Physics and Society
Mapping Resilience and Inequality: A Spatial Analysis of Refugee Communities in Seattle
Rafi Khan and Bo Zhao
Seattle has long been a center for refugee resettlement in the United States, creating multicultural neighborhoods with complex social and spatial dynamics. This study analyzes the refugee experience in Seattle by examining patterns of housing cost burden,
language isolation, religious infrastructure, and crime incidence. These spatial findings are combined with insights from literature on refugee integration, social vulnerability, and community safety. Results show that White Center and Rainier Valley experience severe housing cost burdens and high social vulnerability, indicating significant financial stress and exposure to economic risks.
Language isolation is pronounced, as many residents lack English fluency, limiting access to jobs and essential services. Access to religious and cultural institutions is also uneven, affecting community cohesion and cultural preservation. While citywide crime maps show scattered incidents, evidence indicates that refugees are more often victims than offenders, and that their communities do not increase local crime rates. The paper concludes by recommending policies that strengthen affordable housing, expand
language assistance, support community and cultural spaces, and promote inclusive public safety programs. These findings aim to inform policymakers, educators, and community organizations about the spatial and social dimensions of refugee life in Seattle.
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Chemical Physics
Prospects for Using Artificial Intelligence to Understand Intrinsic Kinetics of Heterogeneous Catalytic Reactions
Andrew J. Medford, Todd N. Whittaker, Bjarne Kreitz et al. (+2 more)
Artificial intelligence (AI) is influencing heterogeneous catalysis research by accelerating simulations and materials discovery. A key frontier is integrating AI with multiscale models and
multimodal experiments to address the "many-to-one" challenge of linking intrinsic kinetics to observables. Advances in machine-learned force fields, microkinetics, and reactor modeling enable rapid exploration of chemical spaces, while operando and transient data provide unprecedented insight. Yet, inconsistent data quality and model complexity limit mechanistic discovery. Generative and agentic AI can automate model generation, quantify uncertainty, and couple theory with experiment, realizing "self-driving models" that produce interpretable, reproducible, and transferable understanding of catalytic systems.
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All authors Andrew J. Medford, Todd N. Whittaker, Bjarne Kreitz, David W. Flaherty, John R. Kitchin
History and Philosophy of Physics
The simplest complexity: The story of the three-body problem
Barak Kol
This article offers a broad-brush account of the Newtonian three-body problem, from its origins with Newton to its vibrant present, emphasizing its enduring influence on theoretical physics. It unfolds through a series of self-contained episodes that illuminate the scientific fields and the paradigm shift that have grown out of this problem.
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Optics
Quadratic Supercontinuum Generation from UV to Mid-IR in Lithium Niobate Nanophotonics
Selina Zhou, Maximilian Shen, Ryoto Sekine et al. (+6 more)
Supercontinuum light sources are widely used for applications ranging from imaging to sensing and frequency comb stabilization. The most common mechanisms for their generation rely on cubic nonlinearities, for instance in
crystals, optical fibers, and integrated photonics. However, quadratic supercontinuum generation (QSCG) offers potential for enhanced energy efficiency and broader spectral coverage because of the typically much stronger nonlinearity and ability to achieve both coherent up- and down-conversion via three-wave mixing processes. Despite such potentials, demonstrations of QSCG in integrated photonic waveguides have been sparse and have barely surpassed their cubic counterparts in terms of spectral coverage and energy-efficiency. Here, we introduce a new dispersion engineering principle and experimentally demonstrate purely quadratic supercontinuum generation in lithium niobate nano-waveguides substantially outperforming previous demonstrations in integrated photonics. In one device, by engineering a near-zero dispersion profile and using a single poling period for quasi-phase matched saturated second-harmonic generation, we achieve robust and energy efficient multi-octave QSCG with only femtojoules of pump pulse energy. In another device, we use a flat dispersion profile with two distant zero crossings of group velocity dispersion (GVD) to achieve broadband difference-frequency generation (DFG) for extending the spectral coverage further into the mid-IR and cover the entire transparency window of lithium niobate from 350 nm to 5000 nm. Our results showcase how DFG-assisted QSCG can access hard-to-access spectral regions in an energy-efficient fashion by properly utilizing dispersion engineering and quasi-phase matching.
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All authors Selina Zhou, Maximilian Shen, Ryoto Sekine, Nicolas Englebert, Thomas Zacharias, Benjamin Gutierrez, Robert M. Gray, Justin Widjaja, Alireza Marandi
Computational Physics · Cross-listed from cs.DC
PCMS: Parallel Coupler For Multimodel Simulations
Jacob S. Merson, Cameron W. Smith, Mark S. Shephard et al. (+5 more)
This paper presents the Parallel Coupler for Multimodel Simulations (PCMS), a new GPU accelerated generalized coupling framework for coupling simulation codes on leadership class supercomputers. PCMS includes distributed control and field mapping methods for up to five dimensions. For field mapping PCMS can utilize discretization and field information to accommodate physics constraints. PCMS is demonstrated with a coupling of the gyrokinetic microturbulence code XGC with a Monte Carlo neutral transport code DEGAS2 and with a 5D distribution function coupling of an energetic particle transport code (GNET) to a gyrokinetic microturbulence code (GTC). Weak scaling is also demonstrated on up to 2,080 GPUs of Frontier with a weak scaling efficiency of 85%.
