Optics
Spectral contraction from Gaussian beams to Helmholtz waves
A. Dominguez-Cruz and B. M. Rodriguez-Lara
We introduce the ratio between the transverse Helmholtz length and the paraxial Gaussian-beam width as the physical parameter governing the contraction from separable Gaussian beams to transverse Helmholtz waves. For a fixed transverse Helmholtz shell within the paraxial angular spectrum, the large-Rayleigh-range limit drives our optical scale ratio towards zero, while the higher-modal-order limit preserves the shell, transforming the isotropic and astigmatic paraxial oscillator
eigenvalue problems into the transverse Helmholtz unit-shell
eigenvalue problem. As our optical scale ratio vanishes, it realizes the algebraic Inönü-Wigner contraction of the isotropic Gaussian-beam $\mathrm{su}(2)$
algebra to the quadratic fixed-shell realization of the transverse Helmholtz $\mathrm{e}(2)$
algebra; conversely, finite nonzero values parametrize the Cayley-Klein deformation. Under the joint limit of vanishing scale ratio and higher modal order, paraxial Hermite-, Laguerre-, Ince-, and Boyer-Wolf-Gaussian beams undergo a spectral contraction in which their two modal numbers fix the shell and determine the single separation parameter labeling the corresponding Cartesian, Bessel, Mathieu, and Weber transverse Helmholtz waves, while preserving parity. Our spectral contraction extends to the wave operators,
symmetry algebras, separation operators, separated equations, and separation spectra.
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Mesoscale and Nanoscale Physics
Strong photogalvanic effect in Weyl materials due to magnetic resonances
Vahid Hassanzade and Vladyslav Kozii
We study the photogalvanic effect in Weyl semimetals under a
magnetic field, focusing on the shift current. Using the Kubo formalism for an ideal, clean Weyl node at zero temperature, we derive a general analytic expression valid for arbitrary light frequency,
Fermi energy, and
magnetic field strength. We identify a series of resonances that can be probed experimentally. To complement the microscopic analysis, we employ the semiclassical Boltzmann approach, which allows us to incorporate finite scattering phenomenologically. Unlike most previous studies using this method, we do not treat the
magnetic field perturbatively; instead, we solve the Boltzmann equation for a Weyl node exactly within the limits of validity of the semiclassical theory. Our solution reproduces the low-frequency resonances and elucidates the role of finite scattering.
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Mesoscale and Nanoscale Physics
All-electrical dephasing-protected spin qubits in altermagnets
José Carlos Abadillo-Uriel, Andrea Maiani, Alberto Cortijo et al. (+2 more)
We propose altermagnetic
semiconductors as a platform for field-free, all-electrically controlled
spin qubits in gate-defined
quantum dots. The momentum-dependent
spin splitting of an altermagnet produces a Zeeman-like
qubit splitting whose magnitude and sign are set by the dot ellipticity, enabling local frequency tunability without external
magnetic fields or micromagnets. Because the splitting is tied to a fixed altermagnetic quantization axis, electric-field noise is longitudinally suppressed at leading order, while quantization-axis fluctuations couple transversely and therefore cause relaxation rather than pure dephasing. The compensated
magnetic order also avoids stray fields, making the platform naturally compatible with superconducting resonators and dispersive
circuit-QED readout through the
qubit's
spin-dependent electric dipole. Starting from an effective
quantum-dot model, supported by a microscopic
lattice model, we derive the single- and two-dot
Hamiltonian models. We show that electric-dipole
spin resonance enables single-
qubit control, while tunable exchange and electrically addressable
qubit frequencies realize fSim two-
qubit gates. The same double-dot architecture also supports singlet-triplet
qubits with electrical control of both exchange and splitting gradients, removing the need for micromagnets or
nuclear-polarization gradients. These results establish altermagnetic
quantum dots as a route to field-free
spin qubits with intrinsic electrical tunability and enhanced dephasing protection.
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All authors José Carlos Abadillo-Uriel, Andrea Maiani, Alberto Cortijo, Ramón Aguado, Rubén Seoane Souto
Mesoscale and Nanoscale Physics
Quantum Back-Action Expands the Excitonic Hilbert Space in a Soft Polar Semiconductor
Arnab Ghosh, Patrick Brosseau, Priya Nagpal et al. (+4 more)
Electronic excitations in solids are commonly described within a hierarchy in which the excitonic
Hamiltonian is defined first and the
lattice acts later through renormalization, relaxation, and dephasing. This picture assumes that the optically accessible excitonic
manifold is already present at the moment of photoexcitation. Here we show that this assumption fails in a soft polar
semiconductor. Using femtosecond coherent multidimensional spectroscopy on lead-halide perovskite nanocrystals, we observe
quantum back-action between an electronic excitation and a collective
lattice-polarization field that expands the excitonic
Hilbert space in real time. The optical pulse first prepares an excitonic polarization, X1. A second configuration, X2, emerges only after the polaron field develops, while coherent X1-X2 coupling appears at later times. State formation and coherence formation are therefore resolved as distinct stages of quasiparticle formation. In contrast, CdSe
quantum dots exhibit the conventional limit in which excitonic states and couplings are present at time zero and are only weakly perturbed by
phonons. The observed diagonal and anti-diagonal splittings increase with nanocrystal size and correlate with radiative oscillator strength, opposite to expectations from simple
quantum confinement. A dynamical polaron-field model describes the
lattice polarization as an order parameter that expands the optically accessible
manifold and generates time-dependent coherent coupling. These results show that strong system-bath coupling can actively create excitonic states and the coherent
manifold in which they evolve.
