Space Physics · Cross-listed from astro-ph.SR
Relation between sunspots and solar EUV irradiance changes during the Gleissberg cycle
Kalevi Mursula
Sunspots are the standard measure of
solar magnetic activity, which are also used to estimate
solar spectral irradiance over centennial time scales. However, because of the lack of homogeneous, century-long spectral measurements, the long-term relation of sunspots and spectral irradiance has not been independently validated. Here we aim to study the relation between sunspots and
solar extreme ultra-violet (EUV) irradiance during the last 130 years, over the latest Gleissberg cycle, also called the Modern Maximum, when sunspot cycle heights varied by a factor of 2.5. We calculate the daily variation of the geomagnetic declination at six reliable, long-running stations, whose amplitude (or range) can be used as a centennial proxy of
solar EUV irradiance. We also compare this geomagnetic proxy to the
solar MgII index of EUV irradiance over the 40-year interval of overlap. We find that sunspot activity dominated over EUV irradiance when cycle heights increased in the early 20th century during the growth and maximum of the Modern Maximum, but EUV irradiance dominated over sunspots during the decay of the MM, when cycle heights decreased in the late 1900s. Our results suggest that the spot-facula ratio varies during Gleissberg cycle -type large oscillations of
solar/
stellar activity. This modifies the estimated
stellar evolution of the relation between brightness and chromospheric activity of the Sun and Sun-like
stars.
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Fluid Dynamics · Cross-listed from math.AP
On the Propulsion of a Rigid Body in a Viscous Liquid by Time-Periodic Force with a Zero Average
Joris Edelmann, Giovanni P. Galdi, Mher M. Karakouzian et al. (+1 more)
We perform analytical and numerical analyses of the propulsion of a rigid body in a viscous fluid subjected to a periodic force with zero average over a period. This general formulation specifically addresses the significant case, where propulsion is generated by the oscillation of a mass located in an internal cavity of the body. We provide a rigorous proof of the necessary and sufficient conditions for propulsion at the second order of magnitude of the force. These conditions are implemented and confirmed by numerical tests for bodies without fore-and-aft
symmetry, while they are silent for bodies with such
symmetry, like round ellipsoids. Consequently, in this case, propulsion can only occur at an order higher than the second. This problem is investigated by numerically integrating the entire set of equations, and the result shows that, in fact, propulsion does occur, thus opening new avenues for further analytical studies.
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All authors Joris Edelmann, Giovanni P. Galdi, Mher M. Karakouzian, Thomas Richter
Plasma Physics
Matthew E. Caplan, Nevin T. Smith, Dany Yaacoub et al. (+3 more)
We present calculations of
diffusion coefficients in grain boundaries in Yukawa
crystals for astrophysics. Our methods follow from our recent work calculating
diffusion coefficients in perfect body-centered cubic
crystals. These
diffusion coefficients show only a weak dependence on the
crystal orientations at the grain boundary and are consistent with those expected for a supercooled
liquid scaled down by one to two orders of magnitude. We argue that the local disorder at the grain boundary produces a landscape of potential barriers similar to that of an amorphous
liquid thin film, significantly reducing activation barriers to diffusive hops relative to the bulk solid. This also introduces a screening dependence, such that boundary
diffusion does not exhibit the same universality as the bulk
crystal. These
diffusion coefficients suggest that grain boundaries may be a dominant source of viscous dissipation in
neutron star crusts.
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All authors Matthew E. Caplan, Nevin T. Smith, Dany Yaacoub, Roberto F. Serrano, Elias Taira, Ashley Bransgrove
Plasma Physics
Significant Amplification of Turbulent Energy Dissipation through the Shock Transition at Mars
Wence Jiang, Hui Li, Nahuel Andrés et al. (+3 more)
Turbulence is fundamental to energy transfer across scales in space and astrophysical
plasmas. Bow shock interactions have long been hypothesized to significantly modify
turbulence in planetary environments, yet the quantification of such effects and their parametric dependencies remain largely unaddressed. Using in situ long-term high-time resolution measurements from NASA's MAVEN mission, we report the first observational characterization of the
evolution and parametric dependence of the
turbulence energy cascade rate $\varepsilon_C$ at magnetohydrodynamic (MHD) scales. Key findings reveal an averaged three-order-of-magnitude enhancement in $\varepsilon_C$ when transitioning from the
solar wind to the magnetosheath. Notably, downstream measurements of oblique and quasi-perpendicular shocks exhibit higher energy dissipation rates than those of quasi-parallel configurations. These results provide the first direct evidence linking shock obliquity to
turbulence amplification, offering key insights into shock-mediated
turbulence in similar but inaccessible systems.