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All authors Jacob S. Merson, Cameron W. Smith, Mark S. Shephard, Fuad Hasan, Abhiyan Paudel, Angel Castillo-Crooke, Joyal Mathew, Mohammad Elahi
Optics
Supercontinuum generation from Topological Edge Supermodes in a short SSH Photonic Crystal Fiber
Daniel Rodriguez-Guillen, Carlos Wiechers and Lorena Velazquez-Ibarra
We introduce a topological photonic-
crystal fiber that embeds a short Su-Schrieffer-Heeger (SSH) chain and supports two edge supermodes. Using full-vector modal analysis and a coupled generalized nonlinear Schroedinger equation, we show that each supermode provides an independent nonlinear channel with a distinct broadening mechanism: the even supermode features two zero-dispersion wavelengths and yields degenerate four-wave mixing sidebands, whereas the odd supermode is all-normal-dispersion and generates a smooth, flat ANDi-type continuum. Exciting a single core prepares a coherent superposition of the two supermodes; cross-phase modulation and inter-parity four-wave mixing then enable energy transfer across detunings inaccessible to either mode alone, producing the broadest and flattest spectrum with new short wavelengths components. Our results establish
topology-enabled modal control as a scalable knob for engineering supercontinuum generation in short SSH topological fibers.
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Biological Physics · Cross-listed from q-bio.QM
Protein generation with embedding learning for motif diversification
Kevin Michalewicz, Chen Jin, Philip Alexander Teare et al. (+4 more)
A fundamental challenge in
protein design is the trade-off between generating structural diversity while preserving motif biological function. Current state-of-the-art methods, such as partial
diffusion in RFdiffusion, often fail to resolve this trade-off: small perturbations yield motifs nearly identical to the native structure, whereas larger perturbations violate the
geometric constraints necessary for biological function. We introduce
Protein Generation with
Embedding Learning (PGEL), a general framework that learns high-dimensional
embeddings encoding sequence and structural features of a target motif in the representation space of a
diffusion model's frozen denoiser, and then enhances motif diversity by introducing controlled perturbations in the
embedding space. PGEL is thus able to loosen
geometric constraints while satisfying typical design metrics, leading to more diverse yet viable structures. We demonstrate PGEL on three representative cases: a monomer, a
protein-
protein interface, and a cancer-related transcription factor complex. In all cases, PGEL achieves greater structural diversity, better designability, and improved self-consistency, as compared to partial
diffusion. Our results establish PGEL as a general strategy for
embedding-driven
protein generation allowing for systematic, viable diversification of functional motifs.
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All authors Kevin Michalewicz, Chen Jin, Philip Alexander Teare, Tom Diethe, Mauricio Barahona, Barbara Bravi, Asher Mullokandov
General Physics
The swinging counterweight trebuchet. On internal forces
Erik Horsdal
The forces that act internally in a trebuchet as it delivers a shot depend on the motions of throwing arm, counterweight and sling. These motions are considered known experimentally or theoretically and given in the form of time-dependent angular coordinates. Explicit expressions in terms of these coordinates and their derivatives to second order are derived for the internal forces. The forces that act immediately after a shot is initiated can be extracted from the equations of motion without solving them, and they are compared with static forces just prior to initiation. Required strengths of the different parts of a trebuchet depend on the internal forces, which also determine sliding friction losses. Illustrative results are given for a specific trebuchet.
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Computational Physics · Cross-listed from cond-mat.mes-hall
Self-Consistent Model for Gate Control of Narrow-, Broken-, and Inverted-Gap (Topological) Heterostructures
Maximilian Hofer, Christopher Fuchs, Moritz Siebert et al. (+8 more)
Even small electrostatic potentials can dramatically influence the band structure of narrow-, broken-, and inverted-gap materials. A quantitative understanding often necessitates a self-consistent Hartree approach. The valence and conduction band states strongly hybridize and/or cross in these systems. This makes distinguishing between electrons and holes impossible and the assumption of a flat charge carrier distribution at the charge neutrality point hard to justify. Consequently the wide-gap approach often fails in these systems. An alternative is the full-band envelope-function approach by Andlauer and Vogl, which has been implemented into the open-source software package kdotpy (arXiv:2407.12651). We show that this approach and implementation gives numerically stable and quantitatively accurate results where the conventional method fails by modeling the experimental subband density
evolution with top-gate voltage in thick (26 nm - 110 nm), topologically inverted HgTe
quantum wells. We expect our openly-available implementation to greatly benefit the investigation of narrow-, broken-, and inverted-gap materials.
