Applied Physics
A Next-Generation Snow Albedo Parameterization for Climate Modeling using Constrained Machine Learning
Andrew Charbonneau, Katherine Deck and Tapio Schneider
We demonstrate a data-driven parameterization for snow albedo using a constrained neural differential equation that directly predicts a range of snow albedo tendencies from standard snow and meteorological inputs. After training with multi-year in-situ and satellite observations from a wide variety of locations, the scheme effectively reproduces daily albedo
evolution across diverse
climate zones, with median error under 7.5% (RMSE ~0.05), a 10-30% improvement over established models. Furthermore, the model generalizes to sites not seen during training and scales from coarser grids to point locations. The scheme can easily incorporate new features as observational networks expand, offering an adaptive and computationally lightweight framework for next-generation land and
climate models.
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Instrumentation and Methods for Astrophysics
Building a Roadmap for Hubble science into the 2030s: Crucial UV spectroscopy of Oe stars in nearby galaxies
A. Wofford, D. Pauli, A.A.C. Sander et al. (+12 more)
Hubble's unique COS G130M+G160M and STIS E140M UV spectral capabilities are essential for characterizing and understanding fundamental properties of main-sequence O-type emission-line (Oe)
stars. These are fast rotators, and some are believed to be spun up in binaries. UV medium resolution observations of these
stars are crucial for understanding massive binaries and their role in
galaxy evolution. Oe
stars are more prevalent at low
metallicity, where they are highly under-studied, but UV spectra of these
stars at all
metallicities are needed. Observations of these
stars in the 2030's with Hubble are particularly important in the era of ultra wide-field IFU optical and transient astronomy surveys. Ultimately, these observations will inform future UV observations with the Habitable Worlds Observatory.
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All authors A. Wofford, D. Pauli, A.A.C. Sander, O. Aranguré, M.S. Oey, O.G. Telford, P.A. Crowther, J. S. Vink, Tomer Shenar, M. Gull, L.P. Martins, S. Simón-Díaz, S. Zharikov, L. M. Oskinova, L.J. Smith
Mathematical Physics
Universal deformations and universal residual stresses in incompressible isotropic Cauchy elasticity
Arash Yavari
We study universal deformations in incompressible isotropic Cauchy elastic solids with residual stress, without assuming any specific origin for the residual stress. Starting from the constitutive representation of the Cauchy stress as an isotropic tensor-valued function of strain and residual stress, we derive the universality constraints for residually-stressed incompressible isotropic Cauchy elastic solids. We show that for the six known families of universal deformations the set of universal deformations is identical to that of incompressible isotropic elasticity in the absence of residual stress. We also show that residual stress does not enlarge the space of universal deformations. We then determine the universal residual stress fields corresponding to the six known families of universal deformations. Assuming that the residual stress field has the same
symmetry as the corresponding universal deformation, the universality constraints reduce to systems of ordinary differential equations that can be solved explicitly. The resulting universal residual stress fields are characterized and discussed for each family.
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Quantum Physics · Cross-listed from cs.IT
Unlocking Exponential and Unbounded Robust Gains in Shannon Capacity of Classical Multiple Access Channels with Causal CSIT via Quantum Entanglement Assistance
Yuhang Yao and Syed A. Jafar
Quantum entanglement assistance is known to improve the Shannon capacity of classical communication networks but the largest gains noted thus far are rather modest (less than 6%), motivating the question: are large capacity gains ever possible? It is shown in this work that in the presence of causal channel state information at the transmitters (CSIT),
quantum entanglement assistance provides a multiplicative capacity advantage that grows exponentially with the number of users K for certain classical K-user multiple access channels with fixed size (binary) alphabet for inputs, outputs and states. Similarly, in the presence of causal channel state information at the transmitters,
quantum entanglement assistance is shown to provide a multiplicative capacity advantage that is unbounded as the size of the state alphabet grows, while the number of users (K=3) and the input and output alphabet (binary) are held fixed. Even with only a few users and small alphabet sizes, substantial multiplicative gains in capacity are found, e.g., with binary inputs, outputs and states, multiplicative gains by factors exceeding 21 and 88 are noted with K=5 and K=7 users, respectively. The gains are robust in the sense that they persist even with noisy
quantum resources, e.g., an exponential (in K) capacity advantage from
quantum entanglement assistance remains available even if each entangled
qubit independently depolarizes completely with probability $\approx$ 30%. The gains are based on
quantum entanglement assistance provided only to the transmitters.
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High Energy Physics (Phenomenology)
BSMArt 2: simpler and faster parameter space scans
Fernando Abreu de Souza, Nuno Filipe Castro, Miguel Crispim Romão et al. (+3 more)
We present version 2 of BSMArt, a powerful yet lightweight scanning tool designed to simplify the exploration of parameter spaces of new physics models. Aside from architectural improvements, simpler installation and expanded documentation with examples, the new version includes additional tools and new machine learning and Monte Carlo scanning
algorithms: Affine MC, Contour Finding, MLScanner, DLScanner, MLS, and CMA-ES. We showcase two variants of CMA-ES scans with physics applications relevant for soft
lepton excesses at the LHC. We demonstrate that it is easily possible to find diverse and interesting parameter points for future testing.
