Plasma Physics
Numerical modeling and simulation on nanosecond laser-target interactions
Jian Wu, Ying Zhou, Minxin Chen et al. (+1 more)
Nanosecond
lasers are widely used in industrial applications as they are relatively inexpensive, and their compactness and robustness are an advantage. Much experimental work has been carried out to understand deeper the interaction between the nanosecond
laser pulses and the targets, as these are complex, transient processes with spatial inhomogeneities. Beside the experiments, the modeling and numerical simulation on the
laser interaction with the target are also crucial for understanding the dynamics of
laser-material interactions and for optimizing
laser processing applications. In this review, the progress of numerical modeling and simulation on nanosecond
laser-target interactions are summarized from the aspects of
laser-target interactions and target-
plasma interface,
laser-
plasma interactions and
plasma radiation, and numerical models on different scales with artificial intelligence advancing. The
laser ablation, mass and energy transfer, and mechanical coupling are discussed in the aspect of the nanosecond
laser-target interactions and target-
plasma interface. The
plasma expansion,
plasma ionization and recombination, and
plasma radiation are discussed in the aspect of the nanosecond
laser-
plasma interactions and
plasma radiation. Then the numerical advances, including microscopic approaches based on molecular dynamics, mesoscopic approaches based on kinetic and statistical physics, macroscopic approaches based on fluid dynamics, and numerical simulations with machine learning are discussed. Finally, the challenges currently being encountered by numerical modeling and simulation on nanosecond
laser-target interactions and its potential development direction are considered.
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All authors Jian Wu, Ying Zhou, Minxin Chen, Xingwen Li
Quantum Physics
Wigner's Friend Paradox Revisited
Peter Reichert and Markus Enz
By assuming (i) a universal, observer-independent
quantum state, by considering (ii) measurement processes with wave function collapse as part of
quantum mechanical time
evolution (also within isolated systems), and by (iii) clearly distinguishing the state of a
quantum system from the knowledge of conscious observers about this state, we suggest a modified Copenhagen interpretation of
quantum mechanics that resolves Wigner's Friend and extended Wigner's Friend paradoxes. The suggested interpretation leads to differences in some outcome probabilities compared to previous analyses which, in principle, make it possible to falsify the suggested modifications or the previous analyses (or both). The fundamental problem of the incompleteness of
quantum mechanics in the Copenhagen interpretation regarding the lack of a precise definition and a mechanistic description of the measurement process (including the collapse of the wave function) is not addressed in this study. However, the argumentation regarding the resolution of Wigner's Friend paradoxes also applies to attempts for such a mechanistic description using collapse models with
stochastic extensions to the Schrödinger equation or trying to model wave function collapse with
unitary time
evolution and irreversibility of the measurement process resulting from
quantum statistical mechanics.
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Soft Condensed Matter
Untrainable elements determine what physical learning remembers
Bijaya Dangol
Physical learning rules such as
equilibrium propagation (EP), coupled learning (CL), and adjoint coupled learning (AL) train resistive networks through local measurements. The learned function is decided by where on the solution
manifold training lands. Two properties could decide it, and they have not been separated: the
circuit's invariance under rescaling every conductance, and the rule's conservation of the mass K = (1/2) sum_e kappa_e^2. We separate them. When every element is trainable, all three vector fields are homogeneous in the conductances, so the initialization scale is provably inert. An element the rule does not adjust breaks that homogeneity whatever its constitutive law. Across twenty
topologies the learned function moves with the initialization scale by a median of twelve percent with fixed rectifiers and eight with fixed linear resistors, against 3e-8 when every element is trainable; a single fixed rectifier produces the whole effect. The conservation law is not what protects the function: AL, which we prove dissipates the mass at exactly twice its own loss, remembers its initialization as strongly as the rules that conserve it, and the
memory survives in runs where K is conserved to 1e-4. Raising the fixed-element count from one to eight multiplies the conservation drift by five thousand and leaves the
memory unchanged, while the all-trainable
circuit under AL drifts comparably and remembers nothing. What the rule's conservation structure does control is solution quality: at matched training loss AL is worse than EP and CL in four of six small
circuits, by a median of three to seven percent, though the ordering is not stable across checkpoints and does not reproduce at fifty nodes. Physical learning therefore carries two independent inductive biases, one belonging to the
circuit and one to the rule, and only the first is a
memory of how the device was built.
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Geophysics
Seismic Properties of Coastal and Inland Sabkhas: Implications for Static Corrections
A. Eleslambouly, M. Y. Ali, A. El Husseiny et al. (+4 more)
Sabkha environments are a prevalent topographic feature in arid coastal areas. Along the Arabian Gulf, sabkhas overlie substantial hydrocarbon reservoirs and exhibit intricate lithological characteristics and an extremely shallow water table. These factors contribute to elevated seismic velocities and signal distortion. Static correction, a crucial initial step in seismic reflection processing, is employed to mitigate the impact of shallow surface layers. In this study, we investigate the variations in seismic properties along the uppermost part of mature and developing sabkhas. We employed high resolution seismic experiments with geophone spacing of 10 cm to explore the upper tens of centimeters. Conventional surveys with a 2m spacing complement this approach to investigate deeper layers. Both sabkhas exhibit a unique characteristic of a partially saturated zone, which affects the seismic velocity, leading to lower velocities and consequently influencing the accuracy of the static correction. The high resolution surveys demonstrated superior accuracy to conventional approaches in determining the top of the partial saturation zone and hardground layer, hence resulting in a more reliable velocity delineation. Moreover, velocities derived from conventional, replacement, and tomogram approaches resulted in unreliable static corrections in mature coastal sabkha compared with developing inland sabkha, attributed to the considerable geological complexity that is characteristic of mature coastal sabkha environments. Carrying out a high resolution seismic survey in sabkha environments is therefore necessary to mitigate near surface velocity effects.