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All authors Maximilian Hofer, Christopher Fuchs, Moritz Siebert, Christian Berger, Lena Fürst, Martin Stehno, Steffen Schreyeck, Hartmut Buhmann, Tobias Kießling, Wouter Beugeling, Laurens W. Molenkamp
Computational Physics · Cross-listed from math.NA
Adaptive hyperviscosity stabilisation for the RBF-FD method in solving advection-dominated transport equations
Miha Rot, Žiga Vaupotič, Andrej Kolar-Požun et al. (+1 more)
This paper presents an adaptive hyperviscosity stabilisation procedure for the Radial Basis Function-generated Finite Difference (RBF-FD) method, aimed at solving linear and non-linear advection-dominated transport equations on domains without a boundary. The approach employs a PDE-independent
algorithm that adaptively determines the hyperviscosity constant based on the spectral radius of the RBF-FD
evolution matrix. The proposed procedure supports general node layouts and is not tailored for specific equations, avoiding the limitations of empirical tuning and von Neumann-based estimates. To reduce computational cost, it is shown that lower monomial augmentation in the approximation of the hyperviscosity operator can still ensure consistent stabilisation, enabling the use of smaller stencils and improving overall efficiency. A hybrid strategy employing different spline orders for the advection and hyperviscosity operators is also implemented to enhance stability. The method is evaluated on pure linear advection and non-linear Burgers' equation, demonstrating stable performance with limited numerical dissipation. The two main contributions are: (1) a general hyperviscosity RBF-FD solution procedure demonstrated on both linear and non-linear advection-dominated problems, and (2) an in-depth analysis of the behaviour of hyperviscosity within the RBF-FD framework, addressing the interplay between key free parameters and their influence on numerical results.
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All authors Miha Rot, Žiga Vaupotič, Andrej Kolar-Požun, Gregor Kosec
Biological Physics · Cross-listed from q-bio.CB
Mechanical activity enables patterning and discrimination at the immune synapse
Tony Wong, Tom Chou, Suraj Shankar et al. (+1 more)
Immune
cells recognize and discriminate antigens through immunological synapses - dynamic intercellular junctions exhibiting highly organized receptor-ligand patterns. While much work has focused on molecular kinetics and passive mechanisms of pattern formation, the role of active mechanical control in patterning and discrimination remains underexplored. We develop a minimal continuum model coupling receptor binding kinetics, membrane deformation, and cytoskeletal forces, with elastohydrodynamic flow in the synaptic cleft. Numerical simulations and scaling analysis reveal that contractile cortical flows arrest coarsening and stabilize long-lived multifocal clusters, whereas active pulling accelerates cluster dissolution and elevates background receptor binding. Nonequilibrium mechanical forces enable adaptive control over the speed, sensitivity, and dynamic range of affinity discrimination in a pattern-dependent manner. Our results highlight how immune
cells exploit cytoskeletal remodeling to robustly regulate antigen recognition through synaptic patterning.
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All authors Tony Wong, Tom Chou, Suraj Shankar, Shenshen Wang
Chemical Physics
Non-Resonant Raman Optical Activity From Phase-Space Electronic Structure Theory
Zhen Tao, Mansi Bhati and Joseph E. Subotnik
In order to model experimental non-resonant Raman optical activity, chemists must compute a host of second-order response tensors, (e.g. the electric-dipole
magnetic-dipole polarizability) and their
nuclear derivatives along a set of vibrational modes. While these response functions are almost always computed within a Born-Oppenheimer (BO) framework, here we provide a natural interpretation of the electric-dipole
magnetic-dipole polarizability within phase space electronic structure theory, a beyond-BO model whereby the electronic structure depends on
nuclear momentum (P) in addition to
nuclear position (R). By coupling to
nuclear momentum, phase space electronic structure theory is able to capture the asymmetric response of the electronic properties to an external field, in sofar as for a vibrating (non-stationary) molecule, dmu/dB \ne dm/dF, where mu and m are the electrical linear and
magnetic dipoles, and F and B are electric and
magnetic fields. As an example, for a prototypical methyloxirane molecule, we show that phase space electronic structure theory is able to deliver a reasonably good match with experimental results in a manner that is invariant to gauge origin G0.
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Optics · Cross-listed from cond-mat.mes-hall
Extinction Coefficients of CdSe, CdS, and CdTe Nanoplatelets in Solution: A Practical Tool for Concentration Determination
Michael H. Stewart, Michael W. Swift, Farwa Awan et al. (+6 more)
Semiconductor nanoplatelets possess exceptional optical properties that make them promising candidates for next-generation optoelectronic applications. However, unlike
quantum dots where absorption spectroscopy alone can determine both size and concentration, nanoplatelets present a significant characterization challenge: the absorption peak position reveals only thickness, providing no information about lateral dimensions or concentration. This limitation forces researchers to rely on time-consuming and costly elemental analysis techniques for complete sample characterization. Here, we present an experimentally verified theoretical framework that predicts the frequency-dependent absorption coefficient of randomly oriented CdSe, CdS, and CdTe nanoplatelets, enabling concentration determination from absorption measurements and lateral size estimates. Our model shows that the integrated absorption coefficient depends universally on nanoplatelet surface area and thickness, yielding a practical tool to extract concentrations without laborious elemental analysis. This approach bridges the characterization gap between
quantum dots and nanoplatelets, offering a streamlined method for rapid sample analysis that could accelerate nanoplatelet research and applications.