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All authors Wence Jiang, Hui Li, Nahuel Andrés, Lina Hadid, Daniel Verscharen, Chi Wang
Optics · Cross-listed from quant-ph
Thermodynamic decoupling in the deep-strong coupling regime
S. Palafox, M. Salado-Mejía, M. Santiago-García et al. (+1 more)
In the deep-strong coupling (DSC) regime, the interaction between light and matter exceeds their bare frequencies, leading to an effective decoupling. Theoretical and experimental evidence for this behavior has relied solely on measurements of local observables at
equilibrium. However, such a local approach is insufficient to accurately describe energy fluxes in critical and nonequilibrium phenomena. Here, we use a two-terminal
quantum junction to derive a thermodynamically consistent global master equation. We demonstrate that the associated heat current, a key nonlocal observable in any
quantum thermal machine, also approaches zero in this extreme coupling scenario, underscoring the role of virtual
photons in the
vacuum ground state. Our results indicate that the decoupling is a more general feature of the DSC regime, with implications for
quantum thermotronics.
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All authors S. Palafox, M. Salado-Mejía, M. Santiago-García, R. Román-Ancheyta
Chemical Physics · Cross-listed from quant-ph
Fragmentation of Virtual Orbitals for Quantum Computing: Reducing Qubit Requirements through Many-Body Expansion
Federico Zahariev, Vassiliki-Alexandra Glezakou and Mark S. Gordon
We introduce
quantum virtual-orbital fragmentation (Q-FVO), a systematic method for reducing the largest active space in correlated
quantum-chemistry calculations. The complete occupied space is retained, the localized virtual space is partitioned into chemically motivated fragments, and the correlation energy is recovered through an inclusion-exclusion many-body expansion. Across six molecular
benchmarks, the largest one-body Q-FVO calculations reduce the
qubit requirement by 46 to 66 percent, while two-body calculations reduce it by approximately 31 to 42 percent relative to the corresponding unfragmented spaces. Two-body expansions recover most of the correlation energy, with errors of 0.9 to 7.5 kcal/mol; three-body expansions are below 1 kcal/mol for all CCSD tests and remain below 2 kcal/mol at CCSD(T). Illustrative statevector UCCSD calculations also reduce implementation-reported
circuit depth while retaining accuracy below 1 kcal/mol. Q-FVO can be nested inside Q-EFMO real-space fragmentation and, in turn, the resulting cluster can be embedded in a Q-EFP environment. The hierarchy therefore reduces
quantum-resource growth along three complementary dimensions: environment, molecular fragments, and virtual-orbital space.
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Optics
Pty-Chi: A PyTorch-based modern ptychographic data analysis package
Ming Du, Hanna Ruth, Steven Henke et al. (+11 more)
Ptychography has become an indispensable tool for high-resolution, non-destructive imaging using coherent light sources. The processing of ptychographic data critically depends on robust, efficient, and flexible computational reconstruction software. We introduce Pty-Chi, an open-source ptychographic reconstruction package built on PyTorch that unifies state-of-the-art analytical
algorithms with automatic differentiation methods. Pty-Chi provides a comprehensive suite of reconstruction
algorithms while supporting advanced experimental parameter corrections such as orthogonal probe relaxation and multislice modeling. Leveraging PyTorch as the computational backend ensures vendor-agnostic GPU acceleration, multi-device parallelization, and seamless access to modern optimizers. An object-oriented, modular design makes Pty-Chi highly extendable, enabling researchers to prototype new imaging models, integrate machine learning approaches, or build entirely new workflows on top of its core components. We demonstrate Pty-Chi's capabilities through challenging case studies that involve limited coherence, low overlap, and unstable illumination during scanning, which highlight its accuracy, versatility, and extensibility. With community-driven development and open contribution, Pty-Chi offers a modern, maintainable platform for advancing computational ptychography and for enabling innovative imaging
algorithms at synchrotron facilities and beyond.
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All authors Ming Du, Hanna Ruth, Steven Henke, Yi Jiang, Viktor Nikitin, Ashish Tripathi, Junjing Deng, Jeffrey Klug, Peco Myint, Tao Zhou, Nicholas Schwarz, Mathew Cherukara, Alec Sandy, Stefan Vogt
Instrumentation and Detectors
Boron Nitride Coatings for the Enhanced Detection of Neutrons in CR-39
Noah DAmico, Sandeep Puri, Ian Jones et al. (+4 more)
The
neutron detection efficiency of Columbia Resin 39 (CR-39)
nuclear track detectors was assessed for AmBe, 252Cf, and D-T (14 MeV)
neutron source spectra. A boron nitride (BN) coating for CR-39 was developed to enhance the
neutron detection efficiency by converting
neutrons into energetic alpha particles through the well-known 10B(n,a)7Li reaction. Separate partially coated CR-39 pieces were exposed to each
neutron source and subsequently analyzed under optical microscope and through large-area Scanning Electron Microscopy (SEM) imaging over the irradiated area. The detection efficiency (tracks per
neutron) was evaluated for each source spectra under optical and scanning electron microscopes and with or without BN coating. This resulted in a comprehensive guide to
neutron detection with various sources using CR-39.
