Papers

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Physics

Monday 15 June

Plasma Physics

Quasiparticles and ion cooling by an electron beam in a strong magnetic field

D.M.Popov and A.I.Milstein

The frictional force arising from the interaction of ions with a magnetized electron beam in a strong magnetic field is investigated. The problem is reduced to the interaction of quasiparticles, or Larmor circles, with ions. A Hamiltonian describing this interaction is derived. The role of various impact parameters in the process of ion cooling is elucidated. The cases of both positively and negatively charged ions are considered.

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General Relativity and Quantum Cosmology

Quasinormal Modes and Hawking Radiation of Black Holes with Primary Scalar Hair

Roman Konoplya, Oleksandr Stashko and Zdeněk Stuchlík

Recently, a new family of asymptotically flat black-hole solutions endowed with primary scalar hair has been discovered in beyond-Horndeski gravity. We study in detail the quasinormal modes spectra, graybody factors, and Hawking radiation of this class of black holes. We demonstrate that presence of primary scalar hair leaves characteristic imprints on the ringdown properties, shifts the quasinormal frequencies, inducing overtone rearrangements, and rise of echoes. While the fundamental modes associated with the light-ring are affected moderately, higher overtones are highly sensitive to the small near-horizon deformation produced by scalar field. In certain parameter regimes, the graybody factors exhibit resonant-tunnelling behavior, which leads to an oscillatory frequency dependence of the Hawking emission rate. Thus, both black-hole spectroscopy and Hawking radiation may provide complementary and distinctive probes of the beyond-Horndeski gravity. Additionally, we demonstrate that the corresponding naked singularites are quantum mechanically singular and do not admit a well-defined dynamics.

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Optics

Spatiotemporal Tracking of Optical Speckles in Turbulent Atmospheric Propagation

Travis M. Crumpton and Luat T. Vuong

The speckle fields produced by optical beam propagation through atmospheric turbulence are typically described using ensemble-averaged intensity and coherence statistics, which obscure the speckle-level dynamics. Here, we investigate the spatiotemporal evolution of speckles generated during Gaussian beam propagation through turbulence by explicitly tracking them as discrete resolvable substructures. We quantify object-level persistence, transverse extent, and trajectories as functions of propagation distance, turbulence strength, and source-plane beam width. Under fixed detection criteria, we observe that a subset of these speckles exhibits measurable width statistics and persistence distributions whose form depends on turbulence strength and source-plane beam size. This object-level framework remains well-defined within the regime of strong turbulence and provides a complementary approach to characterizing turbulent propagation beyond conventional ensemble-averaged metrics.

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Materials Science

Optically Active Fractional Wannier-Center Displacement Drives Giant Second-Harmonic Generation

Hongsheng Pang and Lixin He

Electric polarization is a static ground-state Berry-phase property, whereas second-harmonic generation (SHG) and shift current are dynamical optical responses. Their connection is encoded in the shift vector, whose Brillouin-zone average is governed by the band-resolved Berry-phase polarization difference between the optically connected initial and final states. Here we exploit this geometric relation in quantized formal polarization (QFP) crystals, where symmetry-quantized formal-polarization branches correspond to fractional Wannier-center sectors. First-principles screening identifies noncentrosymmetric QFP materials with giant SHG responses, including $\mathrm{InNbBr}_6$ and $\mathrm{InPS}_3$. Band-resolved Berry-phase analysis shows that their dominant optical transitions connect occupied and low-lying unoccupied states whose Wannier centers lie at distinct fractional Wyckoff positions, producing a large transition-resolved Wannier-center displacement. This displacement gives rise to a large shift vector and a dominant shift-vector-related intraband contribution to the static SHG susceptibility. Our results show that symmetry-quantized formal polarization can become optically active through transitions between fractional Wannier-center sectors, providing a symmetry-guided route to giant SHG and shift-current responses.

