High Energy Physics (Experiment)
Fast Timing at Colliders: From Scintillator Hodoscopes to MicroPattern Arrays
Sebastian N. White
We give a select overview of charged particle timing at
colliders. Roughly speaking, three eras capture the
evolution of timing arrays. While luminosity and multiplicity dictate the detector technologies, there is also a need to review the various approaches to signal capture and processing, and their role in changing conditions for calibration. For the current era–the High-Luminosity LHC upgrades–the technique of dual-threshold timing can significantly simplify the crucial correction for amplitude walk.This correction often spans a time range an order of magnitude larger than the target resolution. Furthermore, because operating conditions vary in the high radiation environment, calibration can no longer be thought of as a one-time procedure. The TOFHIR2C ASIC designed for a CMS upgrade can be configured to provide dual threshold timing. In this report, we use this capability to demonstrate the power of this technique suitable for our new era.}
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Superconductivity
Comment on "Andreev Reflection to Probe Momentum-Dependent Spin Polarization in Altermagnet CrSb"
Igor I. Mazin, Maxim Khodas and Boris Nadgorny
Zhang et al. [Phys. Rev. Lett. 137, 016701 (2026)] report momentum-dependent
spin polarization in the altermagnet CrSb from point-contact Andreev reflection along the (0001), (-1-120), and (10-10) directions. We show that the Andreev
spin polarization they claim to measure is forbidden by
symmetry: it vanishes identically in the diffusive regime for all directions in CrSb, and in the ballistic regime for two of the three orientations measured. It is allowed only along one direction, where the calculated band structure gives ~50%. The large, nearly isotropic values reported follow from an incorrect definition of ballistic Andreev
spin polarization that evaluates the
spin asymmetry at fixed three-dimensional momentum; the Andreev selection rule is local only in the momentum component parallel to the interface. Moreover, the ballistic regime is not demonstrated, and the fitting procedure is flawed.
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Chemical Physics
MolExplain: An Interactive Tool for Explainable Molecular Property Prediction
Pirm Dhararag and Dylan Cashman
The application of machine learning to molecular property prediction has become increasingly prevalent in drug discovery, yet most models operate as black boxes, returning a prediction without revealing which structural features drive it. MolExplain addresses this gap by combining property prediction with sub-structure level visual explainability in an interactive web interface. The system featurizes molecules as Morgan fingerprints, classifies them using a trained XGBoost model, and applies SHAP attribution to produce a smooth heatmap overlay indicating which regions of the molecule contribute for or against the predicted property. Applied to cyclic peptide membrane permeability, the tool's attribution independently recovers the known role of backbone N-methylation in improving passive membrane
diffusion, consistent with established chemistry. While demonstrated on cyclic peptides, the framework is designed to generalize to other molecular properties, positioning MolExplain as a platform for interactive, explainability-driven molecular design.
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General Relativity and Quantum Cosmology
Thin-Shell Black Bounce
Leandro A. Lessa, Renan B. Magalhães and Gonzalo J. Olmo
A recently proposed class of black-bounce solutions sourced by anisotropic fluids, whose exterior reproduces the Reissner-Nordström geometry all the way down to a minimal-area bounce, was put forward by Lessa and Olmo. In this work, we show that this solution conceals a thin-shell structure precisely at the bounce. Motivated by this observation, we construct a new class of black-bounce solutions with static, spherical
symmetry featuring the emergence of a minimal-area bounce supported by a thin shell. This nontrivial topological structure is shown to arise from the degeneracy of the metric at the bounce, where the inverse metric becomes ill-defined, leading to
curvature tensors with distributional discontinuities precisely at that point. As a consequence, a delta-function thin shell of energy-condition-violating matter is necessarily present at the bounce. To generate such solutions, we draw on proposals from
quantum gravity that predict the existence of a fundamental minimum length scale, employing energy density profiles that encode these
quantum-gravitational effects in an effective manner, replacing the point-like description of matter at minimal-length scales with a smeared one. We consider two well-motivated profiles, of Lorentzian and Gaussian type, to generate a novel class of solutions exhibiting the features of either regular black holes or wormholes, whose center conceals a thin-shell bounce. In addition, we investigate the thermodynamics of these compact objects.
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Astrophysics of Galaxies
Calcium Triplet Absorption is Common around Little Red Dots
Jenny E. Greene, Hanpu Liu, Raphael E. Hviding et al. (+29 more)
We present new evidence for an optically thick atmosphere surrounding Little Red Dots (LRDs) in the form of Ca absorption at rest-frame 8500A, the calcium triplet (CaT). Building on the detection of CaT absorption in one local LRD analog (the "Egg", Lin et. al. 2025), we investigate the region around rest-frame 8500A for an archival sample of 17 LRDs ($2 < z < 5$) with JWST/NIRSpec grating data. We detect CaT absorption in three individual sources, and find that on average there is an absorption equivalent width (EW) EW$_{\rm CaT} \approx -5$ A. Among the three detections, two are approaching the deepest absorption seen in integrated light from
stars. Given that the continuum around CaT is probably dominated by the central engine, we argue that the absorbers are likely to be associated with the LRD. Such absorption has not historically been associated with any components of an AGN central engine, but a cool, optically thick photosphere as proposed for LRDs would naturally produce such absorption. The EW$_{\rm CaT}$ that we observe can be matched by hydrostatic atmosphere models at relatively low
metallicity ([M/H]$<-1$) combined with an effective temperature $T_{\rm eff} > 4500$ K. Alternatively, the distribution can be matched at a low photospheric gas density $\rho_{\rm ph}<10^{-11}{\rm~g~cm^{-3}}$ that requires a non-hydrostatic gas structure on dynamical grounds. In the future, metal absorption lines should be a powerful complementary probe of the gas conditions, and possibly the enclosed mass, of LRDs.