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All authors Fernando Abreu de Souza, Nuno Filipe Castro, Miguel Crispim Romão, Mark D. Goodsell, Farid Ibrahimov, Werner Porod
High Energy Physics (Phenomenology)
Muon-induced di-tau production as a probe of new physics
Sudipta Das, Luke Kupari, Mary Hall Reno et al. (+1 more)
The
muon trident process, which involves coherent scattering to produce tau pairs, is a powerful tool for constraining dark sectors. We propose to explore this channel using future high-energy
muon beams with the dedicated active-target detector, High-Energy
Muon Electronic Research Apparatus (HEMERA). The detector would complement
muon beam-dump searches by resolving
prompt signatures and could operate from preparatory facilities involving an individual
muon beam of the full
Muon Collider. We illustrate its capabilities for a leptophilic scalar with Yukawa-like couplings that can mediate thermal dark matter production. With $10^{18}$ incident TeV-scale
muons, even a compact 10 kg silicon-based HEMERA will extend current $B$-factory and $(g-2)_\mu$ bounds by over an order of magnitude in coupling strength. In the leptophilic thermal dark matter paradigm, this search offers a way to probe dark sector targets beyond the
neutrino floor of dark matter direct detection. This provides an additional compelling motivation for the development of high-energy
muon beam infrastructure.
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All authors Sudipta Das, Luke Kupari, Mary Hall Reno, Sebastian Trojanowski
High Energy Physics (Theory)
Carrollian holography with agentic AI: Real mass is imaginary
Reiko Liu, Wen-Jie Ma, Hu Zheng et al. (+1 more)
We introduce LACIA, a verification-driven agentic AI workflow for theoretical physics, and apply it with independent human checks to construct Carrollian conformal bases. We develop the Poincare-Carrollian intertwiner as the central method. It reproduces the celestial and Carrollian conformal bases for massless particles and constructs the missing Carrollian bases for massive and tachyonic particles. The massive basis requires a complex momentum shift in scattering amplitudes.
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All authors Reiko Liu, Wen-Jie Ma, Hu Zheng, Yu-fan Zheng
Quantum Physics
Multi-Qubit Dyadic Phase Fixing for Fault-Tolerant Quantum Compilation
Justin Kalloor, Mathias Weiden, Ed Younis et al. (+2 more)
Fault-tolerant
quantum computing requires translating application-level
quantum circuits into the Clifford+$T$ gate set, where the $T$ gate is the dominant resource cost. Phase kickback is an ancilla-based technique that can dramatically reduce $T$-count for rotations with dyadic angles, but has previously been limited to highly structured
circuit families. We present Dyadic Phase Fixing (DPF), a general multi-
qubit synthesis tool that extends phase kickback to general
quantum circuits. DPF uses numerical
unitary synthesis to greedily extract dyadic angle rotations from any input
circuit. Combined with a decision
matrix to automatically size the final phase gradient register, our end-to-end workflow achieves up to 70% reduction in $T$-count compared to gridsynth and up to 60% compared to Repeat-Until-Success synthesis on a diverse set of
benchmarks. We map these compiled
circuits to a surface-code architecture to evaluate space-time volume, demonstrating up to a 60% reduction in this metric as well. However, for some
circuits and mapping strategies the two metrics diverge significantly, demonstrating that $T$-count alone is a useful but incomplete proxy for fault-tolerant program costs.
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All authors Justin Kalloor, Mathias Weiden, Ed Younis, John Kubiatowicz, Costin Iancu
High Energy Physics (Theory)
BPS Non-Renormalization in the BMN Matrix Model
Sean Colin-Ellerin and Kyriakos Papadodimas
We show in the $(0+1)$-dimensional Berenstein-Maldacena-Nastase
matrix model, dual to M-theory on a pp-wave background, that the coupling can be changed between any two finite, non-zero values using a special class of deformations, known as conjugation deformations. Importantly, we prove that they preserve normalizability of the states. This implies that BPS states in the model cannot lift as the couplings are varied, and hence their (unsigned) number cannot change, except at the free point and Banks-Fischler-Shenker-Susskind point.
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Quantum Physics
Feature Encoding in Quantum Machine Learning: A Survey and Practical Guidelines
Vincenzo Sammartino
The encoding of classical data into
quantum states constitutes the primary performance bottleneck in
Quantum Machine Learning (qml) on Noisy Intermediate-Scale
Quantum (nisq) devices. No existing framework jointly characterises resource cost, expressivity, and noise robustness, nor provides actionable selection guidelines for practitioners. This survey addresses that gap through a systematic review of 66 primary works (2017-2026) assembled via a PRISMA-adapted protocol across five academic databases. Four principal contributions are made. First, a three-axis cost-expressivity-robustness taxonomy classifies all major encoding families - basis, angle, dense-angle, amplitude, data re-uploading, and IQP - along independently measurable axes. Second, closed-form depth-fidelity bounds under nisq decoherence channels identify the critical gate-error rate p* ~ 10^-3 below which amplitude encoding is viable. Third, a unified treatment of
Fourier expressivity, barren-plateau onset, and
quantum kernel concentration as functions of the encoding
circuit provides the first joint trainability analysis. Fourth, a five-regime decision framework maps (D, n, p, tau) - feature dimension,
qubit budget, error rate, and task type - to a hardware-grounded encoding recommendation. The central finding is that for p >= 10^-3, shallow angle-based encodings consistently outperform amplitude encoding in practice, despite the latter's exponential
qubit advantage.
