Astrophysics of Galaxies
Rubin LSST DP2 unveils almost-dark galaxies in the Virgo Cluster
Minh Ngoc Le, Johan H. Knapen, Željko Ivezić et al. (+26 more)
Galaxies with the faintest surface brightness are currently known only in the Local Group. Similar objects should exist beyond our vicinity and are crucial for understanding
galaxy evolution, structure, and dark matter content, yet surveys have not reached the depth required to detect them systematically. We present a population of seven almost-dark
galaxies identified in Data Preview 2 of the Rubin Legacy Survey of Space and Time. They surround M49 in the vicinity of the Virgo Cluster, and exhibit central surface brightnesses in the range of $26.9 - 28.5 \, \mathrm{mag \, arcsec^{-2}}$ in the $g$-band, with half-light radii of $0.6 - 4.6 \, \mathrm{kpc}$ at the distance of Virgo, and
stellar masses of $10^6 - 10^7 \, \mathrm{M_\odot}$. Their characteristics are analogous to those of the faintest and low-mass
galaxies identified among satellite
galaxies And XXI, And XXIII, and And XXV in the Local Group. This discovery demonstrates the power of the forthcoming Rubin LSST 10-year survey to uncover extremely faint
galaxies at scale, promising the large statistical samples needed to constrain the faint-end luminosity function and the nature of dark matter.
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All authors Minh Ngoc Le, Johan H. Knapen, Željko Ivezić, Junais, Aaron Watkins, Dan S. Taranu, Pierre-Alain Duc, Anthony Englert, Erfan Nourbakhsh, J. Anthony Tyson, Jiaxuan Li, Roberto J. Assef, Uzay Aydin, Jose Benavides, Natanael M. Cardoso, Priyanka Chakraborty, Ricardo Demarco, Bililign Dullo, Alister W. Graham, Marc Huertas-Company, Kian-Tat Lim, Jakub Nadolny, Dieu Nguyen, Reynier Peletier, Rossella Ragusa, Kevin Reil, R. Michael Rich, Hector Hernandez-Toledo, Michael H. F. Wilkinson
Quantum Physics
Lazy training of quantum physics informed neural networks
Anderson Melchor Hernandez and Giacomo De Palma
We study the gradient-flow training dynamics of
quantum physics-informed neural networks (QPINNs) for the solution of second-order
elliptic partial differential equations with Dirichlet boundary conditions. We consider parameterized
quantum circuits as function approximators and analyze their overparameterized regime through the lens of the neural tangent kernel (NTK). Our contribution is a nonasymptotic lazy-training theory for QPINNs and their variational formulation: we prove that, for sufficiently large
circuit width, the nonlinear gradient flow is quantitatively approximated by a linearized NTK model, with explicit bounds depending on the number of
qubits,
circuit depth,
circuit light-cone geometry, and the dimension of the domain of the solution to the PDE.
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Cosmology and Nongalactic Astrophysics
Where the Forest Goes Dark: Halo-centered Characterization of High Column Density Systems with IllustrisTNG
Victor R. Soares da Silva, Daniel López-Cano, L. Raul Abramo et al. (+2 more)
High column density systems of neutral hydrogen (HCDs) — Lyman limit systems (LLSs), sub-damped and damped Ly$\alpha$ absorbers (DLAs) — contaminate both the 3D and the 1D statistics of the Ly$\alpha$ forest. Most DLAs are masked out from the analyses, but cleaning
algorithms are not perfect, and weaker LLSs are individually undetectable, so the residual contamination is absorbed into nuisance parameters that dilute the cosmological constraining power. Simulations provide the ideal setting to study this effect, allowing absorption features to be directly traced back to the gas producing them. We identify high-column-density structures on the gas
cells of the TNG50 hydrodynamical simulation, deblend them in velocity space, and split every sightline into HCD-only and forest-only spectra. Applied to
halos at $z \simeq 3$ out to 50 virial radii, it yields each class's covering fraction against impact parameter $b$ and
halo mass. The impact parameter defines the type of absorption appearing in the spectrum: DLAs give way to sub-DLAs at $b \approx 0.11\,R_{200c}$, sub-DLAs to LLSs at $0.3$, and LLSs to the Ly$\alpha$-forest at $0.5$, which covers $\simeq 78\%$ of sightlines at $R_{200c}$. In units of $R_{200c}$ the sequence is nearly mass-independent over three decades in mass, so the virial radius sets the scale of the neutral gas distribution. A single Voigt component recovers the column density of essentially every damped system, but not of LLSs, whose absorption features often arise from several separate contributions from gas structures along the sightline. Our detailed characterization of HCDs gives the first step to the construction of advanced techniques to directly forward-model their contribution to Ly$\alpha$ spectra.
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All authors Victor R. Soares da Silva, Daniel López-Cano, L. Raul Abramo, J. Chaves-Montero, Francisco Maion
Statistical Mechanics · Cross-listed from math.CO
Intractable enumeration problems are like Russian nesting dolls: structural properties of monomer-dimer coverings on two-dimensional quadratic lattices
Yong Kong
Counting the number of coverings of $s$ dimers on two-dimensional quadratic
lattices is considered as intractable and belongs to \#P-complete class. We reveal the structure of the exact solution to the problem and provide an explicit formula for it, which includes $s-1$ nesting sums. This results in an exponential time complexity of $O(2^s)$. The solution is explicitly determined by a sequence that exhibits double-exponential growth.