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All authors Arnab Ghosh, Patrick Brosseau, Priya Nagpal, Dmitry N. Dirin, Rui Tao, Maksym V. Kovalenko, Patanjali Kambhampati
Mesoscale and Nanoscale Physics
Telecom-band site-controlled quantum dots with engineered low fine-structure splitting
Christian C. Ruiz Madera, Paweł Holewa, Paweł Wyborski et al. (+3 more)
Deterministic
quantum light sources emitting at telecom wavelengths with vanishing fine-structure splitting (FSS) are essential components for scalable
quantum communication. While self-assembled Stranski-Krastanov (SK)
quantum dots (QDs) are high-quality emitters, their random positioning and shape-induced anisotropy typically limit their use in entangled-
photon applications. In this work, we demonstrate site-controlled SK growth where InAs/InP QDs nucleate at the symmetric apexes of truncated InP nanopyramids. Confining adatom
diffusion to a small, symmetric nucleation area suppresses anisotropic growth, promoting the nucleation of highly symmetric QDs with FSS reduced to values below our statistically validated resolution limit of $9.2~\mu$eV. At the same time, lithographically defined nucleation sites enable deterministic control of the QD position, overcoming the limitations of conventional SK growth. The high structural quality of single symmetric QDs is evidenced by the single-
photon character of the emission ($g^{(2)}(0)=0.07^{+0.27}_{-0.07}$) spanning the S, C, and L telecom bands, with no evidence of lithography-induced defects affecting emission dynamics. These results demonstrate that tailoring QD
symmetry through nanopyramid growth engineering provides a route toward site-controlled emitters suitable for entangled
photon generation and integrated
quantum photonics devices.
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All authors Christian C. Ruiz Madera, Paweł Holewa, Paweł Wyborski, Meng Xiong, Battulga Munkhbat, Elizaveta Semenova
High Energy Physics (Phenomenology)
Impact of parity-violating deep-inelastic scattering on the weak mixing angle and high-$x$ parton distributions
R. M. Whitehill, M. M. Dalton, T. Liu et al. (+2 more)
We discuss the impact of neutral current parity-violating deep-inelastic scattering (PVDIS) of electrons from
protons and deuterons on the determination of the weak mixing angle, $\sin^{2}{\theta_{\rm W}}$, and parton distribution functions (PDFs) at large parton momentum fractions $x$. Using the JAM global QCD analysis framework, we study the effect of incorporating pseudodata simulated for 11 GeV and 22 GeV Jefferson Lab kinematics, accounting for radiative corrections in a factorized QED+QCD approach and uncertainties from higher twist corrections in $\gamma Z$ exchange. We find that including future PVDIS pseudodata could yield important constraints on the value of $\sin^{2}{\theta_{\rm W}}$ at low $Q^2$ and on the high-$x$ behavior of the strange
quark and $d/u$ PDF ratio. The strong correlation between $\sin^{2}{\theta_{\rm W}}$ and the $x$ dependence of the PDFs demonstrates the necessity for simultaneous analysis of QCD and electroweak quantities to ensure an unbiased determination of the weak mixing angle from PVDIS data.
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All authors R. M. Whitehill, M. M. Dalton, T. Liu, W. Melnitchouk, N. Sato
Plasma Physics
Laser-intensity-spike-dominated hot electron generation from two-plasmon decay instability driven by moderate-bandwidth pulses
C. Yao, Z. H. Cai, X. Wang et al. (+34 more)
Our direct-drive-relevant experiments on the low-coherence Kunwu
laser facility identify two-plasmon decay (TPD) as the primary source of hot electrons, and demonstrate for the first time that broadband
laser pulses enhance TPD. Using particle-in-
cell simulations, we attribute this TPD enhancement and the consequent hot electron production to
stochastic intensity spikes inherent in broadband
laser fields, robust in both weakly- and strongly-driven regimes. These findings suggest that mitigating hot electron generation requires suppressing these intensity spikes.
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All authors C. Yao, Z. H. Cai, X. Wang, X. C. Wang, H. R. Yin, Z. A. Zhu, C. W. Lian, Y. Ji, X. Jiang, S. M. Xu, Y. Y. Yao, L. Y. Yang, J. N. Zhang, D. Meng, T. Peng, H. Wen, C. Z. Xiao, K. Y. Meng, J. Li, R. Yan, P. Yuan, Z. Zhang, L. Hao, Q. Jia, W. Feng, H. H. An, H. Y. Liu, Z. Y. Xie, P. P. Wang, C. Wang, A. Lei, X. H. Zhao, Z. H. Fang, W. Wang, Y. Q. Gu, Y-K. Ding, J. Zheng
Disordered Systems and Neural Networks · Cross-listed from cs.LG
Natural Ungrokking: Asymmetric Control of Which Rules Survive Pretraining
Juliana Li and Diya Sreedhar
Midway through an ordinary pretraining run, a small
language model learns the pronoun-gender rule: cued with a girl's name ("Sue cried because"), it resolves the next pronoun to she, generalizing to held-out probes (0.94 by step 925). By step 3,500 the same model scores near zero on the same probes, although the rule's evidence is still in the training data. We call this within-run reversal natural ungrokking: the corpus decides, with no trace in the loss curve, which learned rules a model keeps. Which rules survive is predictable from one corpus statistic: how often the training stream shows the rule winning. Across un-intervened runs (two corpora, three budgets, three seeds), support frequency decides a rule's fate; the data-to-parameter ratio only modulates how deeply a doomed rule falls. The same emerge-then-collapse dynamics appear in public Pythia checkpoints, collapse depth ordered by model scale as predicted. The forgetting is a displacement: a competing surface pattern out-competes the rule, and the log-probability margin between them crosses zero within 100 training steps of the behavioral collapse. Control over this fate is asymmetric: the same edit that destroys a rule on demand cannot restore it. Flipping support to counter-evidence in place kills the rule with monotone dose-response in two unrelated rules; but injecting support back, even to 450 times the level that naturally sustains it, buys no recovery. Every confirmatory threshold and prediction was pre-registered before the data it governed was read.
