Mathematical Physics · Cross-listed from cs.LG
Reduced-Order Models: The Mother of World Models
Rajat Ghosh
World models – compressed latent representations of an environment that support action-conditioned prediction and planning – are typically presented as a product of modern self-supervised learning. This paper argues that the functional anatomy of a world model was independently developed, deployed, and formally analyzed decades earlier in the model-order-reduction (MOR) and control literature, under different names and for a different purpose: the real-time operation of physical systems. We trace the anatomy across three communities. Low-dimensional models of
turbulence built on proper orthogonal decomposition (POD) supplied latent dynamics learned from data of a chaotic environment; eigenface methods in early computer
vision supplied the encoder-decoder half, including a primitive runtime validity check; and measurement-based POD frameworks for facility thermal control assembled the complete loop – POD coefficients as latent state, parametric dependence on actuator setpoints as action conditioning, modal reconstruction as decoding, and, critically, a priori analytical error bounds as a verification layer that certified when the model's predictions could be trusted in closed loop. We then examine what each tradition possesses that the other lacks: MOR contributes verification, physical grounding, and extreme data efficiency; learned world models contribute nonlinear representation, transferability, and horizon. We argue that the outstanding obstacle to deploying world models in systems that cannot fail – power, thermal, process control – is not predictive fidelity but verifiability, and we outline a research agenda for physics-grounded, verifiable world models that unifies the two lineages.
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Quantum Physics
Self-Specializing Vision-Language Transmon Chip Calibration in a Physics-Grounded Environment
Animesh Tripathy and Aswanth Krishnan
Calibrating a superconducting transmon chip is a sequential decision problem under noise, drift, and a finite budget: an expert must choose experiments, read ambiguous plots, judge fit quality, and revise stale beliefs as the chip drifts. We study whether a
vision-
language agent can close this loop and specialize itself to one physical device without weight updates, via three co-designed artifacts. The first is a physics-grounded simulation environment for transmon chips: calibration observables derive from
circuit-quantized parameters via scqubits, with realistic flux-line distortion, wall-time-scaled and mid-scan drift, and gate leakage, concerns a toy simulator would omit; each tool call advances a modeled clock so drift accrues by wall time, not call count. The second is a
vision-
language agent that runs the loop end to end, calling tools, reading plots, maintaining a structured notebook, and submitting parameters without hidden truth, scored against hidden parameters and gate fidelities measured on the device. The third is gradient-free online adaptation: a reflector reads truth-free anomaly signatures from past attempts and grows a small, human-readable device note appended to the
prompt, admitted by a paired-snapshot accept gate that isolates strategy improvement from drift. On a hard-tier chip under budget pressure, six iterations raised the worst-case CZ fidelity from 0.678 to 0.787 and cut its variance, reproducing at four-
qubit scale; a single accepted note raised CZ fidelity from 0.678 to 0.913 on its paired snapshot. A planted-fault study confirms the note is causal, diagnosing a hardware fault truth-free, its principal value raising the failure floor and cutting variance. The
agent, scoring, and reward transfer to real hardware via a measurement-backend swap; only the accept gate is a simulation affordance, reducing to a held-out-slice or repeat-and-average form.
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Optics
Efficient broadband second-harmonic generation in a multi-pass cell
Arthur Schönberg, Nikolas Rupp, Ana Oliveira e Silva et al. (+6 more)
Second-harmonic generation (SHG) is a widely used nonlinear optical process that has been optimized for high frequency conversion efficiency, broad bandwidths, and optimum spatial and temporal quality of the generated light. However, limitations of the generation efficiency arise due to temporal dispersion and pulse walk-off effects introduced by the nonlinear
crystal. To circumvent these limitations, quasi-waveguide schemes, in particular multi-pass
cells (MPCs), can be employed, providing flexible phase-tuning capabilities. In this work, we demonstrate for the first time broadband and efficient SHG in an MPC. SHG efficiencies of 72% (for 63 fs, 50 uJ pulses) and 47% (for 15 fs, 20 uJ pulses) are obtained by simultaneously matching the relative phase and group delay between the fundamental and second-harmonic fields over multiple passes through the MPC. Our work sets a new record for efficient Gaussian-beam, ultrashort-pulse SHG and provides a general route to address efficiency-bandwidth limitations of nonlinear optical processes.
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All authors Arthur Schönberg, Nikolas Rupp, Ana Oliveira e Silva, Lorenzo Pratolli, Yujiao Jiang, Vincent Wanie, Terence Mullins, Francesca Calegari, Christoph M. Heyl
Quantum Physics
Quantum Kolmogorov–Arnold representation theorem for continuous unitary-valued maps
Sviatoslav V. Dzhenzher
The classical Kolmogorov–Arnold representation
theorem states that any continuous multivariate function can be exactly decomposed into a finite composition of univariate continuous functions and addition operations. This foundational result has recently inspired the development of Kolmogorov–Arnold Networks (KANs) in classical machine learning, as well as their extensions into the
quantum domain (QKANs). In this paper, we establish two
quantum analogues of the Kolmogorov–Arnold representation
theorem for continuous
unitary-valued maps of several variables within an open $1$-neighbourhood of the identity
matrix \(O_1(\mathbf{I}) \subset \mathcal{U}(n)\). First, we prove a representation
theorem that yields an exact additive decomposition inside the
matrix exponent of anti-Hermitian-valued maps. Second, due to the non-commutative nature of
quantum operators, we derive a factorised version expressing the target
unitary map as a finite sequential product of univariate
matrix exponentials. Finally, we provide a concrete topological counterexample based on the lifting property of \(\mathcal{SU}(2)\) to demonstrate that these local representation
theorems cannot be globally extended to the entire
unitary group \(\mathcal{U}(n)\) without encountering fundamental structural obstructions.