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Materials Science
Melting of corundum ({\alpha}-Al2O3) under compression to 8 GPa: A decreasing melting slope
Vladimir L. Solozhenko
Melting of corundum ({\alpha}-Al2O3) has been studied under compression up to 8 GPa using in situ electrical resistivity measurements. The melting temperature increases monotonically from T0 = 2317 K at ambient pressure to 3090 K at 7.7 GPa. Fitting the experimental data to the Simon-Glatzel equation yields the empirical parameters a = 5.60 GPa and c = 0.334, providing a closed-form analytical description of the entire melting boundary. Most significantly, the melting slope, dTm/dp, decreases continuously from 138 K/GPa at ambient pressure down to 78 K/GPa at 7.7 GPa, confirming unequivocal negative
curvature of the melting curve (d2Tm/dp2 < 0). This phenomenon is consistent with the preferential densification of the
liquid phase and the associated reduction in the volume change upon melting as pressure rises. These findings provide a robust empirical standard for the high-pressure melting of corundum, establishing essential constraints for future ab initio simulations, thermodynamic databases, and geophysical models of alumina-rich deep-Earth systems.
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Nuclear Experiment · Cross-listed from stat.ME
Binning-Independent Bayesian Analysis of Time-Dependent Perturbed Angular Distribution data
Franziskus von Spee
We propose a new approach for analyzing Time-Dependent Perturbed Angular Distribution data. In this, a likelihood is constructed with the help of conditional probabilities of single events and binning of time data is avoided. This likelihood is used in a
Bayesian framework to calculate the posterior probability density function for the $g$ factor of interest. This approach is compared to more traditional approaches that use binned data by analyzing simulated
datasets. In many cases the resulting posterior probability densities are observed to be
multimodal and the results can thus often not be summarized with a single Gaussian approximation. We find that results from the new approach are more reliable for low-statistics
datasets.
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Mathematical Physics · Cross-listed from math.AP
Long-time dynamics for the magnetic Schrödinger equation on the torus
Julien Lechaux
We investigate time-dependent semiclassical measures associated with the
magnetic Schrödinger flow on the flat two-dimensional
torus in long-time regimes. Under a
geometric nonvanishing assumption on an effective
magnetic force, we identify two thresholds and prove a dynamical form of
quantum unique ergodicity for such systems. If the time scale $\tau_h \gg h^{-1/2}$, then the configuration marginal is the normalized Lebesgue measure on $\mathbb T^2$. In addition, if $\tau_h \gg h^{-1}$, then the momentum marginal is, conditionally on each regular level set, the normalized invariant measure on that curve.
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Quantum Physics
Enhanced Emission and Two-Photon Interference of Lead-Vacancy Centers in Diamond Solid Immersion Lenses
Koyo Hirai, Eiki Ota, Yiyang Chen et al. (+8 more)
A negatively charged lead-vacancy (PbV-) center in diamond is a novel
quantum system which can be operated at a high temperature above 4 K owing to its large ground state splitting. To unlock the
quantum properties of the PbV- center, the enhancement of the fluorescence intensity is a key issue. Here, we demonstrate enhanced emission from PbV- centers by a factor of approximately 10 using solid immersion lenses (SILs) fabricated on rough diamond surface caused by high-temperature anneal over 2000{\deg}C. Resonant excitation reveals the narrow emission close to the transform-limited linewidth. Furthermore, we demonstrate two-
photon interference using one single PbV- center in an SIL. This enhanced emission and indistinguishability will lead to further development of the PbV- center towards
quantum network node applications.
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All authors Koyo Hirai, Eiki Ota, Yiyang Chen, Ren Kato, Peng Wang, Toshiharu Makino, Takashi Taniguchi, Masashi Miyakawa, Shinobu Onoda, Mutsuko Hatano, Takayuki Iwasaki
High Energy Physics (Phenomenology)
Interpreting quantum coherence of neutrinos in asymptotically flat spacetimes via effective distances: Solution to the paradoxes of the Leggett-Garg inequality and quantum information quantities
Shan Wu and Shu-Jun Rong
In this work, we propose a notion called effective distance to characterize the essential gravitational effects on
quantum coherence of
neutrinos. Employing effective distances, we prove that one can always map
neutrino-oscillation phases in asymptotically flat spacetimes onto the phases in flat spacetime, which is considered as a nontrivial realization of equivalence principle. Hence, the maximal amount of
quantum coherence, quantified by the Leggett-Garg (LG) parameter is independent from background spacetimes, namely, the paradox that the gravitational effects on
quantum coherence of
neutrinos are measure-dependent (Ettefaghi et al.[1]) does not arise. Following the same route, we preclude the gravitational amplifying or damping of amplitudes of the
quantum information quantities for special masses of black holes (Wang et al. [2]). To demonstrate furthermore the independence of
quantum coherence from background spacetimes, we examine the proposal using the LG parameter to identify
quantum-corrected models of spacetimes. For different emission positions of
neutrinos and various
quantum parameters, we find no consistent patterns in oscillating LG curves to discriminate a
quantum metric from the classical one.