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Instrumentation and Detectors
GPU optical photon Monte Carlo for noble liquid detectors: validation against Geant4 in a large liquid argon TPC benchmark
Gabor Galgoczi, Xuyang Ning, Dmitri Smirnov et al. (+2 more)
Optical
photon Monte Carlo simulation is a computational bottleneck for noble
liquid Time Projection Chambers. Design studies require repeated, geometry dependent simulations of timing, wavelength shifting, and optical response, while reconstruction and particle identification workflows need labeled optical
datasets. We present Simphony, a GPU optical simulation tool, formerly EIC-Opticks, built on Opticks with CUDA and NVIDIA OptiX. Simphony implements a GPU version of the Geant4 G4OpWLS wavelength-shifting model and returns Monte Carlo truth for detected hits with low per-
photon overhead. We validate Simphony against Geant4 11.3.2 in a simplified 14.7 kt
liquid argon Time Projection Chamber
benchmark with a two-stage wavelength-shifting shell and idealized
photon counting detector. For three paired 2.5 GeV electron simulations, each producing about 61 M optical
photons, the integrated detected-
photon ratio agrees with Geant at the subpercent level. The detected arrival time and wavelength spectra give $\chi^2/\mathrm{ndf}$ values of 0.98 and 1.08. Contained
muon and near-Cerenkov-threshold
proton samples give $R_N=1.0017\pm0.0008$ and $R_N=1.0005\pm0.0014$, confirming agreement for distinct source
topologies. On an NVIDIA RTX 4090, a stacked launch of four 2.5 GeV electron events transports 243 M optical
photons in $3.03\pm0.06$ s, giving $80.2\pm1.6$ M
photons s$^{-1}$. Relative to a single-thread Geant reference and including GPU overheads and host-device transfers, the optical transport speedup is $1053\pm55$; the end-to-end wall time acceleration is $89\pm5$. These results show that Simphony can make explicit optical
photon Monte Carlo practical for detector development studies and for generating machine learning optical response
datasets.
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All authors Gabor Galgoczi, Xuyang Ning, Dmitri Smirnov, Brett Viren, Chao Zhang
Biological Physics · Cross-listed from cs.LG
Evidence-Guided Neural Architecture Selection under Uncertainty for Subject-Specific Blood Glucose Forecasting
Md Azharul Islam, Dwyer Deighan, Tarunraj Singha et al. (+1 more)
Reliable neural architecture selection is an open challenge in time-series
forecasting under limited, noisy, and heterogeneous data, where standard heuristic architecture design and validation approaches fail to ensure accurate and reliable prediction and generalization. We propose EVIDENT (EVidence-based IDEntification of Neural archiTectures), a framework for architecture selection that integrates
Bayesian training, evidence-based ranking, and task-specific validation under uncertainty. The framework explores the candidate architecture pool and identifies the lowest-capacity model that satisfies a prescribed validation criterion. We demonstrate this method using temporal convolutional networks (TCNs) for individualized blood glucose
forecasting in type 1 diabetes patients. The results show that EVIDENT systematically rejects both under- and over-parameterized TCN architectures on population-level diabetes data, while identifying models that generalize reliably to unseen patients. When multiple architectures are competitive, the framework further supports plausibility-weighted ensemble predictions that enhance predictive performance. Compared with a random-search baseline, EVIDENT identified smaller architectures with more consistent
forecasting performance on unseen patients. These findings establish EVIDENT as a strategy to neural architecture discovery, enabling reliable model selection for high-consequence
forecasting in data-limited and heterogeneous settings.
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All authors Md Azharul Islam, Dwyer Deighan, Tarunraj Singha, Danial Faghihi
High Energy Physics (Theory)
Novel $\mathcal{N}=2$ higher-spin supercurrents
Nikita Zaigraev
We study cubic interactions of $\mathcal N=2$ massless integer-
spin gauge supermultiplets in harmonic superspace. We construct the complete class of abelian $(\mathbf{s},\mathbf{s_1},\mathbf{s_2})$ cubic vertices with the minimal number of space-time derivatives. Such vertices exist only for $\mathbf{s}\geq \mathbf{s_1}+\mathbf{s_2}$ and universally take the form of the gauge prepotential coupled to the conserved higher-
spin supercurrent. For~$\mathbf{s_1}\neq\mathbf{s_2}$, we find the novel complex principal supercurrent, whose real and imaginary parts generate the parity-invariant and the parity-breaking interactions, respectively. The supercurrents are constructed from gauge-invariant $\mathcal N=2$ higher-
spin Weyl supertensors associated with the
spin-$\mathbf{s_1}$ and
spin-$\mathbf{s_2}$ gauge multiplets. These supertensors are defined in terms of unconstrained higher-
spin analytic prepotentials. We also derive the complete set of conserved component higher-
spin currents associated with the $(s,s_1,s_2)$ vertices, including both traceless currents and currents with the non-vanishing trace.
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Instrumentation and Methods for Astrophysics
A Critical UV Legacy: A Hubble Roadmap for HWO Science Readiness
Sarah Peacock, Aiden S. Zelakewicz, Lisa Kaltenegger et al. (+14 more)
The Habitable Worlds Observatory (HWO) will provide the first opportunity to directly image and spectrally characterize terrestrial
exoplanets in the habitable zones of nearby
stars. Maximizing its scientific return requires a comprehensive understanding of the high-energy radiation environments of target
stars, which shape planetary atmospheres and govern the production, destruction, and detectability of biosignatures. Ultraviolet (UV) radiation plays a particularly critical role in atmospheric chemistry. Far-ultraviolet (FUV) and near-ultraviolet (NUV)
photons regulate key photochemical pathways, influence ozone stability, and drive the formation of prebiotic molecules. However, the majority of high-priority HWO target
stars lack high-quality UV observations. Existing
datasets are sparse, heterogeneous, or limited by calibration uncertainties, and no comparable UV observatory is expected for at least 5-10 years (with UVEX offering more limited spectral resolution, wavelength coverage, and sensitivity). The Hubble Space
Telescope (HST) remains the only observatory capable of acquiring high-resolution FUV and NUV spectra for these targets over the next 10-15 years. We therefore advocate for a coordinated HST program to systematically obtain UV spectra of high-priority HWO targets, ideally in conjunction with X-ray observations. This effort is essential for enabling accurate target prioritization, constraining
stellar radiation environments, and ensuring robust interpretation of future HWO observations.