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All authors Noah DAmico, Sandeep Puri, Ian Jones, Andrew Gillespie, Cuikun Lin, Bo Zhao, R. V. Duncan
Optics
Electrical-control of third-order nonlinearity via Fano interference
Deniz Eren Mol, İbrahim Asr{\i}n Üzgüç, Ulaş Eyüpoğlu et al. (+6 more)
Programmable photonic computers necessitate the integration of electrically-tunable compact components into the photonic devices. In the state-of-the-art photonic
quantum computers~(PQCs), phase-shift and displacement gates can be implemented in an electrically-programmable way. An efficient PQC, however, necessitates also the tuning of third or higher order nonlinearity for implementing continuous-variable~(CV) gates at a shorter sequence. Here, we demonstrate that such an optical component can be designed using Fano interference and Stark effect in a nonlinear nano-plasmonic system. We study the coupling of a broadband bright plasmon mode to a narrow linewidth
quantum object(s), QO(s). We show that by shifting the level-spacing of the QO via Stark effect, one can continuously tune the third-order nonlinearity gate within a picosecond response time. We also present finite-difference time domain~(FDTD) simulations that take the retardation effects into account. In addition, we also show that enhancement due to Fano interference degrades if the QOs are positioned randomly as each QO introduces different phases. This reveals the importance of the spatial extent of the QO-ensemble to be employed in the experiments.
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All authors Deniz Eren Mol, İbrahim Asr{\i}n Üzgüç, Ulaş Eyüpoğlu, Kübra Atar, Sena Taşk{\i}ran, Taner Tarik Aytas, Rasim Volga Ovali, Ramazan Sahin, Mehmet Emre Tasgin
Optics · Cross-listed from quant-ph
Picosecond Wireless Synchronization with Entangled Photons via Grid-Based Quantum Coverage in Indoor Optical Systems
Hossein Safi, Mohammad Taghi Dabiri, Mazen Hasna et al. (+2 more)
In this paper, we present a robust
entanglement-assisted synchronization framework for indoor optical wireless systems that explicitly captures the coupling between spatial beam geometry and temporal synchronization accuracy. Unlike conventional approaches that treat beam steering and timing estimation independently, a unified spatio temporal model is developed that links user position uncertainty to the Cramer Rao lower bound of the synchronization error. The framework incorporates key physical impairments, including multipath dispersion, non Gaussian detector jitter, and spatially correlated localization errors. Through analytical modeling and extensive simulations, we show that the proposed system exhibits graceful performance degradation under heavy tailed positioning uncertainty and remains stable in the presence of multipath induced bias. Using realistic single
photon detector parameters, the results indicate that synchronization accuracy below $10$ picoseconds can be maintained across a wide range of operating conditions. This level of precision provides a scalable foundation for
quantum enabled indoor wireless networks.
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All authors Hossein Safi, Mohammad Taghi Dabiri, Mazen Hasna, Iman Tavakkolnia, Harald Haas
Accelerator Physics
Concepts Rookie Book
Dennis Barak, Beau F. Harrison and Adam Watts
This book begins with the basic accelerator knowledge required to understand the latter chapters. This is followed by topics from Fermilab accelerator specifics to general accelerator physics concepts. These chapters are accompanied by descriptions of the instrumentation and utilities required to operate a high-energy physics laboratory. Last, we discuss the role of operators in safety at the lab.
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Optics
Opto-Electronic Clock Regeneration – A Tutorial
Palle Jeppesen and Bjarne Tromborg
A tutorial on opto-electronic clock regeneration at very high bit rates beyond reach with purely electronic solutions is given. Emphasis is placed on sum frequency generation in a nonlinear material such as LiNbO3. We first provide a basic introduction to CR (clock recovery) and a PLL (phase-locked loop); two examples are considered, an input signal frequency step and a slow input signal frequency. Next we discuss opto-electronic clock recovery based on an OPLL (opto-electronic PLL). The OPLL contains a phase comparator consisting of a planar LiNbO3 waveguide, a lowpass filter, a VCO (voltage controlled oscillator) and a local oscillator
laser. The error signal from the comparator determined by the difference in electrical phase between the signal and the VCO controls the VCO. The VCO has two outputs; one that modulates the local oscillator
laser and another that triggers a decision
circuit that samples the output from the OPLL. The VCO is continuously adjusted by the OPLL so that it will ensure sampling of the signal in the optimal moments.