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Geophysics
Period-Inverted Blast-Radius Normalization for a Non-Ablating Hypersonic Reentry Source Using OSIRIS-REx Capsule Infrasound
Elizabeth A. Silber
Cylindrical blast wave theory relates infrasound from hypersonic sources to energy deposition through a characteristic blast radius R_0, yet the normalization constant k in the scaling R_0 = k (E_0/p_0)^(1/2) differs by up to 40% across the formulations examined here. This uncertainty affects period-based source characterization for elevated atmospheric sources relevant to infrasound monitoring. Using infrasound from the OSIRIS-REx Sample Return Capsule reentry on 24 September 2023, observed periods at 39 stations spanning source altitudes of 44-62 km are inverted through a weak-shock propagation model to obtain period-inverted blast radii R_0,obs without prescribing a blast-wave normalization. Combining R_0,obs with aerodynamic drag energy yields a median k = 0.396, with a modified-bootstrap 95% interval of 0.378-0.474 when the reported period-measurement uncertainties are included. This result is consistent with the Sakurai (1965) and Jones et al. (1968)/Plooster (1970) normalizations, while Few (1969) lies outside the reference confidence interval. However, station-level k values exhibit significant along-trajectory structure (Spearman r_s = -0.84, p < 0.001), indicating that k_med is an ensemble-effective normalization rather than a station-invariant constant. The Mach-diameter approximation R_0 ~ M d_m overestimates R_0 by a factor of ~3.4 for this effectively non-ablating source. A period-based relation, R_0 = 23.99 tau - 0.73 (R^2 = 0.991, MAPE = 2.3%), provides a rapid blast-radius
estimator whose residuals show no detectable altitude dependence. These results provide inverse calibration constraints and practical period-based source-characterization relations for OSIRIS-REx-like non-ablating hypersonic entries, while highlighting the need for multi-event validation before broader application.
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Earth and Planetary Astrophysics
A Binary Flux Calibrator Reveals the Scientific Potential of Short-integration JWST MIRI Imaging to Directly Detect sub-Jupiter Exoplanets
Rachel Bowens-Rubin, Mary Anne Limbach, Alexander Venner et al. (+11 more)
We report the direct imaging detection of a
stellar companion to HD 101452 (HIP 56925;
Gaia DR3 5384905720847544192), an A
star historically used as an infrared flux calibrator. The companion was identified from an asymmetry in the
stellar PSF using short-integration (<1 min), noncoronagraphic JWST MIRI imaging from 15 - 25.5$\mu$m that was obtained as part of the absolute flux calibration program CAL 4496. We detect the
stellar companion in four MIRI imaging filters at a projected separation of 1.3 arcsec with a mid-infrared flux ratio of approximately $27\times$ warranting its removal from the ensemble of JWST flux calibrator systems. This detection also demonstrates that noncoronagraphic MIRI imaging can recover companions at separations below $3\lambda/D$ when a reference
star with a closely matched flux level to the science target is available. Using the measured contrast curves from the calibration data, we evaluate the predicted sensitivity achievable with similar short MIRI observations for nearby
stars (<30 pc) that are of interest to the direct-imaging community with comparable brightness to HD 101452 (W4 ~ 6.8 mag). We find that integrations of only 17-42 s are be capable of detecting sub-Jupiter-mass
planets at
solar system-like separations around a subset of neighboring systems if the PSF subtraction is conducted with closely flux-matched references. These results demonstrate that minutes-length, noncoronagraphic MIRI observations can provide a powerful and efficient new avenue for exploring the cold
giant planet population around nearby
stars.
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All authors Rachel Bowens-Rubin, Mary Anne Limbach, Alexander Venner, Kyle Franson, Emily K. Pass, Andrew Vanderburg, Kevin B. Stevenson, Logan Pearce, Taylor L. Tobin, Elisabeth Matthews, Aiza Kenzhebekova, Beth Biller, Ben J. Sutlieff, Klaus Subbotina Stephenson
Astrophysics of Galaxies
Massive Galaxy Halos Contain Less Inner Dark Matter Than Predicted
Yu-Chen Wang, Yingjie Peng, Xiaohu Yang et al. (+17 more)
The mass profiles of
galaxy halos encode how
baryons reshape dark matter distribution, yet direct observational constraints across the full radial range remain scarce. Here we combine
stellar kinematics from MaNGA, H I dynamical measurements from ALFALFA, and independently calibrated
halo masses of SDSS groups to statistically reconstruct the mass distribution of central
galaxies over nearly two orders of magnitude in radius. We demonstrate that H I data alone do not provide reliable total
halo mass estimates, necessitating an independent group-based
halo-mass scale. Compared to the IllustrisTNG and EAGLE simulations, the observational profiles of low-mass
halos are broadly consistent; in contrast, massive observed
halos exhibit systematically lower dynamical masses at the H I radius, lower inner dark-matter masses, and lower central dark-matter fractions (about 4$\sigma$ difference in units of population scatter) at fixed total
halo mass. After subtracting baryonic contributions, the inferred dark-matter profiles remain broadly consistent with an NFW form, but with lower effective concentrations than predicted for massive
halos. These results suggest that the inner dark-matter content of massive
halos has been reduced more significantly than predicted by current hydrodynamical simulations, plausibly due to long-term baryonic
halo heating in massive systems.
