General Relativity and Quantum Cosmology
Exceptional points and near-extremal boundary response in rotating BTZ black holes
Sheng Long, Yu Shi, Zhongwu Xia et al. (+4 more)
We investigate whether the coalescence of long-lived quasinormal modes enhances the boundary response of rotating BTZ black holes. Using exact scalar solutions with mixed Robin boundary conditions and the retarded boundary correlator, we compare frequency-domain resonances and time-domain signals at fixed source and operator normalizations. An exceptional point (EP) can be crossed by varying the
spin alone in a suitably selected fixed theory. Along a distinct near-extremal path that tracks the co-rotating EP surface by tuning the scalar mass and boundary coupling, a taller, narrower resonance coexists with a weaker but longer-lasting double-pole impulse response. The frequency-domain enhancement persists away from the EP and is therefore not unique to mode coalescence. Thus, the EP determines the double-pole structure and Jordan relaxation, but does not by itself determine the response strength, which also depends on the physical path and excitation protocol.
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All authors Sheng Long, Yu Shi, Zhongwu Xia, Huajie Gong, Zhoujian Cao, Qin Tan, Qiyuan Pan
Astrophysics of Galaxies
The JWST Proto-PAH project: Aromatic backbones with extensive aliphatic substitution account for both the aromatic and aliphatic emission
N. Clark, E. Peeters, J. Cami et al. (+18 more)
We find that the aromatic and aliphatic emission bands in four carbon-rich post-asymptotic
giant branch
stars with class D emission arise from a single carrier population: extensive aliphatic decoration of an aromatic skeleton, i.e. molecules with a coherent aromatic backbone and an unusually high aliphatic content. This conclusion is based on JWST NIRSpec and MIRI/MRS spectroscopy, covering 2.88-28.7um. The aliphatic 3.4um feature is stronger than the aromatic 3.3um feature, reversing the ratio seen in sources with typical polycyclic aromatic hydrocarbon (PAH) emission. If the aromatic emission arose from nominal PAHs, the 3.3um feature - unavailable in previous observations - together with the mid-infrared aromatic features, would constrain them to be large (greater than about carbon atoms), compact, and at least partially ionized. These properties predict a strong 8.6um feature. However, the 8.6um feature is weak or absent in all four sources, ruling out PAHs as the source of the aromatic emission. Instead, the emission must arise from the same carriers as the aliphatic emission. The position of the 6.9um feature and the broadened 11-14um out-of-plane emission independently support this. The CH2 and CH3 feature strengths vary across the sample, with the class D2 sources showing higher CH3 content. These carriers are far more aliphatic than the PAHs of planetary nebulae and the interstellar medium. However, they retain the aromatic skeleton that produces their aromatic features.
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All authors N. Clark, E. Peeters, J. Cami, G. C. Sloan, K. Volk, K. E. Kraemer, H. L. Dinerstein, M. A. Gomez-Munoz, G. M. Wahlgren, N. C. Sterling, A. Ricca, A. A. Zijlstra, J. Li, M. Matsuura, D. A. Garcia-Hernandez, R. Sahai, B. Aringer, C. Bhatt, J. Bernard-Salas, D. Das, A. Manchado
Statistical Mechanics
Emergent Wigner magnon crystals in a fully frustrated Heisenberg four-leg tube
Azam Zoshki, Hamid Arian Zad and Jozef Strecka
The ground state, magnetization curves, low-temperature thermodynamics, and heat-engine performance of the fully frustrated
spin-$1/2$ Heisenberg four-leg tube with
antiferromagnetic inter- and intra-plaquette coupling constants J1 and J2 are examined using exact diagonalization, density
matrix renormalization group, and localized-
magnon theory. In the unfrustrated to weakly frustrated regime J2/J1 << 2, the system exhibits a continuous field-driven
quantum phase transition between the gapped Haldane phase and a gapless Tomonaga-Luttinger
quantum spin liquid. In the highly frustrated regime J2/J1 > 2, the system contrarily displays discontinuous field-driven
quantum phase transitions between the Wigner
magnon crystals, which are manifested in zero-temperature magnetization curves as intermediate plateaus at zero, one-quarter, one-half, and three-quarters of the saturation magnetization. The low-temperature
magnetic and thermodynamic properties in this regime are accurately captured by an effective interacting
lattice-gas model of two monomer quasi-particle species constructed from localized one- and two-
magnon states. Finally, we explore a
quantum Stirling heat engine using the fully frustrated four-leg tube as the working medium. The work output and efficiency are strongly suppressed near discontinuous field-induced transitions and reach pronounced local maxima well inside the stability regions of the Wigner
magnon crystals.
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Mathematical Physics · Cross-listed from math.PR
Potential Hessian Ascent IV: Sampling the Sherrington-Kirkpatrick model at $\beta < 1$
Holden Lee, Juspreet Singh Sandhu and Jonathan Shi
We give a
polynomial-time
algorithm to sample from the Gibbs measure of the Sherrington-Kirkpatrick (SK) model with $o_n(1)$ error in total-variation distance (TVD) at any inverse-temperature $\beta < 1$. The
algorithm combines algorithmic
stochastic localization (ASL) with rejection sampling over path-space via Jarzynski's equality (JE). The analysis extends the authors' prior $\beta < 1/2$ result [arXiv:2605.03718] by replacing all global regularity requirements in the
stochastic differential equation (SDE) error analysis with local regularity around likely trajectories. The relaxed regularity is established using Celentano's proof of the local strong convexity of the TAP free energy [arXiv:2208.09550]. The analysis utilizes the cavity interpolation theory and free probability toolkit developed in the authors' previous result, where the former applies nearly verbatim and the latter applies supplemented with Lipschitz and $C^2$ extensions of various functions. The ASL and JE analysis arises from using the TAP free energy as an efficiently computable proxy for the actual free energy of the stochastically localized Gibbs measure [$ \S $ 3, arXiv:2605.03718]. We give a list of \vocab{desiderata} encapsulating the approximation and regularity properties required of the TAP free energy, relaxing those of [$ \S $ 2.5, arXiv:2605.03718] to only require local regularity. These generic desiderata are potentially applicable in other settings where a free energy surrogate exists, giving algorithmic sampling guarantees while bypassing the usual functional inequalities based approach.