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Fluid Dynamics
Interfacial Spectral Memory as a State Variable for Finite-Depth Salt-Finger Exchange
Sriram P. Kalathoor
Thermohaline interfaces in the ocean are often treated through local double-diffusive favorability, yet finite interfaces can also inherit roughness from prior waves, stirring, intrusions, and earlier mixing events. Such inherited geometry can matter because salt fingering does not develop from a flat abstract surface in many geophysical settings. We use controlled three-dimensional direct simulations to test whether the spectral state of a finite rough interface changes the pathway by which salt-finger activity develops between adjacent layers. The density ratio, diffusivity ratio, Prandtl number, interface thickness, roughness amplitude, domain, resolution, and analysis window are held fixed; only the imposed roughness spectrum and, for one pair, the realization are changed. Broad low-mode
memory produces the largest cumulative salt exchange and the earliest finite-depth contact. High-annulus
memory remains localized and intermediate-scale dominated. Mixed
memory produces delayed scale transfer and scalar-rich structure that is robust in integrated exchange and broad-
memory measures across a second realization, while local plume timing and probe amplitudes remain realization-sensitive. The simulations therefore support treating interfacial spectral
memory as an additional state variable for finite-depth double-diffusive exchange, complementary to local thermodynamic descriptors.
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Astrophysics of Galaxies
Jets and Outflows in Young Stellar Objects with the SKAO
Giovanni Sabatini, Gemma Busquet, Carlos Carrasco-González et al. (+48 more)
Jets and
outflows are ubiquitous phenomena associated with the formation of young
stellar objects (YSOs). They play a crucial role in removing angular momentum from the accreting system and in regulating
star-formation efficiency. Theoretical studies and observations with ALMA and VLA have shown that jets and winds may have a crucial role in promoting
dust growth in the envelope-disc system and in shaping the physical and chemical properties of the surrounding environment. Despite these significant advances, many fundamental questions remain unanswered regarding the acceleration, collimation, and chemical impact of jets and
outflows from YSOs. The SKA-project will overcome the limitations of current mm/cm-facilities by enabling high-angular resolution and high-sensitivity cm-observations, crucial for probing jets/
outflows near YSOs.
Radio recombination lines, combined with proper motions, offer a unique opportunity to study the 3D-kinematics of jets. Non-thermal linearly polarised synchrotron emission will allow measuring
magnetic field strength and morphology at unprecedented scales of a few au. Observations of
dust emission in
outflow cavities will allow studying how
dust grows and is eventually transported from the disc to the envelope and back. Finally, the SKA-project will allow exploring the
dust composition and chemical enrichment in shocks, where sputtering/shattering of grains cause the release of their mantles and refractory cores in the gas-phase. Complementary to ALMA's detection of simple and complex organic molecules, the SKAO will probe, for the first time, long carbon chains/rings, several Cl-, Al-, Mg-, and other metal-bearing species (missed by current sub-mm facilities).
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All authors Giovanni Sabatini, Gemma Busquet, Carlos Carrasco-González, Adriana Rodríguez-Kamenetzky, Codella Claudio, Linda Podio, Antonio Martínez-Henares, Josep Miquel Girart, Marta De Simone, Luca Cacciapuoti, Guillem Anglada, Lukasz Tychoniec, Lisa Giani, Manoj Puravankara, Francesca Bacciotti, Rafael Bachiller, Eleonora Bianchi, Guillermo Blázquez-Calero, Tyler L. Bourke, Stefano Bovino, Paola Caselli, Francesco Cavallaro, Cecilia Ceccarelli, Elena Diaz-Marquez, Stefano Facchini, Antonio Garufi, Greta Guidi, Tomoya Hirota, John D. Ilee, Adriano Ingallinera, Izaskun Jiménez-Serra, Valerio Lattanzi, Chin-Fei Lee, Manuela Lippi, Alessandro Lupi, Liton Majumdar, Mayank Narang, Mayra Osorio, Marco Padovani, Jaime Pineda, Isaac Radley, Basmah Riaz, Luis Felipe Rodríguez, Alvaro Sánchez-Monge, Alberto Sanna, Silvia Spezzano, Leonardo Testi, Claudia Toci, Alessio Traficante, Himanshu Tyagi, Grazia Maria Umana
Geophysics
Paleomagnetic signatures of core-mantle interactions inferred from top-heavy thermochemical geodynamo simulations
Souvik Naskar, Jonathan E. Mound, Christopher J. Davies et al. (+3 more)
The time-averaged geomagnetic field provides crucial insights into deep Earth dynamics and thermal core-mantle interactions. Paleomagnetic observations and numerical dynamo simulations are equivocal regarding the longitudinal structure of the time-averaged field, though the latter have often considered a generic buoyancy source, which may obscure distinct signatures of thermal and chemical buoyancy that arise near the equator and poles, respectively. In this study, we present a new suite of top-heavy geodynamo simulations, varying the relative strengths of thermal and chemical driving and comparing the resultant
magnetic signatures to observational field models spanning centuries to tens of thousands of years. None of the spatially-averaged measures of field morphology and variability we tested could robustly distinguish between different levels of chemical driving or the presence of heterogeneous outer boundary heat flux. On the other hand, observational constraints requiring longitudinal variations in time-averaged inclination anomaly are readily matched by simulations with heterogeneous outer boundary thermal forcing, in contrast to those with homogeneous mantle heat flux. Longitudinal field structures are reduced, but not erased, by elevated chemical driving, which also promotes the formation and deepening of polar minima in the radial
magnetic field. Our simulations indicate that both the strong heat flux heterogeneity and chemical driving in Earth's core are likely to result in small but persistent departures from the geocentric axial dipole approximation.