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All authors Jenny E. Greene, Hanpu Liu, Raphael E. Hviding, Rohan P. Naidu, David J. Setton, Bingjie Wang, Ivo Labbe, Vasily Kokorev, Xiaojing Lin, Hollis B. Akins, Anna de Graaff, Joel Leja, Jorryt Matthee, Alberto Torralba, Karl Glazebrook, Rachel Bezanson, Leindert A. Boogaard, Gabriel Brammer, Caitlin M. Casey, John Chisholm, Xiaohui Fan, Lukas Furtak, Seiji Fujimoto, Yan-Fei Jiang, Yilun Ma, Themiya Nanayakkara, Erica J. Nelson, Richard Pan, Eliot Quataert, Anthony J. Taylor, Christina Williams, Adi Zitrin
Mathematical Physics
Comparing the Lee-Yang gap with the mass gap in the sub-critical planar Ising model
Noam Borgnia, Jui-Hui Chung and Jacob Shapiro
We prove that the subcritical mass gap is comparable to the Lee-Yang gap over free-boundary square boxes raised to the power $8/15$. Random-current moment bounds, a correlation inequality and a finite block expansion give the upper bound. The lower bound follows from the Lee-Yang product, the susceptibility and the critical magnetization. We also obtain uniform factorial bounds on the field derivatives of the pressure.
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Instrumentation and Methods for Astrophysics
Convolutional Neural Network for Extraction of $n = 1$ Photon Ring of Black Holes
Courtney Duong, Frank Myhre and Joseph R. Farah
Very-long-baseline interferometry (VLBI) may enable direct imaging of fine, event-horizon scale black hole structures such as the
photon ring. In particular, the $n=1$
photon subring encodes information about black hole
spin in its radial profile and azimuthal brightness modulation, making it a key proxy for spacetime properties. However, the $n=1$ subring overlaps with emission from the $n=0$ subring in observations, requiring isolation of the $n=1$ subring for measurements. We present a convolutional neural network (CNN) capable of extracting the $n=1$ subring from composite images containing $n=0$ and $n=1$ subrings. We simulate $111,000$ $m$-ring images with eht-imaging to train and validate the CNN. The CNN accurately recovers the radial and angular brightness profiles of the $n=1$ subring with a mean normalized cross correlation (NXcorr) of $\sim0.99$. The CNN provides a detection capability by predicting no false positives when input images lack a $n=1$ subring. We perform feature extraction with ringfit to show that the CNN-predicted $n=1$ subring accurately recovers the ground truth radial profiles and azimuthal brightness modulation, demonstrating the CNN's capability to extract
spin-sensitive features. We further test the CNN on black hole images generated by KerrBAM and general relativistic magnetohydrodynamic (GRMHD) simulations, finding that it recovers the overall $n=1$ subring radial profiles while exhibiting discrepancies in the recovered intensity profiles. These results demonstrate the potential of deep learning methods to isolate the $n=1$ subring from overlapping emission, providing a framework for analyzing future high resolution black hole images from proposed VLBI missions such as the Black Hole Explorer (BHEX).
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Solar and Stellar Astrophysics
Asteroseismology and interferometry of the F7V spectroscopic binary $\chi$ Draconis A in the TESS CVZ
Jonatan Rudrasingam, Mikkel N. Lund, Frank Grundahl et al. (+26 more)
We present a detailed analysis of the asteroseismic main-sequence
benchmark star $\chi$ Dra A in the TESS northern CVZ. We aim to derive
stellar mass and radius from asteroseismic modelling of individual mode frequencies and test the asteroseismic mass and radius against an independent dynamical mass and interferometric radius measurement. We determined the dynamical mass of $\chi$ Dra using 618 radial velocity measurements obtained with the SONG
telescope at Tenerife, and 53 relative astrometric measurements. With the PAVO beam combiner at CHARA, we obtained the interferometric radius of $\chi$ Dra A. We determined asteroseismic parameters from 16 sectors of 20-sec cadence TESS photometry. We determined $T_{\rm eff}=6277\pm30$ K, $\rm [Fe/H] =-0.51\pm0.03$ dex, and $[\alpha/\rm Fe]=0.08\pm0.03$ dex from the spectroscopic analysis. For the dynamical fit we obtained a mass of $M_{\rm A}=1.028 \pm 0.004$ $\rm M_{\odot}$ for $\chi$ Dra A, and $M_{\rm B}=0.735 \pm 0.003$ $\rm M_{\odot}$ for $\chi$ Dra B. Combining the derived interferometric angular diameter with dynamical parallax yields an interferometric radius of $R_{\rm A} = 1.159^{+0.029}_{-0.028}$ $\rm R_{\odot}$. In the TESS power spectrum, we identified 38 individual oscillating modes. Using these modes, we modelled the
star with nine independent pipelines to test the resulting model mass and radius against our independently calculated mass and radius. All models yielded masses slightly lower than the dynamical mass. Using asteroseismic scaling relations, we found that scaling masses from corrected scaling relations best reproduce the dynamical mass. The combination of spectroscopy, interferometry, and asteroseismology has yielded precise results for the main component of the $\chi$ Dra system, making it one of the best-characterised main-sequence
solar-like oscillators.