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Instrumentation and Methods for Astrophysics
DHARA: Data Handling and Automated Reduction pipeline for AIMPOL
Namita Uppal, Shashikiran Ganesh, Santosh Joshi et al. (+3 more)
We present an automated data-reduction and analysis for optical linear polarimetric data obtained from a dual-beam polarimeter. The pipeline is optimized for observations acquired with the ARIES Imaging POLarimeter mounted at the Cassegrain focus of the 1.04-m Sampurnanand
Telescope at ARIES. It is implemented using interactive Python routines that process raw images to derive the Stokes parameters, from which the degree of polarization and polarization angle are computed along with their uncertainties. The pipeline framework is designed to handle the reduction of both single-source and crowded-field observations. The identification of extraordinary (e-ray) and ordinary (o-ray) image pairs is a crucial step and is performed using different strategies for single-source and crowded-field data, while subsequent stages, such as photometric and polarimetric analysis, follow a common procedure. We validate the pipeline using observations of polarized standard
stars acquired over multiple epochs between 2017 to 2025, and compare the results with values reported in the literature. To demonstrate the applicability of the pipeline to crowded-field observations, we apply it to polarimetric data of the Alessi~1 open cluster and compare with previously published results derived using traditional reduction methods. In both cases, the polarization parameters derived using the pipeline agree with literature values within $2\sigma$ uncertainties. Although developed for AIMPOL, the pipeline is readily adaptable to any dual-channel imaging polarimeter in which the e-ray and o-ray images are recorded in a FITS image from a single CCD.
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All authors Namita Uppal, Shashikiran Ganesh, Santosh Joshi, Dmitry Blinov, Konstantinos Tassis, Sadhana Singh
Cosmology and Nongalactic Astrophysics
Neutrino mass constraints in the Schwarzschild-de Sitter black-hole dark energy model with ACT DR6 and DESI DR2 data
Sheng-Han Zhou, Tian-Nuo Li, Guo-Hong Du et al. (+4 more)
Recent DESI observations have posed new challenges to $\Lambda$CDM, showing a preference for dynamical dark energy and yielding
neutrino mass constraints within $\Lambda$CDM that approach the lower bound allowed by
neutrino oscillation experiments. In this work, we investigate cosmological constraints on the key
neutrino parameters, $\sum m_\nu$ and $N_{\rm eff}$, within the Schwarzschild-de Sitter black-hole dark energy (SdSDE) framework. We use
cosmic microwave background (CMB) data from Planck and ACT DR6,
baryon acoustic oscillation data from DESI DR2, and type Ia
supernova data from DES-Dovekie and PantheonPlus. We find that SdSDE scenarios prefer a positive
neutrino mass whenever $\sum m_\nu$ is allowed to vary. Using CMB+DESI+DES-Dovekie data, we obtain $\sum m_\nu=0.207^{+0.047}_{-0.052}~{\rm eV}$ for SdSDE+$\sum m_\nu$, reduced to $\sum m_\nu=0.162^{+0.055}_{-0.056}~{\rm eV}$ when $N_{\rm eff}$ is also varied. This arises from the positive correlation between $N_{\rm eff}$ and $\sum m_\nu$, together with the systematic preference of SdSDE for values of $N_{\rm eff}$ below the standard value. Furthermore, the best-fit $\chi^2$ comparison shows that $\Lambda$CDM with extended
neutrino parameters is strongly preferred over the corresponding SdSDE extension. Overall, the positive
neutrino mass preference induced by SdSDE may reflect parameter compensation rather than an improved global fit, a possibility that should be further tested with future high-precision observational data.
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All authors Sheng-Han Zhou, Tian-Nuo Li, Guo-Hong Du, Yi-Min Zhang, Zhao-Yu Li, Jing-Fei Zhang, Xin Zhang
Quantum Gases
Effective potentials for polar molecules under non-orthogonal dual microwave fields
Fulin Deng, Xinyuan Hu, Su Yi et al. (+1 more)
Dual-microwave shielding has emerged as a powerful tool for stabilizing ultracold polar molecules while tuning their intermolecular interactions. However, the two microwave fields are generally not perfectly orthogonal in experiments. Such misalignment introduces an in-plane component of the linearly polarized microwave, whose frequency differs from that of the elliptically polarized field. This component prevents complete cancellation of the dipole-dipole interaction and, more critically, renders the single-molecule dressed state intrinsically time-dependent, so that the conventional time-independent scattering framework is no longer available. Here we develop a Floquet theory that yields an analytic effective potential and enables accurate scattering calculations for polar molecules in non-orthogonal dual microwave fields. We find that, though misalignment weakens the shielding moderately, inelastic losses remain strongly suppressed under experimentally relevant conditions. Meanwhile, misalignment provides additional tunability of the interaction anisotropy and strength, which has been directly applied to recent experimental observations on the gas-to-droplet transition~[Z. Shi et al, arXiv:2508.20518 (2025)] and
Fermi-surface deformation in microwave-shielded molecular gases~[S. Biswas et al, arXiv:2602.22447]. The framework is not restricted to dual-microwave shielding and can be generalized straightforwardly to arbitrary multi-frequency driving, providing a versatile tool for manipulating ultracold polar molecules under complex microwave configurations.