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All authors Souvik Naskar, Jonathan E. Mound, Christopher J. Davies, Hannah F. Rogers, Stephen J. Mason, Andrew T. Clarke
High Energy Physics (Phenomenology)
In-medium QCD splittings beyond the soft, large-$N_c$ and harmonic-oscillator approximations all at once
Marco Leitão, José Guilherme Milhano and Alba Soto-Ontoso
Nearly thirty years ago, Baier, Dokshitzer, Mueller, Peigné, Schiff, and Zakharov (BDMPS-Z) introduced a formalism to calculate the fully differential probability for a high-energy
quark or
gluon to radiate inside a finite-volume QCD
plasma. We report on the first, complete numerical solution to the BDMPS-Z equations for in-medium QCD splittings. Our numerical routines are precise across phase-space, enabling a determination of the in-medium splitting functions that is significantly beyond the state-of-the-art, including finite-energy effects, subleading-color contributions, and a realistic model for parton-medium interactions. We quantify the uncertainties associated with standard approximations in the literature, revealing substantial deviations across phase-space. This work opens a path toward more precise calculations of jet observables and for powerful new constraints of medium parameters from high-energy heavy-ion
collider data.
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Quantum Physics
Estimating Fidelity to a Reference Quantum State
Qisheng Wang
We consider the problem of estimating the fidelity of an unknown
quantum state to a known reference state to within additive error $\varepsilon$. We show that the sample complexity is $O(r^2/\varepsilon^2)$ with optimal $\varepsilon$-dependence when the reference state is of rank $r$, improving the previous best $O(r^2\log^2(1/\varepsilon)/\varepsilon^4)$ due to Utsumi, Nakata, Wang, and Takagi (QIP 2026). We also provide a lower bound of $\Omega(r/\varepsilon^2)$, improving the previous best $\Omega(r/\varepsilon+1/\varepsilon^2)$, with implications to
quantum query complexity. Moreover, we further consider the case where the unknown state is of rank at most $r$ while the reference state can be arbitrary, for which the sample complexity is shown to be $O(r^2/\varepsilon^4)$. As an application, we present an approach to tolerant
quantum state certification, generalizing the exact certification studied in Bădescu, O'Donnell, and Wright (STOC 2019).
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Computational Physics
A one-parameter family of realizability-interior closures for odd-order kinetic moment systems
Somdeb Bandopadhyay
Moment closures at odd truncation order present a fundamental difficulty: the standard Gramian closure saturates the realizability boundary, producing only weak hyperbolicity and failing to preserve Maxwellian
equilibrium. We show that every odd-order closure for the one-dimensional kinetic equation decomposes into a boundary term, the Schur complement of the Hankel moment
matrix, and a positive margin above it. An exact
polynomial identity connects this margin to the
eigenvalues of the flux Jacobian, reducing hyperbolicity to a root-splitting problem. A dimensional argument proves that no margin depending only on density, velocity, and temperature can produce a
hyperbolic system for $M \geq 5$. A one-parameter family $C_{\eta,n}$, $\eta \in [0,1]$, built from normalized Schur-complement ratios, reveals that the Morin-McDonald closure is the arithmetic endpoint of this decomposition. The weighted AM-GM inequality makes the accuracy-robustness tradeoff precise: the
geometric endpoint ($\eta = 0$) is 2-4% more accurate on bimodal
benchmarks, while the arithmetic endpoint ($\eta = 1$, Morin-McDonald) provides the most robust hyperbolicity profile. All members share the same
equilibrium Jacobian, whose spectral radius is 13% ($M = 5$) to 29% ($M = 13$) smaller than Grad's closure, allowing larger CFL time steps. A linearized
entropy exists at every tested order, and for a source-compatible choice of the symmetrizer weights, the BGK source dissipates it near
equilibrium. A smooth nonlinear
entropy exists for $M = 3$ but does not for $M = 5$ or $M = 7$ (certified by linear programming). The closure is validated on bimodal and Mott-Smith
benchmarks, where the interpolated family achieves errors 10-40x smaller than the Gramian or Grad closures, and demonstrated in free-transport Riemann problems at $M = 5, 7, 9, 11$ and BGK Riemann problems at $M = 5$ and $9$.
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Earth and Planetary Astrophysics
Can giant impacts be directly detected in other star systems?