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All authors A. Eleslambouly, M. Y. Ali, A. El Husseiny, A. A. Al Shuhail, F. Bouchaala, S. M. Hanafy, J. Matsushima
Geophysics
Recovery of low-magnitude seismic events before the July 29, 2025, Kamchatka megathrust earthquake using waveform cross-correlation enhanced by the addition of stochastic noise
Ivan Kitov
The July 29, 2025, Kamchatka megathrust earthquake is one of the largest events in the 21st century. It is likely the best-instrumented case, with numerous stations at regional and teleseismic distances, including high-performance seismic arrays of the International Monitoring System (IMS). The waveform cross-correlation (WCC) method applied to seismic arrays allowed a significant improvement in signal detection accompanied by enhancements in phase association
algorithms. Since the WCC detector is the core
algorithm of the matched filter method, its efficiency critically depends on the ambient seismic noise coherency with the template signal, with fully
stochastic noise providing optimal detection conditions. To suppress the coherent noise component and improve WCC detection, we add a numerically generated random noise sequence adjusted in amplitude to the natural noise. This method is similar to noise whitening used in many acoustic applications, but in this study, it is applied before the matched filter is used. The detection threshold gain can be several times higher than that obtained with a pure WCC detector. The recovery of the low-magnitude seismicity obtained by the WCC applied to the IMS arrays and three-component stations prior to the July 29, 2025, Kamchatka earthquake is significantly improved by the random noise addition.
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Data Analysis and Statistics
Rethinking Total Absorption Gamma Spectroscopy Deconvolution: Supervised Machine Learning vs Response-Matrix Methods
J. Balibrea-Correa, E. Nácher, C. Fonseca-Vargas et al. (+1 more)
The extraction of $\beta$-feeding distributions in Total Absorption $\gamma$-ray Spectroscopy constitutes a challenging inverse problem, particularly in
nuclei with complex decay schemes involving a large number of excited states. In such cases, the measured spectrum arises from the superposition of many detector response functions, making the determination of the individual feedings intrinsically ill-posed and highly sensitive to the methodology employed. In this work, we present a systematic comparison between supervised Machine-Learning techniques and Response-
Matrix methods using realistic Monte Carlo simulations of an experimental Total Absorption Spectrometer. Supervised Machine-Learning approaches construct a non-parametric
estimator that infers level feedings from the measured spectrum after a training stage, whereas Response-
Matrix methods determine the feeding distribution by directly minimizing the difference between measured and reconstructed spectra. Our results show that supervised Machine-Learning techniques achieve superior accuracy in the reconstruction of individual feeding intensities, whereas Response-
Matrix methods provide robust and physically consistent initial solutions. These findings support a hybrid strategy in which a Response-
Matrix method is first used to obtain an initial feeding estimate, which is then refined using a supervised Machine-Learning approach to achieve improved overall accuracy.
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All authors J. Balibrea-Correa, E. Nácher, C. Fonseca-Vargas, J. L. Tain
Applied Physics
SH-SAW Acousto-Electric Amplifier in Epitaxial InGaAs on Lithium Niobate on Insulator
Chuan Tian, Christopher Heidelberger and Siddhartha Ghosh
This work demonstrates shear-horizontal surface acoustic wave (SH-SAW) acoustoelectric (AE) amplification on an epitaxial InGaAs / X-cut lithium niobate on
insulator (LNOI)
heterostructure formed by Al2O3-mediated wafer bonding. Deployable passivated devices show a stable fundamental-mode non-reciprocity of 32 dB/mm at 1.11 GHz (30 V bias, 64 mW consumed), while unpassivated devices reach 174 dB/mm across 1.1-2.8 GHz, reported as upper bounds. Device characterization establishes the role of mode-dependent K^2 in determining the achievable gain.
Hall-effect measurements of the transferred InGaAs serve as a quantitative diagnostic: the extracted carrier density, elevated by unintentional silicon doping during epitaxy, accounts for the absolute AE gain when inserted into the analytical model and identifies epitaxial process control as a clear lever for further enhancement. We further identify ambient oxidation of the bare InGaAs surface as a distinct aging mechanism that extinguishes the AE response within weeks, and show that an InP or ALD Al2O3 passivation layer suppresses it, at the cost of redistributing the piezoelectric field away from the channel. These results establish InGaAs-on-LNOI as a compact, low-power platform for non-reciprocal RF components and acoustoelectric delay lines, with strong relevance to in-band full-duplex (IBFD) transceivers and spectrum-efficient wireless front ends.
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Instrumentation and Detectors
The VORTEX cavity for the RADES axion haloscope
Jose María García-Barceló, Cristian Cogollos, Babette Döbrich et al. (+3 more)
One of the major challenges in
axion dark matter haloscope searches is a loss-less tuning mechanism that is able to cover a significant frequency range around the haloscope's central frequency. In this article, we report on the implementation and performance of an
axion haloscope dubbed Vertical-cut Optimised Resonant Tunable cavity for dark matter EXploration (
VORTEX) centred at $8.5$ GHz with a tuning range of around $800$ MHz. The performance of this setup is measured at temperatures in the mK range and compared to simulation. In addition, we test the cavity-mode structure of this cavity type directly via the `bead-pull method' and observe satisfactory agreement with expectations. The arrangement is poised to be used in an upcoming RADES (Relic
Axion Detection Exploratory Setup) data-taking campaign employing a $12$ T solenoid magnet.