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All authors Fulin Deng, Xinyuan Hu, Su Yi, Tao Shi
Solar and Stellar Astrophysics
The recent anomalously weak polar field does not imply a weak field at solar cycle 25 minimum
Zi-Fan Wang, Jie Jiang, Yukun Luo et al. (+3 more)
The ongoing
solar cycle 25 has progressed past its peak of sunspot numbers, being stronger than the previous cycle 24. However, the present polar field is rather weak compared to previous cycles at the same
evolution phase, particularly in the northern hemisphere, where it has been decreasing since mid-2025 till present. A prominent poleward surge is observed to cause the decrease of the polar field. This raises concerns to the polar field at cycle 25 minimum, which is the precursor to the strength of the next cycle 26. To predict whether the polar field at cycle 25 minimum will be weak as expected, we use observation-based statistical properties to predict the active region emergence during the latter half of cycle 25, and use a surface flux transport model to simulate the
evolution of the large-scale
magnetic field. We predict the polar field at cycle 25 minimum to be $-5.62\pm1.61$G in the north and $5.51\pm1.48$G in the south, both stronger than those at cycle 24 minimum. This is because the poleward surge causing the temporal decrease of the polar field originates from a group of active regions that produces net increase to the polar field, instead of active regions with non-Joy's tilt. Our results suggest the weak polar field at present is unlikely to cause a weak minium and an exceptionally weak cycle 26, clarifying that the short term
evolution should not be simply correlated to the long term properties of the
solar large-scale field.
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All authors Zi-Fan Wang, Jie Jiang, Yukun Luo, Ruihui Wang, Xinchun Ma, Jingxiu Wang
Atomic Physics
Calculation of the energy levels and hyperfine structure for Xe~II, Rn~II, and Og~II ions
T. H. Dinh, V. A. Dzuba and V. V. Flambaum
Energy levels, Landé $g$-factors, and hyperfine-structure constants are calculated for the singly ionized noble-gas atoms Xe II, Rn II, and Og II. The calculations are performed using the configuration-interaction method with perturbative treatment of high-lying configurations. Core polarization effects in the hyperfine interaction are included within the time-dependent Hartree-Fock method. Calculations for Xe II are used to test the accuracy of the approach by comparison with available experimental data. The agreement is at the level of about one percent for the energies and typically about ten percent for the hyperfine constants, with better accuracy for states with large hyperfine constants. Predictions are then presented for Rn II and Og II, for which experimental spectroscopic data are limited or absent. Special
attention is paid to Breit and
quantum-electrodynamic corrections to the hyperfine structure in heavy many-electron ions. We show that these corrections may be strongly enhanced by configuration mixing when interacting states with very different hyperfine
matrix elements are separated by small energy intervals. This effect is demonstrated explicitly for odd-parity $J=1/2$ states of Og II. The calculated hyperfine-structure constants for Rn II and Og II provide electronic factors needed for extracting
nuclear magnetic dipole and electric quadrupole moments from future spectroscopic measurements. These results may be useful for experimental studies of radon and oganesson ions and for testing
nuclear models in the superheavy region.
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Materials Science
Martensitic Transformation in Crystal-Amorphous Superlattices of NiTi Shape Memory Alloy
Bhavna Singh and Shivam Tripathi
Shape
memory alloys (SMAs) exhibit unique thermo-mechanical properties arising from reversible martensitic transformation. Tailoring these properties through coherent second phases is effective but is often limited by the difficulty of identifying thermodynamically compatible phases.
Crystal-amorphous superlattices (CAS), in which the second phase is derived from the base material itself, provide an attractive alternative. However, the influence of partial amorphization on martensitic transformation and thermo-mechanical behavior remains largely unexplored. Here, large-scale molecular dynamics simulations are used to investigate temperature- and stress-induced martensitic transformations in CAS-NiTi with different crystalline phase fractions. Partial amorphization fundamentally modifies the transformation pathway, introducing an initial continuous (second-order-like) transformation before the conventional first-order martensitic transformation. The amorphous phase also enhances transformation reversibility, reducing the thermal hysteresis from 275 K in fully crystalline NiTi to 95-110 K in CAS-NiTi. Simultaneously, the elastic modulus and the critical stress for stress-induced martensitic transformation increase by approximately 60-90 percent, depending on the crystalline fraction. These improvements originate from heterogeneous nucleation at
crystal-amorphous interfaces, retained austenite that promotes the reverse transformation, and mechanical constraint imposed by the amorphous phase. These findings establish
crystal-amorphous superlattices as a promising microstructural design strategy for tailoring the thermo-mechanical performance of shape
memory alloys.
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Optics
Bidirectional phase sensitivity in holographic phototransient microscopy
Emmanuel Kotu Robertson, Dennis van de Lockand and Matz Liebel
Mid-infrared photothermal microscopy combines the chemical specificity of infrared absorption with the spatial resolution of visible-light detection, but practical implementations face a persistent trade-off between forward-scattering (FWS) and backward-scattering (BWS) detection geometries. FWS provides quantitative, shape-independent phase contrast but requires two-sided optical access that is difficult to achieve in aqueous or thick samples. BWS offers convenient single-sided access, but its signals are strongly distorted by depth-dependent interference for micron-scale objects. Here we present a bidirectional femtosecond mid-infrared pump-probe
holographic microscope capable of switching between FWS and BWS geometries within a single instrument, and use it to introduce and validate a new imaging modality, internal forward scattering (IFS). IFS exploits the back-reflection generated at the top surface of the mid-infrared-transparent sample substrate as an internally generated forward-scattering illumination wave, isolated from the directly backscattered field via temporal coherence gating. Using polystyrene beads on CaF2 substrates in air, water, and a refractive-index-matched glycerol-water mixture, we show that IFS reproduces the signal magnitudes and temporal dynamics of true FWS measurements while retaining the mechanical simplicity and single-sided accessibility of BWS. These results establish IFS as a practical, quantitative alternative to conventional FWS and BWS geometries for photothermal, and more broadly quantitative phase, imaging, with direct relevance to single-sided imaging of biological or solvent-contained specimens.