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Atmospheric and Oceanic Physics
Weather and Climate Without Fluid Mechanics
Thomas D. DeWitt
Even if it were possible, attempting to model the motion of a fluid in a pipe by tracking each individual molecule would be an extraordinary waste of computation. The emergent laws of fluid mechanics accomplish the same goal on a laptop instead of a datacenter. But a sufficiently complex fluid such as in Earth's atmosphere again requires a datacenter, this time to resolve the many contortions in the fields making up our weather. Might there be some analogous set of emergent laws that would represent the effect of these perturbations without needing their explicit representation on a numerical grid? We argue that the existence of a
symmetry principle implies such laws are likely to exist. The atmosphere is scale invariant, implying that the observed structure at one scale is nothing but a stretched version of that at any other scale, at least within the invariant regime. Though some emergent laws built on scale invariance exist, they are built on a challenging ontological foundation, making them hard to develop further. We propose a path forward, first by introducing a new fundamental building block of the atmosphere that we term a “turbulon”, inspired by a lesser-known generalization of
turbulence theory that accounts for buoyancy. We then construct the Superposition of Turbulons and Eddies Atmospheric Model (STEAM), and show that simulated atmospheric volumes are broadly plausible when compared to state-of-the-art hydrodynamic simulation output. Some aspects of STEAM clearly need improvement, though other statistics reproduce observations better than hydrodynamic models, and visualizations of simulated clouds are strikingly realistic. We estimate STEAM's computational cost to be up to a million times less than hydrodynamic models, suggesting that the Navier-Stokes equations may not, in fact, be required for simulation and prediction of Earth's weather and
climate.
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Fluid Dynamics
Dual Laser and Shadow Particle Image Velocimetry for Multiscale Fluid-Structure Interactions
Adrian Herrera-Amaya and Monica M. Wilhelmus
Experimental Fluid-Structure Interaction (FSI) often involves phenomena that occur simultaneously across vastly different spatial and temporal scales. For example, the separation bubble behind a cylinder and the
vortex interactions in its wake, or the flow produced by an individual swimmer and the flow generated by the movement of the entire swarm. Imaging-based flow studies of such FSI phenomena are challenging and often lead to separate analyses of different flow regions. This work introduces simultaneous shadow and
laser-based Particle Image Velocimetry (PIV) to obtain concurrent near-wall and far-field flow velocity measurements. The experimental setup developed here enables the first simultaneous comparison between shadow- and
laser-based PIV, demonstrating that shadow velocimetry can achieve accuracy comparable to
laser-based measurements at the macro scale. We then use this new combined flow measurement technique to fully capture the velocity field generated by a shrimp-inspired
underwater robot, employing
laser PIV to record the flow surrounding the
robot and shadow PIV to focus on the actuators, imaging regions that the
laser technique cannot resolve due to wall reflections and shadows behind the structures. The simultaneous application of shadow- and
laser-based PIV offers a new experimental avenue for gaining insights into the physics of FSI phenomena.
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Quantum Physics
Encryptability As a Coordinate Choice: Depth-One Homomorphic Federated Learning of Quantum Neural Networks
Marcel Mordarski, Nathan Mani, Arshad Patel et al. (+2 more)
Encrypted training relies on keeping server-side updates low-degree. This constraint traditionally excludes models whose weights inhabit a compact Lie group (notably variational
quantum circuits, where every trainable weight is an $\mathrm{SU(2)}$ rotation). Expressed in Euler angles or discrete alphabets, these updates appear transcendental, historically demanding prohibitive costs: one client–server round per gate, or upwards of $25{,}000$ operations per weight. This penalty is strictly an artefact of coordinates. In the unit-quaternion (
spin) chart, group composition is exactly bilinear (degree two, with coefficients in $\{-1,0,+1\}$). Consequently, encrypted rotation updates cost one multiplicative level and
federated averaging costs zero in any levelled homomorphic scheme, completely eliminating bootstrapping. This implementation-independent algebraic property is confirmed across two cryptographic backends, introducing only $0.0$ and $-2.0\times10^{-12}$ rad of aggregation error. Leveraging this reduction yields a non-interactive protocol for encrypted
federated training of hybrid
quantum–classical networks. It includes correctness proofs for aggregation and sign handling, plus a compilation lemma proving parameterised entanglers add only constant-factor overhead without altering the depth class. Empirically, a paired five-seed study confirms zero measurable utility tax ($\Delta=+9\times10^{-6}$ MSE, $p=0.92$), and a noise-budget ablation falsifies the hypothesis that encryption noise regularises. These convergence trends replicate across
datasets and scale to $20$ clients. Finally, hardware validation on a $156$-
qubit processor achieves $0.9918$ fidelity against a $0.99957$ unencrypted control.