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All authors Jonatan Rudrasingam, Mikkel N. Lund, Frank Grundahl, Arnab Chowhan, Timothy R. Bedding, Poul E. Nissen, Aldo Serenelli, Joel M. J. Ong, Jeppe S. Thomsen, Yaguang Li, Eva Panetier, Sarbani Basu, Owen J. Scutt, Travis S. Metcalfe, Savita Mathur, Mark Lykke Winther, George T. Hookway, Benjamin J. S. Pope, Amalie Stokholm, Desmond H. Grossmann, Jens R. Larsen, Jørgen Christensen-Dalsgaard, Daniel Huber, Mads S. Fredslund, Timothy R. White, Paul G. Beck, Pere L. Pallé, Rafael A. García, Hans Kjeldsen
High Energy Astrophysical Phenomena
Multi-scale variability in the optical afterglow of GRB 251013C from high-cadence LAST observations
R. Konno, E. O. Ofek, S. Garrappa et al. (+8 more)
Context. Optical afterglows of gamma-ray bursts (GRBs) are often described by smooth power-law decays, but deviations such as
flares and rebrightenings provide important constraints on the underlying emission processes. Aims. We investigate the temporal variability of the optical afterglow of GRB 251013C using high-cadence observations, and assess the origin of the observed variability. Methods. We analyze continuous optical observations obtained with the Large Array Survey
Telescope (LAST), complemented by publicly available X-ray data from Swift-XRT. The optical light curve is modeled using a power-law decay with superposed variability components, and contemporaneous optical and X-ray measurements are used to constrain the broadband spectrum. Results. The optical light curve shows pronounced variability on multiple timescales, including broad rebrightening episodes with $\Delta t \sim t$ and superposed faster fluctuations with $\Delta t/t < 1$. The main rebrightening exhibits a structured rise with a clear steepening prior to the peak. The fast variability comprises asymmetric fast-rise, slow-decay features whose durations increase with peak time. The optical flux lies on the extrapolation of the X-ray spectrum, and the spectrum hardens by the same amount whether measured within the X-ray band or from optical to X-ray. Conclusions. We favor a refreshed external-shock interpretation for the main rebrightening. The broadband spectrum and post-peak decay are consistent with slow-cooling synchrotron emission in a wind-like medium. The spectral hardening requires a newly dominant, harder electron population, while the faster optical variability indicates structure within the refreshed ejecta or shocked region.
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All authors R. Konno, E. O. Ofek, S. Garrappa, O. Teboul, E. Waxman, S. Ben-Ami, D. Kovaleva, A. Krassilchtchikov, D. Polishook, E. Segre, E. A. Zimmerman
Earth and Planetary Astrophysics
A Very Fast Symplectic Integrator for Planetary Systems: WHFast512 in x86 Assembly
Rishit Dagli and Hanno Rein
Long-term integrations of planetary systems are used in a variety of astrophysical applications, for example to determine a system's stability. In this paper, we describe significant speed and accuracy improvements to the WHFast512 integrator. By completely rewriting WHFast512 in x86 assembly, we gain fine-grained control over CPU instructions and are able to keep the entire simulation state in CPU registers, only writing to
memory when an output is required. We also reduce the number of branches in the code, improve the Kepler solver's speed and accuracy with a convergence check, switch the
Hamiltonian splitting to Jacobi coordinates, implement
symplectic correctors, and add support for ejection and collision detection. As a
benchmark we run simulations of the
Solar System with all eight
planets and general relativistic corrections for 5 Gyr. With our improvements, we can integrate this system in 9 hours, more than 8x faster than the standard version of WHFast. This makes WHFast512 by far the fastest N-body integrator for this kind of simulation. We run extensive tests to verify the integrator's accuracy, with a particular focus on removing any long-term bias, and show that the accuracy is now five orders of magnitude better for typical setups compared to the earlier version of WHFast512. The new WHFast512 integrator is freely available in the REBOUND integrator package.
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Quantum Physics
Thermalization and dephasing in an isolated system of coupled qubits
Jukka P. Pekola and Bayan Karimi
A system evolving unitarily does not dephase or thermalize by definition. Yet, if one considers a part of a
unitary system, situation is different. Here we analyze an isolated set of coupled
qubits taking one
qubit at a time as a subsystem, and writing self-consistently a weak-coupling master equation for it. Weakly anharmonic oscillators and ideal
qubits (two-level systems) demonstrate dephasing, i.e. the diagonal elements of the density
matrix reach a steady-state in the long-time limit, and the off-diagonal elements of ideal
qubits decay exponentially. For the linear coupling between the
qubits, only the degenerate ones interact, and the system does not reach thermal distribution. However, non-linearity, in our analysis in form of three-wave mixing, ensures a thermal distribution in the long time limit, where the temperature is determined uniquely by the energy in the initial non-thermal state. Finally, we present a potential experimental scheme based on a superconducting
quantum circuit.