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Quantum Physics
Geometric modulation of transition and survival intensities in non-Hermitian systems
Ryu Frieson, Takashi Oka and Hideaki Obuse
The time
evolution of non-Hermitian systems is generally nonunitary. Dynamics governed by time-dependent non-Hermitian
Hamiltonians lead to a variety of novel phenomena, one of which is state amplification or suppression induced by the complex Berry phase. Here, we extend the framework of
geometric modulation to multi-level systems and show that both transition and survival intensities can be modulated. We apply our theory to the non-Hermitian Landau-Zener (LZ) problem. First, we show that, in the half-LZ problem, both the transition and survival probabilities exhibit nonreciprocity due to the complex Berry phase. In the non-Hermitian standard LZ problem, only the survival intensity is known to exhibit nonreciprocity, whereas the transition intensity does not. However, the physical origin of this nonreciprocal behavior remains unclear. In this work, we show that the nonreciprocity originates from the complex Berry phase.
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Statistical Mechanics
Finite-Time Thermodynamics of Battery Discharging: Power-Efficiency Trade-Off and Optimization
Rui-Han Liu, Yun-Qian Lin and Yu-Han Ma
Battery discharging is governed by a fundamental trade-off between output power and energy conversion efficiency due to internal dissipation. In this paper, we demonstrate that such a trade-off universally yields a
parabolic envelope $P\propto\eta(1-\eta)$. The efficiency at maximum power is exactly one half, mirroring the well-known half-Carnot limit in finite-time thermodynamics. To extend this bound into practical operational rules, we formulate a multistage constant-current discharging (MSCD) schedule subject to simultaneous real-time load demands and a global discharging deadline. Analytical resolution via the Karush–Kuhn–Tucker conditions reveals a remarkably compact optimal policy: $I_{i}^{\star}=\max(I_{i}^{-},I_{0})$. Under this rule, stages limited by external demand run exactly at their minimum required currents, while all remaining stages are elevated to a uniform baseline $I_{0}$ fixed by the deadline constraint. By tracing the dissipation–time Pareto front, we quantify how internal resistance shifts the operational boundaries and sharpens the trade-off corner. This analysis establishes a rigorous thermodynamic baseline for the scheduling layer of battery management systems, offering natural extensions to nonlinear models incorporating temperature and state-of-charge dependencies.
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High Energy Physics (Experiment)
RTL Fault Injection of a Deployed Graph Neural Network Trigger for Belle II
Georgios Sotiropoulos, Marc Neu, Tanja Harbaum et al. (+2 more)
As particle physics detectors grow in scale, High Energy Physics experiments must process ever-increasing data volumes. Level-1 trigger systems, implemented on Field-Programmable Gate Arrays and increasingly using neural-network
algorithms, filter this data in real time. However, their proximity to the interaction point exposes them to radiation, which can corrupt outputs, stall processing pipelines, or damage hardware, with significant financial and scientific consequences. In this work, we present the first Register Transfer Level fault-injection study of a deployed Level-1 hardware neural-network trigger, GNN-ETM in the Belle II trigger system. We target three failure modes most consequential to a real-time trigger pipeline: deadlocks, timeouts, and packet-integrity violations. Through two complementary campaigns, we inject 1 442 840 Single-Event Upsets across 211 245 signals. We find a monitoring asymmetry in the existing verification infrastructure and propose inter-stage liveness monitoring as a more accurate alternative to output-only observation, showing that Mean Time To Failure estimates from the two approaches differ by up to 78.7%. The resulting per-stage data identifies the highest-priority hardening targets.
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All authors Georgios Sotiropoulos, Marc Neu, Tanja Harbaum, Torben Ferber, Jürgen Becker
Mesoscale and Nanoscale Physics
Comparative Evaluation of Encapsulation Methods for Endohedral Doping of Single-Wall Carbon Nanotubes
Cristian M. Borja-Peña, Martin Magg, Hussein Slim et al. (+10 more)
Single wall carbon nanotubes (SWCNTs) are promising building blocks for nanoelectronic and optoelectronic devices, yet reliable and stable doping, particularly n type, remains challenging due to strong environmental sensitivity and competing extrinsic effects. Encapsulation of charge transfer molecules within the SWCNT cavity offers a promising route to stable doping while preserving the nanotubes outer surface for subsequent processing. Here, we systematically investigate the filling of arc discharge SWCNTs with the electron donor tetrathiafulvalene and electron acceptor tetracyanoquinodimethane, comparing different methods for filling, including melt filling, solution reflux, and
vacuum phase sublimation. We follow the entire processing workflow from raw, unfilled powders to aqueous dispersions and employ density gradient ultracentrifugation to separate filled from empty nanotubes as well as metallic from semiconducting ones. Encapsulation efficiency and electronic modification are assessed using absorption spectroscopy, resonant Raman scattering, thermogravimetric analysis, X-ray photoelectron spectroscopy and electron paramagnetic resonance. Finally, we introduce a complementary
vacuum-phase method that removes externally adsorbed molecules without extensive solvent washing, enabling cleaner encapsulated systems.