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All authors Michael H. Stewart, Michael W. Swift, Farwa Awan, Liam Burke, Christopher M. Green, Barbara A. Marcheschi, Igor L. Medintz, Todd D. Krauss, Alexander L. Efros
Fluid Dynamics
Hydrodynamics of Flapping Foils Undergoing Irregular Motion with Application to Wave-Assisted Propulsion
Harshal S. Raut, Jung-Hee Seo and Rajat Mittal
Flapping foils are widely studied as bioinspired propulsors, yet most investigations have focused on regular, sinusoidal kinematics. In realistic environments, however, irregular motions arise naturally due to environmental disturbances, fluid-structure interactions, and control inputs, but their hydrodynamic consequences remain largely unexplored. One system where response to irregular forcing is particularly relevant is wave-assisted propulsion (WAP) systems where free-to-pitch submerged foils generate thrust due to wave-induced heaving. We employ time-accurate flow simulations of
elliptic WAP foils subjected to irregular waves at three different sea-states to gain insights into this system. Our results demonstrate that irregular heaving and pitching can generate greater mean thrust than energetically equivalent sinusoidal heaving. Moreover, a spring-based pitch-limiting mechanism yields higher thrust than an angle-limiter under the same conditions. By leveraging a previously developed leading-edge
vortex (LEV) model, we uncover the mechanisms driving this thrust enhancement and highlight the critical interactions between unsteady flow structures and foil dynamics. These findings provide new insights into flapping-foil propulsion in irregular environments and have direct implications for the design and optimization of WAP systems.
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Chemical Physics
Relativistic unitary coupled cluster method for ground-state molecular properties
Kamal Majee, Somesh Chamoli, Malaya K. Nayak et al. (+1 more)
We propose a relativistic
unitary coupled cluster (UCC) expectation value approach for computing first-order properties of heavy-element systems. Both perturbative (UCC3) and non-perturbative (qUCC) commutator-based formulations are applied to evaluate ground-state properties, including the permanent dipole moment (PDM),
magnetic hyperfine structure (HFS) constant, and electric field gradient (EFG). The results are compared with available experimental data and those from conventional coupled cluster (CC) calculations. The non-perturbative commutator-based approach truncated at the singles and doubles level (qUCCSD) exhibits markedly better agreement with both CCSD and experiment than the perturbative UCC3 method, likely due to its improved treatment of relaxation effects.
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All authors Kamal Majee, Somesh Chamoli, Malaya K. Nayak, Achintya Kumar Dutta
Optics · Cross-listed from quant-ph
Source-device-independent monolithically integrated QRNG in a black box with generation rate in excess of 30 Gbit/s
Peter Seigo Kincaid, Lorenzo De Marinis, Francesco Testa et al. (+2 more)
Quantum mechanics provides a secure means of generating random numbers, with applications in fields spanning scientific simulation to cryptography. The first source-device-independent monolithically integrated
quantum random number generator is reported. With a generation rate of 35 Gbit/s, the device is based on an InP photonic integrated
circuit with a
quantum vacuum state
entropy source, sampled by heterodyne coherent detection using an optical local oscillator. The entire device is conveniently housed in a black box and includes all the necessary driving and signal conditioning electronics, with electrical interfaces only; the exhibited security, compactness, and fast generation rate make the generator suitable for applications in QKD.
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All authors Peter Seigo Kincaid, Lorenzo De Marinis, Francesco Testa, Nicola Andriolli, Giampiero Contestabile
Fluid Dynamics
A diffuse-interface method for the containerless freezing of three-phase flows in complex geometries
Jiangxu Huang, Chengjie Zhan, Zhenhua Chai et al. (+1 more)
In this work, we first propose a diffuse-interface model for the freezing processes of three-phase flows in complex geometries, and the core of the model to intergratge the Navier-Stokes equations for fluid flows, a modified phase-field equation for gas-
liquid interfaces, and an enthalpy approach for solid-
liquid phase-change processes in a unified diffuse-interface framework. The volume expansion or shrinkage of the
liquid phase caused by the density change during the phase-change process is considered by introducing a mass source term into the continuity equation. The wettability effect in such a gas-
liquid-solid multiphase system is also included in the phase-field free energy, thereby avoiding the direct discretization of wetting boundary condition on the complex fluid-solid boundary. Then, we develop a mesoscopic
lattice Boltzmann (LB) method to solve the diffuse-interface model for the freezing processes in multiphase systems, and test the accuracy and efficiency of the LB method through some
benchmark problems, including the conduction-induced freezing in a semi-infinite space, the three-phase Stefan problem, the droplet solidification on the flat and curved surfaces. It is found that the numerical results are in good agreement with the experimental data and theoretical solutions. Finally, the LB method is further extended to study the freezing dynamics of multiphase flows in a fracture and porous medium, and the numerical results show that the developed method is efficient in the study of freezing processes of multiphase flows in complex geometries.