Pavan Tanna, Simon Lock, Amy Bonsor et al. (+2 more)
Giant impacts, collisions between
planet-sized bodies, play an important role in
planet and moon formation. As we enter a new era of large-scale surveys, such as
Gaia and LSST at the Vera C. Rubin observatory, there is potential to directly observe the remnants produced in such events and gain insights into the process of
planet formation. Here, by modelling the emission and cooling of a series of
giant impact remnants, we show that
giant impacts are detectable as a sudden brightening followed by gradual dimming in the optical and near-infrared.
Giant impacts between Earth-composition
planets were simulated using the smoothed particle hydrodynamics code {\small SWIFT}, with total colliding masses ranging from 0.2 to 4 $M_{\oplus}$. By constraining the location of the photic surface of the post-impact bodies produced by the simulations, the initial luminosities of post-impact bodies were found to be between $5\times10^{-5}$ and $10^{-1}$
solar luminosities, with luminosity falling roughly exponentially on a timescale between 1 and 2000 days. Based on our results, along with estimates for
planet and
giant impact occurrence rates, we anticipate that between 0 and 14 terrestrial
giant impacts will be observed in the full release of
Gaia epoch photometry in DR4, with at least a comparable number found by LSST. Identifying the remnants of multiple
giant impacts will offer a powerful constraint on the frequency of
giant impacts in the
galaxy and hence the role of such collisions in
planet formation.
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All authors Pavan Tanna, Simon Lock, Amy Bonsor, Simon Hodgkin, Cathie. J. Clarke
Materials Science
Epitaxial Strain Activates Altermagnetic Spin-Splitting Torques in RuO2(100)
Qi Jia, Seung Gyo Jeong, Seungjun Lee et al. (+10 more)
The altermagnetic nature of rutile RuO2 remains under active debate: bulk measurements indicate a nearly nonmagnetic ground state, whereas thin-film studies have reported
symmetry-dependent transport signatures consistent with altermagnetism. Here, we provide experimental evidence that altermagnetic
spin splitting in RuO2 is a strain-stabilized emergent state rather than an intrinsic bulk property. Angular-resolved
spin-torque measurements reveal a
symmetry-selected
spin Hall response characteristic of altermagnetic
spin splitting, which is strongest in the strained regime but progressively suppressed as the
lattice relaxes toward the bulk limit. Complementary
magnetic measurements further reveal enhanced coercivity and exchange-bias behavior exclusively in strained films, indicating the emergence of a strain-stabilized
magnetic state. First-principles calculations reproduce the strain-dependent
evolution of the Neel order and
spin-split electronic structure, supporting the experimental observations. Together, these results establish altermagnetic
spin splitting in RuO2 as a strain-stabilized emergent state and provide a unified explanation for the long-standing discrepancy between bulk and thin-film observations.
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All authors Qi Jia, Seung Gyo Jeong, Seungjun Lee, Denis Tonini, Anand Santhosh, Yifei Yang, Xiangrui Li, Brahmdutta Dixit, Shuang Liang, Yu-Chia Chen, Tony Low, Bharat Jalan, Jian-Ping Wang
Physics and Society
The Allure of Complete Discovery as Passage: Broadening the Range of SETI Research Ideas via Futures Literacy and Triple-Loop Learning
George Profitiliotis
This paper argues that, although it principally refers to extraterrestrial rather than human affairs, SETI's imaginary is a social imaginary proper, as it is implicitly linked in an intrinsic, non-trivial, co-constitutive way to a social imaginary of humanity's future. Specifically, SETI's imaginary is an imaginary of a society of sapient extraterrestrials that makes possible the achievement of a desirable future of humanity through the former's discovery by the latter. Moreover, it argues that the range of SETI research ideas, which get bundled in non-fictional conviction narratives promising SETI's imaginary, is currently limited because actualizing this desirable future state of humanity after such a discovery relies on a "complete discovery". Finally, an intervention is offered in the form of a hands-on workshop for SETI scientists, which could help them reveal, reframe, and rethink the role that this imaginary for a desirable "post-discovery" future of humanity plays in their present research ideas.
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Materials Science
Primary damage and mechanical degradation of WTaCrV refractory high-entropy alloy: effects of solid-solution and chemical ordering
Yihan Wu, Pengfei Yu, Yaohong Suo et al. (+1 more)
As advanced
nuclear reactors demand novel irradiation-tolerant materials, this study investigates the radiation damage and mechanical degradation of the promising WTaCrV refractory high-
entropy alloy (RHEA). To isolate complex nanoscale chemical effects, we propose an atomistic modeling strategy comparing Average-Atom (AA), random solid-solution (RSS), and local chemical order (LCO) configurations using newly developed interatomic potentials. Collision cascades simulations reveal that the number of Frenkel pairs follow NRSS > NLCO > NAA at the same radiation dose. While the RSS effect accelerates defect generation due to rugged energy landscapes, LCO enhances
lattice cohesion to mitigate radiation damage. Despite more primary defects in the RSS and LCO configurations compared with the AA configurations, the RSS and LCO effects can suppress radiation-induced mechanical degradation. Irradiation severely degrade the homogenized AA model but exert a limited impact on the strength and flow stress of the RSS and LCO models. This exceptional resistance is driven by inherent
lattice distortion resulting from interactions among different
alloy elements, which outweighs point defect induced
lattice disruptions. Moreover, the complex interactions between deformation twins and point defects cause confined plastic flow, elevating flow stress in the RSS and LCO models. The findings provide atomistic guidance for performance assessment of next-generation structural materials for extreme
nuclear environments.