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All authors Sarah Peacock, Aiden S. Zelakewicz, Lisa Kaltenegger, Breanna A. Binder, José A. Caballero, Lía Corrales, Kevin France, Cynthia Froning, Eric Mamajek, Seth Redfield, Tyler Richey-Yowell, Keighley Rockcliffe, Edward Schwieterman, Riccardo Spinelli, Noah Tuchow, David Wilson, Allison Youngblood
Solar and Stellar Astrophysics
Entropy-mode imprints in the solar corona: non-exponential damping and phase shifts of compressive oscillations
Dmitrii Kolotkov, Sergey Belov and Mohamed Sherif
Magnetohydrodynamic (MHD) waves in coronal loops provide key seismological diagnostics through their characteristic time signatures. While fast and slow magnetoacoustic modes are routinely exploited, the
entropy mode, despite being another eigenmode of the system, remains largely inaccessible due to its non-propagating and non-oscillatory nature. We identify possible observable time-domain signatures of the
entropy mode and its indirect effects. Our approach exploits the intrinsically non-adiabatic conditions of the
solar corona, under which the
entropy mode is closely linked to the compressive slow mode. We consider a one-dimensional coronal loop model with field-aligned thermal conduction, where standing slow and
entropy modes are simultaneously excited. We show that the
entropy mode leaves distinct imprints on the total loop temperature and density perturbations. Specifically, its rapid decay relative to the slow mode produces a non-exponential damping profile during the initial oscillation cycles and introduces a pronounced asymmetry between the upper and lower temperature and density envelopes. These effects arise naturally from the superposition of two exponentially decaying components with different damping timescales. Furthermore, deviations from the canonical quarter-period phase shift between temperature/density and velocity perturbations in the standing slow mode are explained by the
entropy-mode effect. We conclude that the
entropy mode may be detected through its impact on compressive oscillations. Revealing its role in non-exponential damping, envelope asymmetry, and phase shifts of compressive oscillations makes the
entropy mode potentially accessible to observations and lays the foundation for
solar and
stellar seismological applications.
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Cosmology and Nongalactic Astrophysics
The DESI results impact the local determination of $H_0$
Michael S. Turner and Dragan Huterer
Measurements of
baryon acoustic oscillations (BAO) by the Dark Energy Spectroscopic Instrument (DESI) have revealed evidence for dark energy that evolves. If local distance measurements are analyzed with the $w_0w_a$ models preferred by the DESI measurements, the value for the Hubble constant can be as much as $2.5\,\mathrm{km\,s^{-1}Mpc^{-1}}$ smaller than the value obtained assuming $\Lambda$CDM. When these $w_0w_a$ models are further constrained by
cosmic microwave background (CMB) and type Ia
supernova (SNIa) data, the downward shift is $1.1 \pm 0.38\,\mathrm{km\,s^{-1}Mpc^{-1}}$ (DESI + CMB) and $0.5 \pm 0.1\,\mathrm{km\,s^{-1}Mpc^{-1}}$ (DESI + CMB + SNIa). The dependence of local determinations of $H_0$ on the background cosmology, combined with the fact that the low-
redshift cosmology is not well constrained, is relevant to the Hubble tension.
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Superconductivity
Fermiology and the Candidate Chiral Superconductor in Rhombohedral Tetralayer Graphene
Sandesh S. Kalantre, Ben H. Alexander, Julian May-Mann et al. (+11 more)
Chiral superconductivity, in which the phase of the superconducting order parameter winds in momentum space, has long been sought for its close link to topological superconductivity. Recent work reported a
superconductor in rhombohedral multilayer
graphene emerging from a time-reversal
symmetry broken normal state, suggesting that it could be a
chiral superconductor. However, the possibility of chirality depends on the
symmetry and structure of the normal-state
Fermi surface, which have not been directly measured. Here we measure
quantum oscillations in rhombohedral tetralayer
graphene over a broad range of the phase diagram, including the superconducting region. At densities well above the onset of superconductivity, we reproduce previously-reported oscillations consistent with a
spin- and valley-polarized quarter metal with a single simply-connected
Fermi pocket. As the carrier density is reduced, we find a transition to a complex "multitone" state that persists through the superconducting region. This state's spectrum of
quantum oscillations is incompatible with a simply-connected quarter metal. The next-simplest candidate normal states suggested by our microscopic modeling (fully-polarized annular, nematic, and three-pocket states) are inconsistent with our measurements, albeit difficult to rule out entirely. The normal state is thus seen to be richer than previously envisaged, reshaping the search for the superconducting mechanism and the possible chirality of the pairing channel.