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All authors Marcel Mordarski, Nathan Mani, Arshad Patel, William Knottenbelt, Roberto Bondesan
Materials Science
Dual Topological Channels in a Programmable Mechanical Metamaterial
Soroush Soltani and Jihong Ma
Topological mechanical metamaterials generally derive their robustness from one of two distinct mechanisms: kinematic
topology, which localizes zero-frequency floppy modes through
geometric compatibility, or band
topology, which localizes finite-frequency waves through topological bandgaps. Because these mechanisms arise from fundamentally different physical principles, mechanical systems are typically engineered to exploit either static or dynamic topological functionality, but not both simultaneously. Here we demonstrate that a single mechanical metamaterial can host two independent topological channels governing static and dynamic response within the same architecture. Using a generalized rotor-chain
lattice with two coupled rotational degrees of freedom per unit
cell, we realize the coexistence of a topological polarization mode and a finite-frequency topological band mode. We show that the two channels are governed by distinct invariants and can be programmed independently through geometry, angular asymmetry, and stiffness dimerization. Remarkably, despite being governed by distinct topological invariants and controlling different physical responses, the two channels undergo topological transitions at a common
symmetry-controlled critical geometry. Experimental measurements using scanning
laser Doppler vibrometry confirm simultaneous localization of a boundary floppy mode and a finite-frequency domain-wall state in the same structure. These results establish dual topological channels as a general design principle for multifunctional mechanical metamaterials and demonstrate how static deformation and dynamic wave transport can be programmed independently within a single architecture.
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Astrophysics of Galaxies
The JWST Proto-PAH project. Computational modeling of the emission carriers
A. Ricca, G. C. Sloan, E. Peeters et al. (+8 more)
The infrared spectra of many carbon-rich post-asymptotic
giant branch
stars are dominated by emission features from aromatic and aliphatic hydrocarbons, but the chemical structure of the carriers remains unidentified. Class D sources show unusual emission profiles with strong aliphatic emission, providing a stringent test of carrier candidates. Here we investigate whether hydrogenated carbonaceous molecular particles can be the carriers of these features. Rather than assuming candidate geometries we generate the initial structures using ab initio molecular dynamics simulations and optimize them using density functional theory. We then compare the computed emission spectra to JWST NIRSpec and MIRI/MRS observations of Class D sources. The structures providing the best agreements contain sizeable domains with defect-bearing aromatics and hydrogenated-aromatics connected by aliphatic bridges, in contrast to the "arophatic" cluster model of isolated two- to three-ring aromatics connected by aliphatic and olefinic bridges. As a representative example, we discuss in detail the molecular particle C130H96 (radius of 5.5 A) and compare its computed spectrum to the JWST spectra of IRAS 05110-6616, a Class D2 source with apparent shifts of the aromatic C-H out-of-plane bands. The calculated spectra are in qualitative agreement with the observed 3 micron profile, the aliphatic C-H bending bands, the broad 8 micron feature, the 11-14 micron C-H out-of-plane region, and the bands at 16 and 21 microns. We hypothesize that UV photo-driven fragmentation of such molecular particles releases aromatics linked by aliphatics, followed by the formation of polycyclic aromatic hydrocarbons and fullerenes as these objects evolve into planetary nebulae.
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All authors A. Ricca, G. C. Sloan, E. Peeters, J. Cami, N. Clark, M. Matsuura, R. Sahai, J. Bernard-Salas, D. A. Garcìa-Hernàndez, J. Li, C. Bhatt
Superconductivity
Superconductivity in Noncentrosymmetric NbReSi: Beyond Harmonic and Adiabatic Limits
Shashi B. Mishra, Sohair ElMeligy and Pratibha Dev
The noncentrosymmetric
superconductor NbReSi (Tc=6.5 K) is being actively explored for unconventional pairing that is allowed by its broken inversion
symmetry. Despite broad experimental interest, what drives its superconductivity remains an open question. We show that the electronic states at the
Fermi level are dominated by Nb and Re $d$-states. Vibrations of the same heavy-metal framework contribute more than 95% of the electron-
phonon coupling, with the strongest coupling arising from the sublattice-selective breathing mode involving strongly bonded Re atoms. Harmonic Migdal-Eliashberg theory overestimates Tc by more than 60%. The zero-point anharmonic hardening of these modes reduces the coupling by 20%. The leading vertex correction becomes important as well despite low
phonon energies due to the contribution of spatially localized Re-d orbitals to the electronic band structure near the
Fermi level. Together, anharmonicity and vertex corrections bring the calculated Tc and superconducting gap into close agreement with experiment, establishing NbReSi as a moderately coupled,
phonon-mediated
superconductor whose quantitative description requires going beyond harmonic Migdal–Eliashberg theory.
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Earth and Planetary Astrophysics
Hot Rocks Survey VI: An anomalously hot dayside for the rocky planet GJ 357 b
Merlin Zgraggen, Brice-Olivier Demory, Hannah Diamond-Lowe et al. (+15 more)
As part of the JWST Hot Rocks Survey, we analyzed a JWST/MIRI F1500W secondary-eclipse observation of GJ 357 b, a rocky
exoplanet orbiting a nearby M
dwarf. We also performed a new global analysis of the GJ 357 system, combining TESS photometry, a JWST/NIRSpec transit observation, the MIRI secondary eclipse, radial velocities, and
Gaia parallax measurements to obtain a self-consistent set of
stellar and planetary parameters. We measure an occultation depth of $200.5 \pm 12.7,\mathrm{ppm}$, corresponding to a dayside brightness temperature at $15,\mu\mathrm{m}$ of $T_{\mathrm{b},15,\mu\mathrm{m}}=923^{+39}_{-38},\mathrm{K}$. The inferred brightness temperature substantially exceeds the zero-Bond-albedo, no-redistribution, disk-integrated bolometric dayside reference temperature of $686 \pm 14,\mathrm{K}$. The measured eclipse depth differs from the tested zero-albedo, grey airless-surface model by $5.2\sigma$ and is also inconsistent with the high-mean-molecular-weight atmospheric models considered here, including pure CO$_2$, pure H$_2$O, and N$_2$ with 100 ppm CO$_2$. Possible explanations for the excess emission in the MIRI/F1500W band include wavelength-dependent surface emissivity, localized hot regions, or atmospheric temperature structures and opacity sources not included in the tested models. Follow-up mid-infrared eclipse spectroscopy would constrain the shape of the dayside emission spectrum and help test the proposed surface and atmospheric explanations.