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History and Philosophy of Physics
Philip Warren Anderson
Premala Chandra, Piers Coleman and Clare C. Yu
Philip Warren Anderson was a pioneering theoretical physicist whose work fundamentally shaped our understanding of complex systems. Anderson received the Nobel Prize in Physics in 1977 for his groundbreaking research on localization and magnetism, yet he did so much more. His work on magnetism included antiferromagnetism, superexchange, the Kondo problem and local
magnetic moments in metals. Anderson pointed out the importance of disorder through his work on localization, non-crystalline solids and
spin glasses. In superconductivity, he is known for the dirty
superconductor theorem, showing the gauge-invariance of the BCS theory, his study of flux creep, and for his collaboration with experimentalists to realize the Josephson effect. Anderson's resonating valence bond theory may yet play an important role in high temperature superconductivity. Anderson was also fascinated by broken
symmetry, and he laid the theoretical groundwork for what is now known as the Anderson-
Higgs mechanism, showing how gauge
bosons can acquire mass - an insight that played a foundational role in the Standard Model of particle physics. In his seminal "More is Different" paper, Anderson argued that the collective emergent phenomena that arise in complex interacting systems cannot be deduced from their fundamental parts. Anderson's legacy endures not only through the lasting impact of his scientific work but also through his influence on generations of physicists who continue to explore the rich landscape of collective behavior in nature.
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Atomic Physics · Cross-listed from cond-mat.quant-gas
Trapping, manipulating and probing ultracold atoms: a quantum technologies tutorial
Louise Wolswijk, Luca Cavicchioli, Giuseppe Vinelli et al. (+12 more)
Engineered ultracold atomic systems are a valuable platform for fundamental
quantum mechanics studies and the development of
quantum technologies. At near zero absolute temperature, atoms exhibit macroscopic phase coherence and collective
quantum behavior, enabling their use in precision metrology,
quantum simulation, and even information processing. This review provides an introductory overview of the key techniques used to trap, manipulate, and detect ultracold atoms, while highlighting the main applications of each method. We outline the principles of
laser cooling,
magnetic and optical trapping, and the most widely used techniques, including optical
lattices and tweezers. Next, we discuss the manipulation methods of atomic internal and external degrees of freedom, and we present atom interferometry techniques and how to leverage and control interatomic interactions. Next, we review common ensemble detection strategies, including absorption and fluorescence imaging, state-selective readout, correlation and
quantum non-demolition measurements and conclude with high-resolution approaches. This review aims to provide newcomers to the field with a broad understanding of the experimental toolkit that underpins research in ultracold atom physics and its applications across
quantum science and technology.
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All authors Louise Wolswijk, Luca Cavicchioli, Giuseppe Vinelli, Mauro Chiarotti, Ludovica Donati, Marcia Frometa Fernandez, Diego Hernández Rajkov, Christian Mancini, Paolo Vezio, Tianwei Zhou, Giulia Del Pace, Chiara Mazzinghi, Nicolò Antolini, Leonardo Salvi, Vladislav Gavryusev
Atomic Physics · Cross-listed from astro-ph.HE
The Opacity Project: R-Matrix Calculations for Opacities of High-Energy-Density Astrophysical and Laboratory Plasmas
Anil K. Pradhan and Sultana N. Nahar
Accurate determination of opacity is critical for understanding radiation transport in both astrophysical and laboratory
plasmas. We employ atomic data from R-
Matrix calculations to investigate radiative properties in high-energy-density (HED)
plasma sources. Specifically, we analyze environments such as the base of the convective zone (BCZ) of the Sun 2 x 10^6$ K, N_e = 10^{23}/cc and the inertial confinement fusion (ICF) device at the Sandia Z facility 2.11 x 10^6 K, N_e = 3.16 x 10^{22}/cc. We calculate Rosseland Mean Opacities (RMO) within a range of temperatures and densities and analyze how they vary under different
plasma conditions. In this study, we specifically focus on electron collisional and Stark ion microfield broadening effects on autoionizing resonances in photoabsorption cross sections. Our results are relevant to astrophysical models, particularly in the context of the
solar opacity problem, and provide insights into discrepancies between theoretical calculations and experimental measurements. In addition, we investigate the equation-of-state (EOS) and its impact on opacities. In addition, we examine the equation-of-state (EOS) and its impact on opacities of the "chemical picture" Mihalas-Hummer-Dappen EOS with respect to level populations of excited levels included in the R-
matrix calculations. This study should contribute to improving opacity models of HED sources such as
stellar interiors adn laboratory fusion
plasma experiments.
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Atmospheric and Oceanic Physics
CSU-PCAST: A Dual-Branch Transformer Framework for medium-range ensemble Precipitation Forecasting
Tianyi Xiong, Haonan Chen, Kelly Mahoney et al. (+3 more)
Accurate medium-range precipitation
forecasting is essential for hydrometeorological risk management but remains challenging for both numerical weather prediction (NWP) systems and data-driven models. We present CSU-PCAST, a deep learning-based ensemble
forecasting framework for global precipitation prediction. The model is trained using ERA5 atmospheric and surface variables at 0.25{\deg} resolution with precipitation labels from NASA's IMERG
dataset. CSU-PCAST uses 57 prognostic variables and static geographical fields to predict both atmospheric states and 6-h accumulated precipitation. The framework employs a Swin
Transformer backbone with
stochastic noise conditioning, temporal
embeddings, and a dual-branch decoder for precipitation and non-precipitation variables. During inference, CSU-PCAST is initialized from operational GFS analyses and generates 30 ensemble members out to 15 days using an autoregressive strategy. Evaluation against GEFS over the full year of 2023 shows improved precipitation forecast skill at short lead times, including higher Critical Success Index (CSI) and lower RMSE during the first several forecast days. CSU-PCAST also reduces GEFS wet bias for light precipitation and dry bias at heavier precipitation thresholds. Probabilistic verification demonstrates lower CRPS, higher Brier Skill Scores at several thresholds, and improved ensemble reliability relative to GEFS, although both systems remain underdispersive. A case study of the Sanba extreme precipitation event further shows improved spatial structure and exceedance-probability guidance. These results demonstrate the potential of CSU-PCAST for short-to-medium-range ensemble precipitation
forecasting while highlighting remaining challenges in extreme precipitation prediction and ensemble calibration.