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All authors Jose María García-Barceló, Cristian Cogollos, Babette Döbrich, David Kittlinger, Diego Nicolas Lobato-De La Cruz, Walter Wuensch
Astrophysics of Galaxies
Determining Total Infrared Luminosities from Submm Measurements of High Redshift Galaxies
Maria Emilia De Rossi, George H. Rieke, Christina C. Williams et al. (+6 more)
Determining total infrared luminosities for very high
redshift galaxies is important to estimate the rate of
star formation in heavily
dust-embedded environments. It is also challenging because the most sensitive far infrared observatory, Herschel, was limited in sensitivity and its deepest measurements are subject to confusion noise. Thus, these determinations largely depend on ALMA, observing in the mm- and/or submm-wavelengths, which sample only the long-wavelength part of the spectral energy distributions (SEDs). Luminosities are conventionally estimated with modified blackbody fits to these measurements, but do not include the emission in the mid-infrared by warmer
dust; there is evidence that this mid-IR component may be relatively strong in very high-
redshift galaxies compared with local ones. A correction factor must be applied to the modified black body luminosities to derive the total infrared luminosity. We study infrared SEDs using simulations tuned to
galactic conditions typical of high-z
galaxies. We find that the different behaviors of infrared SEDs are dominated by a single key physical parameter, the luminosity density. This allows us to estimate the corrections for the missing mid-infrared luminosity in a general way. We find that a factor of ~ 1.6 - 1.7 (0.2 dex) is appropriate in most circumstances, with a larger factor of ~ 1.75 - 1.85 (~ 0.25 dex) up to 2 (0.3 dex) necessary for high
redshift (z > 4)
galaxies at the highest luminosities, > 10^{12} Lsun. These corrections are needed to estimate
star formation rates based on total infrared luminosity.
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All authors Maria Emilia De Rossi, George H. Rieke, Christina C. Williams, Volker Bromm, Jianwei Lyu, Meredith A. Stone, Yang Sun, Christopher N. A. Willmer, Yongda Zhu
Atomic Physics
Collimation of dense atomic beams by Swept Velocity Shelving
Francesca Famà, Benedikt Heizenreder, Ananya Sitaram et al. (+4 more)
Engineering continuous, high-flux, and collimated atomic beams is a useful resource for metrology and material deposition. Developments in this area have been essential for the
evolution of cold-atom based
quantum experiments, yet the ubiquitous balanced-force methods such as transverse molasses cooling degrade at high atomic flux due to absorption-induced force imbalance. We introduce a collimation scheme that combines the use of a broadband transition for velocity shifting with a narrowband transition for velocity selection, enabling velocity-selective beam collimation without relying on balanced-power counter-propagating beams. Collimated atoms are shelved in a long-lived internal state, reducing the total light scattering and providing a state-heralded collimated beam. Simulations using strontium as a model system show a highly effective collimation process that does not suffer from absorption-induced force-imbalance and experimental results agree well with these predictions.
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All authors Francesca Famà, Benedikt Heizenreder, Ananya Sitaram, Camila Beli, Robert J.C. Spreeuw, Stefan A. Schäffer, Florian Schreck
Solar and Stellar Astrophysics
Quasi-Keplerian Be-Star Disks with Mimicking Viscosity
Michel Cure, Ignacio Araya, Rodrigo Meneses et al. (+5 more)
Classical Be
stars are fast-rotating B-type
stars with gaseous quasi-Keplerian disks formed by equatorial ejection of material. While the viscous decretion disk (VDD) model reproduces many observed properties, the role of radiative line driving in shaping these disks remains unclear. We investigated the combined influence of viscosity and radiative acceleration on the hydrodynamic structure of Be
star disks by coupling the m-CAK theory of line-driven winds with a mimicking viscous prescription governed by the parameter $\gamma_{\rm vis}$. We solved the steady-state hydrodynamic equation of motion using Hydwind for typical B-type
stellar parameters in transonic $\Omega$-slow
outflows. We analyzed the velocity and density structures and derived the mass-loss rates and radial velocities at the adopted outer integration radius, $r=50\,R_\ast$. The combined action of line driving and viscosity yields regular m-CAK $\Omega$-slow solutions for equatorial
outflow with a VDD-inspired rotational prescription. For quasi-Keplerian exponents ($\gamma_{\rm vis} \simeq 0.5$) and near-critical rotation ($\Omega \approx 0.96$–$0.99$), the models produce an outflowing disk with an m-CAK-type critical point at $r_{\rm c} \lesssim 20$–$30\,R_\ast$. At $50\,R_\ast$, these quasi-Keplerian solutions reach radial velocities of $76.9$–$139.2\,\mathrm{km\,s^{-1}}$. Within the present 1D parameterized framework, the m-CAK line force yields stationary solutions without imposing an outer boundary condition. Our results provide a controlled 1D test of how a VDD-inspired rotational prescription modifies the
topology of stationary m-CAK $\Omega$-slow solutions. The model is an exploratory bridge toward future non-Sobolev multidimensional radiation-hydrodynamic treatments that recover quasi-Keplerian rotation and modest
outflow velocities of Be disks.
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All authors Michel Cure, Ignacio Araya, Rodrigo Meneses, Matias Montesinos, Roberto O. J. Venero, Catalina Arcos, Abigali Rodriguez, Lydia S. Cidale
Adaptation and Self-Organizing Systems
Synchrony by Birth and Death
K. P. O'Keeffe
A population of oscillators typically synchronizes because coupling pulls their phases together. Here we consider malthusian oscillators whose coupling is demographic: oscillators are born and die at rates determined by their phases, generating an effective coupling without any phase velocity interaction. We find this coupling can synchronize a population, select a collective frequency, and produce a nongeneric fourth-root onset of coherence. These collective dynamics admit an exact reduction: a population with $m$ frequency classes reduces to $3m$ ordinary differential equations. This is the malthusian analogue of the Ott–Antonsen reduction for Kuramoto oscillators.