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All authors Yihan Wu, Pengfei Yu, Yaohong Suo, Lei Zhang
High Energy Physics (Phenomenology)
New effect in neutrino spin oscillations in transversal matter currents with nonstandard interactions
Inna Kozlovskaya and Alexander Studenikin
We perform a systematic study of a new phenomenon of
neutrino spin and
spin-
flavor oscillations induced by transverse matter currents, based on the developed
quantum treatment of the phenomenon. Both standard and nonstandard interactions of
neutrinos with the external medium are taken into account. As an example, the oscillations in question are considered under the conditions of a binary
neutron star merger model.
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Strongly Correlated Electrons
Spin modulations in the Rashba-Hubbard chain – a tensor network study
Jozef Genzor, Roman Krčmár, Andrej Gendiar et al. (+2 more)
Uniform
spin-orbit coupling in an open single-band Hubbard chain is an exactly removable \(SU(2)\) gauge field at the
Hamiltonian level, but not at the level of laboratory-frame
spin correlations. We study this separation using density
matrix renormalization group calculations for the repulsive one-dimensional Rashba-Hubbard chain. For open boundary conditions, a site-dependent
spin rotation maps the model with hopping \(t\) and Rashba
spin-orbit strength \(\lambda\) onto the ordinary Hubbard chain with renormalized hopping \(t_\lambda=\sqrt{t^2+\lambda^2}\). Consequently, charge and energy diagnostics are affected only through the bandwidth renormalization, which is quadratic in weak \(\lambda/t\).
Spin correlations, however, respond already at linear order because the same transformation rotates the local
spin basis by the wave vector \(k_{\rm so}=2\arctan(\lambda/t)\). We use DMRG to verify this observable consequence across the filling diagram of finite open chains. The filling structure follows the gauge-equivalent Hubbard model, whereas the
spin structure factor shows the predicted
spin-orbit sidebands. A dominant Hubbard-chain
magnetic wave vector \(k_0\) is transformed into components at \(k_0\pm k_{\rm so}\), folded into the open-chain Brillouin zone. At half filling, where \(k_0=\pi\), the two sidebands fold onto a single, in-plane,
spin spiral wave with \(k=\pi-k_{\rm so}<\pi\). Away from half filling, the incommensurate Hubbard
spin response splits into two distinct
spin-orbit-shifted components, producing a real-space beating pattern. Our results provide a filling-resolved tensor-network
benchmark for the exactly removable limit of one-dimensional
spin-orbit coupling, and establish a controlled reference point for ladders, multiorbital chains, rings, proximitized wires, and higher-dimensional Hubbard systems where
spin-orbit coupling can no longer be gauged away.
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All authors Jozef Genzor, Roman Krčmár, Andrej Gendiar, Chia-Min Chung, Denis Kochan
Fluid Dynamics
A Gaussian-based spatially weighted loss formulation for Physics-Informed Neural Networks with Shocks
Kheir-eddine Otmani, Abdelhalim Azzouz, Nourelhouda Groun et al. (+1 more)
Physics-informed neural networks (PINNs) often struggle to resolve shocks because smooth neural representations and globally averaged residual losses tend to underemphasize localized high-gradient regions. We introduce a residual-tracked Gaussian weighting strategy that represents the spatial distribution of the PDE-residual loss through a small number of learnable parameters, without resampling the collocation points or prescribing the shock location. The Gaussian center and width are updated from the evolving PDE residual, allowing the weighting field to follow stationary and moving shocks during training without prior knowledge of their positions or trajectories. The method is assessed using one-dimensional low-viscosity Burgers problems and a two-dimensional Euler Riemann problem with four interacting shocks. For $\nu=5\times10^{-4}$, the relative $L_2$ error decreases from approximately $45\%$ to $13\%$ for the stationary shock and from $33\%$ to $14\%$ for the moving shock, compared with a standard PINN. In the two-dimensional problem, the maximum absolute density error decreases from $1.08$ to $0.62$. These results show that a compact, dynamically localized residual weighting can substantially improve PINN resolution of shock-dominated solutions while retaining the original collocation set and avoiding prescribed shock trajectories.
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All authors Kheir-eddine Otmani, Abdelhalim Azzouz, Nourelhouda Groun, Esteban Ferrer
Cosmology and Nongalactic Astrophysics
Cosmology from Synergies Between SKAO Surveys and Gravitational Wave Observations
Tessa Baker, Alberto Colombo, Steven Cunnington et al. (+11 more)
Both
radio surveys and gravitational wave observations have the potential to probe unprecedented volumes in the Universe with systematics independent of existing cosmological probes. This gives them the potential, especially in combination, to solve some of the outstanding issues in cosmology. Here we show how the use of
radio observations as electromagnetic signals tracing large scale structures can be used to provide information on gravitational wave standard sirens. By providing a way to link luminosity distance to
redshift, this combination can constrain the expansion history of the Universe, and provide information on the Hubble constant ($H_0$). We describe the utility of SKA-Mid neutral hydrogen (\hi) intensity maps, \hi\
galaxy redshift surveys, and continuum
galaxy surveys compared to and in conjunction with large contemporaneous optical surveys. Such
radio tracers provide a unique, large volume and high
redshift information for gravitational wave source, capable of probing effectively the expansion history of the Universe $H(z)$.