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All authors Tianyi Xiong, Haonan Chen, Kelly Mahoney, Jingyin Tang, Tim Smith, Janice Bytheway
Medical Physics
Acoustic Emission Cascade Predicting Progression to Failure of Rock and Bone
Andrew P. Bunger, Yunxing Lu, Ayyaz Mustafa et al. (+1 more)
Quasi brittle materials such as rock and bone are understood to fail via microcrack coalescence. The accompanying Acoustic Emission (AE) event rate is known to increase as failure progresses. Here we examine the progression of the AE event rate for both rock and bone under conditions where failure progresses under fixed loading. The experiments for rock entail subjecting granite beams to a fixed loading under three point bending and monitoring the time-dependent failure. For bone, human cadaver skulls are loaded under pinning loads similar to those used for immobilization of the head for neurosurgical procedures. AE rates are shown to be consistent with a rate dependent material failure law including a quasi-linear cascade of the inverse AE energy rate in the lead up to failure that is shown here to arise because of a coupling wherein a response rate is a power law of a driver and the driver is, in turn, a power law of the accumulated response. For both materials and experimental configurations this cascade provides warning of impending failure. For granite beams there is accurate prediction of failure time over the final 30 percent of the specimens lifetimes, which ranged from 35 seconds to two days. For skull fracture, the commencement of the failure cascade provides 30-70 seconds for warning of failure, which would be sufficient for basic remedial action to avoid patient injury in a
surgical application.
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All authors Andrew P. Bunger, Yunxing Lu, Ayyaz Mustafa, Michael M. McDowell
Computational Physics · Cross-listed from math.NA
Well-Posedness and Approximation of Weak Solutions to Time Dependent Maxwell's Equations with $L^2$-Data
Harbir Antil
We study Maxwell's equations in conducting media with perfectly conducting boundary conditions on Lipschitz domains, allowing rough material coefficients and $L^2$-data. Our first contribution is a direct proof of well-posedness of the first-order weak formulation, including solution existence and uniqueness, an energy identity, and continuous dependence on the data. The argument uses interior-in-time mollification to show uniqueness while avoiding reflection techniques. Existence is via the well-known Galerkin method (cf.~Duvaut and Lions \cite[Eqns.~(4.31)–(4.32), p.~346; Thm.~4.1]{GDuvaut_JLLions_1976a}). For completeness, and to make the paper self-contained, a complete proof has been provided. Our second contribution is a structure-preserving semi-discrete finite element method based on the Nédélec/Raviart–Thomas de Rham complex. The scheme preserves a discrete Gauss law for all times and satisfies a continuous-in-time energy identity with stability for nonnegative conductivity. With a divergence-free initialization of the
magnetic field (via potential reconstruction or constrained $L^2$ projection), we prove convergence of the semi-discrete solutions to the unique weak solution as the mesh is refined. The analysis mostly relies on projector consistency, weak-* compactness in time-bounded $L^2$ spaces, and identification of time derivatives in dual spaces.
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Optics
Multipolar Decomposition of Magnetic Circular Dichroism in Arbitrarily Shaped Magneto-Dielectric Scatterers
Jhon James Hernández-Sarria, João Paulo Silva Dias, Luciano Leonel Mendes et al. (+3 more)
Multipole expansion methods have been primarily used for analyzing the electromagnetic scattering from non-
magnetic isotropic dielectric scatterers, and studies about the scattering from
magnetic objects seem to be lacking. In this work, we used the multipolar expansion framework for decomposing the electromagnetic scattering by dielectric particles with
magnetic properties. Magnetization current contributions were explicitly accounted for by using the vector spherical harmonics to compute the electric and
magnetic multipole contributions of arbitrary order. The exact analytical expressions for the corresponding spherical multipole coefficients were employed, with the scattering efficiencies being used to distinguish the dielectric and
magnetic contributions of each multipole. This enables the analysis of scattering from arbitrarily shaped, anisotropic, and inhomogeneous
magnetic scatterers. It also provides a tool for studying non-reciprocal devices that exploit
magnetic resonances in
magnetic-dielectric materials. Calculations were made for an experimentally feasible system, namely for ferrite-based scatterers operating in the microwave regime. These materials are of interest in
radio frequency (RF) applications due to their
magnetic activity. We demonstrated analytically that the
magnetic circular dichroism in a
magnetic-dielectric scatterer in the Faraday geometry can be decomposed into individual multipole contributions. The analytical results indicate that multipole resonances associated with magnetization currents can be even stronger than multipole contributions from conventional dielectric currents. It is worth noting that these analytical results were verified through comparison with numerical results from finite element method (FEM) simulations in COMSOL Multiphysics.