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Quantum Physics
Generative IQP Circuit Learning with Physics-Informed Latent Initialization
Chen-Yu Liu, Leonardo Placidi, Marco Ballarin et al. (+1 more)
Quantum generative learning based on instantaneous
quantum polynomial-time (IQP)
circuits can benefit from efficient classical training strategies. A recent latent adaptation framework for IQP-based generative modeling transfers shared
circuit parameters across instances of the same task with different hyperparameters while adapting only a low-dimensional latent variable for each new instance. However, existing approaches initialize this latent variable randomly, which can limit optimization efficiency and performance. In this work, we introduce a physics-informed latent initialization scheme for IQP generative learning to improve upon existing random initialization schemes. Motivated by the platonic representation hypothesis, we use latent representations extracted from a classical physics-informed neural network (PINN) surrogate to initialize the latent variables of the
quantum model for the solution of the Burgers' equation. The initialized IQP model is then adapted on a higher-resolution solution domain. We find that this structured initialization consistently outperforms random latent initialization, yielding improved adaptation behavior and stronger generative accuracy across multiple viscosity settings. These results show that classical surrogate representations can provide useful inductive bias for
quantum generative models and offer a practical route to improved initialization in IQP-based learning.
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All authors Chen-Yu Liu, Leonardo Placidi, Marco Ballarin, Enrico Rinaldi
Mathematical Physics · Cross-listed from math.AP
Some remarks on structured Keyfitz-Kranzer systems
Ralph Saxton and Katarzyna Saxton
Several applications for systems of conservation laws of the form $U_t + (\Phi (U) U)_x =0$, $U: R_t\times R_x\rightarrow R^n$ , $n\geq 2$, with $\Phi (U) = \phi (r, \Theta): R^n\rightarrow R$, $r = |U|$, and $\Theta = U/|U|\in S^{n-1}$, are obtained by imposing structural conditions to provide a classification framework for solutions dependent on the form of $\phi(U)$. By prescribing the
evolution of a particular
eigenvalue, we can categorize classes of such functions, $\phi$, for which this
evolution is met, into depending on either a scalar field $z=rK(\Theta)$, where $K: S^{n-1}\rightarrow R$, or on the vector field $\Theta$, and find for which the amplitude of solutions may blow up in finite time. As a consequence, solutions to the corresponding Riemann problems can be divided into those with are classical and those which involve delta-shocks and/or
vacuum states.
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Materials Science
Automating the analysis of micron-scale synchrotron diffraction data on inhomogeneous polycrystalline samples: a solid oxide electrolysis cell case study
Liam A. V. Nagle-Cocco, Christopher A. Crain, Michael J. Dzara et al. (+6 more)
A novel approach to post mortem characterisation of electrochemical and photovoltaic devices is spatially-resolved diffraction using a hyper-focused, micron-width x-ray beam to examine the distribution of degradation products and strain, a technique called $\mu$-XRD. Aside from the experimental difficulties associated with beam focusing and sample preparation, which are themselves non-trivial, the analysis of resulting data is complex and challenging, with full Rietveld analysis rarely attempted in literature. The difficulty lies in the size of the data, which may consist of hundreds or even thousands of diffraction patterns with very different crystallographic phase compositions depending on position within the device, and the difficulty in fitting the data due to the presence of many phases at the same position, including possible degradation products which may be difficult to index and assign to known phases. In this paper, we present a fully-automated open access Python routine for performing phase identification and Rietveld analysis on 2D
datasets of diffraction pattern taken at micron-scale positions, measured over the cross-section of a chemically inhomogeneous device with polycrystalline phases. Solid
oxide electrolyser
cells are a promising technology for green hydrogen production which can utilise waste heat to split water at higher efficiencies than low-temperature electrolysis techniques such as
polymer electrolyte membranes, but exhibit many degradation modes due to the high operating temperatures. We present a case study using our analysis protocol on an SOEC fragment encompassing the air electrode, cation
diffusion barrier, electrolyte, and fuel electrode. With modification, this protocol could be applied to other devices such as all-solid-state batteries, wet-electrolyte battery electrodes, solid
oxide fuel
cells, photovoltaic devices, and metal-
oxide pseudocapacitors.
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All authors Liam A. V. Nagle-Cocco, Christopher A. Crain, Michael J. Dzara, Mathias A. Kiefer, Madeline G. Port, Tolga Han Ulucan, Madeline Van Winkle, Oscar Hathaway, Nicholas A. Strange
High Energy Astrophysical Phenomena
Energy-dependent Optical/Near-infrared and X-ray Correlations in Swift J1727.8-1613
Ruican Ma, Federico Vincentelli, Diego Altamirano et al. (+5 more)
We present a timing analysis of the black hole transient Swift J1727.8-1613 during its intermediate state. We use coordinated broadband X-ray observations from Insight-HXMT (2-150 keV), together with optical data from ULTRACAM (g_s and i_s bands) and near-infrared data from HAWK-I (K_s band), obtained on 2023 September 9. As shown by previous studies, the
Fourier power spectrum shows a strong quasi-periodic oscillation (QPO) in the K_s, i_s and X-ray bands. Cross-correlation analysis reveals a complex coupling between the optical/near-infrared (OIR) and X-ray emission, including a delayed optical anti-correlation, a strong infrared correlation, and a pronounced dependence of these features on X-ray energy, suggesting multiple Comptonisation regions. In contrast, the lag properties do not change at the QPO frequency, displaying an OIR lag of ~60-80 ms up to 150 keV. We discuss these results in the context of small-scale jet and hot
accretion flow scenarios.