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All authors Tessa Baker, Alberto Colombo, Steven Cunnington, Ulyana Dupletsa, José Fonseca, Ian Harrison, Konstantin Leyde, Simone Mastrogiovanni, Riccardo Murgia, Dounia Nanadoumgar-Lacroze, Tommaso Ronconi, Giulio Scelfo, Matteo Schulz, Marta Spinelli
Cosmology and Nongalactic Astrophysics
The Cosmic Ray Life Cycle in Galaxy Clusters
Francesco de Gasperin, Marcus Brüggen, Henrik Edler et al. (+3 more)
Within the
cosmic web, gravitational energy, linked to the formation and growth of the Universe's largest structures and the activity of active
galactic nuclei (AGN), is converted to heat through processes such as
turbulence and shock waves. These processes have a fundamental impact on the
evolution of
galaxy clusters. For example, they lead to the amplification of
magnetic fields and the production of
cosmic ray (CR) electrons that emit continuum
radio waves via synchrotron emission. This produces sources on scales of the entire hosting clusters. These large
radio sources in
galaxy clusters are often classified based on their morphological appearance as
radio halos, cluster
radio shocks (
radio relics), and other types. To understand the CR acceleration processes in
galaxy clusters (and beyond), and to gain a comprehensive view of these sources, including their long-term interactions, SKA
telescope should conduct both deep observations of a carefully selected sample of nearby clusters as well as shallower wide-area surveys. Thanks to their capabilities - in particular the sensitivity to polarised and low-frequency emission - SKA-Mid (Bands 1 and 2) and SKA-Low are ideally suited to probing
magnetic field structures in
galaxy clusters, as well as the large reservoir of low-energy CRs that may be accelerated by yet-unexplored microphysical mechanisms. The high sensitivity to low-frequency emission will also be fundamental to detect the long term actions and interactions of these phenomena over gigayear timescales.
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All authors Francesco de Gasperin, Marcus Brüggen, Henrik Edler, Reinout J. van Weeren, Tiziana Venturi, Gianfranco Brunetti
High Energy Physics (Theory)
Non-invertible symmetries in the axiverse, and the imaginary wormholes
Daniele Licciardello and Luca Martucci
We study the
symmetry structure of four-dimensional axiverse effective field theories with multiple
axions coupled to abelian gauge sectors, including their extensions to broad classes of N=1 models. We identify the invertible and non-invertible generalized
symmetries, and discuss the associated
symmetry-breaking mechanisms together with the resulting hierarchies of energy scales. In particular, we discuss the
quantum-gravitational breaking of non-invertible
axion shift
symmetries predicted by the existence of wormholes and the recently proposed Imaginary Distance Bound. In N=1 axiverses, these wormhole-based arguments imply that towers of BPS EFT instantons play a distinguished role and generate infinitely many superpotential terms.
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Cosmology and Nongalactic Astrophysics
Cosmology with Tully-Fisher HI Galaxy Surveys
Joël Mayor, Anthony Carr, Khaled Said et al. (+7 more)
The SKA Observatory will enable measurements of the Tully-Fisher relation for statistical samples of HI selected
galaxies out to unprecedented depths and
redshifts thanks to its unique combined spatial and spectral sensitivity. This chapter explores the transformative potential of such surveys for cosmology, in particular in the field of peculiar velocity measurements. We briefly review the present observational landscape for Tully-Fisher HI
galaxy surveys and existing peculiar velocity
datasets, and compare them with predictions for SKAO Tully-Fisher HI
galaxy surveys with AA* and AA4 configurations of the SKA-Mid array. We discuss the extended range of cosmology science cases covered and enabled by such surveys.
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All authors Joël Mayor, Anthony Carr, Khaled Said, Gabriella De Lucia, Anastasia Ponomareva, Philip Bull, Stefano Camera, Ainulnabilah Nasirudin, Marta Spinelli, Robert Yates
Mesoscale and Nanoscale Physics
Strong coupling regimes of an organic exciton mirror in a microcavity
Christoph Bennenhei, Lukas Lackner, Moritz Gittinger et al. (+7 more)
The coherent, periodic energy transfer between light- and matter excitations characterizes the strong coupling regime of cavity
exciton-polaritons, resulting, in the simplest case, in a Rabi-doublet in the spectral domain. We demonstrate a peculiar regime of strong light-matter coupling, which arises when photonic cavity modes couple to an ultra-thin excitonic mirror. We embed a 12 nm J-aggregated thin film in an open microcavity and tune the coupling strength from weak to the onset of ultrastrong coupling. At resonance, the excitonic mirror selectively changes dielectric to metallic field boundary conditions adding a 2{\pi} phase, which links optical cavity modes of different order. Our work gives an exciting perspective to ultra-fast cavity switches and photonic devices based on excitonic optical elements.
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All authors Christoph Bennenhei, Lukas Lackner, Moritz Gittinger, Falk Eilenberger, Marvin F. Schumacher, Arne Lützen, Ivan Shelykh, Christoph Lienau, Martin Esmann, Christian Schneider
Mesoscale and Nanoscale Physics
Residual orbital magnetization governs the anomalous Hall effect in altermagnets
Yufei Zhao, Yiyang Jiang, Kamal Das et al. (+2 more)
In altermagnets that exhibit anomalous
Hall effect, the small remanent magnetization exists but has been treated as too small to be relevant to the
Hall response. In this work, we point out that this dismissal is incomplete because the generalized Středa relation ties the intrinsic anomalous
Hall conductivity ($\sigma_{xy}$) to the orbital magnetization ($M_z$, the topological component from the modern orbital magnetization) by $\sigma_{xy}=-e\frac{\partial M_z}{\partial \mu}$. We reveal a microscopic mechanism to generate net orbital moment from the interplay of local
crystal field and
spin-orbit coupling for MnTe-type altermagnets, in which the
magnetic anisotropy generates weak net magnetization without invoking exchange between neighboring
spins (e.g., Dzyaloshinskii-Moriya interaction). Our work indicates that residual orbital and
spin magnetization is an intrinsic thermodynamic property that governs anomalous transport in unconventional antiferromagnets, including altermagnets and noncollinear antiferromagnets.