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Space Physics

Direct Observations of Magnetic Reconnection in the Solar Wind Current Sheets near Mars

Chi Zhang, Chuanfei Dong, Xinmin Li et al. (+10 more)

Magnetic reconnection is a fundamental and ubiquitous process in astrophysical plasmas that converts magnetic energy into plasma kinetic and thermal energy. Throughout the heliosphere, the solar wind is permeated with current sheets (CSs), providing a natural laboratory for investigating this process. Using measurements from NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, we report the first direct observations of magnetic reconnection occurring within the solar wind CSs near Mars. Specifically, MAVEN observed the classic Petschek-type reconnection exhaust regions, evidenced by bifurcated magnetic field signatures and Alfvenic ion outflows. Notably, the observed exhaust region appears to be large-scale, significantly exceeding the typical thickness of solar wind CSs near Mars. This suggests that magnetic reconnection may significantly broaden the CS. Our results underscore the ubiquity of magnetic reconnection across heliocentric distances and may provide new insights into the large-scale evolution of the solar wind and the development of turbulence within it.

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All authors Chi Zhang, Chuanfei Dong, Xinmin Li, Han-Wen Shen, Jasper Halekas, Tai Phan, Christian Mazelle, Yuki Harada, Hongyang Zhou, Jiawei Gao, Liang Wang, Shannon Curry, David L. Mitchell

High Energy Physics (Phenomenology)

LIGO, LISA and Ultralight Axion-like Dark Matter

Lawrence M. Krauss

Interferometric searches for axion-like dark matter (ALP DM) via the induced photon birefringence in a coherent background have been proposed and analyzed by several authors over the past decade, with tabletop experiments (LIDA, ADBC, DANCE) reporting first results and detailed calculations available for both ground-based (LIGO, GEO600 via DarkGEO) and space-based (LISA, TianQin, Taiji, BBO via Gué et al. and Yao et al.) gravitational-wave detectors. We revisit this class of measurements within the framework of Krauss (2019), and provide a detailed treatment of the interplay between the DM coherence length $\lambda_{\rm coh}$, the interferometer arm length $L$, and the detector transfer function, with attention to the distinct suppression regimes $\lambda_{\rm coh} > L$ (cancellation) and $\lambda_{\rm coh} < L$ (random walk). For LIGO the sensitivity is set by the Fabry-Pérot arm cavity response peaking sharply near the cavity free spectral range, reproducing the results of Nagano et al.; the naive single-pass estimate substantially overstates the reach and cannot be applied directly. For LISA, with the polarization-sensitive modification proposed by Gué et al. or Yao et al., the natural mass range $m_a \sim 4\times10^{-19}$–$4\times10^{-16}$ eV (LISA science band) is accessible and the projected reach $g_{a\gamma\gamma}\lesssim {\rm few}\times 10^{-13}$ GeV$^{-1}$ (realistic optical-metrology noise) improves on the CAST bound over most of the band by up to about two orders of magnitude. We discuss directional signatures from the Galactic DM wind, both annual and sidereal, as a discrimination tool for candidate signals. Local DM substructure with anisotropic velocity dispersion can shift and enhance the reach in specific mass windows.

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Optics

Optimization of photonic waveguide bends for low index contrast material platforms

Ritu Jangra, Kushagra Agarwal, Posa Harsha Vardhan et al. (+2 more)

Compact and low loss waveguide bends are vital for enhancing the integration density of on chip photonic devices. The bend loss becomes extremely critical, particularly for compact bends in low index contrast platforms such as Indium Phosphide. To address this issue, we introduce an elliptical width modulated bend, which exhibits low loss. For example, at 6 micrometers radius bend loss for elliptical width modulated bend is 0.22 decibels per 90 degrees, resulting in about 40 percent and 27 per cent reduction compared to conventional circular bends and circular width modulated bends, respectively with only a 15 per cent increase in footprint providing a better loss area trade off. Additionally, conventional effective index based analytical models do not account for the impact of width modulation. In this work, we develop an enhanced analytical bend loss formulation that incorporates these effects and validates its accuracy through close agreement with full three dimensional Finite Difference Time Domain simulations.