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All authors Ruican Ma, Federico Vincentelli, Diego Altamirano, Alexandra Veledina, Poshak Gandhi, Piergiorgio Casella, Tariq Shahbaz, Sian Woahene-Demehin
Earth and Planetary Astrophysics
Optical and acoustic ground effects simulations from terminal defense asteroid disruption via the PI method
Brin Bailey, Alexander N. Cohen, Philip Lubin et al. (+5 more)
Our simulations suggest that PI ("Pulverize It"), a NASA Phase II NIAC study, is an effective multi-modal approach for planetary defense that can operate in extremely short interdiction modes (with intercepts as short as hours prior to atmospheric entry) as well as long interdiction time scales with months to years of warning. The basic process is complete disruption of the threat via fragmentation. In scenarios with sufficiently long warning time, the fragment cloud spreads enough to miss Earth, resulting in no ground effects. In "worst-case" scenarios, when the warning time is short, the fragments (typically <10 m in diameter) will enter Earth's atmosphere, where their energy is dissipated in a series of ground-level optical pulses and de-correlated shock waves, mitigating any significant damage. We investigate the optical and acoustic ground effects through a set of simulation codes that model the interaction of asteroid fragments with Earth's atmosphere following terminal threat interception. Even in short-warning time cases where fragments enter the atmosphere, our simulations suggest that threats mitigated by the PI method produce vastly less damage on the ground when compared to the same unfragmented case, yielding optical energy deposition below 200 kJ/m$^2$ and shock wave over-pressures under 3 kPa. Our simulations support the proposition that threats like 2023 PDC, the hypothetical 800 m diameter asteroid from the 2023 Planetary Defense Conference impact exercise, can be effectively mitigated through fragmentation. We find that a terminal defense mitigation scenario that disrupts 2023 PDC into 1 million fragments with an intercept of 60 days before ground impact results in minimal ground effects.
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All authors Brin Bailey, Alexander N. Cohen, Philip Lubin, Darrel K. Robertson, Mark Boslough, Sasha Egan, Elizabeth A. Silber, Dharv Patel
Chemical Physics
Transcorrelated Random-Phase Approximation
Abdallah Ammar, Enzo Monino, Anthony Scemama et al. (+2 more)
We extend the random-phase approximation (RPA) to the non-Hermitian transcorrelated (TC)
Hamiltonian, which explicitly includes three-body interactions generated by a Jastrow correlation factor. We consider both the direct RPA (dRPA) and RPA with exchange (RPAx). We apply the resulting TC-dRPA and TC-RPAx methods to calculate ground-state correlation energies and vertical excitation energies for atoms (\ce{He} and \ce{Ne}) and small molecules (\ce{H2O}, \ce{NH3}, \ce{CH4}, and \ce{H2CO}). For ground-state correlation energies, the TC treatment substantially improves accuracy and accelerates basis set convergence, reducing errors by nearly an order of magnitude relative to conventional RPA calculations. By contrast, it yields only marginal improvements in vertical excitation energies. We attribute this limited effect to the ground-state optimization of the Jastrow factor, which does not adequately capture the distinct electronic character of excited states. These results establish TC-RPA as an accurate and computationally efficient approach to ground-state energetics, while highlighting the need for state-specific Jastrow optimization to achieve reliable descriptions of excited states.
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All authors Abdallah Ammar, Enzo Monino, Anthony Scemama, Emmanuel Giner, Pierre-François Loos
Materials Science
An End-to-End Differentiable Forward Model for High-Energy Diffraction Microscopy
Hemant Sharma, Nina Andrejevic, Simon Zhang et al. (+1 more)
High-Energy Diffraction Microscopy (HEDM) recovers crystallographic orientation, strain, and grain position from rotating-
crystal X-ray diffraction patterns. Existing forward models in far-field (FF), near-field (NF), and point-focused (pf) HEDM are not differentiable, which forecloses gradient-based joint parameter refinement, physics-informed regularisation, and
Bayesian uncertainty quantification. We present the first end-to-end differentiable HEDM forward model covering all three geometries, implemented in PyTorch with pixel-exact agreement against the established MIDAS reference simulators (162/162 FF, 2304/2304 NF including a non-zero detector-tilt sweep, and 1088/1096 pf-HEDM spots matched). Three demonstrations validate the framework: joint orientation-strain-position recovery in NF-HEDM at ~6 nm precision; round-trip refinement on a real 214-grain alpha-Ti FF-HEDM
dataset reaching 100% grain recovery from a 1.5 degree initial perturbation with residuals matching the production fit to 0.3%; and joint refinement of all per-detector geometry parameters and per-grain state on a synthetic four-panel FF-HEDM setup, recovering panel rotations about the beam axis to ~10 mu-rad and a global rotation-axis wedge to ~26 mu-rad. The framework is released as the open-source midas-diffract package (pip install midas-diffract).
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All authors Hemant Sharma, Nina Andrejevic, Simon Zhang, Mathew Cherukara
Materials Science
Ultrafast Nonthermal Lattice Destabilization and Suppression of Polar Optical Scattering in Electronically Excited $\alpha$-SiO$_2$ from First-Principles and Deep Neural Network Potential Modeling
Iyyappa Rajan Panneerselvam, Mark Yeung, Charlotte Palmer et al. (+2 more)
We present a multiscale first-principles-to-machine-learning approach to investigate ultrafast
lattice dynamics in electronically excited $\alpha$-SiO$_2$. Ab initio molecular dynamics (AIMD) based on electronic-temperature-dependent density functional theory (DFT) are used to train electronic-temperature-dependent deep neural network potentials (DNNPs). The use of DNNPs enables atomistic modeling at near-DFT accuracy of large $\alpha$-SiO$_2$
cells with thousands of atoms. In particular, DNNPs allowed us to obtain accurate
phonon band structures and molecular dynamics (MD) of $\alpha$-SiO$_2$ excited by a sudden increase in electronic temperature. With increasing electronic temperature, $T_e$, pronounced
lattice destabilization of $\alpha$-SiO$_2$ is found, as evidenced by violations of elastic stability criteria, substantial volumetric expansion, a sharp reduction of the bulk modulus, and progressive weakening of Si-O bonding due to antibonding-state occupation. From the electronic and
phonon band structures, we estimated the Frohlich coupling constant, which decreases as $T_e$ increases, suggesting a crossover to a nonpolar phase of $\alpha$-SiO$_2$ at elevated electronic temperature. This is corroborated by the Bader charge analysis. We also suggest that polar optical
phonon scattering should be strongly suppressed at $T_e > 2$ eV. From large-
cell DNNP-MD simulations, we show that a well-defined thermal
equilibrium, as defined by the Maxwell-Boltzmann distribution, is not achieved over the first few hundred femtoseconds. This behavior explains the non-monotonic equilibration of the kinetic temperature after a sudden rise of $T_e$. After $T_e$ is raised to 2.6 eV, Si and O atoms first equilibrate separately at two different temperatures, suggesting an atomic fluid phase, in agreement with recent experimental and theoretical findings.