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All authors Jiangxu Huang, Chengjie Zhan, Zhenhua Chai, Changsheng Huang
Optics
Impact of Surface Passivation on the Efficiency and High-speed Modulation of III-V GaAs/AlGaAs Nanopillar Array LEDs
Bejoys Jacob, João Azevedo, João Lourenço et al. (+3 more)
III-V
semiconductor nanolight sources with deep-subwavelength dimensions ($<<$1 ${\mu}$m) are essential for miniaturized photonic devices such as nanoLEDs and nanolasers. However, these nanoscale emitters suffer from substantial non-radiative recombination at room temperature, resulting in low efficiency and ultrashort lifetimes ($<$100 ps). Previous works have predominantly studied surface passivation of nanoLEDs under optical pumping conditions, while practical applications require electrically driven nanoLEDs. Here, we investigate the influence of surface passivation on the efficiency and high-speed modulation response of electrically pumped III-V GaAs/AlGaAs nanopillar array LEDs. Surface passivation was performed using ammonium sulphide chemical treatment followed by encapsulation with a 100 nm silicon nitride layer deposited via low-frequency
plasma-enhanced chemical vapour deposition. Time-resolved electroluminescence measurements reveal differential carrier lifetimes (${\tau}$) of ~0.61 ns for nanoarray LEDs with pillar diameters of ~440 nm, a record-long lifetime for electrically driven GaAs-based nanopillar arrays. Under low injection conditions, the devices exhibited carrier lifetimes of ~0.41 ns, indicating successful suppression of non-radiative effects and a low surface velocity, ranging from $S$~0.7$\times$10$^4$ cm/s to 2.7$\times$10$^4$ cm/s. This reveals a potential high internal
quantum efficiency $IQE$~0.45 for our nanoLEDs operating under very high injection conditions, limited only by Auger recombination and self-heating effects at high current density. These miniaturized nanoLEDs with high radiative recombination efficiency and sub-ns modulation response pave the way for optical data communications, energy efficient optical interconnects, AR/VR displays, and neuromorphic computing applications.
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All authors Bejoys Jacob, João Azevedo, João Lourenço, Filipe Camarneiro, Jana B. Nieder, Bruno Romeira
Computational Physics · Cross-listed from quant-ph
Optimal quantum reservoir learning in proximity to universality
Moein N. Ivaki, Matias Karjula and Tapio Ala-Nissila
The study of the boundary between classically simulable and computationally complex
quantum dynamics is fundamental to understanding which physical resources may enable enhanced information-processing capabilities. We investigate this within the framework of
quantum reservoir computing by introducing a tunable $N$-
qubit random
circuit model, where a fraction $p$ of Clifford gates are probabilistically substituted with nonstabilizing conditional-$\hat{T}$ gates. We establish a direct correspondence between the reservoir's performance on temporal processing tasks and its
entanglement spectrum statistics and long-range nonstabilizer resource content. To assess scalability, we study the scaling of the anti-flatness of states in the large-$N$ limit at a fixed
circuit depth ratio $d/N \sim \mathcal{O}(1)$. This is taken as a witness to concentration of measures, a known impediment to learning in thermalizing systems. We demonstrate that the learnability and scalability of the reservoir can be continuously controlled by the parameter $p$, allowing us to navigate from classically tractable to maximally expressive
quantum dynamics. These architecture-agnostic results provide a general strategy for designing tunable and expressive
quantum reservoirs, highlighting how certain nonclassical properties control average-case intrinsic learnability and functionality.
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Computational Physics
Stable rational approximations for parabolic equation methods
Adith Ramamurti, Joseph F. Lingevitch, Jonathan C. Lighthall et al. (+1 more)
Modern
parabolic equation (PE) methods for wave propagation rely on application of a variety of fractional-powered differential operators. Rational approximations of these operators need to properly map their spectra onto the complex plane, accurately handling propagating modes while annihilating evanescent ones. Standard approaches for stable and accurate rational approximations include rotating the branch cut of the operators or imposing stability constraint equations, and have yielded accurate results for wave propagation in a variety of fluid, elastic, and fluid-elastic waveguides. The stability constraint method, however, does not yield operators that are stable for all fluid-elastic waveguides, and a recent study of waveguides comprised of a thin elastic layer overlaying a thick fluid layer revealed instabilities in the approximations derived from rotated operators. In this paper, we demonstrate the applicability of a different rational approximation method, the recently-developed adaptive Antoulas-Anderson (AAA)
algorithm, to simulations of wave propagation using the fluid-elastic
parabolic equation. We find that simulations using operators approximated using the AAA
algorithm provide excellent agreement with reference solutions, with errors in transmission loss comparable to, and often less than, that of simulations using the rotated operator method. In addition, we find that the AAA
algorithm allows for the application of the split-step Padé method to fluid-elastic waveguides, which yields a large gain in computational efficiency.
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All authors Adith Ramamurti, Joseph F. Lingevitch, Jonathan C. Lighthall, Michael D. Collins
Computational Physics · Cross-listed from cond-mat.mtrl-sci
First-Principles Investigation of Sr2PrSbO6 Double Perovskite: An Emerging Aspirant for Electrocatalysis, Plasmonic, Photonics, Thermoelectric and Solar Cell Applications
Md. Mohiuddin and Alamgir Kabir
In this study, we investigate the structural properties, chemical stability, and electronic, optical, and thermoelectric properties of $\mathrm{Sr_2PrSbO_6}$ using first-principles calculations based on Density Functional Theory (DFT). The goal of this study is to evaluate its potential contribution to next-generation electrocatalysts, optoelectronic devices, and thermoelectric systems. The structural optimization reveals that $\mathrm{Sr_2PrSbO_6}$ crystallizes in a stable cubic perovskite structure with space group $Fm\bar{3}m$. The calculated formation energy indicates high thermodynamic stability, confirming the viability of $\mathrm{Sr_2PrSbO_6}$ for practical applications. The electronic band structure calculations show that $\mathrm{Sr_2PrSbO_6}$ is a wide bandgap
semiconductor with a direct bandgap of $3.488~\mathrm{eV}$ at the $\Gamma$-point. The calculated density of states (DOS) indicates significant contributions from O $2p$, Sb $5p$, and Pr $5d$ orbitals. Optical property calculations, including the dielectric function and absorption coefficient, reveal strong absorption in the UV regions, making $\mathrm{Sr_2PrSbO_6}$ a promising candidate for optoelectronic applications such as UV light-emitting diodes (LEDs) and photovoltaic-thermoelectric (PV-TE) tandem systems. At room temperature, the calculated dimensionless quantity $ZT$ is $0.33$, which indicates this material as a possible candidate for thermoelectric applications. Our results will serve as a
benchmark for future experimental and theoretical research on the properties of this material.