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All authors Merlin Zgraggen, Brice-Olivier Demory, Hannah Diamond-Lowe, João M. Mendonça, Erik Meier Valdés, Mark Fortune, Kathryn D. Jones, Daniel Kitzmann, Millie Smith, Natalie H. Allen, Prune C. August, Amélie Gressier, Måns Holmberg, Jegug Ih, Lars A. Buchhave, Néstor Espinoza, Neale P. Gibson, Kevin Heng
Astrophysics of Galaxies
Breaking the AGB Color Degeneracy with Variability and H$_2$O: A Consistent Picture of AGB Chemistry, Dust, and the J-Region Across Environments
Caroline D. Huang, Massimo Marengo, Antonio Capodagli et al. (+7 more)
Resolved asymptotic
giant branch (AGB) populations present many observational puzzles. We consider three often treated separately: photometric C/O classification boundaries must be redrawn empirically in new environments; hydrostatic model grids are too blue in bands sampling H2O absorption; and J-region (JAGB) luminosities can differ between fields of a single
galaxy. Pulsation connects them into a coherent picture. Using SPHEREx spectroscopy of AGB
stars in the Large Magellanic Cloud (LMC) with JWST/NIRCam photometry and HST time-series of the SN Ia host M101, placed on a common scale by synthetic photometry, we investigate how AGB variability, surface chemistry, and circumstellar
dust depend on environment. We develop an F182M index sensitive to 1.9$\mu$m H2O absorption that chemically classifies variable AGB
stars and reveals oxygen-rich (O-rich)
stars degenerate with carbon-rich (C-rich)
stars in broadband colors. Because these features arise in extended atmospheric layers, hydrostatic grids struggle to reproduce them. Pulsation and circumstellar
dust are asymmetrically linked: nearly all
stars with substantial infrared excess are variable, while many variables show little
dust. This supports mass loss initiated by pulsation and enhanced by
dust formation. Variable O-rich AGB
stars in M101 are up to ~0.7 mag redder than their LMC counterparts in
dust-sensitive colors, consistent with more efficient silicate-
dust production at higher
metallicity, while C-rich populations depend less on environment. Color windows that select C-rich
stars cleanly in the LMC are therefore 33-68% O-rich in the metal-rich M101. This challenges the J-region's universality as a standard candle while evading standard self-consistency checks. We recommend combining variability, or the infrared excess that implies it, with photometry of molecular features to improve AGB classification at 0.75-5.0$\mu$m.
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All authors Caroline D. Huang, Massimo Marengo, Antonio Capodagli, Adam G. Riess, Louise Breuval, Stefano Casertano, Patricia A. Whitelock, Gagandeep S. Anand, Randall K. Smith, Wenlong Yuan
Soft Condensed Matter
Material and thermal properties of MgCl2 molten salt by ab initio and machine-learning molecular-dynamics simulations
Roberto Llovera, María Andrea Barral, Verónica Vildosola et al. (+2 more)
We study the structural, thermophysical and dynamical properties of molten MgCl2 over a wide temperature range using Ab Initio Molecular Dynamics (AIMD) and molecular dynamics simulations based on machine-learning interaction potentials (MLIPs). MLIPs can achieve near-AIMD accuracy at a fraction of the computational cost, enabling simulations of larger systems and longer timescales. This opens up the possibility of studying the system under out-of-
equilibrium conditions, which in turn allows for the calculation of physical properties, such as the thermal conductivity or viscosity, that cannot be obtained reliably for the typical time and length scales accessible to AIMD. We follow two complementary approaches to develop and evaluate the MLIPs. Firstly, we develop a Deep Potential (DP) from scratch using AIMD trajectories at different temperatures. Secondly, we also evaluate two out-of-the-box foundation models and a fine-tuned version of one of them. The fine-tuning is performed using configurations from the AIMD trajectories originally used to train the Deep Potential. We compare the predictions of the trained DP, the foundation models and AIMD simulations with the available experimental data and provide a comprehensive calculation of the most important physical quantities of molten MgCl2. We compute densities, radial and angular distribution functions, thermal conductivity, heat capacity, viscosity and
diffusion coefficients over the 1000-1600 K temperature range. This range is relevant to important technological applications such as thermal energy storage, generation IV
nuclear reactors and concentrated
solar power systems. Finally, we briefly review the accuracy and performance of the different MLIPs versions used throughout the work.