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All authors Ritu Jangra, Kushagra Agarwal, Posa Harsha Vardhan, Nandana P K, Naresh Kumar Emani

Optics

Mid-infrared snapshot spectral imaging via nonlinear radial dispersion

Jianan Fang, Kun Huang, Ruiyang Qin et al. (+2 more)

Mid-infrared (MIR) spectral imaging provides chemically specific contrast through molecular vibrational fingerprints, yet snapshot acquisition remains severely limited by the lack of high-sensitivity detectors and efficient spectral encoding mechanisms. Here we introduce snapshot MIR spectral imaging based on intrinsic nonlinear radial dispersion, in which wavelength-dependent phase matching simultaneously enables frequency upconversion and spectral multiplexing. Different spectral components are mapped to distinct output angles within a 4$f$ imaging architecture, enabling single-shot spectral encoding without external dispersive elements. In combination with speckle illumination encoding, spectral information is compressed and recovered without additional coding components. Leveraging nonlinear upconversion to the visible, the approach achieves room-temperature MIR spectral imaging with sensitivity approaching 1 photon/pixel/pulse across a broad spectral range from 2.5 to 4.0 $\mu$m. This work transforms spectral encoding from an external optical function into an inherent property of the nonlinear imaging process, providing a general route to high-sensitivity snapshot MIR spectral imaging.

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All authors Jianan Fang, Kun Huang, Ruiyang Qin, Jixi Zhang, Heping Zeng

Optics

Integrated Terahertz Photonic Receiving Frontend with Link Noise Outperforming Electronics

Yuansong Zeng, Zixi Wang, Liga Bai et al. (+13 more)

Terahertz technology is a key enabler for sixth-generation (6G) wireless networks, yet its application is constrained by increasingly severe free-space loss at high frequencies. To efficiently retrieve weak signals at the receiving end, a compact frontend that features both a high-gain antenna and a low-noise signal-detection chain is critical. Current transistor-based THz electronic frontends face significant challenges in meeting these demands because both on-chip antenna efficiency and transistor noise performance degrade rapidly when approaching their cut-off frequencies. Photonic technology provides an alternative solution to circumvent the transistor bandwidth limit, yet most microwave photonic links to date exhibit noise performance substantially worse than state-of-the-art electronics. Here, we demonstrate low-noise integrated THz photonic frontends that deliver undegraded link noise performance across three major THz windows from 140 to 450 GHz, and outperform electronic frontends in the upper two windows. We achieve this through co-design of high-gain on-chip THz antenna array and broadband THz-optic modulator on a single thin-film lithium niobate (TFLN) chip, leading to distributed reception of free-space THz signals and continuous coherent build-up of the THz-optic conversion process with unprecedented efficiency. Combined with an efficient heterodyne detection chain, our integrated frontends exhibit effective isotropic noise figures of 13.6 and 16.2 dB at 250 and 450 GHz, respectively, both setting new benchmarks in their respective bands. We further demonstrate 6G-oriented multi-link communication up to 20 Git/s. Our integrated frontends represent a significant step towards compact, cost-effective and energy-efficient THz wireless systems in 6G and beyond.

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All authors Yuansong Zeng, Zixi Wang, Liga Bai, Yuansheng Tao, Yiwen Zhang, Yifan Wu, Zhe Ding, Xiangzhi Xie, Zhaoxi Chen, Lu Zhang, Shi-Wei Qu, Jun Hu, Hanke Feng, Chi Hou Chan, Xianbin Yu, Cheng Wang

Quantum Physics

Enhancing Quantum Machine Learning with Anyons

Da Zhang, Wen-Qiang Liu, Zhaohui Wei et al. (+1 more)