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All authors Iyyappa Rajan Panneerselvam, Mark Yeung, Charlotte Palmer, Brendan Dromey, Lorenzo Stella
Astrophysics of Galaxies
EWOCS-VIII: Internal kinematics and expansion of Westerlund 1 from VVVX proper motions
C. Ordenes-Huanca, A. Bayo, M. Guarcello et al. (+12 more)
Westerlund 1 (Wd1) is the most massive young
star cluster known in the Milky Way and a key laboratory for studying the early dynamical
evolution of massive clusters. Owing to its high extinction, the internal kinematics of its intermediate-mass
stellar population remain largely unexplored. We aim to characterize the internal kinematic properties of Wd1 using a homogeneous census of near-infrared (NIR) selected cluster members and their proper motions (PMs). We considered PMs from the VIRAC2 catalog, based on multi-epoch VVV/VVVX observations. For $1286$ candidate members previously identified through NIR photometry and astrometry (Paper I), we computed their PMs relative to the cluster mean motion and analyzed them as a function of position and radius. We also investigate radial trends, test the robustness of the results against the assumed cluster center, and search for preferred directions of motion. We detect a statistically significant signature of expansion in the outer regions of Wd1, with the radial component of the relative PMs increasing with distance from the cluster center. The expansion appears asymmetric, with the strongest gradient detected along a PA$=84\degree \pm 8\degree$ in the plane of the sky and with $5.9\sigma$ significance. We also find hints for inward radial motions in the central region, consistent with ongoing mass segregation, but only at $\approx 2\sigma$ significance. Taken together, these results are consistent with a nearly monolithic formation scenario.
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All authors C. Ordenes-Huanca, A. Bayo, M. Guarcello, M. Zoccali, A. Rojas-Arriagada, Nicholas J. Wright, S. Sciortino, F. Damiani, K. Muzic, V. Almendros-Abad, M. Andersen, R. Bonito, M. Haberle, T. J. Haworth, L. Prisinzano L. Prisinzano
Instrumentation and Methods for Astrophysics
LUVCam: A high-performance, low-cost, UV/optical camera for the future of astronomy in space
Aaron Tohuvavohu, Suresh Sivanandam, Jean-Christophe Fronteddu et al. (+23 more)
Astronomy-grade cameras with robust performance and heritage in the space environment have long been costly, substantially limiting capacity for space-based astronomy and creating a resource barrier to access. Additionally, ultraviolet observations have historically been limited by the low
quantum efficiency of most sensors in this wavelength range. The LUVCam program is designed to address both issues by providing a high-performance, low-cost, UV/optical camera system sufficiently capable to support a wide-array of space-based astronomy missions. LUVCam features a large format, low-noise, large pixel, and high
quantum efficiency, commercial-off-the-shelf back(front)-side illuminated CMOS sensor, packaged with custom built readout electronics, firmware, and thermomechanical structure to provide both superlative science capability and precision on-sensor guidance at fast cadence to allow for stable high-resolution imaging. LUVCam is ITAR-free and cheap to fabricate, opening up new opportunities for access to space
telescopes. Here we introduce LUVCam, describe its performance characteristics, and the rapid implementation of a technology demonstration for flight. LUVCam, coupled with a small aperture custom-built UV
telescope, has been on orbit since July 2024 and has achieved Technology Readiness Level (TRL) 7. LUVCam is manifested for several more near-term orbital missions, including a second technology demonstration CubeSat for launch in 2026, and will provide both focal plane cameras for QUVIK, a two-channel UV transient astronomy mission.
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All authors Aaron Tohuvavohu, Suresh Sivanandam, Jean-Christophe Fronteddu, Patrick Nkwaria, Gavin Hay, Shaojie Chen, Sarik Jeram, Albert Lau, Jacob Taylor, Mark Barnet, Andras Pal, Mohamed Shaaban, Ajay S. Gill, Julia Empey, Emma Seabrook, Coby Silayan, Dhwanil Patel, Braden Seefeldt-Gail, Phil R. Van-Lane, Scott Christie, Christopher D. Matzner, Chris Damaren, Maria Drout, Filip Munz, Jakub Řípa, Norbert Werner
Materials Science
Giant Exfoliation Induced Magnetic Coercivity in Fe$_3$GaTe$_2$
Lingrui Mei, PeiYu Cai, Sang-Eon Lee et al. (+6 more)
Permanent magnets with strong anisotropy and high coercivity underpin modern information and energy technologies, yet rare-earth-free alternatives remain limited. Here, we show that thickness engineering via mechanical exfoliation induces hard
magnetic behavior in the van der Waals ferromagnet Fe$_3$GaTe$_2$. Bulk
crystals exhibit Curie temperatures above 350 K but negligible room-temperature coercivity. When thinned below 100 nm, the coercive field is dramatically enhanced, reaching nearly 1 T at room temperature for in-plane fields which is comparable to values of conventional hard magnets. Micromagnetic analysis reveals a crossover in magnetization reversal from domain-mediated processes in bulk samples to quasi-coherent rotation in thin flakes, driven by increased effective anisotropy and suppressed domain formation. This thickness-dependent transition enables tuning of
magnetic hardness without chemical modification. Combined with high saturation magnetization and robust room-temperature performance, Fe$_3$GaTe$_2$ emerges as a promising rare-earth-free material for spintronic applications. Its layered structure further allows integration into van der Waals
heterostructures, where large in-plane coercivity can stabilize
magnetic states against perturbations and interlayer coupling, offering potential for high-density nonvolatile
memory and domain-wall-based devices.