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All authors Roberto Llovera, María Andrea Barral, Verónica Vildosola, Florencia Cantargi, Claudio Pastorino
General Relativity and Quantum Cosmology
Rotating Weyssenhoff fluids in linearized Einstein-Cartan theory
Emmanuele Battista, Salvatore Capozziello and Francesco Giovinetti
The Weyssenhoff fluid expands the ordinary perfect-fluid description of general relativity by taking into account the intrinsic
spin of its constituent particles. Within the linearized regime of Einstein-Cartan theory, we investigate the exterior geometry produced by isolated slowly rotating Weyssenhoff fluids, i.e., sources endowed with both macroscopic and microscopic angular momenta. Our work represents an extension of the foundational analysis of Arkuszewski, Kopczyński and Ponomariev, which was restricted to the static fluid configuration. Under the assumptions of stationarity and axial
symmetry, we derive the explicit expression for the linearized stress-energy tensor of the source and obtain the corresponding metric through a multipole expansion. The ensuing solution exhibits a generalized Lense-Thirring structure, with both the gravitoelectric and gravitomagnetic sectors affected by the
quantum spin and macroscopic rotation. We also discuss some phenomenological implications of the model, including the gyroscope precession and the Sagnac effect, along with potential experimental probes of the predicted corrections.
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Accelerator Physics · Cross-listed from eess.SY
From Routing Delay Shifts to Silent Data Corruption: Neutron-Induced SEU Effects in AXI-Based Zynq UltraScale+ MPSoCs
Mostafa Darvishi
SRAM-based FPGA system-on-chip devices are vulnerable to single-event upsets (SEUs) in configuration
memory, which may perturb programmable routing resources and degrade communication fabrics. In modern Zynq UltraScale+ MPSoCs, such routing disturbances can introduce small propagation delay shifts that remain logically transparent yet compromise AXI-based data transfers and lead to silent data corruption. Although routing delay degradation and AXI interconnect failures have been studied independently, their experimental correlation under
neutron irradiation has not been established. This work presents a cross-layer investigation on a ZCU104 platform integrating routing-dominated delay sensors with an AXI interconnect
benchmark comprising replicated accelerators.
Neutron irradiation experiments were conducted on the fully operational system, while a frame-level configuration fault injector implemented via the internal configuration access port enables controlled upset emulation. Measured routing delay events are statistically correlated with communication failures, and cross-sections for both timing shifts and AXI malfunctions are derived. The results experimentally demonstrate how
neutron-induced routing perturbations propagate into system-level silent data corruption in UltraScale+ MPSoCs, providing insight for resilience-oriented AXI-based design in
neutron-rich environments.
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Instrumentation and Methods for Astrophysics
FOTO: Figure-Level Semantic Search for Astronomy
Hurum Maksora Tohfa and Francisco Villaescusa-Navarro
Astronomy papers carry much of their content in figures, but literature search indexes text, so there is no way to find a plot by describing what it shows. We present FOTO, a figure-level search tool over 482,750 captions from 53,839 peer-reviewed astro-ph papers. Each figure is indexed once by its title and caption, embedded with a 110M-parameter open model that runs locally, and a large
language model is applied only to the retrieved shortlist, where it verifies real figures rather than generating references to ones that do not exist. Held to the harder figure-level criterion, FOTO recovers the target for 29 to 79% of queries at recall 20 depending on register, against 6 to 20% for Pathfinder and 8 to 16% for Semantic Scholar on the easier paper-level criterion, and it beats the paid
embedding API it replaced. Reranking the shortlist then raises recall at 1 from 0.667 to 0.875 on detailed queries and from 0.071 to 0.571 on vague ones. Openly available models match or beat paid LLM models for verification
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Mathematical Physics
The importance of the change-of-variables integration technique in deriving the PDFs of important probability distributions
Jorge P. Arpasi
The purpose of this article is to explicitly describe how the integration technique known as the change of variables is used in graduate-level Probability and Statistics courses. Throughout the article, we employ this integration technique seven times across various examples and results. We demonstrate that four applications of this technique are required to derive the probability density function (PDF) of the Student's t-distribution.
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Solar and Stellar Astrophysics
The 91T/99aa-like Type Ia Supernova 2019vrq, Part II: 3D, Non-LTE, Low-Amplitude, Pulsating Delayed-Detonation Models of a Promising Standard Candle
Peter Hoeflich, Yi Yang, J. Craig Wheeler et al. (+11 more)
We analyze the overluminous, 91T/99aa-like Type~Ia SN 2019vrq, based on light curves(LCs) and spectropolarimetric time-series. We employ 3D-radiation-hydrodynamical, full non-LTE simulations of low-amplitude, radially-pulsating-off-center-delayed-detonations(PDD) of a possibly rotating near-M(Ch) mass white
dwarf (WD) to reproduce the LCs and spectra. The progenitor originates from a 7 Mo main-sequence
star of
solar metallicity. The explosion yields 0.86Mo of 56Ni and 0.023Mo of 58Ni. The latter falls a factor of 10 below that of `classical' delayed-detonations for 91T/99aa-like SNe, a diagnostic that is directly testable with JWST. The slow deflagration leaves a bound, pulsating WD. The detonation is triggered at 0.8 Mo. LCs and spectra require an outer 0.11 Mo of unburned material with twice-
solar Fe, plausibly the ashes of an earlier, unsuccessful explosion, and low-level mixing of
nuclear-statistical-
equilibrium(NSE) elements. The spectra reflect early high ionization followed by recombination, with the photosphere shifting from intermediate-mass-element- to NSE-dominated layers about a week before maximum. The early high-velocity (HV) CaII IR3 line (likely produced by an aspherical density shell at 24,000km/s of 0.01 Mo) arises from an ionization sandwich rather than a double structure in abundances. After Ca recombines, the CaII IR3 wing reaches 33,000km/s well beyond the HV component. The low polarization is due to low scattering in an iron-group-dominated photosphere, consistent with asphericities <20% and resulting in a directional luminosity dependence 10-15% from the outer layers, and a dispersion of 35% in total. The LC-shape provides a further probe of asphericity, consistent with the locally tested polarimetry limits and relevant for high-z cosmology.