The power of quantum computing and quantum machine learning relies on harnessing uniquely quantum phenomena as computational resources. While superposition, coherence and entanglement have been central to this effort, the role of particle exchange statistics remains largely unexplored. Here, we introduce a quantum kernel framework that unifies bosonic, fermionic, and anyonic (fractional) exchange statistics within a single learning paradigm. We study this family of kernels from three perspectives. At the representation level, Haar-averaged effective-dimension analysis shows that fractional exchange phases access feature-space directions inaccessible to the purely symmetric or antisymmetric limits. At the level of kernel geometry, the corresponding Gram matrices show greater separation from the distinguishable-particle baseline and reduced label-dependent model complexity. Finally, on learning benchmarks, anyonic kernels consistently outperform their bosonic and fermionic counterparts, with stronger target alignment and more favorable class geometry. Together, these findings show that exchange statistics reshape the structure and geometry of quantum feature space, leading to enhanced learning performance. Our work identifies particle exchange statistics as an overlooked computational ingredient for quantum machine learning and provides the first systematic comparison of quantum learning models across exchange phases.

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All authors Da Zhang, Wen-Qiang Liu, Zhaohui Wei, Zhang-Qi Yin

Solar and Stellar Astrophysics

Vector Magnetic Field associated with an Active Region Filament Observed by SUNRISE III/SCIP in the Ca II 8542 Å Line

Takuma Matsumoto, Yukio Katsukawa, Masahito Kubo et al. (+38 more)

We report high-spatial-resolution spectropolarimetric observations spatially associated with a solar filament, obtained with the SUNRISE Chromospheric Infrared spectro-Polarimeter (SCIP) onboard the SUNRISE III balloon-borne solar observatory on 15 July 2024. The observed filament was located near the solar disk center, adjacent to an active region, and remained quiescent for at least two hours during the observing period. SCIP recorded full Stokes profiles in the Ca II 8542 Å line, revealing clear signatures of linear polarization produced by the transverse Zeeman effect. The detected linear polarization signals within the filament region exceeded the 2$\sigma$ noise level and exhibited a characteristic Zeeman double-lobe spectral shape that distinguishes them from polarization due to scattering. The magnetic field strength derived using the weak field approximation is approximately -80 G along the line of sight and 300-500 G in the transverse direction. These values likely reflect the magnetic properties of the filament and its supporting chromospheric environment. The orientation of the magnetic field vector is nearly parallel to the filament axis in its northeastern portion, while the southeastern part of the filament extends outside the field of view. To our knowledge, this is the first unambiguous detection of linear polarization associated with a solar filament with the Ca II 8542 Å line. Our results open a new diagnostic window on the vector magnetic structure of solar filaments in the lower chromosphere, complementing existing He I based diagnostics that probe the upper chromosphere.

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All authors Takuma Matsumoto, Yukio Katsukawa, Masahito Kubo, Yusuke Kawabata, Takayoshi Oba, Ryohtaroh T. Ishikawa, Yoshihiro Naito, Hirohisa Hara, Toshifumi Shimizu, Fumihiro Uraguchi, Toshihiro Tsuduki, Kazuya Shinoda, Tomonori Tamura, Yoshinori Suematsu, Carlos Quintero Noda, Sami K. Solanki, Andreas Lagg, Achim Gandorfer, Jose Carlos Del Toro Iniesta, Pietro Bernasconi, Thomas Berkefeld, Alex Feller, Tino L. Riethmüller, Alberto Álvarez-Herrero, H. N. Smitha, David Orozco Suárez, Bianca Grauf, Michael Carpenter, Alexander Bell, Valentín Martínez Pillet, Francisco Javier Bailén, Julian Blanco Rodríguez, Juan Sebastián Castellanos Durán, Edvarda Harnes, Johannes Hölken, Francisco A. Iglesias, Azaymi L. Siu Tapia, Hanna Strecker, Dušan Vukadinović, Pablo Santamarina Guerrero, Nour E. Raouafi

