamics of the Heisenberg model in various settings, including the Ising and XYZ limits with different interaction ranges and random couplings. Benchmarks with analytical and exact numerical approaches show that ML-MCTDH accurately captures the time evolution of one- and two-body observables in both one- and two-dimensional lattices. A comparison of ML-MCTDH with the discrete truncated Wigner approximation (DTWA) demonstrates that our approach excels in handling anisotropic models and consistently provides better results for two-point observables in all simulation instances. Our results indicate that the multilayer structure of ML-MCTDH is a promising numerical framework for handling the dynamics of generic many-body spin systems.