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All authors Yu-Chen Wang, Yingjie Peng, Xiaohu Yang, Luis C. Ho, Dingyi Zhao, Jing Dou, Hao Fu, Zeyu Gao, Qiusheng Gu, Fangzhou Jiang, Yukun Liu, Roberto Maiolino, Houjun Mo, Canpo Su, Bitao Wang, Kai Wang, Bingxiao Xu, Feng Yuan, Kunyao Zhao, Xingye Zhu
Earth and Planetary Astrophysics
An Updated Model for Epsilon Eridani b and Prospects for Imaging with the Roman Coronagraph
Jorge Llop-Sayson, Andre Fogal, James Mang et al. (+15 more)
Epsilon Eridani b, the nearest known Jupiter analog, has its orbit and mass constrained from radial velocity (RV) and absolute astrometry, and its atmosphere from JWST/NIRCam imaging upper limits in Sanghi et al. 2026. Here we follow up that work with a self-consistent model of Epsilon Eridani b that treats all available data within a single
Bayesian framework. We extend the RV data with new measurements, update the treatment of the astrometry data with a new model, and include the NIRCam observations with a grid of evolutionary and atmospheric models. We find a mass of 0.91+-0.06 M_Jup and an orbit consistent with previous work. The imaging data helps constrain
planet effective temperature, atmospheric
metallicity and surface
gravity. The constraints are dependent on model assumptions: for an atmosphere in chemical
equilibrium, an otherwise low statistically significant feature in one of the epochs is recovered as the
planet at high confidence. When assuming chemical disequilibrium, the posteriors exhibit a bimodal distribution, with one mode consistent with zero flux and the other coinciding with the flux of the tentative feature. Consistent with previous work, the clear atmosphere models are found to be viable at very enhanced
metallicity, whereas the cloudy models yield more moderate values. Applying these models to the Roman Coronagraph, we find that the predicted reflected-light fluxes place every cloudy atmosphere our fit allows within the instrument's expected sensitivity. A non-detection would be very constraining: a final contrast sensitivity of 2e-9 would rule out all cloudy atmospheres under our model assumptions.
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All authors Jorge Llop-Sayson, Andre Fogal, James Mang, William Thompson, Clarissa R. Do Ó, Aniket Sanghi, Isabela G. Huckabee, Laurent Pueyo, Charles Beichman, Geoffrey Bryden, Marie Ygouf, András Gáspár, Schuyler Wolff, Jarron Leisenring, Dimitri Mawet, Tiffany Meshkat, Caroline V. Morley, Jean-Baptiste Ruffio
Fluid Dynamics
IB-Flows: an open-source multi-GPU immersed boundary code for fluid-structure interaction
Giovanni Vagnoli, Martino Andrea Scarpolini, Fabio Guglietta et al. (+4 more)
We present IB-Flows, an open-source, multi-GPU solver for the direct numerical simulation of incompressible fluid-structure interaction (FSI) problems. The code couples a second-order finite-difference fractional-step Navier-Stokes solver on a staggered Cartesian grid with two immersed boundary methods: a Lagrangian method based on moving least-squares (MLS) interpolation and an Eulerian sharp-interface method. Rigid bodies are advanced with a quaternion-based Newton-Euler solver, while deformable surfaces embedded in three-dimensional flows are described by a structural solver based on the interaction potentials; a predictor-corrector scheme provides either loose or strong fluid-structure coupling. Non-Newtonian fluids with shear-thinning or shear-thickening rheology are handled through a strain-rate-dependent viscosity, and the same framework accommodates subgrid-scale eddy-viscosity models for large-eddy simulations of turbulent flows. The solver is written in CUDA Fortran with MPI domain decomposition, so that the fluid, interpolation and structural kernels are all executed on the GPUs, while the distributed transposes required by the Poisson and implicit solvers are further accelerated by the cuDecomp library through GPU-aware communication. Strong- and weak-scaling tests show near-ideal intra-node scaling and good multi-node efficiency. The solver is validated against a set of
benchmark problems spanning wall-bounded
turbulence, rigid-body and deformable-body fluid-structure interaction, and a biomedical application. IB-Flows is intended as a reproducible reference implementation for immersed boundary FSI simulations on modern GPU clusters and as a transparent platform to be used for tackling multiphysics problems.