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Optics
Exceptional broadband absorption of nanoporous gold explained by plasmonic resonances at dangling ligaments
Muhammad Salman Wahidi, Maurice Pfeiffer, Xinyan Wu et al. (+3 more)
Nanoporous gold (npAu) has emerged as a potential candidate for many optical applications exploiting its large surface to volume ratio and high broadband absorption. However, the physical origin of its enhanced visible and near infrared absorption remained unclear and till now was not explicable by simplified models. Here, we have employed leveled-wave approximants to simulate the optical response of realistic npAu structures. First, our simulations reproduced well the experimental absorption spectra. Second, we identify multiple resonances in the gaps between dangling ligaments that occur at the top and bottom surfaces of npAu films as the key contribution to the broadband absorption. These resonances at the surface of npAu cannot be captured by bulk effective medium models and should be considered separately as a surface effect. The additional absorption due to dangling ligaments contributes up to 70 % to overall absorption of npAu. Our results provide deeper insights into the absorption behavior of npAu, indicating promising avenues for photocatalysis and sensing applications.
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All authors Muhammad Salman Wahidi, Maurice Pfeiffer, Xinyan Wu, Fatemeh Ebrahimi, Manfred Eich, Alexander Yu. Petrov
Biological Physics
Inheritance Entropy: A Model-Independent Method to Probe the Hereditary Structure of Cell Lineage Trees
Alessandro Allegrezza, Riccardo Beschi, Domenico Caudo et al. (+14 more)
Human bone marrow stromal
cells (BMSC) include skeletal stem
cells with ground-breaking therapeutic potential. However, BMSC colonies have very heterogeneous in vivo behaviour, due to their different potency; this unpredictability is the greatest hurdle to the development of skeletal regeneration therapies. Colony-level heterogeneity urges a fundamental question: how is it possible that one colony as a collective unit behaves differently from another one? If
cell-to-
cell variability were just an uncorrelated random process, a million
cells in a transplant-bound colony would be enough to yield statistical homogeneity, hence washing out any colony-level traits. A possible answer is that the differences between two originating
cells are transmitted to their progenies and collectively persist through an hereditary mechanism. But non-genetic inheritance remains an elusive notion, both at the experimental and at the theoretical level. Here, we prove that heterogeneity in the lineage
topology of BMSC clonal colonies is determined by heritable traits that regulate
cell-cycle exit. The cornerstone of this result is the definition of a novel
entropy of the colony, which measures the hereditary ramifications in the distribution of inactive
cells across different branches of the proliferation tree. We measure the
entropy in 32 clonal colonies, obtained from single-
cell lineage tracing experiments, and show that in the greatest majority of clones this
entropy is decisively smaller than that of the corresponding non-hereditary lineage. This result indicates that hereditary epigenetic factors play a major role in determining cycle exit of bone marrow stromal
cells.
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All authors Alessandro Allegrezza, Riccardo Beschi, Domenico Caudo, Andrea Cavagna, Alessandro Corsi, Antonio Culla, Samantha Donsante, Giuseppe Giannicola, Irene Giardina, Giorgio Gosti, Tomas S. Grigera, Stefania Melillo, Biagio Palmisano, Leonardo Parisi, Lorena Postiglione, Mara Riminucci, Francesco Saverio Rotondi
Computational Physics · Cross-listed from cond-mat.mtrl-sci
Stability Criteria and Optoelectronic Properties of Mg3ZBr3 (Z = As, Sb, Bi) Perovskites for Evaluating the Performance in PIN Photo Diode
Md Mohiuddin, Mohammed Mehedi Hasan and Alamgir Kabir
The toxicity and stability issues of lead-based perovskites motivate the search for non-toxic, durable alternatives. This work examines lead-free $\mathrm{Mg_3ZBr_3}$ ($Z=\mathrm{As,Sb,Bi}$) halide perovskites as optoelectronic materials, with emphasis on $\mathrm{Mg_3AsBr_3}$ and $\mathrm{Mg_3SbBr_3}$. First-principles calculations establish cubic $Pm\bar{3}m$ frameworks stabilized by strong Mg–Br linkages, and indirect band gaps of $2.0645\,\mathrm{eV}$ for $\mathrm{Mg_3AsBr_3}$ and $1.6533\,\mathrm{eV}$ for $\mathrm{Mg_3SbBr_3}$ obtained using hybrid functionals. Optical spectra show a rapid rise in absorption above the gap and an increasing static dielectric response along $\mathrm{As}\rightarrow\mathrm{Sb}\rightarrow\mathrm{Bi}$, indicating strengthened light–matter coupling.