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All authors Jhon James Hernández-Sarria, João Paulo Silva Dias, Luciano Leonel Mendes, Nicolò Maccaferri, Osvaldo N. Oliveira Jr., Jorge Ricardo Mejía-Salazar
Applied Physics
Magnetic tunnel junction as a real-time entropy source: Field-Programmable Gate Array based random bit generation without post-processing
Troy Criss, Ahmed Sidi El Valli, Naomi Li et al. (+2 more)
We demonstrate a method to generate application-ready truly random bits from a
magnetic tunnel junction driven by a Field-Programmable Gate Array (FPGA). We implement a real-time feedback loop that stabilizes the switching probability near 50% and apply an XOR operation, both on the FPGA, to suppress short-term correlations, together mitigating long-term drift and bias in the bitstream. This combined approach enables NIST-compliant random bit generation at 5~Mb/s without post-processing, providing a practical hardware solution for fast and reliable true random number generation. Beyond cryptographic applications, these capabilities open opportunities for
stochastic hardware accelerators, probabilistic computing, and large-scale modeling where real-time access to unbiased randomness is essential.
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All authors Troy Criss, Ahmed Sidi El Valli, Naomi Li, Andrew Haas, Andrew D. Kent
Optics
Phonon Polaritons and Epsilon Near Zero Modes in Sapphire Nanostructures
Milad Nourbakhsh, Kiernan E. Arledge, Vincent R. Whiteside et al. (+3 more)
Surface
phonon polaritons (SPhPs) are promising candidates for enhanced light–matter interactions due to their efficient and low-loss light confinement features. In this work, we present unique light-matter interactions in saphhire within its Reststrahlen bands (RBs) across the long-wave infrared (LWIR) spectrum ($\omega = 385$-$1050~\mathrm{cm}^{-1}$). Particularly, we investigated the nanocone-patterned sapphire resonator array, with specific
attention to its in-plane and out-of-plane permittivity components. Through
Fourier transform infrared spectroscopy measurement and full-wave photonic simulations, we identified a range of optical excitations in the RBs, including three SPhPs, two
hyperbolic volume
phonon polaritons (HVPhPs), and one epsilon-near-zero (ENZ) mode. The depth-resolved confocal Raman spectroscopy revealed strongly enhanced Raman signals on the nanostructured surface, suggesting the mode coupling between
phonons and
phonon-polaritons, which was further confirmed by the finite element modeling of polarizability. This exploratory study provides in-depth insights into the dynamics of LWIR
phonon polaritons and ENZ modes in the nanostructured sapphire, indicating its great potential for innovative nanophotonic applications.
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All authors Milad Nourbakhsh, Kiernan E. Arledge, Vincent R. Whiteside, Jiangang Ma, Joseph G. Tischler, Binbin Weng
Atomic Physics · Cross-listed from cond-mat.quant-gas
Radial selection rule for the breathing mode of a harmonically trapped gas
Miguel Tierz
Within a fixed hyperangular channel $s>0$ of a harmonically trapped system, the $1/R^2$ perturbation is absorbed exactly into a shift of the channel parameter, $s\to s_\eta$, so the single-channel model remains a harmonic oscillator with a shifted inverse-square term: radial gaps stay at $2\hbar\omega$ exactly and no monopole spectral weight appears at forbidden frequencies at any order. The first-order cancellation is also proved independently by a compact algebraic argument in which the ket and bra contributions cancel pairwise; this is the main new result. Substituting single-channel quantities into the established $m_1/m_{-1}$ sum-rule bound yields $Q^{-1}$ scaling of the sum-rule estimate ($Q\equiv 2q+s+1$, $q$ the radial
quantum number) with an explicit coefficient; its finite-temperature average has a low-$T$ plateau and a $1/T$ high-$T$ tail. All results hold for any real $s>0$. The Laguerre
polynomial identities extend formally to three dimensions, but exact 3D results show $q$-dependent contact corrections along $SO(2,1)$ ladders, so the physical interpretation there requires a separate derivation.