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All authors Giovanni Vagnoli, Martino Andrea Scarpolini, Fabio Guglietta, Joshua Romero, Massimiliano Fatica, Roberto Verzicco, Francesco Viola
Disordered Systems and Neural Networks · Cross-listed from cs.AI
Flag Game: A Toy Model for Mechanistic Swarm Interpretability
Elizabeth Pavlova and Hidenori Tanaka
Emergent coordinated behaviors of AI
agents are starting to present critical safety risks. A key phenomenon driving these behaviors is the rapid formation and spread of beliefs about the world, and mechanistic understanding is crucial for collective
alignment. To this end, we introduce the Flag Game, a toy model for studying the mechanisms of collective belief formation. Concretely, a hidden country flag defines the ground truth, and each bounded
agent directly observes only a private crop but can exchange beliefs and weigh social evidence from peers. Despite its simplicity, the Flag Game reproduces rich collective phenomenology: non-monotonic scaling of performance with population size, accuracy gains from social-awareness prompting and team diversity, and strong effects of organizational structure. In particular, we identify that collective belief collapse at small population sizes turns into collective belief polarization as the population grows. This polarization causes the performance decline at large population sizes, but creates diversity in collective beliefs. Finally, we dissect the mechanisms underlying collective belief collapse and polarization with two complementary approaches. We first introduce social
circuit attribution, a technique to predict which
agent, and what view, matters most to collective dynamics, and verify its predictions by causal interventions on
agents, tracing how
agent patching changes collective outcomes. However, the efficacy of causal interventions on
agents decreases as the population grows. We therefore develop a statistical mechanical theory for larger populations and verify that it matches the empirical phase diagram. Together, these results take a first step toward mechanistic swarm interpretability, a science of how the properties of individual
agents and their communication give rise to emergent collective behavior.
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Chemical Physics
Floquet-Plasmon Enhanced Charge Transfer at Catalytic Interfaces
Annabelle Canestraight, Phillip Christopher and Vojtech Vlcek
Plasmonic excitation of metallic nanostructures can generate energetic carriers capable of transferring charge into nearby adsorbed molecules, providing a possible pathway for driving chemical transformations. In many theoretical descriptions of this process, charge transfer is determined by the
equilibrium electronic structure of the molecule and substrate together with the time-dependent carrier distribution produced during plasmon decay. However, the intense transient electric fields associated with localized surface plasmons can also dynamically perturb the molecular electronic structure itself on ultrafast timescales. In this work, we investigate how these time-dependent fields modify the molecular spectral function and influence charge injection at catalytic interfaces. Using a model of CO2 adsorbed on Au(111), we compute the real-time molecular Green's function within a correlated frontier-orbital active space under plasmon-like driving. We find that the driving field rapidly produces transient Floquet-type replica bands in the molecular density of states, opening additional resonant pathways for hot-carrier injection that are absent without external driving or in time-local descriptions. Coupling the evolving molecular spectrum to a time-dependent hot-electron distribution described within a two-temperature Sommerfeld framework, we predict large enhancements in quasiparticle spectral overlap that governs injection during plasmon dephasing. These results suggest that dynamically generated non-
equilibrium spectral structure may play an important role in plasmon-assisted catalysis and provide a framework for studying driven catalytic interfaces beyond static electronic structure descriptions.
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Quantum Physics
Comparing magic state cultivation methods using matrix product states
Tom Hartweg and Asier Piñeiro Orioli
Magic state cultivation prepares high-fidelity magic states at low expected space-time costs; however, the exact performance of some schemes is unsettled due to the difficulty in simulating non-Clifford
circuits. Here, we use
matrix-product states (MPS) based methods to compute the exact performance of two types of fold-transversal cultivation schemes: (i) the Sahay et al method based on the regular surface code S gate, and (ii) a method we propose based on a partially fault-tolerant fold-transversal S gate. We show that for the former protocol at $d=5$, the $|T\rangle$ output reaches similar logical error rates to the $|S\rangle$ output, traditionally used as a cheap full Clifford proxy. This contrasts with the $\sim10\times$ discrepancy reported for the $d=5$ colour-code scheme of Gidney et al. We also find that our new $d=5$ scheme has $\sim1.3\times$ lower expected space-time cost while still reaching $10^{-9}$ logical error rate. We show that MPS and Clifford-augmented MPS (CAMPS) perform on par with or even better than the recently introduced near-Clifford simulator Clifft on the hardest $d=5$ regular surface code scheme. Additionally, to speed up simulation, we propose a new pre-screening method based on simple Pauli propagation, lowering by up to three orders of magnitude the required number of exact simulations, and use several simulator-agnostic sampling methods such as subset sampling.
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Materials Science
Divergence between long- and short-wavelength magnon damping in spinel ferrites
Christopher T. Parzyck, Octave Duros, Hari Paudyal et al. (+14 more)
The realization of practical, high-speed magnonic devices requires engineering
magnetic materials with low dissipation over wide frequency ranges. While optical and microwave probes are used to infer the damping of low energy/long wavelength modes, the degree to which these $q\sim0$ properties translate into higher-energy, finite-momentum modes remains an important open question. Here, we utilize a combination of
ferromagnetic resonance (FMR) and resonant inelastic x-ray scattering on spinel ferrites Li$_{0.5}$Al$_x$Fe$_{2.5-x}$O$_4$ to probe
magnons in both the short- and long-wavelength limits. We observe that aluminum substitution both markedly reduces the
magnon bandwidth and drastically shortens the high-$q$
magnon lifetimes, in sharp contrast to the ultralow
magnon damping inferred from FMR. These findings demonstrate a disparity between how non-
magnetic substituents impact
magnon damping in the long- and short-wavelength limits, providing a new perspective for assessing candidate materials for magnonic devices.