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All authors Sandesh S. Kalantre, Ben H. Alexander, Julian May-Mann, Jonah Herzog-Arbeitman, Marisa Hocking, Qingrui Cao, Kenji Watanabe, Takashi Taniguchi, David Goldhaber-Gordon, Andrew J. Mannix, Trithep Devakul, Yves H. Kwan, Daniel E. Parker, Aaron Sharpe
Astrophysics of Galaxies
Bulk vs. turbulent motions at the centres of galaxy clusters: AGN-driven turbulence according to TNG-Cluster
Bipradeep Saha, Annalisa Pillepich, Joey Braspenning et al. (+3 more)
The highly dynamic intracluster medium (ICM) influences cluster thermodynamic
evolution and probes key physical processes. Quantifying the non-thermal motions is therefore essential for understanding cluster physics and interpreting high spectral-resolution X-ray observations from
telescopes like XRISM. We quantify bulk and turbulent gas motions in 352
galaxy clusters at $z=0$ (${\rm M_{200c}=10^{14.3-15.4}\, M_\odot}$) from the TNG-Cluster suite of magneto-hydrodynamical
galaxy simulations. We use a multi-scale filtering Reynolds decomposition to separate total gas velocities into bulk (coherent) and turbulent (small-scale fluctuations) components. We primarily focus on the hot X-ray emitting gas in the central core regions. According to TNG-Cluster, majority of the ICM has subsonic
turbulence but with broad velocity distributions reaching $\mathcal{M}_{\rm Turb}\sim 10$ and large cluster-to-cluster variations. In cluster centres,
turbulence contributes less than half of the total velocity dispersion $(\sigma_{v\rm,Turb } \sim 0.5 ~\sigma_{v,\rm Total})$ for most clusters, with typical turbulent velocity dispersions of $50-75$ km s$^{-1}$ across the mass range, and with sub per cent levels of turbulent pressure support. Clusters that are strong cool cores, or have X-ray cavities, or experienced recent SMBH feedback energy injections exhibit systematically larger turbulent velocity dispersions and more prominent turbulent velocity tails. On average, the turbulent velocity dispersion peaks in cluster centres, decreases slightly to a minimum at $0.1-0.2 \, R_{\rm500c}$, then rises again. Our analysis shows that SMBH feedback is a key driver of
turbulence in cluster cores, generating strong but short-lived motion alongside high-velocity
outflows. It also calls for caution for interpreting XRISM observations.
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All authors Bipradeep Saha, Annalisa Pillepich, Joey Braspenning, Marine Prunier, Dimitris Chatzigiannakis, Dylan Nelson
General Relativity and Quantum Cosmology
Running Vacuum in the expanding Universe: a unified QFT paradigm for Inflation and Dark Energy
Joan Solà Peracaula
The concordance $\Lambda$CDM model, based on a rigid $\Lambda$-term for the entire
cosmic history, has been in crisis for a long time. In our expanding Universe, an evolving $\Lambda$ with the expansion is intuitively much more reasonable. In the running
vacuum model (RVM) framework, based on
quantum field theory (QFT) in curved spacetime,
quantum effects induce a
vacuum energy density (VED) $\rho_{\rm vac}=\Lambda/(8\pi G)$ which is a function of the Hubble rate $H$ and its time derivatives, $\rho_{\rm vac}=\rho_{\rm vac}(H, \dot{H},\ddot{H},\dots)$. Currently, $\rho_{\rm vac}$ evolves very slowly with the expansion, $\delta\rho_{\rm vac}\sim {\cal O}(m_{Pl} ^2 H^2)$, and this fact provides a possible fundamental origin of dark energy (DE), conceived as dynamical
vacuum energy. In the RVM, Newton's $G$ is also evolving, but much more slowly (logarithmically with $H$): $G=G(\ln H)$. In the very early universe, the
vacuum fluctuations induce higher (even) powers, e.g. $\sim H^4$, capable of triggering fast inflation in a very short period, in which $H$ is very large and approximately constant. This is the mechanism of `RVM-inflation'. It does not require an `inflaton' field since inflation is brought about by pure QFT effects on the dynamical background. It differs from Starobinsky's inflation, where $H$ is never constant. Furthermore, the dynamics of $\rho_{\rm vac}(H)$ and $G(H)$ can also have implications on the frequently discussed possibility that the fundamental `constants' of Nature can be mildly evolving with the
cosmic expansion. Putting things together, a unified QFT framework of dark energy and inflation ensues as a realistic theory for the description of the universe as a whole on fundamental grounds. In it, dynamical VED is predicted and is much welcomed, since it fits in with current DESI measurements, preferring dynamical DE over a rigid $\Lambda$ term.
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Chaotic Dynamics
Tricriticality and chaos in a generalized Allee-logistic map
Marcelo A. Pires, José S. Andrade Jr. and Hans J. Herrmann
We present a novel nonlinear dynamical model, the generalized Allee-logistic (GAL) map given by $x_{t+1} = r x_t (1 - x_t) G(x_t)$ where $G(x_t) = m (x_t - h) + 1 - m$ incorporates the Allee effect with magnitude $m$ and threshold $h$. The case $m = 0$ yields the logistic map with a continuous transition to extinction. Conversely, $m = 1$ recovers a previously studied model that undergoes only a discontinuous extinction-to-active transition. Between these extremes, the GAL map exhibits nontrivial phenomena, including tricriticality with a closed-form expression for the tricritical point and a universal crossover function. Under a small external input, we verify Widom-like relations. We also note that the Allee effect disfavors the onset of chaos. Our work establishes additional bridges between analytically tractable chaotic maps, nonequilibrium tricriticality, and Allee effects.