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Solar and Stellar Astrophysics
TIC 366240660 - A Dynamically Active Triple With a Very Short Outer Period of 30.5 Days
S.A. Rappaport, T. Borkovits, G. Torres et al. (+17 more)
Methods: We analyze TESS photometric data, radial velocity measurements, and eclipse timing variation curves for the triple
star system, TIC 366240660, with a photodynamical code to infer the properties of all three
stars and orbital motions. Results: With an outer orbital period of only 30.5 d, this is the second most compact triple reported in the literature. We have determined the masses and $T_{\rm eff}$ values of the three
stars with an accuracy of about 1% and the radii to about 2%. The inclination angles of the two planes, and the mutual inclination angle are found with an accuracy of better than 1/3$^\circ$. The system is determined to be quite flat (to within 1/2$^\circ$), but with an outer eccentricity of $e_{\rm out} \simeq 0.33$. We find that the properties of the secondary
star of the inner binary are completely inconsistent with the
evolution of a single
star in isolation, and it must have transferred most of its envelope to the current primary
star in the inner binary during a prior episode of mass transfer. The eclipse timing variation (ETV) curve derived from the TESS photometric data shows that, in addition to a typical dynamical delay curve at the period of the outer orbit, there is also a much larger amplitude anomalous sinusoidal-like delay with a period of 840 d. This latter feature in the ETV curve is not yet describable in simple analytic terms, but it appears certain that it can be explained by the near integer ($\simeq$13:1) ratio of the outer to the inner orbital periods. Conclusions: We have extensively explored the exotic and anomalous ETVs of this highly compact triple system and found that they can exceed hours for the inner binary eclipses, and several days for the outer orbital eclipses. We provide a preliminary explanation for how these are related to the 13:1 mean motion resonance of the outer to inner orbits.
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All authors S.A. Rappaport, T. Borkovits, G. Torres, H.-L. Chen, P. Zasche, D. Vokrouhlický, B. Deme, M. Mašek, H. Kučáková, R. Uhlař, M. Wolf, Z. Garai, T. Pribulla, I.B. Bíró, I. Csányi, Z. Dencs, D. Latham, T. Mitnyan, V.B. Kostov, B.P. Powell
Chemical Physics
Near Chemical Accuracy From Size-Consistent Padé Resummed Møller-Plesset Perturbation Theory
Kyle Bystrom, Timothy C. Berkelbach and Diptarka Hait
Padé resummation of the correlation energy from Møller-Plesset (MP) perturbation theory is not size-consistent and is therefore seldom used. We present an orbital-based Padé resummation of the MP2 and MP3 self-energy operators, whose trace yields a size-consistent correlation energy. We find that damping the third-order same-
spin contribution leads to substantially increased accuracy, with the resulting same-
spin damped orbital Padé resummed (SSD-OPMP3) approach attaining near-chemical accuracy (mean absolute error $\sim$ 1 kcal/mol) for total atomization energies of non-multireference molecules in the W4-17
dataset against the gold standard CCSD(T) method. Excellent performance surpassing CCSD is also obtained for other molecular
datasets such as those containing barrier heights, noncovalent interactions, dipole moments, static polarizabilities, and transition-metal chemistry. SSD-OPMP3 is thus a highly accurate electronic structure method with the same noniterative $O(N^6)$ cost as MP3, filling a gap in the cost/accuracy hierarchy of wavefunction methods.
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Materials Science
Nanoscale Sr$_2$IrO$_4$ Freestanding Thin-Films for Flexible Electronics
Sujan Shrestha, Matthew Coile, Menglin Zhu et al. (+7 more)
We report the structural and optical properties of nanoscale Sr2IrO4 freestanding thin-films fabricated using a water-soluble Sr3Al2O6 layer. The coherent
lattice structure,
phonon modes, two-
magnon Raman scattering, and optical absorption spectra of the Sr2IrO4 nanomembrane are analogous to those of the layered iridate epitaxial thin-films and single
crystals. Remarkably, the formation of 3-unit-
cell-thick SrIrO3 and interfacial composite layers alleviates antiphase boundaries at the Sr2IrO4/Sr3Al2O6 interface, resulting in structurally-robust nanomembranes. Our experimental results show that this freestanding thin-film approach of layered
oxides can provide techniques for tuning or realizing unprecedented states beyond conventional thin-film methods, suggesting a pathway in achieving flexible layered-
oxide electronics.
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All authors Sujan Shrestha, Matthew Coile, Menglin Zhu, Maryam Souri, Jiwoong Kim, Rina Pandey, Joseph Brill, Jinwoo Hwang, Jong-Woo Kim, Ambrose Seo
High Energy Physics (Theory)
Dual symmetry breaking and magnetic charge screening
Saulo Carneiro
We extend a Lagrangian formulation of dual electrodynamics by introducing electric and
magnetic Higgs scalar fields. The scalars couple to Mandelstam nonlocal potentials which enter the electric and
magnetic sectors. We consider the
vacuum in which only the
magnetic scalar has a nonzero expectation value. The generalised Maxwell equations remain local even though the scalar couplings are nonlocal. In this phase the local electric potential keeps a massless pole while the
magnetic sector acquires a mass. The electric interaction is therefore Coulombian at large distances while the pole-pole and charge-pole interactions become short ranged. The
magnetic charge is then screened in the sense of the Swieca
theorem while the electric charge is not. The Dirac condition is inherited from the symmetric phase as a quantisation rule for the microscopic electric and
magnetic couplings. We also comment on screened monopoles as possible dark sector degrees of freedom.