Phonon dispersions lack imaginary branches, confirming dynamical stability, and exhibit large mode anharmonicity (Grüneisen signatures) consistent with soft-
lattice heat transport. Moving down the pnictogen series expands the
lattice and lowers the Goldschmidt tolerance factor, while enhanced pnictogen–Br $p$-orbital hybridization and stereochemically active $n\mathrm{s}^{2}$ lone pairs (Sb, Bi) narrow the band gap and increase the optical dielectric response. Elastic analyses confirm Born stability and moderate stiffness, with Hill-averaged bulk
moduli decreasing from approximately $44\,\mathrm{GPa}$ ($\mathrm{Mg_3AsBr_3}$) to $35\,\mathrm{GPa}$ ($\mathrm{Mg_3BiBr_3}$). Drift–
diffusion $p$–$i$–$n$ simulations qualitatively track band-edge-limited spectra, aligning with the computed gaps. Together, these results position these materials as promising lead-free candidates for stable thin-film photodiode and photovoltaic applications.
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Applied Physics
Electromagnetic Field Exposure Assessment and Mitigation Strategies for Wireless Power Transfer Systems: A Review and Future Perspectives
Akimasa Hirata, Teruo Onishi, Naoki Shinohara et al. (+10 more)
Wireless power transfer (WPT) technologies are increasingly being applied in fields ranging from consumer electronics and electric vehicles to space-based energy systems and medical implants. While WPT offers contactless power delivery, it introduces electromagnetic field (EMF) emissions, necessitating careful assessment to address safety and public health concerns. Exposure guidelines developed by ICNIRP and IEEE define frequency-dependent limits based on internal quantities, such as electric field strength and specific absorption rate, intended to prevent tissue nerve stimulation < 100 kHz and heating > 100 kHz, respectively. Complementing these guidelines, assessment standards including the International Electrotechnical Commission (IEC)/IEEE 63184 and IEC Technical Report 63377, provide practical procedures for evaluating the EMF exposure in WPT systems. This review offers a comparative overview of major WPT modalities, with a focus on recent developments in computational dosimetry and standardized assessment techniques for the complex, non-uniform fields typical of WPT environments. It also discusses electromagnetic interference with medical devices and exposure scenarios involving partial body proximity and various postures. A notable observation across modalities is the considerable variability, often spanning an order of magnitude, in the allowable transfer power, depending on the field distribution and assessment approach. Remaining challenges include the lack of harmonized guidance for intermediate frequencies and localized exposure, underscoring the importance of further coordination in international standardization efforts. Addressing these issues is essential for the safe and widespread deployment of WPT technologies.
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All authors Akimasa Hirata, Teruo Onishi, Naoki Shinohara, Valerio De Santis, Yinliang Diao, Mauro Feliziani, Takashi Hikage, Junqing Lan, Francesca Maradei, Keishi Miwa, Alexander Prokop, Yujun Shin, Seungyoung Ahn
Computational Physics
LENNs: Locally Enhanced Neural Networks for High-Fidelity Modeling in Solid Mechanics
Zhihong Lai, Luyang Zhao and Qian Shao
Despite prior advances in PINNs, significant challenges remain in localized solid mechanics problems because of the limitations of single network formulations in simultaneous resolution of smooth global responses and near-tip singularities, and inadequacy in discontinuity representation, leading to unstable training and limited accuracy. To address the challenges, we propose Locally Enhanced Neural Networks (LENNs) that characterize localized discontinuities in solid mechanics via multilevel modeling. In particular, this novel framework employs a global network for the bulk solution and activates a local network in localized area for non-smooth response, coupled through a smooth window function that enables weighted superposition of local and global solutions. Moreover, the local network embeds additional functions that encode the discontinuous information into the input to capture localized non-smooth mechanical behaviors. Finally, the composite solution is substituted into the total potential energy functional for unified optimization. With this structure, the method resolves the conflict of single network in representing both smooth global and singular local fields without additional interface-loss terms and amplifies the contribution of localized critical features in energy optimization. We focus on a series of numerical experiments in solid mechanics to demonstrate the performance of the method. Results show that LENNs perform well in addressing localized discontinuous problems and provide accurate predictions for both displacement and stress fields.
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Fluid Dynamics
Characterizing primary atomization of cryogenic LOX/Nitrogen and LOX/Helium sprays by visualizations coupled to Phase Doppler Interferometry
Nicolas Fdida, Yves Mauriot, Lucien Vingert et al. (+2 more)
There is a need for experimental data in conditions representative injection in rocket engines to validate or initiate droplet formation models used in numerical simulations. A new cryogenic vessel was built upon the MASCOTTE test bench to study the atomization of a single oxygen
liquid jet, under non-reactive conditions, with simultaneous optical diagnostics. A test plan was built to explore the fiber-type regime occurring in
liquid rocket injection systems, with a fixed Reynolds number and a large range of Weber number and momentum flux ratio, compared to existing studies. High-speed images are used to describe qualitatively the fiber-type regime and to visualize were droplets are present, in order to prepare the drop-size measurements. A Phase Doppler Interferometer is used to measure the size and velocity of droplets produced by atomization of a
liquid oxygen jet by a co-flowing gas. Droplet size and velocity measurements were performed with a PDI close to the nozzle exit in order to provide data on droplets produced by the primary atomization process, which can be useful for numerical simulations initialisation. The radial evolutions of the axial velocity and of the drop size distribution show similar trends as observed in the literature. The axial velocity is investigated for different operating conditions with helium or nitrogen as atomizing gas, showing an increase on the side of the spray. The radial
evolution of the droplet size shows a translation of the drop size distribution on the edge of the spray towards the smaller sizes, indicating that the biggest
liquid elements stay close to the LOX jet.