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Applied Physics
Real-time dynamics of VCMA-assisted switching of magnetic tunnel junctions
Marco Hoffmann, Shaohai Chen, Gunasheel Kauwtilyaa Krishnaswamy et al. (+5 more)
Voltage control of
magnetic anisotropy (VCMA) induced by charge accumulation is typically considered as an ultrafast process, enabling energy-efficient and high-speed magnetization switching in spintronic devices. In this work, we investigate the real-time dynamics of VCMA-assisted switching of
magnetic tunnel junctions via relaxation in a
magnetic field. We show that device-dependent charging effects and
magnetic granularity in the free layer limit the switching speed at applied voltages close to the critical switching threshold. Increasing the voltage or the applied
magnetic field reduces the incubation delay and total switching time to below a few ns. Micromagnetic simulations incorporating the finite charging times of the tunnel junction and the granularity of the
magnetic film reproduce the experimental results, providing critical insights into optimizing VCMA-driven magnetization control for
memory and logic applications.
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All authors Marco Hoffmann, Shaohai Chen, Gunasheel Kauwtilyaa Krishnaswamy, Hang Khume Tan, Sherry L. K. Yap, James Lourembam, Anjan Soumyanarayanan, Pietro Gambardella
History and Philosophy of Physics
From Drag to Invariance: The Experimental Pressure Behind Special Relativity
Galina Weinstein
This paper completes a three-part study of Einstein's 1905 special relativity by reconstructing the experimental pressures that shaped his thinking from 1895 to June 1905. Following Stachel's historiographical line, I trace Einstein's path under the cumulative weight of a series of recalcitrant experiments:
stellar aberration, Arago's prism test, Fresnel's partial-drag account, Boscovich's proposal of a water-filled
telescope, Fizeau's water-tube result, ether-drift null experiments, and the magnet-conductor induction asymmetry. Lorentz's electron theory attempted to domesticate these findings within a fragile ether framework, while Einstein, still loyal to Maxwell's equations, became increasingly troubled by their conflict with Galilean kinematics. The paper examines Einstein's temporary adherence to emission theory and its decisive breakdown in light of Fizeau's result. In this reconstruction, the 1905 paper does not emerge as a kinematic postulate ex nihilo, but as a principled resolution forced by an interconnected complex of experimental anomalies.
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Atomic Physics
Atomic state interferometry for complex vector light
Kuntal Samanta, Sphinx J. Svensson, Sonja Franke-Arnold et al. (+1 more)
Features of complex vector light become important in any interference effects, including scattering, diffraction, and non-linear processes. Here we are investigating the role of polarization-structured light in atomic state interferometers. Unlike optical or atomic path interferometers, these facilitate local interference between atomic transition amplitudes and hence the orthogonal optical polarization components driving these transitions. We develop a fully analytical description for the inter action of generalized structured light with an atomic four state system, that is multiply connected via optical as well as
magnetic transitions. Our model allows us to identify spatially dependent dark states, associated with spatially structured absorption coefficients, which are defined by the geometry of the polarization state and the
magnetic field direction. We illustrate this for a range of optical beams including polarization
vortices, optical skyrmions and polarization
lattices. This results in a new interpretation and an enhanced understanding of atomic state interferometry, and a versatile mechanism to modify and control optical absorption as a function of polarization and
magnetic field
alignment.
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All authors Kuntal Samanta, Sphinx J. Svensson, Sonja Franke-Arnold, Niclas Westerberg
Optics
Color Routing and Beam Steering of Single-Molecule Emission with a Spherical Silicon Nanoantenna
Maria Sanz-Paz, Nicole Siegel, Guillermo Serrera et al. (+7 more)
Single-
photon emitters radiate as electric dipoles, which limits light collection efficiency and complicates integration into flat photonic devices. Developing nanophotonic structures capable of directing
photon emission with tunable angular distributions in the visible spectrum has been pursued for applications ranging from integrated optical systems to discrimination of molecular species. To date, such directional control has been achieved using components whose overall footprint is larger than the emission wavelength and often rely on lossy plasmonic components. Here, we employ the DNA origami technique for deterministic nanoscale assembly, positioning single fluorophores in nanometric proximity to a single silicon spherical nanoparticle and demonstrate unidirectional emission with forward-to-backward intensity ratios up to ~7 dB. Furthermore, we show that a single silicon nanosphere
antenna can function as a color router or a beam steerer depending on its size, emitter spectral range and emitter-nanoparticle distance.
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All authors Maria Sanz-Paz, Nicole Siegel, Guillermo Serrera, Javier Gonzalez-Colsa, Fangjia Zhu, Karol Kolataj, Minoru Fujii, Hiroshi Sugimoto, Pablo Albella, Guillermo P. Acuna
Chemical Physics · Cross-listed from cond-mat.stat-mech
Kinetics of Peierls dimerization transition: Machine learning force-field approach
Ho Jang, Yang Yang and Gia-Wei Chern
We present a machine learning (ML) force-field framework for simulating the non-
equilibrium dynamics of charge-density-wave (CDW) order driven by the Peierls instability. Since the Peierls distortion arises from the coupling between
lattice displacements and itinerant electrons, evaluating the adiabatic forces during time
evolution is computationally intensive, particularly for large systems. To overcome this bottleneck, we develop a generalized Behler-Parrinello neural-network architecture – originally formulated for ab initio molecular dynamics – to accurately and efficiently predict forces from local structural environments. Using the locality of electronic responses, the resulting ML force field achieves linear scaling efficiency while maintaining quantitative accuracy. Large-scale dynamical simulations using this framework uncover a two-stage coarsening behavior of CDW domains: an early-time regime characterized by a power-law growth $L \sim t^{\alpha}$ with an effective exponent $\alpha \approx 0.7$, followed by a crossover to the Allen-Cahn scaling $L \sim \sqrt{t}$ at late times. The enhanced early-time coarsening is attributed to anisotropic domain-wall motion arising from electron-mediated directional interactions. This work demonstrates the promise of ML-based force fields for multiscale dynamical modeling of condensed-matter
lattice models.