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Instrumentation and Methods for Astrophysics
Emerging Technologies for Astrophysics Missions: Workshop Summary Report
Brendan P Crill, Nicholas Siegler, Dan Sirbu et al. (+3 more)
NASA's Astrophysics Division convened the Emerging Technologies for Astrophysics Missions (ETAM) Workshop in March 2025 at the Ames Research Center in Silicon Valley, California. The workshop's goal was to identify emerging technologies that could critically impact or enable future space missions-including concepts previously considered unachievable. Four key technology areas were examined: Astrophotonics, Artificial Intelligence and Machine Learning, Advanced Materials, and
Quantum Sensors. Approximately 60 participants from academia, industry, government laboratories, and NASA centers attended. The workshop fostered an inspiring and collaborative atmosphere that encouraged interaction among experts both within and across disciplines. The workshop's three-day novel format featured landscape presentations outlining the state of each field, followed by breakout sessions where participants, grouped in their own disciplines, identified high-impact technologies for astrophysics missions. Cross-pollination sessions then brought together experts from multiple technology domains to foster interdisciplinary insights. The event successfully identified several high-priority emerging technologies (summarized in subsequent sections of this report). In addition to the field-specific insights, the workshop also produced five key cross-cutting suggestions for the NASA Astrophysics Division to consider.
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All authors Brendan P Crill, Nicholas Siegler, Dan Sirbu, Luc Peterson, Sanaz Vahidinia, Ryan Watkins
Cosmology and Nongalactic Astrophysics
Basis function expansions of the two-point correlation function and reconstruction of the cosmological distance scale
Fatima Abd Alrahman, Farnik Nikakhtar, Marcello Musso et al. (+2 more)
The shape of the correlation function of
galaxy pairs can be used as a cosmological distance indicator. Most
estimators of this shape require that one bin the pair counts, and considerable effort is expended in finding the optimal bin size. Cosmological constraints are then derived, in a separate step, by fitting to the binned pair counts. By projecting the pair counts on a suitable basis set, it is possible to estimate the pair correlation function without binning. Recent work suggests that, in the context of estimating the cosmological distance scale from
galaxy clustering data,
polynomials and half-integer generalized Laguerre functions are particularly useful bases. We show how to use these bases to measure the correlation function and estimate the reconstructed distance scale in a single step. Our analysis includes the effects of shot-noise and
cosmic variance, and highlights the benefits of projecting pair counts onto orthogonal basis functions.
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All authors Fatima Abd Alrahman, Farnik Nikakhtar, Marcello Musso, Aseem Paranjape, Ravi K. Sheth
Solar and Stellar Astrophysics
Using Machine Learning to Model Stellar Collisions in our Galactic Center
Tristan C. Sand, Sanaea C. Rose, Elena González Prieto et al. (+9 more)
Direct collisions in the inner pc of the
Galactic center can alter the orbits and properties of
stars. The outcome of a collision depends on a number of parameters, including the masses and ages of the
stars, the impact parameter, and the initial relative velocity. We utilize the newly developed $\verb|collAIder|$, a machine learning tool developed to predict the outcomes of
stellar collisions, to bridge 3D hydrodynamic simulations of
stellar collisions with a dynamical model of the
Galactic center. Our results show a substantial population of stripped
stars, $\sim$$10\%$ of the initial
stellar population, produced by mass loss during high-speed collisions.
Stellar mergers are less frequent, with about $5\%$ of the
stars experiencing a collision-induced merger. We also find that high-speed, nearly head-on collisions can completely disrupt the
stars. These destructive collisions are usually preceded by 10 or more collisions, which gradually reduce the mass of the
star before it is ultimately destroyed. We estimate that mass loss during
stellar collisions injects roughly $(2.5-8)\times 10^5$ M$_\odot$ of gas into the surrounding environment. Most of this gas is injected into the inner $0.1$ pc and about $90\%$ is retained within the cluster and may be accreted onto the supermassive black hole.
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All authors Tristan C. Sand, Sanaea C. Rose, Elena González Prieto, James C. Lombardi, Jr., Charles F. A. Gibson, Fulya K{\i}roğlu, Kyle Kremer, Christopher E. O'Connor, Enrico Ramirez-Ruiz, Frederic A. Rasio, Tjitske Starkenburg
Materials Science
Impact of Chemical Clustering on the Structural, Topological, and Functional Properties of Ba(Zr$_x$Ti$_{1-x}$)O$_3$: An Atomistic Simulation Study
Matias Baldassin, Rodrigo Machado, Marcelo Sepliarsky et al. (+1 more)
Barium zirconate titanate, Ba(Zr$_x$Ti$_{1-x}$)O$_3$ (BZT), is a leading lead-free candidate for high-performance electronic components due to its highly tunable ferroelectric-to-relaxor transition. In this study, we employ molecular dynamics simulations to investigate the effects of local chemical clustering on the structural and functional properties of BZT in both ferroelectric (x = 0.2) and relaxor (x = 0.4) regimes. Crucially, we demonstrate that Zr clustering induces a significant enhancement of local polarization across both compositions. Rather than a purely volume-driven effect, this enhancement is fundamentally governed by a spatial redistribution of local structural phases (rhombohedral, orthorhombic, and tetragonal); Zr segregation forms larger, continuous Ti-rich regions that expand highly polar rhombohedral domains and foster cooperative dipolar
alignment. This cooperative coupling thermally stabilizes the local polar order, systematically elevating the Curie, maximum permittivity, and Burns temperatures. Focusing on the relaxor composition (x = 0.4), chemical segregation promotes the formation of resilient, swirling polar topological textures,categorized into
vortices circulating around Zr-rich clusters and interstitial
vortices localized within the Ti-rich
matrix. These topological structures act as effective pinning barriers against polarization reversal, driving pronounced electrical hardening with elevated coercive fields. Ultimately, these findings establish a quantitative link between nanoscale compositional heterogeneity, polar domain
topology, and macroscopic performance, providing a robust framework for engineering lead-free perovskites via local chemical order control.