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Statistical Mechanics
Opinion dynamics on social proximity disordered networks
Fellipe Aranha, Giuliano G. Porciúncula, Adauto J. F. de Souza et al. (+2 more)
Understanding how local social pressure shapes collective opinion formation is essential in modern society, with implications in sociology, politics, finance, and technology. Complex networks are a powerful framework for investigating these processes and for representing social interactions in emergent phenomena, and canonical models such as random, scale-free, and small-world networks remain most relevant when Euclidean
geometric proximity and contiguous interactions are not the dominant organizing factors. Our investigation explores the effects of Gabriel graphs, a spatially embedded network that utilizes proximity-based interactions, on social opinion dynamics. Using a
geometric disorder parameter that randomly displaces
agent coordinates, we transition from square
lattices of social interactions to spatial random networks that preserve local constraints while introducing strong topological heterogeneity. Opinion dynamics operate through social pressure, with a level of nonconformity that affects dissent among opinions. We analyze magnetization, susceptibility, and Binder's fourth-order cumulant to characterize the emergence and breakdown of global social consensus. The model exhibits second-order phase transitions whose behavior depends on both
geometric disorder and nonconformity levels. We use volumetric scaling and provide a reference frame appropriate for characterizing criticality in regular and heterogeneous interaction
topologies. We find that the standard critical exponents remain compatible with the two-dimensional Ising universality class. Furthermore, the results suggest that spatially constrained, planar, and globally connected interaction
topologies preserve the dimensionality of space in critical dynamics analysis.
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All authors Fellipe Aranha, Giuliano G. Porciúncula, Adauto J. F. de Souza, Paulo R. A. Campos, André L. M. Vilela
Earth and Planetary Astrophysics
Sky-Plane Velocity Distributions of Interstellar Objects and Implications for Their Detection
Cassidy E. Walker and Darryl Z. Seligman
In the past decade, three macroscopic-scale interstellar objects have been discovered, implying that a larger
galactic population exists. In this paper, we investigate the possibility that the rapid sky-plane velocities of interstellar objects may preclude their discovery. We provide an analytic solution for the apparent sky motion of an object on an arbitrary orbit observed at an arbitrary location which is more efficient and requires less overhead than the numerical approach. This formula is applied to evaluate the typical sky motion of an interstellar object as a function of its orbit and limiting magnitude/distance. We generate three synthetic populations of $\sim10^5$ interstellar objects within heliocentric spheres of radii 1.2, 3.0, and 5.0 AU, and calculate the sky motion for these objects when they reach a range of limiting magnitudes for multiple populations of interstellar asteroids and comets. The sky motions of the three known interstellar objects are broadly characteristic of populations with similar absolute magnitudes. Moreover, the intrinsically brighter objects reach detection magnitude thresholds at lower on-sky speeds than the dim objects, and active comets at even lower speeds for the same apparent magnitudes. The tails of these distributions extend to speeds faster than the discovery motion of 1I. Therefore, the potentially rapid sky motion of interstellar objects should be taken into account when attempting to link
hyperbolic trajectories in survey data.
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High Energy Astrophysical Phenomena
Constraining Orbital Eccentricity of a Supermassive Black Hole Binary Candidate PKS 2131-0211
Avinash Kumar Paladi, A. Gopakumar, Sushmita Agarwal et al. (+1 more)
A detailed analysis of the decades-long
radio light curve of blazar PKS 2131-021 showed epochs of sinusoidal variations in the
radio flux density time-series as detailed in O'Neill et al. (2022). The observed sinusoidal flux modulation arises naturally from relativistic Doppler boosting of the jet when the jet-emitting supermassive black hole (SMBH) orbits its companion. For SMBHs in circular orbits, this scenario yields sinusoidal light curves, offering a simple kinematic explanation for the observed variability in PKS 2131-021. We present an approach that incorporates the effects of orbital eccentricity into the Kinematic Orbital model for PKS 2131-021, using the Keplerian parametric solution to describe the SMBH binary orbit. Using the available
radio light curve data, we demonstrate that the proposed SMBH binary likely possesses a residual orbital eccentricity, which we constrain through detailed
Bayesian parameter estimation studies to be 0.053 \pm 0.015 with a Bayes factor of 3.15 over the circular model. However, when the analysis accounts for the presence of red noise in the data using a Damped Random Walk (DRW) process, the circular model is preferred, giving an eccentricity upper limit of e < 0.15. Nevertheless, our efforts reveal that the Circular+DRW model is strongly favored. This model consistently recovers a coherent periodic signal across all
datasets, with the orbital period remaining well-defined even when accounting for broader uncertainties. This analysis incorporated archival observations from the Haystack Observatory, the University of Michigan
Radio Astronomy Observatory (UMRAO), and the Owens Valley
Radio Observatory (OVRO), spanning the period from 1975 to 2021, compiled by O'Neill et al. (2022).