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Chemical Physics
Stoichiometrically-informed symbolic regression for extracting chemical reaction mechanisms from data
Manuel Palma Banos, Joel D. Kress, Rigoberto Hernandez et al. (+1 more)
A data-driven computational method is introduced to extract chemical reaction mechanisms from time series chemical concentration data. It is realized through the use of dynamic symbolic regression in which a sparse analytical form for a dynamical system is discoverable from the underlying data. We specifically develop the stoichiometrically-informed symbolic regression (SISR) method to address a standing challenge in complex chemical reaction networks: Given a time-series
dataset of concentrations of several components, what is the mechanism and the associated rate constants? SISR finds the optimal mechanism, kinetic equations and rate constants by combining differential optimization with a genetic optimization approach that searches a symbolic space of possible reaction mechanisms. Use of SISR in several paradigmatic examples spanning linear and nonlinear reaction schemes results in excellent agreement between true and predicted mechanisms, including when the method is applied to noisy data. The advantages of a stoichiometrically-informed approach such as SISR to address reaction discovery is illustrated through comparison with the use of generic state-of-the-art data-driven approaches.
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All authors Manuel Palma Banos, Joel D. Kress, Rigoberto Hernandez, Galen T. Craven
Plasma Physics · Cross-listed from astro-ph.HE
Magnetic Field-Line Curvature and Its Role in Particle Acceleration by Magnetically Dominated Turbulence
Samuel Sebastian and Luca Comisso
We employ first-principles, fully kinetic particle-in-
cell simulations to investigate
magnetic field-line
curvature in magnetically dominated turbulent
plasmas and its role in particle acceleration through
curvature-drift motion along the motional electric field. By varying the fluctuation-to-mean
magnetic-field ratio $\delta B_0/B_0$, we examine
curvature $\kappa$ statistics and their connection to particle acceleration. The
curvature probability densities display broad power-law wings, scaling linearly in $\kappa$ below the peak and developing hard high-$\kappa$ tails for $\delta B_0/B_0 \gtrsim 1$. As the mean field strengthens, the high-$\kappa$ tails steepen, and large-
curvature events are suppressed when $\delta B_0/B_0 \ll 1$. The probability density functions of
magnetic field-line contraction, ${\bf v}_E \cdot {\bf \kappa}$, with ${\bf v}_E$ the field-line velocity, develop power-law tails well described by a symmetric Pareto distribution, characteristic of
stochastic energy exchanges, with the tails becoming harder as $\delta B_0/B_0$ increases. Our guiding-center analysis shows that
curvature-drift acceleration accounts for a substantial fraction of the energization via the motional electric field, and that it strengthens with increasing $\delta B_0/B_0$. For well-magnetized particles,
curvature-drift acceleration typically exceeds ${\bf\nabla}B$ drift, polarization drift, and betatron contributions. These results identify
curvature-drift acceleration as a principal pathway through which magnetized
turbulence transfers energy to nonthermal particles in astrophysical
plasmas.
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Fluid Dynamics · Cross-listed from cond-mat.soft
Aging in the Flow Dynamics of Dense Suspensions of Contactless Microparticles
Jesús Fernández, Loïc Vanel and Antoine Bérut
This study demonstrates that the free-surface flow dynamics of dense piles of contactless silica microparticles depend on the resting period prior to flow. Microfluidic rotating drum experiments reveal that longer resting times lead to delayed flow onsets and reduced flow velocities, both evolving logarithmically with the resting time. These aging-like effects are more pronounced for thermally driven creep flows in piles with initial tilting angle below the athermal angle of repose, in contrast to piles initially tilted above this repose angle, where
gravity-driven flows tend to gradually erase aging effects. Moreover, we show that the packing fraction does not change during the resting period, and that aging occurs in both monodisperse and polydisperse piles, indicating that crystallization is not required for the time-dependent behavior to appear. Remarkably, vigorous agitation that re-disperses the particles fully restores the piles to their initial state, demonstrating that the observed effects are not due to sample degradation. These findings evidence a form of aging in quiescent suspensions intermediate between colloidal and granular media, where thermal fluctuations, still significant relative to particle weight, progressively stabilize the system, making it more resistant to flow and deformation.
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