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All authors Matias Baldassin, Rodrigo Machado, Marcelo Sepliarsky, Marcelo G. Stachiotti
Geophysics
Time Distribution of Heavy Rainfall in Brazil: Empirical Huff Curves from 290,164 Sub-Daily Storm Events
Marcus Nobrega Gomes Junior, André Simões Ballarin and Paulo Tarso Sanches de Oliveira
Temporal rainfall distributions are widely used in design storm construction; however, many countries with limited sub-daily observations, such as Brazil, still rely on frameworks developed under different hydroclimatic conditions. This mismatch may introduce bias in hydrological design and water resources estimation. Here, we develop the first national-scale empirical Huff curves for Brazil using sub-daily rainfall observations. We compiled data from 3,164 stations and, after quality control, retained 290,164 storm events from 1,045 stations spanning 2010 to 2025. Empirical cumulative rainfall mass curves were constructed and fitted using seventh-degree
polynomials at station, biome, state, and municipality scales. Our findings show a dominance of first-quartile (Q1; front-loaded) storm patterns, occurring at 94.4% of stations nationally, increasing to 99.2% in the Amazon and Cerrado biomes and decreasing to 88.7% in the Atlantic Forest. The national Q1 median curve closely matches the Huff (1967) reference (MAE = 0.045; Dmax = 0.097), with narrow bootstrap uncertainty. Q1 dominance is robust to inter-event time definition, with 84.7% of stations showing consistent classification across 2 to 12 h thresholds. A Soil Conservation Service Curve Number experiment across 579 headwater catchments shows that Brazilian curves increase design peak discharge by a median of 8% and up to 11% in the Cerrado relative to the Illinois reference, indicating potential underestimation when using non-local distributions. Biome-, state-, and municipality-scale parameters are provided as open data and through an interactive platform, offering locally calibrated design-storm alternatives for Brazil.
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Mathematical Physics
Lee-Huang-Yang Energy for Dilute Bose Gases: an Upper Bound for General Potentials
Giulia Basti, Morris Brooks, Serena Cenatiempo et al. (+2 more)
We establish an upper bound for the ground state energy density of a dilute Bose gas, interacting through a general short-range, repulsive potential. To reach this goal, we extend the approach recently introduced in [1] for hard spheres.
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All authors Giulia Basti, Morris Brooks, Serena Cenatiempo, Alessandro Olgiati, Benjamin Schlein
Mathematical Physics · Cross-listed from math.DG
The dHYM equation on crepant resolutions of Calabi-Yau cones
Eder M. Correa
In this paper, we study the deformed Hermitian-Yang-Mills (dHYM) equation on the non-compact Calabi-Yau
manifold $Z = {\rm{Tot}}({\bf{K}}_{X})$, where $X$ is a rational homogeneous variety. Since $X$ is a Fano variety, $Z$ is a resolution of the singularity at the vertex of the affine cone ${\rm{Aff}}(X)$, provided the cone is built using the anticanonical polarization ${\bf{L}} = {\bf{K}}_{X}^{-1}$. Using the cohomogeneity-one
symmetry of the
Ricci-flat Kähler metric obtained via the Calabi ansatz on $Z$, we reduce the fully nonlinear PDE underlying the dHYM equation to a scalar, asymptotically autonomous ordinary differential equation (ODE). From this, we determine the exact condition on the topological phase that guarantees global existence of solutions. As an application, we show that every holomorphic line bundle over $Z$ admits a smooth, globally defined Hermitian connection solving the dHYM equation, provided the total phase lies in an explicit open interval determined by the Lie-theoretic data. Also, we prove a
rigidity result classifying the exact
geometric conditions under which the dHYM solution collapses into a classical Hermitian-Yang-Mills (HYM) connection. The results established generalize previous constructions and provide a substantial new class of examples. Furthermore, the approach presented allows one to study the behavior of the dHYM solutions through ODE methods. Using this approach, we construct the first explicit non-trivial example of a Hermitian-Einstein connection on a line bundle over a non-toric Calabi-Yau
manifold which is not dHYM.
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Astrophysics of Galaxies
A radial basis of massless potential-density pairs
E.V. Polyachenko and I.G. Shukhman
In the
matrix method for linear perturbations of spherical
stellar systems, the perturbed potential and density are expanded over a set of potential-density pairs. For radial perturbations, mass conservation makes the coefficient of $1/r$ in the perturbed potential vanish, so that the potential decays faster than $1/r$. Starting from the $\ell=0$ Hernquist–Ostriker family, we construct in closed form a set of potential-density pairs whose potentials decay as $r^{-p}$ with a prescribed $p\ge2$, the tail containing all subsequent integer powers. For $p=2$ each pair is individually massless, and the potential of the $n$-th pair is expressed through a single Jacobi
polynomial. We derive the combination weights, the leading tail coefficients and the Gram
matrix analytically; the Gram
matrix is banded with half-width $p-1$ (tridiagonal at $p=2$). The $n$-th potential element has exactly $n-1$ nodes, spread from $r\sim n^{-2}$ to $r\sim n^{2}$, so that the set resolves both the centre and the far periphery. As a test, the expansion of the dilation-mode potential of the isochrone model converges exponentially and carries no parasitic mass at any truncation, in contrast to the standard set.