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All authors Christopher T. Parzyck, Octave Duros, Hari Paudyal, Noah M. Edmiston, Katya Mikhailova, Lerato Takana, Daisy O'Mahoney, Sauviz P. Alaei, Daniel J. Foster, Hiroki Suga, Naoya Kurahashi, Jun Miyawaki, Michael E. Flatte, Georgi Dakovski, Yuri Suzuki, Durga Paudyal, Wei-Sheng Lee
High Energy Astrophysical Phenomena
Radiation-Driven Magnetic Fields in Sub-Keplerian Accretion Flows: An Alternative to MRI
Mukesh Kumar Vyas and Asaf Pe'er
Large scale
magnetic fields play a crucial role in shaping the dynamics and structure of the inner parts of
accretion disks and the resulting jets from the vicinity of black holes and
neutron stars. Currently, the primary mechanism considered for generating and amplifying large scale
magnetic fields in
accretion disks is the magneto-rotational instability (MRI). Here we show that non-conservative radiation fields provide a rapid and independent mechanism for generating and amplifying
magnetic fields in
accretion flows. A luminous, compact corona generates a radiation-driven poloidal field that is subsequently amplified by differential rotation, yielding quadratic
magnetic-field growth and, over a broad range of coronal luminosities and sizes and MRI amplification locations, magnetization on timescales comparable to or shorter than those of the MRI. The mechanism therefore provides not merely an alternative to MRI, but an additional and, over a substantial region of parameter space, dominant channel for
magnetic-field generation from initial conditions with zero
magnetic field. Since the radiation-driven source arises directly from the non-conservative nature of the radiation field, such
magnetic-field generation is an inevitable consequence of sufficiently strong and anisotropic radiation sources in black-hole
accretion flows. More generally, the mechanism requires only a non-conservative radiation field and differential
plasma motion, and is therefore expected to operate in a broad range of luminous astrophysical systems, including active
galactic nuclei, gamma-ray bursts, and
tidal disruption events.
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Instrumentation and Methods for Astrophysics
Characterization of the CSST Survey Camera CCDs: I. basic electro-optical performance
Zun Luo, Hu Zhan, Youhua Xu et al. (+8 more)
The Chinese Space-station Survey
Telescope (CSST) is a flagship mission designed to carry out a large-area high-resolution multiband imaging and slitless spectroscopic survey over a decade. The survey's science drivers, ranging from precision cosmology to
stellar astrophysics, impose stringent requirements on the performance of its focal plane detectors. This paper is the first in a series that present ground-based characterization of the 31 flight-model charge-coupled devices (CCDs) of the CSST Survey Camera. Measurements of basic electro-optical performance are reported here. Key results include: full-well capacity >80 ke (limited by the test electronics), non-linearity <1.4% in the range of 7-70 ke, median readout noise 3.6 e, dark current <0.02 e/pix/s at the operating temperature of -85 degree celsius, high
quantum efficiency across the survey's spectral range (255-1000 nm), typical pixel response non-uniformity <1%, and charge transfer efficiency >99.9994% at the flat-field level of 10 ke. All 31 CCDs meet or exceed the Survey Camera's specifications. These measurements establish a performance baseline and provide inputs for CSST image simulation and data processing pipelines
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All authors Zun Luo, Hu Zhan, Youhua Xu, Qiuyan Luo, Yuhe Song, Fajun Li, Li Shao, Zhe Huang, Haonan Chi, Huaipu Mu, Xiaolei Meng
Optics
Correlation geometry and topology of structured optical beams
Jyrki Laatikainen and Olga Korotkova
Correlation geometry and
topology in a random, scalar beam carrying Orbital Angular Momentum (OAM) in $L$ modes are shown to be linked to the real and imaginary parts, respectively, of its orbitalization
matrix (OM). The OM is obtained by filtering the cross-spectral density in the polar
Fourier basis at a given cross-section and radius for each pair of OAM indices. The symmetric real part of the OM has the diagonal canonical form, specifying the ellipsoid-like correlation geometry of the beam. The skew-symmetric imaginary part of the OM has the Darboux canonical form, enabling decomposition into $N\leq L/2$ mutually orthogonal circulation states and $L-2N$ trivial circulation-free states, mutually orthogonal and $L-2N$ trivial circulation states thereby defining the $N$-dimensional orbitalization
torus associated with the correlation
topology of the beam. The canonical forms are then used to define the degrees of linear and circular orbital anisotropy and stability, and the degrees of linear and circular orbitalization, in analogy with corresponding quantities in 2D and 3D polarization theory. These results demonstrate the emergence of fundamentally new correlation structures in random multimode OAM-carrying light, not accessible in lower-dimensional systems and absent in the deterministic limit.
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Quantum Physics
Continuous variable distributed quantum sensing in integrated photonics
Bethany Puzio, Oliver M. Green, Joel F. Tasker et al. (+7 more)
Distributed
quantum sensing is an emerging application of
quantum networking, where entangled probe states are employed to sense combinations of delocalized parameters with enhanced precision relative to using separable states. Squeezed states of light are a
prime resource for experimental demonstrations of
entanglement-enhanced sensing, because they can be generated and entangled deterministically. Existing distributed
quantum sensing experiments have been fundamentally limited in scalability due to their bulk-optic architectures. Meanwhile, integrated photonics provides a scalable and compact platform for
quantum sensors. Here we demonstrate
entanglement-enhanced sensing of linear functions of four phase shifts in an integrated photonic
circuit. We find an
entanglement-enhanced precision of 0.199(16) dB below the shot noise limit compared to 0.041(18) dB for separable states. A four-mode entangled state is generated on-chip with
entanglement verification and phase sensing also performed on-chip with an array of four integrated homodyne detectors.