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All authors Cristian M. Borja-Peña, Martin Magg, Hussein Slim, Yamaldi M. Bakary, Timm Swoboda, Cedric Desroches, Denys Kurylo, Kazuhiro Yanagi, Marianna Sledzinska, Benjamin S. Flavel, Salomé Forel, Wim Wenseleers, Sofie Cambré
Astrophysics of Galaxies
A steep mass transition for bar-driven ISM structuring revealed by PHANGS-JWST
Eric Emsellem, Jessica Sutter, Ryan Chown et al. (+26 more)
Galactic bars play a critical role in the secular
evolution of their hosts by reorganising the ISM. We use a sample of 57
star-forming disc
galaxies observed with JWST at 3 and 7.7 $\mu$m to probe how the spatial distribution of PAH emission, as a structural marker of the cold ISM, depends on
stellar mass and bar presence. We find evidence for a "watershed" at a
stellar mass of $10^{10}$ Msun, marking a fundamental transition in the bar-driven distribution of PAH emission. This confirms trends previously predicted by numerical simulations and observed via ionised gas or UV light. While lower-mass
galaxies exhibit a disordered and clumpy distribution of PAH emission regardless of bar presence, higher-mass barred hosts display well-structured dynamical features traced by PAH emission with significant gas reservoirs (e.g., discs and rings) within the central 15% of the bar radius (Rb). Furthermore, we observe a systematic depletion of PAH emission within the [0.2-0.8] Rb range in barred systems with
stellar masses above $10^{10}$ Msun. Such central discs, rings, and associated radial dips ("bar deserts") appear to be a mass-dependent phenomenon: ubiquitous in massive
galaxies but mostly absent in lower-mass counterparts. In contrast to the structured features in massive hosts, the disorganised ISM in lower-mass
galaxies masks commonly observed bar-driven signatures. This suggests that tracer selection and
dust obscuration may significantly bias observed bar fractions. Our study underlines two regimes of secular
evolution, with different impacts and observability of bar-driven processes: it reaffirms bars as primary drivers of rapid secular
evolution in
galaxies above $10^{10}$ Msun$, while their impact is significantly reduced or delayed below this threshold. It further underscores the need to account for these processes when modelling
galaxy evolution in cosmological simulations.
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All authors Eric Emsellem, Jessica Sutter, Ryan Chown, Adam Leroy, Debosmita Pathak, Eva Schinnerer, Thomas Williams, Karin Sandstrom, Oscar Agertz, Francesco Belfiore, Amelia Fraser-McKelvie, Kirsten Larson, Janice Lee, Jay Gonzàlez Lobos, Sharon Meidt, Miguel Querejeta, Sophia Stuber, Pierrick Verwilghen, Oleg Egorov, Damian Gleis, Jonathan Henshaw, Justus Neumann, Yixian Cao, Daniel Dale, Daizhong Liu, Elias Oakes, Marina Ruiz Garcìa, Dave Thilker, Elizabeth Watkins
Mathematical Physics · Cross-listed from math.SG
Two-boost problem for the rotating Kepler problem
Jagna Wiśniewska
The two-boost problem in space mission design asks whether two points of phase space can be connected with the help of two boosts of given energy. In this article we provide a positive answer for the rotating Kepler problem by generalizing the definition of Lagrangian Rabinowitz Floer homology from the class introduced in [4] to a strictly broader class, and computing the corresponding homology in this more general setting. The principal technical challenge is the non-compactness of the energy hypersurface both near the collision singularity and in the infinity.
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Cosmology and Nongalactic Astrophysics
Evading the CMB $\mu$-distortion bound on Supermassive Primordial Black Hole seeds with Non-Gaussian tails
Sanket Dave, Sheng-Feng Yan, Amara Ilyas et al. (+1 more)
Supermassive black holes (SMBHs) powering
quasars at $z \gtrsim 6$ are difficult to grow from
stellar mass remnants, motivating seeds from
primordial black holes (PBHs) with masses $10^5-10^7 M_{\odot}$. This range is constrained by the COBE/FIRAS bound on the CMB $\mu$-distortion, which limits the small-scale
curvature variance to $\sigma_\zeta^2 \lesssim 10^{-4}$. For Gaussian perturbations, the variance fixes the far tail of the one-point probability distribution function (PDF), making the PBH abundance negligible. We call this the Gaussian barrier. The barrier can be evaded only if the variance probed by the distortion is decoupled from the tail probability controlling collapse. We implement this idea in the non-perturbative $\delta N$ formalism and relate asymptotic PDF tails to the global shape of the $\delta N$ map. Four Gaussian-cored families are analyzed: generalized-normal, stretched-exponential, power-law, and log-normal tails. After standardizing each family to unit variance, we impose the FIRAS cap and compute the distortion-limited PBH abundance in the tail-shape parameter space. The ordinary exponential tail produced by standard single-field non-attractor dynamics is still too light to reopen the seed window. Algebraic tails from fractional-potential dynamics, and sufficiently heavy log-normal tails treated as a phenomenological proxy for multiplicative dynamics, can supply seed-relevant abundances while respecting the distortion bound.