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All authors Avinash Kumar Paladi, A. Gopakumar, Sushmita Agarwal, Fazal Kareem
Plasma Physics
Behavior of kinetic instabilities in a dynamically forming resonant distribution
E. J. Hartigan-O'Connor, T. Barberis, E. G. Devin et al. (+2 more)
Instabilities driven by energetic particles are central to the physics of a burning
plasma. The majority of kinetic simulations and reduced models assume that the unstable distribution is already fully established when energetic-particle-driven modes grow unstable. In realistic scenarios, however, energetic particles may accumulate in the resonance on an effective timescale comparable to the growth rate of the instability, meaning that the formation of the resonant distribution and the growth of the unstable mode must be treated concurrently. We study the behavior of these instabilities in the presence of such a dynamically forming distribution, evaluating two distinct metrics which measure how close a mode is to its linear stability threshold and how close a mode remains to its nonlinear stability threshold. It is found that saturation at large $\omega_b/\nu_\text{eff}$ (where $\omega_b$ is the bounce frequency of deeply trapped particles and $\nu_\text{eff}$ is the effective scattering rate at a resonance), normally associated with strongly driven excitation, can be achieved even if dynamically the mode remains at all times near its nonlinear stability threshold. We extend existing analytic models for near-marginal and far from marginal modes allowing for a time-dependent linear growth rate, deriving explicit expressions for the mode amplitude
evolution. These formulas are shown to agree with nonlinear kinetic simulations. The discrepancies between the case of a dynamically forming distribution and the case of a fully formed distribution are shown to be particularly pronounced for energetic particle distributions which relax diffusively.
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All authors E. J. Hartigan-O'Connor, T. Barberis, E. G. Devin, A. Bierwage, V. N. Duarte
Optics
Push-Pull acousto-optic modulator based on non-suspended thin-film lithium niobate on silicon substrate
Haorui Ni, Sunil Bhave and Mengyue Xu
Acousto-optic modulators (AOMs) are particularly attractive for microwave-to-optical conversion,
quantum transduction, and optical frequency manipulation. For these applications, chip-scale AOMs that combine high efficiency, broad bandwidth, and low optical loss are highly desirable. Although suspended and resonant AOMs can enhance modulation efficiency, they typically suffer from stability concerns and limited bandwidth. Here, we demonstrate a non-suspended built-in push-pull AOM on a thin-film lithium niobate (TFLN) on silicon substrate that simultaneously offers high efficiency and relatively broad bandwidth. We further investigate the orientation dependence of electromechanical coupling in X-cut TFLN by fabricating devices with different acoustic propagation directions and identify an optimized orientation for enhanced acousto-optic transduction. Our low-loss device achieves a half-wave voltage-length product of 1.004 V cm at 0.842 GHz with an interaction length of 400 micrometers, together with a relatively wide acousto-optic modulation bandwidth of 132.5 MHz. These results pave the way for efficient, practical integrated photonic-phononic links.
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Instrumentation and Detectors
The MuFusE Large-Volume Diamond Anvil Cell for Exploring Muon-Catalyzed Fusion at Higher Pressures and Temperatures
J.D. Kalow, J.T. Hinchen, G. Harris et al. (+45 more)
A new large-volume diamond anvil
cell (DAC) has been developed for the
Muon-catalyzed Fusion ($\mu$CF) Experiment (MuFusE), enabling the compression and heating of deuterium-tritium (d-t) mixtures to pressures and temperatures needed to advance $\mu$CF research. The MuFusE DAC achieves the large sample volumes necessary for high-precision fusion measurements while integrating cryogenic loading, all-metal sealing, and flexible bellows to maintain a secure environment during
cell compression. Combined with remote pneumatic actuation and secondary containment, the DAC safely managed a 25 Ci tritium inventory while providing a clear optical path for in situ measurements of sample pressure and composition via
laser spectroscopy. Utilizing 5 mm diameter diamond anvils oriented in the path of a high-intensity
muon beam, the apparatus achieved a stable sample volume of 19.2 mm$^3$ at
liquid density, pressures up to 933 MPa and temperatures up to 400 K -
benchmarks that significantly exceed previously reported limits for static d-t targets.
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All authors J.D. Kalow, J.T. Hinchen, G. Harris, E. Koukina, D.M. Harrington, P.C. McDaniel, N.J. Brennan, A. Golossanov, I.D. Spool, D. Zajac, M. Mundt, S. Varner, M. Russell, S. Bull, K. McCormack, D. Mayer, L.E. Knaian, M. Khandaker, W. Stadolnik, W.R. Cutler, A. Sampat, K. Lau, J. Betances, C. Fagan, C.R. Shmayda, M. Koch, K. Payne, N.J.L. MacFadden, J. Simon, K. Peterson, A. Gami, S. Machavarapu, A. Tejeda, J. Katz, J.A. Allen, R. Chaney, K. Kem, I. Kiniti, E. Garcia Badaracco, K.R. Lynch, P. Gandhi, C.J. Johnstone, E. Niner, C.C. Petitjean, A. Antognini, W.T. Shmayda, S.O. Newburg, A.N. Knaian
Mathematical Physics · Cross-listed from math.OC
Mean–Fluctuation Dynamics at the Edge of Stability
Antonin Chodron de Courcel
We study the dynamics of gradient descent in the Edge of Stability regime, where the learning rate is large enough to induce persistent oscillations in the trajectory, which has been linked to better generalization performance. We introduce the mean–fluctuation dynamics, a tractable continuous-time model coupling the window-averaged trajectory to its fluctuation covariance. Among our contributions, we rigorously derive this model from gradient descent in a sharp-valley framework, characterize its stationary states and their linear stability, and establish precise connections with other effective dynamics. Numerical experiments illustrate these predictions and their finite-time limitations. We also study our model in the overparametrized regime of wide two-layer networks at a fixed learning rate, where we rigorously derive a kinetic equation describing weights and their fluctuations as a Wasserstein-2 gradient flow, for which we prove well-posedness, a mean-field limit, and conditional convergence results.