Mathematical Physics · Cross-listed from math.PR

Eyring-Kramers asymptotics for infinite-dimensional stochastic gradient systems

Morris Brooks and Giacomo Di Gesù

We study small-noise asymptotics for a class of reversible stochastic evolution equations in infinite dimensions. The dynamics are of the form \[ dX_t=-A\nabla F(X_t)\,dt+\sqrt{2\beta^{-1}A}\,dW_t, \] where $F$ is a regular multi-well potential, $A$ is a selfadjoint mobility operator, $W$ is a cylindrical Brownian motion and $\beta\gg 1$ is the inverse noise strength. The invariant measure is a Gibbs perturbation of a Gaussian reference measure, and the resulting framework covers, in particular, the stochastic Allen-Cahn and stochastic Cahn-Hilliard equations on bounded intervals. In the double-well case, we derive a sharp asymptotic formula for the first nonzero eigenvalue of the generator. This gives an infinite-dimensional Eyring-Kramers law for the spectral gap, with exponential rate determined by the communication height and leading prefactor determined by the local quadratic behavior at the relevant minima and saddle points. Our approach provides a general strategy for lifting finite-dimensional Eyring-Kramers analysis to infinite-dimensional stochastic gradient systems.

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Astrophysics of Galaxies

The Dynamics of Old Inner Galaxy Stars in Milky Way-mass Galaxies Using FIRE-2 Simulations

Emma Tasso, Madeline Lucey, Robyn Sanderson et al. (+2 more)

Understanding how galaxies like the Milky Way assembled over cosmic time remains a central question in astrophysics. Understanding the processes that shaped their formation and evolution is greatly enhanced by the joint use of observational data and high-resolution cosmological simulations. Old stars in the inner regions of galaxies serve as powerful tracers of early dynamical events, having formed during the initial stages of galaxy assembly and retaining the kinematic imprints of those formative periods. We investigate the kinematic properties of old (age $>10$ Gyr) inner galaxy ($r_\mathrm{GC}<5$ kpc) stars in thirteen Milky Way-mass galaxies from the FIRE-2 cosmological zoom-in simulations, focusing on their origin, orbital structure, and kinematic alignment with the disk. Our analysis reveals that old stars in the inner galaxy are more likely to have been formed in their host galaxy, although accretion is seen most prominently during the earliest stages of galaxy formation. Many of these accreted stars tend to occupy kinematically hot orbits compared to their counterparts formed in the host galaxy, although some stars formed in-galaxy also retain kinematically hot orbits. Disk-like dynamics are present throughout all age bins, and are most prominent as age decreases. Although some old stellar populations retain disk-like structure, the prominence of this rotational component varies significantly across galaxies and between star populations. These results emphasize the diversity of early galaxy assembly histories and suggest that coherent angular momentum in accreted material can leave detectable kinematic signatures in present-day stellar halos.

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All authors Emma Tasso, Madeline Lucey, Robyn Sanderson, Aritra Kundu, Lina Necib

Sunday 14 June

Chemical Physics · Cross-listed from cs.LG

Equivariant Cellular Sheaves for Molecular Electronic Structure: Bridging Sheaf Cohomology and E(3)-Equivariant Hamiltonian Learning

Krishna Harish

Equivariant message-passing networks are the standard model for molecular property and interatomic-potential prediction, and recent work predicts the electronic Hamiltonian itself in an E(3)-equivariant way. Separately, topological deep learning has extended graph networks to cellular sheaves. Our central observation is structural: in a localized atomic-orbital basis, the molecular single-particle Hamiltonian, after a constant shift that makes it positive semidefinite, is the Laplacian of a cellular sheaf on a regular cell complex built from the molecule. Making the restriction maps O(3)-steerable two-center kernels from bond geometry recovers the Slater-Koster form as a special case and yields an E(3)- and permutation-equivariant operator. Three consequences follow. First, the zeroth sheaf cohomology H^0 = ker L is a topological invariant equal to the non-bonding (zero-mode) orbitals, recovering the classical alternant non-bonding-orbital count as a lower bound. Second, the Hodge 1-Laplacian lets higher cells (rings) carry cycle and delocalization information through H^1. Third, the model strictly generalizes E(3)-equivariant message-passing networks and CW networks, and inherits the anti-oversmoothing of non-trivial sheaf diffusion. We prove equivariance, expressivity, and cohomological-correspondence results for the Equivariant Cellular Sheaf Networks, and validate them numerically: the Hamiltonian-to-sheaf embedding is exact to machine precision, the cohomology dimension reproduces non-bonding-orbital counts across eleven conjugated molecules, the sheaf Laplacian is O(3)-equivariant to machine precision, and the equivariant model attains lower error and rotation generalization on a directional electronic target. Our contribution is this sheaf-theoretic formalization and its invariants, not equivariant Hamiltonian prediction itself.