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All authors Sanket Dave, Sheng-Feng Yan, Amara Ilyas, Yi-Fu Cai
Materials Science
Self-Driven Atomic Dispersion in Graphitic Layers
Zhaoxi Chen, Yulu He, Zhuoran Yao et al. (+9 more)
Carbon-supported single-atom catalysts maximize metal utilization, but how metal nanoparticles transform into isolated atoms within carbon remains unclear. We show that metal nanoparticles can undergo a self-driven dispersion process under hydrocarbon oxidation conditions, transforming into single atoms that are confined in carbon
matrix. Using Pt-catalysed hydrocarbon oxidation as a model, we combine operando electron microscopy, near-ambient-pressure X-ray photoelectron spectroscopy and mass spectrometry to track coupled structural and chemical
evolution. Graphitic carbon grows at step edges of Pt nanoparticle, continuously reconstructing Pt surface and generating undercoordinated sites for atom release. In-situ generated CO accumulates at the metal-carbon interface, weakening bonding and facilitating self-amplified atom release and migration. Defective carbon overlayers then trap, stabilize and transport liberated atoms, while oxidative etching preserves interfacial access of reaction-gas. Similar behaviour across other metals suggests a general atomization pathway for single-atom catalyst synthesis, yielding products with electrocatalytic hydrogen production activity beyond standard commercial
benchmarks.
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All authors Zhaoxi Chen, Yulu He, Zhuoran Yao, Jian Liu, Jun Cai, Ziyi Fan, Wenjun Zhang, Lei Lei, Zupeng Chen, Bo Yang, Zhi Liu, Zhu-Jun Wang
Optics
Exceptional light propagation via generalized bulk-edge correspondence
Heitor da Silva, Sergey K. Ivanov, Isaac Suárez et al. (+2 more)
In topological photonics, the bulk-edge correspondence is conventionally imported by direct analogy with electronic systems, overlooking the fundamentally distinct spacetime
symmetries of Maxwell's and Schrödinger's equations. In this work, we challenge this prevailing paradigm by demonstrating that non-trivial bulk
topology alone is insufficient to guarantee localized edge states in photonic platforms. Using a Su-Schrieffer-Heeger-inspired photonic
crystal, we unveil a generalized bulk-edge correspondence intrinsically shaped by the relativistic nature of electromagnetic waves. This constraint imposes a strict frequency cutoff, a feature fundamentally absent in electronic topological
insulators, which enables a new regime of frequency-controlled spatial localization near the cutoff. Furthermore, we demonstrate that this generalized correspondence is polarization-dependent: transverse electric (TE) and transverse
magnetic (TM) edge modes exist in different parameter regimes and exhibit distinct dispersion relations, including distinct zero-dispersion points. Our framework redefines the theoretical boundaries of topological photonics, unlocking new opportunities for polarization-selective dispersion engineering and robust pulse propagation in topological photonic platforms.
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All authors Heitor da Silva, Sergey K. Ivanov, Isaac Suárez, José R. Salgueiro, Albert Ferrando
Earth and Planetary Astrophysics
H.K. Vedantham, A. Strugarek, C.K. Louis et al. (+12 more)
Stars interact with their
exoplanets though
gravity, radiation,
plasma and
magnetic fields.
Stellar plasma and
magnetic fields impose electrodynamic effects on
exoplanet atmospheres and interiors that include heating, aurorae and atmospheric mass loss. The
planets in turn can excite Alfvénic disturbances that are dissipated on the
star leading to chromospheric heating and
flares. This interaction, broadly called
magnetic star-
planet interaction (M-SPI), can also generate
radio signatures both from the
star and the
exoplanet. The
radio emission encodes information on the dynamics/energetics of the interaction, the
magnetic field strength and
topology of the emitter and the orbital/rotational geometry of the system – information that is difficult or in some cases implausible to obtain by other means. Yet we do not have a conclusive detection of M-SPI in the
radio band primarily due to sensitivity limitations and scarce observing time spent monitoring promising targets. Here we describe the scientific motivation to study M-SPI in exoplanetary systems, to get progress in understanding its predicted signal strength and phenomenology. We argue that the SKA
telescopes can make a transformative contribution to
exoplanet science by detecting M-SPI in the
radio band but this will require substantial observing time – similar to that afforded to successful optical-band searches for M-SPI signatures.
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All authors H.K. Vedantham, A. Strugarek, C.K. Louis, J.R. Callingham, L. Peña-Moñino, M. Pérez-Torres, P. Zarka, E. Mauduit, N. Duchêne, P. Amado, S. Bloot, R. D. Kavanagh, A. A. Vidotto, L. Lamy, C. Tasse
General Relativity and Quantum Cosmology
Conformal symmetries and MOTS stability
Abbas M. Sherif
Let $\{\Sigma_t\}$ be a spacelike foliation of a spacetime $\mathcal{M}$, and suppose each $\Sigma_t$ is foliated by 2-surfaces $\mathcal{S}$ with spacelike unit normal in $\Sigma_t$. We show that under mild energy conditions, a MOTS $\mathcal{S}$ that intersects integral curves of past-pointing conformal Killing vector field lying in the normal space of $\mathcal{S}$ is strictly stable and evolves smoothly to a spacelike horizon. We also show that if the restriction of the divergence of the vector field to $\mathcal{S}$ is non-negative, $\mathcal{S}$ is unstable, and if negative and $\mathcal{S}$ is a 2-sphere, $\mathcal{S}$ must be strictly stable.
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High Energy Physics (Phenomenology)
Polarized Nucleon as a Topological Dipole
Kenji Fukushima and Tomoya Uji
We show that a polarized nucleon generically carries a dipole distribution of topological charge density. This topological dipole follows robustly from the definition of the topological form factor and the pseudoscalar nature of the topological charge density. The strength of the topological dipole is fixed, in the
chiral limit, by the
flavor-singlet axial charge. We demonstrate the mechanism in a two-
flavor chiral soliton model with vector
mesons and the $U(1)_A$ anomaly, where the rotation of the
soliton induces a singlet pseudoscalar profile and realizes the predicted dipole pattern. We also discuss possible experimental probes through exclusive $\eta$, $\eta^\prime$ production and directed-flow-like pseudoscalar-
meson asymmetries correlated with
magnetic fields or vorticity in relativistic heavy-ion collisions.