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All authors Lingrui Mei, PeiYu Cai, Sang-Eon Lee, Yue Li, Shyam Raj Karullithodi, Vadym Kulichenko, Charudatta Pathak, Elton J. G. Santos, Luis Balicas
High Energy Physics (Phenomenology)
Galactic cold clouds constraints on sub-GeV DM and asteroid-mass PBHs
Asier Salces Pérez and Pedro de la Torre Luque
We show that the ionization of molecular and atomic clouds provides a novel probe of dark matter scenarios producing low-energy $e^+e^-$ pairs through annihilation, decay, or Hawking evaporation of
primordial black holes. We derive constraints on MeV-scale dark matter with masses between $\sim1$ and $100$ MeV, as well as on
primordial black holes in the mass range $10^{14}$–$3\times10^{17}$g. By modeling the propagation of electrons and positrons inside these clouds, we show that uncertainties in charged-particle transport constitute the main limitation of this method. Nevertheless, for the most physically motivated propagation scenarios, the resulting constraints remain competitive with the strongest bounds currently available. We also identify the cloud properties that maximize the sensitivity to dark matter-induced ionization and discuss how larger samples of clouds, together with improved modeling of
cosmic-ray ionization and cloud structure, could substantially enhance the reach of this technique. Our results establish molecular and atomic cloud ionization as a promising and complementary probe of sub-GeV dark matter and evaporating
primordial black holes.
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Instrumentation and Methods for Astrophysics
Multi-sensor fusion for fine-guidance and milliarcsecond-level attitude estimation of balloon-borne telescope
Philippe Voyer, Maya Amit, Steven J. Benton et al. (+44 more)
Balloon-borne
telescopes rely on fine-guidance systems to achieve milliarcsecond image stability despite residual disturbances from the balloon environment. In these systems, the Fast Steering Mirror (FSM) stabilizes the image in two focal-plane axes, but leaves systematic, field-dependent residual motion induced by boresight roll. This effect, referred to as roll leakage, becomes more important for wider fields of view. In this work, roll leakage is characterized using data from the 2023 Superpressure Balloon-borne Imaging
Telescope (SuperBIT) science flight. SuperBIT is a 0.5-m near-ultraviolet to near-infrared
telescope that demonstrated milliarcsecond-level image stability during its 45-night science flight. We find that passive focal-plane
star-camera measurements correlate strongly with independent roll measurements across a large set of science exposures, showing that boresight roll frequently drives residual focal-plane motion. We then develop a simulation framework combining optical ray tracing, asynchronous guide-
star measurements, estimation, and FSM control to study this behavior. The framework is used to compare single-
star and multi-
star guidance architectures under realistic flight disturbances. For the SuperBIT geometry, we find that multi-
star estimation reduces average roll-induced science-field image motion by 31.8%, increasing to 77.4% for a representative geometry of GigaBIT, SuperBIT's planned larger-aperture successor. These results motivate further investigation of multi-
star fine-guidance architectures for GigaBIT.
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All authors Philippe Voyer, Maya Amit, Steven J. Benton, Benjamin E. Boyd, Anthony M. Brown, Giulia Cerini, Paul Clark, Matthew Craigie, Christopher J. Damaren, Tim Eifler, Spencer W. Everett, Aurelien A. Fraisse, Leo W. H. Fung, Ajay S. Gill, Suren Gourapura, Eric Habjan, John W. Hartley, David Harvey, Bradley Holder, Eric M. Huff, Mathilde Jauzac, William C. Jones, David Lagattuta, Gavin Leroy, Jason S.-Y. Leung, Lun Li, Thuy Vy T. Luu, Richard Massey, Jacqueline E. McCleary, Adyn Miles, Johanna M. Nagy, C. Barth Netterfield, Emaad Paracha, Susan F. Redmond, Jason D. Rhodes, Andrew Robertson, L. Javier Romualdez, Sayan Saha, Jürgen Schmoll, Mohamed M. Shaaban, Ellen Sirks, Sut Ieng Tam, Simon Tartakovsky, Georgios N. Vassilakis, André Z. Vitorelli, Bryce Warren, Alfredo Zenteno
Mesoscale and Nanoscale Physics
Engineering micro-disorder for macro-performance in magnetic nanoparticles
Jonathan Leliaert and Elizabeth M Jefremovas
Spin disorder, inherent to
magnetic nanoparticles, has traditionally been regarded as a detrimental feature, with materials-engineering efforts largely focused on producing ”perfect particles” containing as few defects as possible. Alongside this pursuit of perfection, however, an alternative framework has emerged in recent years that reframes intra-particle disorder as an ”ugly duckling” whose functional potential remains to be unlocked. In this Perspective, we review the emerging concept of disorder engineering in
magnetic nanoparticles, identify its current challenges, and outline promising future directions. From a theoretical standpoint, progress requires moving beyond the widely used macrospin approximation, which severely restricts the description of intra-particle degrees of freedom. Micromagnetic modelling, in contrast, treats magnetisation as a continuous vector field and thereby enables (i) the explicit representation of intra-particle degrees of freedom, linking microstructural features to internal magnetisation textures, and (ii) direct correspondence with polarized small-angle
neutron scattering, an experimental technique that provides quantitative access to ensemble-averaged
magnetic correlations on nanometre length scales. The field must now advance towards falsifiable and uncertainty-aware models with structurally motivated parameters and predictions that can be tested against independent experimental observables. The overarching goal is to establish quantitative relationships between particle structure, intra-particle magnetisation textures, and macroscopic functionality, thereby transforming
spin disorder from an elusive hidden variable into an engineerable design parameter.