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All authors Peter Hoeflich, Yi Yang, J. Craig Wheeler, Dietrich Baade, Aleksandar Cikota, Elham Fereidouni, Divya Mishra, Sagiv Shiber, Maximo Marengo, Tyco Mera, Chris Ashall, Kyle Medler Cameron Medler, Lluis Galbany, Mark M. Phillips
Optics
Energy-selective control of noise-assisted multipulsing by weak optical seeding in the dissipative-soliton-resonance regime
Vladimir L. Kalashnikov, Alexander Rudenkov, Evgeni Sorokin et al. (+1 more)
We investigate how weak optical injection changes single-pulse operation in a
laser in the dissipative-
soliton-resonance regime. The energy scans show that a small injected field suppresses multipulsing and extends predominantly single-pulse operation to higher energies. Further increasing the seed power makes this extended range nonuniform: regions of enhanced multipulse formation alternate with regions of suppression. We analyze timing and optical-phase fluctuations of the injection field. At the lowest energies, these fluctuations cause continuous-wave and multipulse generation to dominate the
laser output. At the highest energies, injection-field phase fluctuations promote multiple pulses, whereas time fluctuations suppress them. Deterministic calculations without noise or injection show that both single pulses and prepared pulse pairs can persist under the same settings. We show that the spectral
entropy of a dissipative
soliton reflects changes in individual pulse spectra and pulse interference. It characterizes the probabilistic transition between single- and multipulse regimes, but it does not, by itself, predict in detail which regime the
laser will form. Together, the results connect the energy-selective action of optical injection to pulse formation and structure, while distinguishing persistence of a prepared pulse from its formation out of a background.
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All authors Vladimir L. Kalashnikov, Alexander Rudenkov, Evgeni Sorokin, Irina T. Sorokina
Soft Condensed Matter
Shear stress during self-assembly encodes stiffness of network-based materials
Lens M. Dedroog, Olivier Deschaume, Carmen Bartic et al. (+4 more)
The mechanical properties of network-based materials have been extensively studied under qui- escent conditions, yet their self-assembly in nature occurs mainly in a mechanically stressed envi- ronment. Here, we show that the stiffness of collagen networks, one of the main building blocks of the mammalian extracellular
matrix, can be tuned by applying shear stress during gelation, which first strains and aligns the material, then triggers a dramatic irreversible increase in the elastic modulus. This stiffening is anchored by maintaining the stress until the gel is fully matured. Using particle-based simulations, we show that the underlying microscopic mechanism is likely generic to a broad class of network-based systems and arises from two synergetic effects: changes in the network orientation and
topology through the formation of permanent contacts that stabilize the system. Our findings are rationalized using a
rigidity percolation framework and offer a general principle for encoding elasticity in biological and synthetic networks.
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All authors Lens M. Dedroog, Olivier Deschaume, Carmen Bartic, Yovan de Coene, Erin Koos, Minne P. Lettinga, Mehdi Bouzid
Strongly Correlated Electrons
Yutaka Itoh
We study the effects of zero-point
spin fluctuations on the
nuclear spin-
lattice relaxation rate 1/$T_1$ around a two-dimensional
antiferromagnetic quantum critical point in the self-consistent renormalization theory. For a weak mode-mode coupling constant $y_1 < $ 0.1, the finite temperature behavior of 1/$T_1$ across the
quantum critical point resembles that for only the thermal
spin fluctuations. For a strong mode-mode coupling constant $y_1 > $ 0.1, 1/$T_1$ takes its local maximum as a function of temperature in the nearly
antiferromagnetic state. Experimental observation of the local maximum in the $^{63}$Cu
nuclear spin-
lattice relaxation rate 1/$T_1$ of lightly-doped
superconductors La$_{2-x}$Sr$_x$CuO$_4$ with $x$ = 0.06-0.10 is associated with the effects of the zero-point
spin fluctuations. The two-dimensional
magnetic quantum critical point and the role of the zero-point
spin fluctuations are discussed in the electron
spin dynamics of underdoped
superconductors La$_{2-x}$Sr$_x$CuO$_4$.
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Pattern Formation and Solitons · Cross-listed from q-bio.PE
Prevalence and the rate of antigenic evolution are jointly determined in an eco-evolutionary SIR model
Daniel Gomez and Joshua B. Plotkin
Influenza A persists by continually changing the antigens that its host population recognizes. How fast it evolves and how many hosts it infects are not independent, because the immunity that selects new variants is produced by the infections the pathogen has already caused. We analyze a model of Andreasen et.\ al.\ that captures this eco-evolutionary feedback, and we extend it to the case where infection may kill the host. In the model infected and recovered hosts are distributions over a one-dimensional antigenic space coupled by cross-immunity. The endemic state is a traveling pulse: the infected distribution keeps a fixed shape and advances through antigenic space at constant speed. In the limit of weak antigenic mutation we construct the pulse asymptotically and find that: (i) the speed of antigenic
evolution decreases as prevalence rises, (ii) less standing antigenic variation accompanies either faster or slower antigenic
evolution, depending on whether pathogens differ in immune evasion or host lifespan (iii) the total number of infected hosts is largest at an intermediate virulence when the host birth rate is sufficiently low.