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All authors Nicolas Fdida, Yves Mauriot, Lucien Vingert, Arnaud Ristori, Marie Théron
Fluid Dynamics
Characterization of a kerosene liquid jet injected in a high temperature Mach 2 supersonic crossflow
Nicolas Fdida, Nathan Mallart-Martinez, Thomas Le Pichon et al. (+1 more)
Near field
liquid structures and penetration of a kerosene jet injected in a Mach 2 crossflow were studied experimentally in the LAPCAT-II Dual Mode Ramjet Combustor at Onera, using high spatial and temporal resolution imaging techniques. The experiments performed in this study provide measurements in high temperature conditions, with kerosene as
liquid fuel to bring new data in these conditions. The fuel spray is injected through a single orifice, perpendicularly to the supersonic flow, at temperatures from ambient to 1500 K and jet-to-crossflow momentum flux ratio from 3.1 to 8.6. Five different test cases are defined to show independently the influence of the injection ratio and the supersonic flow temperature on the
liquid jet atomization. A high spatial resolution imaging system is used to detail the characteristic spatial scales of this atomization process in the supersonic crossflow. The surface waves and droplets produced in the windward side of the
liquid jet are characterized qualitatively. High-resolution visualizations bring a new insight of the droplet trajectories in the leeward region of the jet. Schlieren imaging is used to detail the complex shock wave structures in such a supersonic flow. Penetration of the kerosene jet is measured by shadowgraphy and schlieren imaging in five test cases and compared to other studies of the literature whenever it is possible. High-speed schlieren performed at 210 kHz is also performed to capture the temporal dynamics of the shocks and measure the
liquid jet velocity.
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All authors Nicolas Fdida, Nathan Mallart-Martinez, Thomas Le Pichon, Axel Vincent-Randonnier
Optics
Interface States in Space-Time Photonic Crystals: Topological Origin, Propagation and Amplification
Alejandro Caballero, Thomas F. Allard and Paloma A. Huidobro
Studying the
topology of spatiotemporal media poses a fundamental challenge: their remarkable properties stem from breaking spatial and temporal
symmetries, yet this same breaking obscures their topological characterization. Here, we show that space-time
symmetries persist in
crystals with travelling-wave modulations whose velocities can be either lower (subluminal) or higher (superluminal) than the speed of light, enabling the study of their topological properties and the prediction of spatiotemporal interface states. For each modulation regime, we use a Lorentz transformation to a frame in which the modulation depends on only one of the transformed variables. Then, we identify a conserved joint parity-time-reversal
symmetry in the new variables that enforces the quantization of a spatiotemporal Zak phase, elevating it to a $\mathbb{Z}_2$ topological invariant. Finally, we calculate the associated interface states and uncover unique features arising from time-varying effects, including selective directional amplification, propagation along subluminal and superluminal boundaries, frequency- and momentum-converted replicas, and broadband amplification even in the absence of momentum gaps. Our framework holds for spatiotemporal modulations of any velocity, unifying a wide class of systems that includes photonic time
crystals, and clarifying their topological origin.
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Atomic Physics
Probing Nuclear Interactions Through Isotope Shift Spectroscopy of Mercury
Thorsten Groh, Felix Affeld and Simon Stellmer
We present precision isotope shift spectroscopy of the $\mathrm{6s^{2}}\, {}^{1}\mathrm{S}_{0}{\rightarrow\,}\mathrm{6s\, 6p}\, {}^{3}\mathrm{P}_{1}$ intercombination line and the $\mathrm{6s\,6p}\, {}^{3}\mathrm{P}_{1}{\rightarrow\,}\mathrm{6s\,6d}\, {}^{3}\mathrm{D}_{J}$ ($J=1,2$) transitions in neutral mercury, performed on the five naturally abundant even isotopes, including the low-abundant isotope ${}^{196}\mathrm{Hg}$. Using
laser-cooled atoms in a magneto-optical trap, we achieve uncertainties down to $20\,\mathrm{kHz}$, resolving the isotope shift to a fractional uncertainty of ${\sim}\,2{\,\times\,}10^{-6}$. A King plot analysis comparing our ${}^{1}\mathrm{S}_{0}{\rightarrow}{}^{3}\mathrm{P}_{1}$ data to previous results on the $\mathrm{6s\,6p}\,{}^{3}\mathrm{P}_{2}{\rightarrow\,}\mathrm{6s\,7s}\,{}^{3}\mathrm{S}_{1}$ line reveals a nonlinearity with $4.9\,\sigma$ significance. Our generalized King plot nonlinear decomposition analysis discusses potential contributions from quadratic ($\propto \delta\langle r^{2}\rangle^{2}$) and higher order field shifts ($\propto \delta\langle r^{4}\rangle$) also induced by
nuclear deformation. These measurements yield new insights into the structure of the $\mathrm{Hg}$
nucleus and provide
benchmarks for
nuclear-structure models. They further establish mercury as a potential platform to search for hypothetical Yukawa-type
boson-mediated forces coupling electrons to
neutrons.
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