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All authors Bethany Puzio, Oliver M. Green, Joel F. Tasker, Jonathan Frazer, Tamzin Ellis, Benjamin D. J. Sayers, Rachel N. Clark, Alex S. Clark, Giacomo Ferranti, Jonathan C. F. Matthews
Quantum Physics
Securing quantum error correction against misleading advice from AI agents
A. Bar{\i}ş Özgüler
Can an attacker turn influence over an artificial intelligence (AI) adviser into a harmful
quantum error-correction update? We identify an ambiguity in passive syndrome records that obstructs recovery selection, then show how additional calibration measurements support certified recovery updates under uncertainty and drift. In an odd-distance square toric code with error-free preparation, syndrome measurements, and recovery operations, opposite coherent $X$ rotations produce identical passive syndrome-history distributions. Yet a fixed phase correction can help at one sign and harm at the other. A terminal logical measurement on known encoded calibration states supplies the missing sign information. A separate evaluator accepts an update only when calibration uncertainty and a justified drift bound certify improvement over the current recovery, without assuming that the adviser recommends correctly. In simulated advice attacks, calibration-confidence checks reject harmful proposals while retaining beneficial updates under honest advice. We derive sufficient limits on calibration age that require improvement through deployment. In matched simulations, a validated channel-specific bound retains more beneficial updates than the general bound after accounting for evaluation time, while preventing the tested harmful activations under the stated drift assumption. A separate surface-code experiment includes
stochastic circuit faults and noise changing during acquisition. Deterministic controllers achieve at least as many beneficial updates with the same observations. Violating the drift assumption permits harmful acceptance in the toric experiment. The results identify information required for recovery selection, establish conditional guarantees against harmful updates, and quantify the recovery improvements forgone through conservative acceptance.
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Materials Science
An Atlas and Design Rules for Single- and Dual-Atom Alloys
Fabian Berger, Yicheng Wang, E. Charles H. Sykes et al. (+1 more)
A long-standing goal across heterogeneous catalysis, materials science, and condensed matter physics is to design
alloys with prescribed local atomic arrangements. Recent experiments show that dilute trimetallic
alloys unlock chemistries inaccessible to bimetallics, but realizing this potential requires knowing which dopant structures form across an enormous compositional space. Using density functional theory screening, we construct an atlas spanning transition metal single- and dual-atom
alloys in Cu and Ag surfaces, which we validate by scanning tunneling microscopy. The stability follows an electron count: dopants pair most strongly when their combined d-electron count approaches ten. Host metal and surface facet can be used to tune the resulting active site motifs, while size mismatch and
spin explain variations around this trend. We further introduce a reactor-anchor concept, in which one dopant anchors a second, otherwise bulk-segregating dopant at the surface. Together, these results establish design principles for engineering
alloys with targeted active site structures.
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All authors Fabian Berger, Yicheng Wang, E. Charles H. Sykes, Angelos Michaelides
Computational Physics · Cross-listed from cs.LG
Double descent is the principle of least action
Congzhou M Sha
The test error of a model plotted against its number of parameters $d$ falls, peaks when the model can just fit the training data, and falls again, exhibiting the double descent phenomenon. We explain the phenomenon with statistical mechanics. The training trajectory of a
stochastic gradient-based method is a particle wandering over the energy landscape of the training loss at an induced temperature $T$, and a run that has equilibrated visits every parameter vector of a given training loss equally often, the fundamental postulate of statistical mechanics, with probability given by the Boltzmann distribution. Because training starts at an initial point and has only finite time to diffuse, it carries an effective weight decay, which makes every parameter a quadratic degree of freedom. The equipartition
theorem then distributes the energy among the $d$ degrees of freedom in shares of $T/2$, so at a fixed training loss adding parameters lowers the temperature and drives the Boltzmann distribution toward the stationary path. Finally, adding parameters can only lower the $L^2$ norm of the stationary path, so a solution sampled at fixed loss is less likely to be large with increasing $d$, effectively increasing weight regularization.
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High Energy Physics (Theory)
When duality changes the poles: $SL(2,\mathbb{Z})$ transformations of linear response EFTs
Andrea Amoretti, Daniel K. Brattan and Jonas Rongen
We study how $SL(2,\mathbb Z)$ transformations act on pole-truncated linear-response effective theories in $(2+1)$ dimensions. For correlators meromorphic within a finite low-frequency domain, the EFT data include both derivative-expanded transport coefficients and the retained non-hydrodynamic poles. Since the $S$-transformation inverts the optical conductivity and exchanges its poles and zeros, it does not necessarily commute with the infrared truncation. We derive explicit maps for static susceptibilities, the Einstein relation and AC transport coefficients. In the purely hydrodynamic sector the map closes on the original transport data, while in quasihydrodynamic regimes the transformed pole positions and, in general, residues constitute additional infrared data. We test the construction in the alternatively quantised D3/D5 probe-brane system, where an EFT retaining one original gapped pole can correspond to transformed EFTs retaining zero, one or two. The
holographic results verify the analytic maps and exhibit an inverse-Drude conductivity at large values of the control parameter.