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Optics
Skyrmion topology of scalar waves in real and momentum space
Nai H. Kwong, Ewan M. Wright, Jan Wingenbach et al. (+4 more)
Generalizations of
magnetic skyrmions to the context of other areas of physics, such as plasmonics, optics (including microcavity polaritons) and even water waves have become an important research topic. However, the generalization of the skyrmion number in such systems is still the subject of active research. While
magnetic skyrmions textures are inherently formed by vectors (
magnetic spin vectors), recent developments in other areas of physics have generalized the concept of skyrmions and skyrmionic patterns to the case in which scalar fields are used to define 3-component pseudo-
spin vectors. This gives rise to a wide variety of skyrmion-like textures, depending on the detailed functional forms of the scalar fields. For example, steady-state outgoing waves in driven-dissipative polariton systems fail to have a well-defined global skyrmion number in real (configuration) space but can have one in momentum space. We classify the skyrmion integral for various scalar fields with different asymptotic behaviors in real space as well as momentum space, and in both cases give conditions for the skyrmion number not to exist, or be integer, half-integer or non-integer. Examples of physical systems to which our analysis can be applied include polariton condensates, water waves and gain-guided
lasers.
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All authors Nai H. Kwong, Ewan M. Wright, Jan Wingenbach, Roman Lebs, Harald Giessen, Stefan Schumacher, Rolf Binder
Astrophysics of Galaxies
Collisional excitation of E- and Z-ethanimine to model cold molecular clouds
Francesca Tonolo, Vivek Vijay, Ernesto Quintas-Sánchez et al. (+5 more)
Context. Ethanimine is a prebiotically relevant complex organic molecule that has been proposed as a key precursor of amino acids in the interstellar medium. To date, both its E and Z isomers have only been detected toward the Sgr B2(N) molecular cloud. The pronounced non-local thermodynamic
equilibrium (non-LTE) effects predicted for this molecule require accurate collisional rate coefficients for reliable astrophysical modeling and future astronomical searches. Aims. We aim to provide the first collisional
datasets for both ethanimine isomers with the main cold molecular clouds collision partners, He and para-H2, in order to support non-LTE radiative-transfer modeling. Methods. State-to-state rate coefficients for collisions with He were computed by integration over mixed close-coupling (CC) and coupled-states (CS) scattering cross sections at different energy ranges. In addition, comparisons with mixed
quantum-classical theory (MQCT) calculations performed for both He and para-H2 collisions enabled the derivation of transition-specific scaling factors, which were applied to predict collisional rate coefficients for para-H2. Results. We present the first state-to-state collisional
datasets for both E- and Z-ethanimine in collision with He and para-H2, including all rotational transitions involving levels below 50 cm-1 and over the 5-100 K temperature range. Conclusions. The
datasets reported here provide the first collisional information suitable for non-LTE modeling of ethanimine in cold interstellar environments. They represent a key step toward more reliable abundance determinations and may facilitate future astronomical detections of both ethanimine isomers beyond Sgr B2(N).
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All authors Francesca Tonolo, Vivek Vijay, Ernesto Quintas-Sánchez, Adrian Batista Planas, Carolin Joy, Richard Dawes, François Lique, Dmitri Babikov
Quantum Physics
Disentangling Expressibility, Symmetry Protection, and Hardware Noise in Variational Quantum Simulation of the Two-Flavor Schwinger Model
Karthikeya Machiraju, Krishna Sujith and Kaustav Bhowmick
Existing
quantum simulations of the two-
flavor Schwinger model have run at a single
lattice size, and it is not known how far the variational approach can be pushed or which weakness stops it first. Following the model from N = 2 to 6 staggered
lattice sites, we find that the binding constraint at reachable sizes is hardware noise rather than
circuit expressibility or trainability, and identify N = 3 as the immediately viable extension of existing trapped-ion experiments. The energy error of a charge-conserving ansatz collapses onto one function of p/d, the ratio of variational parameters to physical-sector dimension, and falls by more than two orders of magnitude as p/d rises through order unity, giving the expressibility condition L(4N - 1) >= binom(2N,N) for L
circuit layers. The condition is local in chemical potential: at N = 3 the layer count sufficient at zero chemical potential leaves a 74.38% error near the first-order boundary, while one further layer reaches 0.08%. Charge conservation also protects trainability and prevents charge-sector leakage: as the
qubit count doubles from 4 to 8, the normalized gradient variance falls to 1/3.56 of its starting value for the constrained ansatz, versus 1/13.57 for an unconstrained
circuit. Comparing a global contraction with per-gate local noise, a fixed-parameter control shows that the noise model, not whether the optimizer runs inside the noisy loop, sets how strongly noise degrades the first-order transition. At N = 4, a noiseless control reaches 0.12% mean error, whereas the same
circuit at 1.00% depolarizing noise reaches 25.69 to 52.81%.
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High Energy Astrophysical Phenomena
Spectral and Polarization Properties of Coherent Radio Emission from Relativistic Magnetized Pair Plasma Shocks
Yuanhong Qu, Joonas Nättilä and Lorenzo Sironi
Fast
radio bursts (FRBs) are millisecond-duration
radio transients whose emission mechanism remains an open question. The so-called synchrotron maser instability in relativistic magnetized shocks is a leading candidate for FRBs produced outside the compact object magnetosphere, yet its spectral and polarization predictions have not been systematically explored. We present three-dimensional particle-in-
cell simulations of relativistic magnetized pair
plasma shocks with upstream magnetization $\sigma > 1$ and bulk Lorentz factor $\gamma_0 = 10$, assuming a plane-parallel shock geometry and neglecting radiative cooling, and compute the spectra and polarization of the precursor maser emission for an arbitrary line of sight. For on-axis observers aligned with the shock-propagation direction, the X-mode dominates the emission. The O-mode power increases at off-axis viewing angles and is primarily associated with currents parallel to the upstream background
magnetic field. Assuming a spherical shock, we find full-width-at-half-maximum fractional bandwidths of $\Delta\nu/\nu_0\simeq0.57$ and $0.82$ for $\sigma=3$ and $6$, respectively. For highly magnetized shocks, the intrinsic emission bandwidth accounts for most of the spectral width, while high-latitude contributions provide additional broadening. The integrated emission remains highly linearly polarized near the spectral peak, with a nearly constant polarization angle due to the dominance of the X-mode. Our results suggest that synchrotron maser emission can produce spectra with bandwidths and high linear polarization degrees compatible with observations of some non-repeating FRBs, and may provide testable signatures for distinguishing shock-powered FRBs from other emission mechanisms.