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Atmospheric and Oceanic Physics

Aircast-Mars: A Mars Foundation Model for Global Weather Forecasting with HEALPix-Aware Convolutions

Manmeet Singh, Saptarishi Dhanuka, Naveen Sudharsan et al. (+3 more)

Foundation models for planetary atmospheres promise fast, lightweight surrogates of expensive general circulation models (GCMs) for mission planning and scientific inquiry. Here we present Aircast-Mars, a deep-learning weather prediction system for Mars trained on the Ensemble Mars Atmosphere Reanalysis System (EMARS) v1.0. We regrid temperature, zonal wind, and meridional wind fields across 28 vertical levels onto a hierarchical equal-area isolatitude pixelization (HEALPix) mesh at Nside = 64 (~110 km resolution) and train a HEALPix-aware 2D U-Net inspired by the DLESyM architecture to predict the next hourly atmospheric state. The model employs custom inter-face padding that respects the topology of the 12-face HEALPix sphere and modern ConvNeXt residual blocks with capped Gaussian Error Linear Unit (GELU) activations. While containing 4.3 million trainable parameters, a compact size compared to terrestrial weather foundation models, the network achieves a best validation Mean Squared Error (MSE) of 1.58e-5 in normalized units. Recursive autoregressive rollouts remain stable and physically coherent for 25 hours (one Martian sol), with Root Mean Square Error (RMSE) growing monotonically from ~0.004 at t + 1 h to ~0.031 at t + 25 h without divergence. Compared to a baseline 3D U-Net, the HEALPix-aware architecture reduces validation loss by more than an order of magnitude while using fewer parameters. The model generates a one-hour forecast in approximately 0.5 seconds on a single GPU, offering several orders-of-magnitude speedup over traditional numerical GCMs. These results demonstrate that parsimonious, geometry-respecting neural architectures can capture synoptic-scale Martian atmospheric dynamics and provide a foundation for planetary-scale weather forecasting.

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All authors Manmeet Singh, Saptarishi Dhanuka, Naveen Sudharsan, Houman Owhadi, Krista M. Soderlund, Alphan Altinok

Instrumentation and Detectors

Precessing magnetic particles as ac magnetic field sensors

A T M Anishur Rahman

Electromagnetic waves are widely used including in defense, biomedicine, and fundamental science. Their efficient detection determines how we communicate, defend against adversaries, diagnose diseases and perform search and rescue operations. In this article, exploiting the precession of a levitated magnetic particle in vacuum, we show that weak electromagnetic waves down to the femtotesla level can be detected. It is also shown that such a sensor has a large dynamic range over a millitesla, is continuously tunable over many gigahertz and can detect frequencies with sub-hertz resolutions. The direction of arrival of the incoming electromagnetic wave can also be found relatively easily.

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Popular Physics

The Optics of Shadow Bands

Branko Sretenović

Shadow bands are transient, rippling patterns of light and dark that may appear in moments before and after totality in a solar eclipse. Despite centuries of reports, their physical origin has remained unresolved. This article develops a geometric-optical solution in which the Sun's extended structure produces a celestial analog of Young's double-slit experiment, generating an interference and fringes on the ground. The analysis combines solar limb geometry and a wave-based formulation that yields quantitative predictions for fringe width and spacing. Some other properties of shadow bands are also analyzed.