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Solar and Stellar Astrophysics
Oscillating dynamo models with a time-nonlocal $\alpha$ effect
Günther Rüdiger, Manfred Schultz and Alfio Bonanno
The traditional $\alpha$ effect is extended by the first temporal derivative, so that in turbulent flows the
magnetic field entering the induction process is effectively sampled in the past. As a consequence, dynamo excitation becomes easier and cycle times are prolonged relative to solutions obtained from the local standard formulation. The temporal shape of the
magnetic cycles is also modified, with rise times becoming shorter than decline times, so that the profiles acquire a characteristic “sawtooth” appearance. In the nonlocal formulation, the induced
magnetic-field amplitudes acquire an additional dependence on the correlation time. For fixed dynamo number, the field amplitude reaches a maximum at a certain correlation time. For correlation times larger than this peak value, the model can reproduce Waldmeier-type trends known from
solar sunspot observations. If the actual correlation time fluctuates around this value, the long-term
magnetic cycle can occasionally enter weak-cycle episodes reminiscent of grand minima such as the Maunder minimum. For smaller dynamo numbers close to the critical one, however, rather long correlation times are required for this behaviour to occur.
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High Energy Physics (Phenomenology)
Comprehensive reconstruction of collider events with hypergraph representation learning and graph-conditioned diffusion
Lining Mao, Yvonne Peters, Ethan Simpson et al. (+1 more)
In particle
collider experiments, event reconstruction is the task of inferring the kinematics of short-lived particles produced in the hard scatter from the stable final states recorded by detectors. We decompose event reconstruction into two primary tasks: assigning measured jets and charged
leptons to parent particles, and predicting unmeasured
neutrino kinematics. We present VyPER, a novel
geometric learning framework that represents
collider events as hypergraphs with a physics-inspired
topology. VyPER combines the supervised classification of hyperedges for particle assignment with a
diffusion model for predicting
neutrino kinematics, leveraging a joint loss function to optimize both reconstruction tasks within a unified framework. We showcase VyPER across several
proton-
proton collision processes, comparing its performance to existing analytical and machine-learning-based reconstruction techniques. In doing so, we demonstrate that accurate event reconstruction is achievable across a diverse range of Standard Model physics processes, opening new avenues for precision measurements in the
Higgs boson, electroweak, and top-
quark sectors.
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All authors Lining Mao, Yvonne Peters, Ethan Simpson, Zihan Zhang
Soft Condensed Matter
Geometry-Controlled Relaxation Spectra in Viscoelastic Fluids
Niloyendu Roy, Rupayan Saha, Debankur Das et al. (+2 more)
Soft materials store, dissipate and release mechanical stresses through relaxation processes that often span many orders of magnitude in time. Such relaxation spectra are widely used to infer internal material dynamics and are usually regarded as fingerprints of microscopic complexity, disorder, or heterogeneity. Here we show that a broad relaxation spectrum can instead be generated by the geometry of mechanical excitation itself. Using rotationally driven colloidal dimers in a wormlike micellar fluid with a dominant bulk relaxation time of order one second, we demonstrate that torsional driving converts distance from the driven object into relaxation time. This produces a geometry-controlled hierarchy of relaxation modes: orientational
recoils persist for hundreds of seconds and encode past torque protocols over comparably long times. Particle velocimetry reveals rapid angular-momentum transport away from the probe, in contrast to the slow relaxation of stored torsional stress. A continuum shell model captures the observed
recoil dynamics and the selective suppression of long-lived contributions under spatial confinement. Our results show that geometry can transform a material with simple intrinsic relaxation into a system with long-lived, space-dependent
memory, suggesting a route to tune material dynamics through mechanical excitation rather than composition, with potential implications for microscopic mechanical
memory elements.
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All authors Niloyendu Roy, Rupayan Saha, Debankur Das, Matthias Krüger, Clemens Bechinger
General Relativity and Quantum Cosmology · Cross-listed from math.HO
The suppression thesis in Riemann's Habilitationsvortrag
Victor Tapia
In 1854 Riemann presented his Habilitationsvortrag Über die Hypothesen welche der Geometrie zu Grunde liegen to the Faculty of Philosophy of the University of Göttingen. The lecture does not contain analytical developments and Riemann never explained the reason for this choice. According to Dedekind this choice was done in order to make the lecture understandable to the non-mathematician professors of the Faculty. This is the suppression thesis. Nevertheless, in 1851, three years before, Riemann has presented his Inauguraldissertation Grundlagen für eine allgemeine Theorie der Functionen einer veränderlichen complexen Grösse to the same professors of the Faculty of Philosophy. The Inauguraldissertation contains many analytical developments but, on that occasion, they were not suppressed. Therefore, the presence of non-mathematician professors is unrelated with the presence or absence of analytical developments in the lectures. The ideas contained in Riemann's Habilitationsvortrag –
manifold, line element,
curvature– were so new at the time that there was not even a proper
language to express them. Therefore, Riemann was forced to adopt a non-technical expository style. This explanation for the absence of analytical developments in Riemann's Habilitationsvortrag is more credible than the suppression thesis.
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