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Mathematical Physics
Asymptotics for partition functions of random normal matrix models with singularities
Kohei Noda
We study determinantal planar Coulomb gases with a smooth radial potential, a smooth radial perturbation, jump-type singularities (including the bulk, semi-hard, hard, and soft-edge regimes), and a hard wall region given by a centered disk, a disk complement, or an annulus. We obtain explicit asymptotic expansions of the partition functions up to and including the term of order $1$. Our results unify and generalize many of the earlier works.
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Mesoscale and Nanoscale Physics
Influence of Electrostatic Environment on the Proximity Spin-Orbit Coupling in Graphene on Transition-Metal Dichalcogenides
Bert Jorissen, Bart Partoens, Aires Ferreira et al. (+1 more)
We investigate the proximity-induced
spin-orbit coupling (SOC) in
graphene on transition-metal dichalcogenide (TMD)
heterostructures using a tight-binding approach. The tight-binding parameters of an effective 4-band model describing the low-energy physics of the
graphene layer are extracted as a function of twist angle, material composition (MoS${}_2$, MoSe${}_2$, WS${}_2$, WSe${}_2$), band
alignment, and charge-transfer dipole. We investigate the effect of a charge-transfer dipole induced on the chalcogen layer closest to
graphene, which is typically neglected in tight-binding models but included in ab initio calculations through charge redistribution. In addition, we explore the influence of variations in the band
alignment. We find that the
spin-valley and Rashba
spin-orbit coupling energies as well as the so-called Rashba phase, governing the orientation of momentum-space
spin textures, show a strong dependence on the twist angle and electrostatic tuning. Our results suggest that variations in band
alignment and charge redistribution contribute to the spread of
spin-orbit parameters reported in the literature.
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All authors Bert Jorissen, Bart Partoens, Aires Ferreira, Lucian Covaci
Mathematical Physics · Cross-listed from math.PR
Mesoscopic transition for $\beta$-ensembles at intermediary temperature
Charlie Dworaczek Guera, Gaultier Lambert and Luke Peilen
This paper establishes a mesoscopic central limit
theorem for linear statistics of $\beta$-ensembles or log-gas, as the dimension $N\to\infty$, in the temperature regime $1/N\ll\beta(N)\le 1$. For simplicity, we assume that the potential is one-cut regular and analytic. In this regime, the size of the fluctuations depends on $\beta(N)$ and the mesoscopic scale. We show that there is a transition at a critical $\eta\asymp 1/ N\beta(N)$ between a Random
Matrix regime, where the limiting variance is given by the $\mathsf{H}^{1/2}$-norm and a Poisson regime where the limiting variance is given by the $L^2$-norm. We also describe the critical regime. The proof of the CLT relies on optimal local laws at intermediate temperatures and Stein's method for $\beta$-ensembles. In particular, in this regime, it is necessary to construct new correction terms to the classical
equilibrium measure to obtain a suitable re-centring of linear statistics and describe their fluctuations. We also obtain a free energy expansion.
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Astrophysics of Galaxies
First Trigonometric Parallax Measurements with the KVN and VERA Array (KaVA)
Nobuyuki Sakai, Daisuke Sakai, Noriyuki Kawaguchi et al. (+26 more)
To demonstrate the astrometric capability of the combined Korean VLBI (Very Long Baseline Interferometry) Network (KVN) and VLBI Exploration of
Radio Astrometry (VERA) Array (KaVA), we conducted six-epoch VLBI observations of 22-GHz H$_{2}$O masers associated with the
star-forming region W3(OH). Two atmospheric calibration methods, (1) GPS and (2) JMA (Japan Meteorological Agency) mesoscale analysis data, and two phase-reference sources were independently applied to the astrometric analysis. Trigonometric parallaxes of W3(OH) were successfully measured with all calibration strategies, including the first successful parallax measurement using JMA calibration. The combined-fit parallax is 0.497$\pm$0.024 mas, corresponding to a distance of 2.01$^{+0.10}_{-0.09}$ kpc. This value is consistent with the previous Very Long Baseline Array (VLBA) result of 0.489$\pm$0.017 mas. KaVA achieved a 55$\%$ higher signal-to-noise ratio in phase-referenced maps than VERA, in good agreement with theoretical expectations. These results suggest that KaVA will enable trigonometric parallax measurements of 22-GHz H$_2$O masers that are difficult to observe with VERA alone because of low flux densities and/or limited $uv$ coverage. A flux variation from 510\,$\pm$\,50 to 3900\,$\pm$\,400 Jy was detected in W3(OH) over a one-year observing campaign and is attributed to two nearby maser features separated by only $\sim$64 AU at 2.01 kpc. The brightest feature showed a decrease in linewidth with increasing peak flux density, consistent with unsaturated maser amplification, whereas no similar trend was found for the other feature, suggesting different responses to the same amplification conditions, possibly owing to differences in saturation state and internal velocity structure.