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Mesoscale and Nanoscale Physics
Substrate-Mediated Persistent Photodoping in WSe2/hBN Field-Effect Transistors Enabled by Defect States in SiO2
Sung-Ha Kim, Seong-Yeon Lee, Tae-Jeong Kim et al. (+6 more)
Photodoping plays an important role in determining the optoelectronic response of two-dimensional
semiconductor devices; however, the origin of the responsible trap states remains unclear. In this work, we investigate UV-induced photodoping in multilayer WSe2 field-effect transistors (FETs) based on WSe2/hBN
heterostructures on SiO2/p-Si substrates. Wavelength-dependent measurements reveal pronounced n-type photodoping under 405 nm illumination, whereas the effect is orders of magnitude weaker under 640 nm excitation and for p-type photodoping. Furthermore, when the SiO2 layer is removed, both n-type and p-type photodoping are strongly suppressed, demonstrating that the
oxide layer is essential for persistent photodoping. Analysis of defect-state distributions in amorphous SiO2, together with first-principles calculations for hBN defects, shows that the experimental observations cannot be explained by defects in hBN. Instead, the results indicate that defect states in the SiO2 substrate act as charge reservoirs that facilitate charge transfer and long-term carrier trapping. These findings highlight the dominant role of substrate-related trap states in UV-induced photodoping and photogating behavior in WSe2 FET devices.
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All authors Sung-Ha Kim, Seong-Yeon Lee, Tae-Jeong Kim, Beomkyu Shin, Young-Jun Yu, Kenji Watanabe, Takashi Taniguchi, Soungmin Bae, Ki-Ju Yee
High Energy Physics (Theory)
Exact Schwarzian Metric Factor and Holographic Wilson-Loop Screening
Miguel Tierz
We evaluate exactly the radial metric factor $h(\zeta)$ generated by Schwarzian averaging in the AdS$_2$ throat of an extremal Reissner–Nordström AdS$_5$ black brane. The result is a Gaussian integral against $\coth(\pi y)$, valid at all radial depths, which Mordell's identity turns into an exact Appell–Lerch $q/q^\ast$-series representation. The dual series identifies the nonperturbative scale $e^{-\pi^2 C/\zeta}$ missed by any finite near-boundary truncation. The third parametric derivative required by the evaluation generates the quasimodular Eisenstein series $E_2$, absent from the classical Mordell identity. From the integral representation we prove that $\mathcal{G}_0(\zeta):=h(\zeta)/\zeta^2$ is completely monotone and hence has no interior minimum, so any confining minimum produced by a finite near-boundary truncation is an artifact. We also compute the exact relative variance of the Schwarzian kernel, which makes the averaged-metric approximation error quantitative and shows that the absence of a confining minimum is robust across moment-based effective geometries. Applied to the temporal rectangular Wilson loop, the exact throat gives algebraic screening, $E(L)\sim -\kappa_{\rm IR}/L^2$, the Wilson-loop diagnostic of the semi-local
quantum-
liquid IR of the extremal RN brane. A numerical check in a simple matched geometry confirms that the screened saddle is the dominant string configuration, and an exact-versus-truncated force comparison shows that the apparent constant-force regime of the fourth-order truncation is not a feature of the exact geometry.
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Instrumentation and Methods for Astrophysics
Vector Apodizing Phase Plates for the ELT: From prototype to final optics for METIS and MICADO
J.A. van den Born, R. Landman, D.S. Doelman et al. (+12 more)
The first generation of instruments for the upcoming Extremely Large
Telescope (ELT) will allow for the direct imaging of
exoplanets that were previously below the sensitivity or resolution limits of existing facilities through various different High Contrast Imaging capabilities. Both METIS and MICADO will feature one or more Vector Apodizing Phase Plates (vAPP), a type of pupil-plane coronagraph based on
liquid crystal technology that allows for broadband phase modification to create zones of high contrast around an observed point source. The METIS vAPPs will operate at L- and M-band wavelengths between 3.1 and 5.1 $\mu$m, while the MICADO vAPP is optimized for shorter wavelengths in the J, H and Ks bands between 1.15 and 2.32 $\mu$m. In this work, we will provide a brief introduction to this type of coronagraph, followed by a discussion of the commonalities and differences between the METIS and MICADO vAPP designs. In the last year, the final optics have been in production. During preparations for the manufacturing and also during the production phase,various challenges were encountered related to coating inclusions, uniformity of the optically active layers and adhesion between the substrates. Through simulations and empirical findings, we argue that the effects of these imperfections on the on the final optical performance are limited. We will present the expected contrast curves, discuss the current status and reflect on the implications for on-sky observations with METIS and MICADO.
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All authors J.A. van den Born, R. Landman, D.S. Doelman, F. Snik, Y. Nishie, Y. Watanabe, M. Shoda, F.C.M. Bettonvil, E. Aranzana, J.H.H. Rietjens, T.P.G. Wijnen, P. Baudoz, O. Absil, G. Orban de Xivry, D. Dolkens
High Energy Physics (Theory)
Graph Neural Networks for the Graphical Bootstrap
Rigers Aliaj, Gabriele Dian, Reza Doobary et al. (+1 more)
We study a graph classification problem involving over 20 million graphs, arising from high-order perturbative computations of correlators in planar $\mathcal{N}=4$ super-Yang–Mills, a model closely related to the theory of the strong
nuclear force. We
benchmark graph neural networks, including graph
transformers, achieving robust generalization to larger graphs with up to $99.996\%$ ROC AUC. Then, we analyze how the models can be used to gain a computational speedup compared to the traditional graphical bootstrap
algorithm, through shrinking the redundant data by up to $85.5\%$ at the level of denominator graphs. Finally, we study the
embeddings of the models to investigate their interpretability.