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Materials Science
Anomalous Pressure-Enhanced Polarization in Sliding Ferroelectrics
Lujin Min, Sahas Kamat, Ameer Mustafa et al. (+8 more)
Hydrostatic pressure commonly suppresses polarization in conventional displacive ferroelectrics by weakening the off-center ionic distortion. Sliding ferroelectrics may provide a contrasting case because their polarization arises from stacking-dependent interlayer charge transfer rather than intra-unit-
cell ionic displacement. Here, hydrostatic pressure is shown to enhance, rather than suppress, the polarization of parallel-stacked
bilayer boron nitride, a prototypical sliding ferroelectric. A
graphene layer placed on top of a ferroelectric boron nitride
bilayer is used for sensing the
evolution of polarization under pressure. The pressure enhances both the interlayer potential and the ferroelectric polarization, with the latter increasing approximately linearly by 80% up to 1.66GPa. These results establish hydrostatic compression as a tuning parameter for sliding-ferroelectric polarization, with potential implications for ultrathin slidetronic
memory devices.
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All authors Lujin Min, Sahas Kamat, Ameer Mustafa, Nguyen The Duy, Kyle Nadel, Junhao Lin, Kenji Watanabe, Takashi Taniguchi, Daniel Bennett, Brad J. Ramshaw, Kenji Yasuda
Quantum Physics
Construction of Partial Join Graphs with Perfect State Transfer in Shunt Decomposition-Based Quantum Walks
Banita Katuwal, Y Lakshmi Naidu, Srinath M S et al. (+1 more)
In this paper, we define directed partial join graphs with signed couplings and construct discrete-time
quantum-walk transition operators for these graphs using the shunt-decomposition framework. The resulting transition operators apply to several important graph families, including complete graphs with loops, circulant partial joins, complete bipartite graphs, tensor powers of complete bipartite graphs, all with signed couplings. For each family, we identify the corresponding structure of the transition operator and derive necessary and sufficient conditions for periodicity and perfect state transfer (PST), when one of the two directed regular graphs admits PST. Based on these results, we identify two types of state transfer; internal PST, which occurs between vertices within the same graph, and coupling PST, which occurs between two components of join graphs. We further develop a double-cover construction for directed partial join graphs and derive conditions for periodicity and PST when the associated transition operators do not necessarily commute. Using this construction, we establish PST results for double covers of complete graphs with loops. In particular, we provide an example in which the complete graph \(K_n\) does not exhibit PST for \(n\geq4\), whereas a suitable partial join of \(K_n\) exhibits PST when \(n=2^m\), \(m\geq2\). Hence, these results extend the class of graph families admitting PST in shunt-decomposition-based
quantum walks and provide a unified framework for studying
quantum state transfer in graph joins, products, and covers.
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All authors Banita Katuwal, Y Lakshmi Naidu, Srinath M S, Supriyo Dutta
High Energy Physics (Experiment)
Direct Neutrino Communication Through the Earth: NuMI-Calibrated Simulation and Far-Field Sensitivity
Sven-Patrik Hallsjö
Neutrinos can pass through substantial matter, potentially enabling direct links where electromagnetic paths are obstructed, but their weak interactions make reception difficult. We present two separate calculations. First, a repeated OOK/CRC simulation calibrated to the published NuMI-MINERvA selected-event mean correctly accepts 65.7% of simulated packets with a 40-bit payload and an eight-bit CRC after five repetitions, with about 587 s mean latency under assumed external synchronization. Varying the input mean across its approximate Poisson counting interval gives 60-72% correct acceptance; this is a sensitivity range, not a joint confidence interval. Second, a distinct idealized far-field model gives 24.4 MW peak
neutrino-carried on-slot power for a 10 kt receiver at 5,000 km, conditional on 3 GeV
neutrinos, 1 mrad divergence, 50% selection efficiency, unit
flavor survival, zero background and one-second slots. Neither result establishes a practical long-baseline source or measured CRC performance.
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Materials Science
Revealing Polar Walls in CsPbBr3: Herringbone Structure and Formation Pathway
Weilun Li, Qimu Yuan, Michael B. Johnston et al. (+1 more)
Domain walls in ferroic materials can host nanoscale functionalities absent from the periodic
crystal, offering new opportunities to control electronic transport and polarization in
semiconductor devices. Metal halide perovskites demonstrate important photophysical properties; however, their ferroic properties remain unclear. Here we discover a hierarchical herringbone network of polar walls within the non-polar halide perovskite CsPbBr3 comprising ferroelastic twin walls and antiphase walls. Atomic-scale imaging reveals that both wall types comprise nanoscale regions whose inversion-
symmetry is broken compared to the surrounding bulk
lattice. In-situ heating experiments show that these interfaces form sequentially during
symmetry-lowering phase transitions, revealing a different formation pathway compared with 'conventional'
oxide perovskites. These polar nano-walls, together with their enclosed
topology, may impact carrier transport. This reveals a previously unrecognized structural motif in CsPbBr3, providing new insights into their photophysical and optoelectronic behavior.
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All authors Weilun Li, Qimu Yuan, Michael B. Johnston, Joanne Etheridge