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Fluid Dynamics

Quasi-material finite-time rotationally coherent sets in photospheric supergranulation

Francisco J. Beron-Vera

Supergranular flows organize transport in the solar photosphere over spatial and temporal scales much larger than granulation. While coherent vortical motions have been identified using objective Lagrangian diagnostics such as the Lagrangian-averaged vorticity deviation (LAVD), rotational coherence captures only one aspect of coherent flow organization. Here we introduce finite-time rotationally coherent sets (FTRCS) by combining the inflated dynamic Laplacian (IDL), which identifies finite-time quasi-material coherent regions, with LAVD-based rotational diagnostics. The IDL extracts coherent structures with finite lifetimes, while LAVD identifies those exhibiting enhanced intrinsic rotation. Application to photospheric velocity fields shows that instantaneous vortical features do not necessarily correspond to finite-time rotationally coherent structures. The analysis also illustrates the effect of compressibility: coherent sets may form through persistent contraction associated with convergent transport, rather than through the persistence of rotating material regions. The combined IDL–LAVD approach separates finite-time transport coherence from intrinsic rotational organization in time-dependent flows.

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Popular Physics

Mass Extinctions by Gravitational Tides

Daniele Fargion

Past and recent observations suggest that many planetary mass or dwarf planet objects may exist in the outer Solar System. Gravitational perturbations may occasionally bring some of them into the inner Solar System. The early, rare collision between the early Earth and a Mars sized body is generally invoked to explain the formation of the Moon. More probable than a direct impact, are grazing or near Earth flybys of similar objects. Such passages may have left strong tidal signatures: giant waves, large volcanic episodes, sea regressions, coherent meteor showers, and major climatic perturbations. These mechanisms could have contributed to several major biological mass extinctions over the past $600$ million years, as suggested by peculiar correlations in the geological record. Similar events may have occurred several times during the earlier history of Earth. Accretion of mini planets by largest planets and in particular by the Sun may also have occurred many more times over the last four billion years. Possibly producing additional temperature variations on planets and Earth.

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Geophysics

Mechanism of production and deviation from the standard Gutenberg-Richter law of the big earthquakes (An analysis of big earthquakes)

Bogdan Felix Apostol

We describe two self-replicating mechanisms of energy accumulation in the seismic focus, which modify the Gutenberg-Richter law in the region of the big earthquakes. The first mechanism acts for magnitudes smaller than a narrow region of large critical magnitudes; it slows down the energy accumulation and may produce precursors. The second mechanism acts above that region, and accelerates the energy accumulation; the precursors may be absent. Both mechanisms reduce the Gutenberg-Richter excedence distribution. On the left of the critical region the Gutenberg-Richter magnitude probability density is unchanged, while on the right the probability density is reduced. The procedure described in this paper introduces a critical-magnitude region (range) as an additional fitting parameter. The results may bear relevance upon the recent concepts of "self-arresting" and "dragon-king" earthquakes. The two self-replicating mechanisms may introduce a magnitude gap between the two types of big earthquakes, and two branches in the excedence law, in the vicinity of the critical region.

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Popular Physics

Quantum Cinema: An Interactive Cinematic Exploration of Quantum Computing Hardware via Generative World Models