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All authors Nobuyuki Sakai, Daisuke Sakai, Noriyuki Kawaguchi, Shuangjing Xu, Bo Zhang, Taehyun Jung, Chungsik Oh, Jeong-Sook Kim, Soon-Wook Kim, Hiroshi Imai, Yuanwei Wu, Maria Rioja, Niu Liu, Zehao Lin, Ibnu Nurul Huda, Shuaibo Bian, Leonid Petrov, Jingdong Zhang, Takaaki Jike, Yoshiaki Tamura, Jeong Ae Lee, Hao Ding, Koichiro Sugiyama, Kazuhiro Hada, Kiyoaki Wajima, Kazuya Hachisuka, Mareki Honma, Kee-Tae Kim, Se-Jin Oh
Quantum Physics
Effective Study of Superconducting Quantum Circuits
Carlos Raul Javier Valdez, Hector Hugo Hernandez Hernandez and Guillermo Chacon-Acosta
We apply the momentous
quantum mechanics formalism to the non-perturbative study of superconducting
circuits in the transmon regime, deriving effective equations of motion for the bare Josephson junction (JJ), the cavity–JJ system, and a dissipative resonator. A Gaussian closure on the hierarchy of
quantum moments resums the full cosine nonlinearity into the closed-form effective
Hamiltonian $\tfrac{1}{2}[V(\phi+\phi_s)+V(\phi-\phi_s)]$, which is non-perturbative and preserves the periodicity and boundedness of the Josephson potential at all phase amplitudes; the standard Kerr (Duffing) approximation is recovered as a special case. We derive the
quantum-dressed frequency $\omega_{\rm eff}=\Omega_p\sqrt{\cos(\phi_{\rm zpf}/\phi_0)}$, and
benchmark the effective dynamics against exact Mathieu-function diagonalization, with the
quantum width $G^{2,0}(t)$ providing the most sensitive diagnostic of the closure's validity and marks the boundary of the Gaussian approximation more sharply than $\langle\hat\phi\rangle(t)$ does. We compare the Caldirola–Kanai, Bateman, and Lindblad descriptions: the Bateman dynamics, quantized with a switched
symplectic structure, preserves the Heisenberg bound, admits exact closed-form moment solutions, and reproduces the Lindblad
benchmark for weak damping, i.e., within the analytic error bound $(\lambda/\omega_1)^2\,\phi_{\rm zpf}^2$.
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Materials Science
Correlations of Spectroscopic and Dielectric Properties of Hafnia-Zirconia Nanoparticles
Yuriy O. Zagorodniy, Eugene A. Eliseev, Petr Jiricek et al. (+11 more)
In this work we analyze correlations of X-ray photoelectron and diffraction spectra, and dielectric properties of hafnia-zirconia nanoparticles (the chemical compositions Hf0.4Zr0.6O2 and Hf0.6Zr0.4O2, and the average size of 7.5 nm) prepared by the solid-state organo-nitrate synthesis and annealed in air. The phase state of the nanoparticles, determined by the X-ray diffraction spectroscopy, is the coexistence of the nonpolar monoclinic (42 - 76 mass %) and orthorhombic (56 - 24 mass %) phases. Concentration of the oxygen vacancies was estimated from the X-ray photoelectron spectroscopy. The increase in the intensity of the dielectric permittivity maximum observed near 350 - 450 K in a PVDF
matrix with embedded Hf0.4Zr0.6O2 nanoparticles can be related with an increase in oxygen vacancy concentration. Theoretical calculations, based on Landau-Ginzburg-Devonshire theory, explain the increase of the dielectric permittivity in Hf0.4Zr0.6O2 nanoparticles compared to Hf0.6Zr0.4O2 nanoparticles.
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All authors Yuriy O. Zagorodniy, Eugene A. Eliseev, Petr Jiricek, Jana Houdkova, Lesya Demchenko, Oksana V. Leshchenko, Victor N. Pavlikov, Ihor V. Pleskach, Anna O. Diachenko, Mikhail D. Volnyanskii, Oleksandr S. Pylypchuk, Myroslav V. Karpets, Mikhail P. Trubitsyn, Anna N. Morozovska
Fluid Dynamics
Silk-templated Nanostrips as Superprotonic Fibre Sensors
Jianhui Zhang, Ahmed Salem, Robert Tidswell et al. (+4 more)
Transforming textile fibres into sensors can facilitate continuous physiological monitoring for improving human healthcare. Coating fibres with electronic conductors can help detect physiological stimuli but their sensitivity scales with thickness and often lowers the fibre mechanical flexibility.
Proton conductors are potential alternatives; however, they suffer from fragile physical interfaces, and sluggish kinetics. Here, we report a bio-templated, scalable strategy to create superprotonic interfaces using natural silk fibres. We exploit ordered nanofibrils on silk fibres to selectively grow continuous metal-organic framework (MOF) nanostrips. This patterned, ca. $10\,\mu\mathrm{m}$-diameter fibre-structure provides low-defect interfacial pathways for ultrafast
proton transport, yielding conductivities up to 40 $S\,cm^{-1}$ - two orders of magnitude above the state of the art - with millisecond response and high mechanical robustness. The individual micro-thread sensors facilitate respiratory monitoring with a mean bias of 0.01 breaths $min^{-1}$ in volunteer testing, unaffected by human movement and readily capture breathing signature in high-flow oxygen therapy devices. We integrate arrays of micro-thread sensors in textiles and exploit deep learning to demonstrate high-resolution spatiotemporal humidity mapping in dynamic flow-fields and resolve asymmetric respiratory patterns that elude conventional single-point detectors. Our results should have broad-ranging implications, e.g. in wearable health monitoring, bioelectronics, and human-machine interfaces.
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All authors Jianhui Zhang, Ahmed Salem, Robert Tidswell, Haowei Wang, Vikramjeet Singh, Laurence B. Lovat, Manish K. Tiwari