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Mathematical Physics
Free to Interacting Map for Crystalline SPT Phases: Equivariance vs Crystalline Equivalence
Daniel Sheinbaum and Omar Antolín-Camarena
Freed and Hopkins developed an ansatz for classifying interacting SPT phases using invertible field theories with a natural Free to Interacting (FTI) map from free
fermion phases. This ansatz has been generalized to include crystalline phases and a crystalline equivalence principle (CEP). However, motivated by failure of the CEP for weak free
fermions and the FTI, here we generalize the original Freed and Hopkins ansatz to a fully equivariant version for symmorphic crystallographic
symmetries and show there is a natural equivariant FTI map from symmorphic crystalline weak free
fermions. We further discuss why this equivariant ansatz is both mathematically and physically more natural than the spatial
symmetry extension by Freed and Hopkins and why full equivariance should hold over the CEP.
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Mathematical Physics · Cross-listed from math.CO
A new upper bound on the dimer constant of $\mathbb{Z}^3$
Qidong He
We prove that the dimer constant of the cubic
lattice is bounded above by $0.452130$, improving the previous best upper bound of $0.457547$ obtained by Lundow (2001) using the transfer-
matrix method of Ciucu (1998). Our construction instead uses diagonal transfer layers and an inequality of Csikvári (2017) to relate the spectral radius of the resulting
matrix to the dimer constant, rather than exploiting
symmetry special to the rectangular
torus. We reduce the dimension of the transfer
matrix using a compression method similar to Lundow's. Finally, we use a variant of the Collatz–Wielandt formula, derived from an asymptotic result of Friedland–Schneider (1980), to obtain a monotone sequence of upper bounds converging to the true spectral radius, each of which can be computed without forming the full
matrix.
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Astrophysics of Galaxies
SDSS-V Local Volume Mapper (LVM): The Integrated Light and Internal Rotation of Omega Centauri
Maximilian Häberle, Dmitry Bizyaev, Alina Boecker et al. (+34 more)
The SDSS-V Local Volume Mapper (LVM) is a wide-field integral field spectroscopic survey of the Southern Milky Way plane, the Magellanic Clouds, and nearby Local Group
galaxies. We use Early Science observations of the whole body of the nearest
nuclear cluster, Omega Centauri, to extend the LVM beyond its primary interstellar-medium science case. The wide LVM field allows us to precisely map $\omega$ Cen's line-of-sight rotation out to $\sim 3r_{HL}$ or $15^\prime$, reaching a maximum value of $(8.4 \pm 0.8)$ km s$^{-1}$ at $r \approx 4.7^\prime$. Within the central region, comparisons with existing VLT MUSE oMEGACat data show explicitly that the unresolved-light signal is dominated by a small number of bright
stars, with an effective sample size of only $\sim$12 per resolution element. Using
Gaia DR3 as an external reference, we verify that the SDSS-V's LVM reduction pipeline recovers integrated
stellar fluxes to 1-4 % across six magnitudes of surface brightness. Our resulting total spectrum of $\omega$ Cen is one of the highest S/N integrated spectrum for any globular or
nuclear star cluster. We use it to test four widely-used SSP template libraries against resolved age-
metallicity ground truth from oMEGACat. All templates recover an old, metal-poor population. But, even at S/N $\sim$1300, the inferred mean ages and mean [Fe/H] vary by $\sim$7 Gyr and $\sim$0.4 dex, respectively, across libraries and wavelength ranges, reflecting a systematic floor for integrated-light studies of old multi-population systems.
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All authors Maximilian Häberle, Dmitry Bizyaev, Alina Boecker, Callie Clontz, Bruno Dias, Antoine Dumont, Evgeniya Egorova, Anja Feldmeier-Krause, José G. Fernández-Trincado, Pablo García, Thomas M. Herbst, Thomas Hilder, Hector Javier Ibarra-Medel, Amy M. Jones, Ralf Klessen, Nick Konidaris, Kathryn Kreckel, Alejandra Z. Lugo-Aranda, Alfredo Mejía-Narváez, Nadine Neumayer, Hans-Walter Rix, Alexandre Roman-Lopes, Sebastián Sánchez, Saroon Sasi, Anil Seth, Amrita Singh, Peter Smith, Rodolfo de J. Zermeño, Zixian Wang, Guillermo A. Blanc, Joel R. Brownstein, Niv Drory, Oleg Egorov, Evelyn J. Johnston, Ivan Katkov, Juna A. Kollmeier, Sorya Lambert
Statistical Mechanics
Exact Results for the Symmetric Dyson Exclusion Process
Ali Zahra, Jerome Dubail and Gunter M. Schutz
The symmetric Dyson exclusion process (SDEP) is an exclusion process on the
lattice with a long-range logarithmic Coulomb-type interaction. It appears in several equivalent forms: as symmetric random walkers conditioned, in the Doob-transform sense, not to collide; as the maximal-activity limit of a conditioned SSEP; and as a ground-state transform of the
spin- 1/2 XX chain. In this work, we exploit this latter representation to obtain exact
evolution formulas from deterministic initial configurations. The resulting determinantal kernel is expressed through a finite interpolation expression in terms of Lagrange
polynomials, leading to explicit density
evolution in finite and infinite
lattices. For the melting of a densely packed block, we show that the full hierarchy of density moments is governed by a finite-dimensional
polynomial algebra, and we identify Catalan numbers in the leading time coefficients. We also derive the Euler-scale density profile and the arctic curve separating frozen and
liquid regions, and show that they coincide with conjectured hydrodynamic results obtained in a previous work.
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