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All authors Yufei Zhao, Yiyang Jiang, Kamal Das, Chao-Xing Liu, Binghai Yan
Astrophysics of Galaxies
The evolution of the galaxy gas-phase mass-metallicity relation from $z=15$ to $z=0$ in the COLIBRE cosmological simulations
Piyush Sharda, Joop Schaye, Robert J. McGibbon et al. (+8 more)
We present the
evolution of the
galaxy gas-phase mass-
metallicity relation (MZR) from $z=15$ to $z=0$ in the COLIBRE cosmological hydrodynamical simulations. Amongst other novel features, COLIBRE follows the multiphase interstellar medium with gas allowed to cool to $\sim 10\,\mathrm{K}$, and includes a new chemistry model in which hydrogen and helium are tracked in non-
equilibrium, metals are allowed to mix and diffuse, and the chemical network is coupled to a self-consistent live
dust model. Using fiducial COLIBRE runs spanning particle masses from $10^5\,\mathrm{M_{\odot}}$ to $10^7\,\mathrm{M_{\odot}}$ and box sizes $25 - 400\,\mathrm{cMpc}$, we derive the median, mass-weighted MZRs for
star-forming
galaxies and compare them with a comprehensive compilation of observational data and other simulations. COLIBRE reproduces the observed MZR across
cosmic time, notwithstanding the systematic uncertainties in observational measurements of the gas-phase oxygen abundances. The simulations show excellent numerical convergence and uniquely probe the full
stellar mass range sampled by current observations across all
redshifts. We find that the MZR is already in place at
cosmic dawn ($z \approx 10$), and shows no
evolution until $z \approx 5$. The slope of the MZR becomes shallower at low
redshifts. The turnover at the high-mass end is largely governed by feedback from active
galactic nuclei (AGN), whereas the low-mass end of the MZR sensitively depends on the strength of feedback from core collapse
supernovae. Variations in the
star formation efficiency or depletion of oxygen on
dust grains have a more minor impact on the MZR. We identify key physical processes that shape the MZR across
cosmic time and highlight where future observations can further constrain
galaxy formation models.
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All authors Piyush Sharda, Joop Schaye, Robert J. McGibbon, Alejandro Benítez-Llambay, Evgenii Chaikin, Carlos S. Frenk, Jacqueline Hodge, Filip Huško, Sylvia Ploeckinger, Alexander J. Richings, Matthieu Schaller
Mathematical Physics
Homogeneity, Isotropy, and Determinism Force a Quadratic Spacetime Interval: A Derivation of Relativity Without Light
Deon Nicholas
We show that a few physical principles – smoothness, homogeneity, isotropy, and the determinism of inertial motion – force the invariant interval governing the geometry of spacetime to reduce to a quadratic form, without presupposing the existence of light or electromagnetic phenomena. Formalizing these as axioms about an "invariant interval" function $D:\mathbb{R}^n\to\mathbb{R}$ ($n\geq 3$), we find that smoothness and homogeneity force $D$ to be homogeneous of degree $p > 0$; determinism – that an inertial worldline be uniquely fixed by its initial point and direction – makes its geodesics straight lines; and isotropy – that the isometry group act transitively on each level set, with the stabilizer of a reference direction reversing every transverse direction – forces $D(v) = C\,(v^T S v)^{p/2}$ for a nondegenerate symmetric
matrix $S$ and $p > 0$, with $p = 2$ (so that $D$ is exactly quadratic) when $S$ is indefinite. Thus the only admissible invariant intervals are powers of nondegenerate quadratic forms. The signature of $S$ is otherwise free: the definite case is Euclidean geometry and the indefinite case includes both Minkowski and ultrahyperbolic geometries, the two cases distinguished by the absence or presence of a null cone.
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Fluid Dynamics
Poisoning effect of ammonia on the performance and transport process of proton exchange membrane fuel cells
Yaxian Han, Wei Gao, Yichao Huang et al. (+2 more)
Ammonia is a high-density hydrogen energy carrier and can be decomposed to produce hydrogen for use in fuel
cells. However, a significant challenge in ammonia-decomposition-based fuel
cell applications is the unavoidable presence of trace ammonia
impurity, which can poison the fuel
cell, but the poisoning mechanism remains unclear. To address this, a three-dimensional numerical model of
proton exchange membrane (PEM) fuel
cells with ammonia
impurities is established to explore the transport process and underlying poisoning mechanism. The influences of key factors, including ammonia concentration, operating temperature, operating humidity, and membrane thickness, are studied. The poisoning mechanism is analyzed from the perspectives of the distributions of
proton conductivity, current density, and dissolved water content. The results show that ammonia diminishes the
cell performance by substantially reducing the
proton conductivity of both the PEM and the anode catalyst layer. Higher operating temperatures and higher operating humidity can alleviate ammonia poisoning. Decreasing the membrane thickness can also help to mitigate ammonia poisoning, but may lead to less uniform current distribution.
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All authors Yaxian Han, Wei Gao, Yichao Huang, Tianyou Wang, Zhizhao Che