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All authors Rigers Aliaj, Gabriele Dian, Reza Doobary, Paul Heslop
Instrumentation and Methods for Astrophysics
White Paper on Phototrophic Biosignatures: Research Priorities for the Search for Life on Other Worlds
Nancy Y. Kiang, Christopher Gisriel, Robert E. Blankenship et al. (+32 more)
Photosynthesis is of
prime interest in the telescopic search for life beyond the
Solar System, because, on Earth, oxygenic photosynthesis produces two strong "biosignatures," global scale signs of life that can be seen from space: atmospheric oxygen and the Vegetation Red Edge (VRE). The VRE is the spectral reflectance signature of plant leaves, characterized by a step-like increase in reflectance from the red to the near-infrared. The absorption in the red is due to chlorophyll $\textit{a}$ (Chl $\textit{a}$). While Chl $\textit{a}$ dominates our
planet, the Earth harbors diverse phototrophic organisms in niche environments possessing other pigments that produce edge-like spectral features across the UV-VIS-NIR, naturally suggesting diverse signatures that could be found on other
planets where phototrophic life is adapted to other
stars. However, the astrobiology community is very much at an early stage in its ability to constrain the probability that an observation of another
planet has detected a sign of photosynthetic life. This white paper identifies critical research questions to advance to a predictive capability the search for phototrophic biosignatures. These questions pertain to the origins, key features, diversity, and potential for alternative adaptations in fundamental aspects of light harvesting; the electron transfer pathway in photosynthesis; rhodopsin-based
proton-pumping; and carbon fixation. We discuss the need to constrain how
evolution and ecology affect the scaling up of these molecular mechanisms to be potentially detectable by a direct imaging mission. The research questions and recommendations presented here are cross-linked to those posed by the NASA Astrobiology Strategy 2015, and to the Focus Areas of the upcoming NASA Decadal Astrobiology Exploration Strategy (DARES).
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All authors Nancy Y. Kiang, Christopher Gisriel, Robert E. Blankenship, Mary N. Parenteau, Hazel A. Barton, Oded Béjà, Anthony J. Burnetti, Ligia F. Coelho, Saleheh Ebadirad, Nathan M. Ennist, Yuka Fujii, Colin Gates, R.J. Graham, Keiichi Inoue, Betül Kaçar, Yu Komatsu, Émilie A. Laflèche, Nicoletta La Rocca, Elisabetta Liistro, Jonathan Lindsey, Timothy Lyons, Carolina A. Martinez-Gutierrez, Taro Matsuo, Victoria Meadows, Gary F. Moore, Massimo Olivucci, Kevin E. Redding, Edward W. Schwieterman, Tejinder Singh, Kenji Takizawa, Anna Grace Ulses, Junko Yano, Felisa Wolfe-Simon, Michael L. Wong, Anastasia G. Yanchilina
Quantum Physics
ORBIT-Q: Dual-axis benchmarking of autonomous agents in scientific quantum programming
Shi-Xin Zhang and Yu-Qin Chen
Autonomous coding
agents perform well on many conventional programming tasks, but scientific computing demands a rigorous validation paradigm that extends beyond simple functional test completion: generated code must preserve physical fidelity, differentiable workflows, framework-native semantics, and scalable representations. We introduce Open Research
Benchmark for Integrated Tasks in
Quantum Computing (ORBIT-Q) to address this gap. At its core, ORBIT-Q contributes a carefully curated suite of complex, research-level
quantum workflows that serves as a challenging testbed for modern scientific programming. ORBIT-Q combines a rigorous multi-tier verification pipeline to support two orthogonal comparisons: different
agent harness and model configurations at a fixed
quantum software framework, and different
quantum software frameworks at a fixed
agent. In our systematic evaluations, TensorCircuit-NG (TC) exhibits the highest capability and performance efficiency among the evaluated
quantum software frameworks under
agent-driven programming, and Codex with GPT-5.5 is the strongest tested
agent configuration on TC. However, a significant performance and design gap remains between frontier autonomous
agents and human expert reference implementations. We further evaluate two efficiency dimensions:
agent-side resource use and artifact-side runtime. Together, these results establish ORBIT-Q as a rigorous
benchmark for autonomous scientific programming, framework-
agent synergy, and
quantum software performance.
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Strongly Correlated Electrons
Winding charge density wave: intertwining of structural chirality and phase topology of electronic order
Shun Asano and Youichi Yanase
We propose a class of
chiral charge density waves (CDWs), dubbed winding CDWs, that exhibit macroscopic chirality despite a single ordering wavevector. In screw-symmetric
chiral crystals,
chiral phonons drive a Peierls instability that selects a definite
crystal angular momentum channel, thereby endowing the CDW with an integer azimuthal phase winding dictated by the selection rule governing electron-
phonon coupling. We further extend this framework to achiral
crystals with discrete rotational
symmetry and demonstrate that spontaneous
symmetry breaking stabilizes a winding CDW with either handedness, realizing an achiral-to-
chiral phase transition. Our results reveal a fundamental link between the geometry of
chiral structures and the phase
topology of electronic orders.
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