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Materials Science
Hydrogen-induced lattice cohesion weakening favors atomic displacement
Liang Gao, Yiran Mao, Markus Wilde et al. (+9 more)
Atomic displacement – the fundamental process underlying diverse deformation and damage phenomena in metals, from irradiation defect production to stress-driven dislocation motion – is governed by interatomic cohesion strength. Here,
lattice-dissolved hydrogen (LDH) occurring in metals under direct hydrogen exposure is identified to effectively weaken
lattice cohesion, and thereby facilitating atomic displacement and dislocation movement upon plastic deformation in sub-threshold stress regime. This atomic-scale insight provides a physically transparent mechanism for hydrogen-enhanced localized plasticity implicated in hydrogen embrittlement. We quantitatively verify the hydrogen-induced
lattice cohesion weakening effect on metal surfaces exposed to low-energy hydrogen
plasma, where massive defects are generated despite the absence of sufficient ion momentum for direct displacement damage. By unprecedentedly quantifying the cohesion-weakening effect of LDH independently from defect-trapped H, we establish a new paradigm to understand hydrogen embrittlement.
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All authors Liang Gao, Yiran Mao, Markus Wilde, Xiaoou Yi, Cong Li, Shiwei Wang, Thomas Schwarz-Selinger, Jan Coenen, Richard Kembleton, Sebastijan Brezinsek, Christian Linsmeier, Guanghong Lu
Astrophysics of Galaxies
Strong [OIII]$+$H$\beta$ emitters dominated the ionizing budget at $z\sim7$
Isak Wold, Sangeeta Malhotra and James Rhoads
We quantify the ionizing
photon production at $z\sim7$ using the deepest spectroscopically confirmed sample of strong [OIII]$+$H$\beta$ emitters (rest-frame EW$>740$ A) in the Abell 2744 field. Leveraging ultra-deep UNCOVER F410M imaging ($5\sigma\sim29$ AB) and gravitational
lensing, we probe an order of magnitude deeper than previous JWST WFSS [OIII] studies, reaching a luminosity limit of $\log(L_{\rm{[OIII]}+\rm{H}\beta}/\text{erg s}^{-1})=41.3$. Our rest-frame optical emission-line selection probes some of the youngest, metal- and
dust-poor
galaxies, identifying a large population of continuum-faint, ionizing candidates. NIRSpec follow-up of a luminosity-representative subset confirms $72\%$ of targets, providing detailed characterization of 18 emitters. Balmer decrements reveal negligible
dust, while strong-line diagnostics indicate extremely low
metallicities ($12+\log(\text{O/H})=6.8\text{--}7.7$). With typical [OII]/[OIII] ratios of $0.054\pm0.007$, we infer an average Lyman continuum escape fraction near the canonical $f_{\text{esc}}=20\%$. Correcting for the spectroscopic confirmation rate, we find that these high-EW emitters represent $56\pm12\%$ of the total UV-selected population by number density. Integrated to our survey limits, the ionizing budget of these emitters ($\log(\dot{N}_{\rm ion}/{\rm s}^{-1}\,\text{Mpc}^{-3})=50.63\pm0.05$) accounts for $\sim70\%$ of the total budget required for reionization at $z\sim7$. This result is consistent with empirical
benchmarks. These results establish [OIII]$+$H$\beta$ selection as a powerful,
dust-insensitive probe, showing that known
galaxy populations significantly power reionization.
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High Energy Astrophysical Phenomena
How Common Are Common Envelopes? Quantifying Their Role in Forming Gravitational-Wave Sources
Floor S. Broekgaarden, Ana Lam, Sasha Levina et al. (+14 more)
A central goal of gravitational-wave astronomy is to use merging binary black hole (BBH), black hole-
neutron star (BHNS), and binary
neutron star (BNS) systems as fossils to reconstruct the formation and
evolution of massive
stars across
cosmic time. In practice, this inference relies on population-synthesis models that map massive
stellar binaries to merging compact objects. However, these models disagree on the dominant orbital-hardening mechanisms within isolated binary
evolution, particularly on whether common-envelope (CE)
evolution is required. To address this, we compile and systematically compare formation-channel predictions from more than 200 isolated-binary population-synthesis simulations, organized within a unified hierarchical taxonomy. We find that BBH and BHNS formation pathways span nearly the full allowed range from CE-dominated to without-CE-dominated
evolution (0-100%), while often predicting similar merger rates, revealing a fundamental degeneracy: merger-rate measurements alone do not uniquely constrain the underlying evolutionary pathways. In contrast, BNS formation proceeds almost exclusively through channels involving at least one CE phase (>90-100%), suggesting CE
evolution plays a qualitatively different role in BNS than in BBH and BHNS formation. The relative contributions of with-CE and without-CE pathways are governed primarily by assumptions controlling mass-transfer stability, angular-momentum loss, CE efficiency, and
supernova physics, which often act non-linearly and in correlated fashion, such that trends from one-at-a-time parameter variations do not generalize across simulation frameworks. Robust interpretation of gravitational-wave populations will therefore require transparent formation-channel definitions, reproducible analysis pipelines, systematic cross-code comparisons, and observational constraints that extend beyond merger rates alone.
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All authors Floor S. Broekgaarden, Ana Lam, Sasha Levina, Jakub Klencki, Kyle A. Rocha, Lieke van Son, Steffani M. Grondin, Monica Gallegos-Garcia, Brian D. Metzger, Enrico Ramirez-Ruiz, Angela Twum, Melanie Santiago, Julia Haynes, Tyler B. Smith, Amedeo Romagnolo, Edo Berger, Lucas M. de Sá