Aoyu Zhang, Dongping Liu and Luyao Zhang

Quantum computing promises transformative advances across science and industry, yet the physical hardware that enables these computations remains invisible to the public: quantum processors operate inside sealed dilution refrigerators at temperatures near absolute zero, making direct observation impossible. This "imagination gap" between quantum computing's growing societal impact and the public's ability to visualize it represents a significant barrier to quantum literacy and workforce development. We present Quantum Cinema, an open-source, browser-based interactive application that closes this gap by transforming invisible quantum hardware into explorable, cinematic experiences using generative world models. Quantum Cinema guides users through a four-act narrative – from the foundational Nobel Prize-winning science of quantum entanglement, through curated video introductions to three major quantum computing architectures (trapped-ion, neutral-atom, and superconducting systems), into immersive three-dimensional generative worlds that make invisible quantum phenomena observable, and finally to interactive radar-chart comparisons grounded in real quantum device specifications. All three-dimensional environments are generated using WorldLabs' generative world model platform and are scientifically grounded in curated metrics from Amazon Web Services (AWS) Braket quantum hardware. Quantum Cinema requires no installation, no specialized hardware, and no quantum computing background. It is designed to serve two distinct communities: scholars and developers seeking to replicate or extend the platform, and educators, researchers, and science communicators seeking an intuitive tool for explaining quantum hardware to diverse audiences. This paper describes the system architecture, the generative world model pipeline, use cases for both communities, and directions for future work.

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Fluid Dynamics

Theory and internal structure of ADER-DG method for partial differential equations

I.S. Popov

Highly accurate stability boundary values for the ADER-DG method are obtained for arbitrary degrees $N$ of basis polynomials. In the linear case, stability is violated precisely when one of the matrix eigenvalues reaches $\lambda = -1$, regardless of the phase $\theta$. A rigorous mathematical framework for the stability is developed. The stability condition is significantly simplified, reducing it to the problem of calculating the roots of polynomials in the Courant number $\mathrm{CFL}$. The maximum of the Courant numbers $\mathrm{CFL}_{\rm max}(N)$ are calculated. These results are new and very convenient for practical use. A comparison of the obtained results with existing results reveals differences that may be significant for the selection of calculation parameters, especially for high degrees $N$. It is shown that widely used existing estimates $\mathrm{CFL}_{\rm max}(N) \propto 1/(2N+1)$ are overestimated. An interesting qualitative asymptotic $\mathrm{CFL}_{\rm max}(N) \propto 1/(N+1)^{2}$ is obtained. A rigorous direct proof of the approximation is presented. Approximation orders $p = N+1$ for arbitrary degrees $N$ are rigorously derived. A set of numerical experiments is carried out to apply the ADER-DG method to solving both a linear advection equation and an Euler system of equations. The results obtained in these calculations confirm the theoretical results well. In particular, an excess of the Courant number over the $\mathrm{CFL}_{\rm max}(N)$ by even 1% in the linear case immediately leads to significant instability of the numerical solution. The obtained estimates of the boundary Courant number in the nonlinear case are somewhat underestimated – by no more than 5%, which is due to the diffusivity and stability of the approximate Riemann solver. Empirical convergence orders are obtained, which are in good agreement with the theoretical results.

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High Energy Astrophysical Phenomena

Misspecification in amortized X-ray spectral inference: a detection benchmark, a gain shift three schemes cannot see, and marginalizing it out

Karan Akbari

Amortized neural posterior estimation fits X-ray spectra in milliseconds, and pipeline use will lean on post-hoc checks to catch detector systematics the simulator misses. We measure what those checks see, on simulated spectra from real XMM-Newton EPIC-pn and NICER responses. Of four misspecification families, an unmodelled 6.4 keV line and partial covering are catchable per spectrum (AUC 0.97 and 0.84). A wrong continuum family reaches 0.66. One flow passed every recovery check yet under-covered (coverage deviation 0.114), and a converged NICER flow (0.011) fails simulation-based calibration on all five parameters. Recovery metrics do not certify calibration. Three schemes catch the line: the posterior-predictive check, importance sampling against the exact Poisson likelihood (effective sample size, 0.68-0.82), and the nested-sampling evidence (count-controlled, $-67$ to $-892$ nats). None catches the 3 per cent gain shift, 2.4 to 14.4 times the EPIC-pn energy-scale accuracy (AUC 0.44-0.54; 36-cell means 0.50 and 0.49 on both responses; paired evidence $+0.33 \pm 1.37$ nats). The effective sample size stays null-consistent from 0.1 to 10 per cent, realistic amplitudes included. The shift still biases the photon index by $+0.02$ (0.03 to 0.11$\sigma$) at both count levels. Retraining with a per-simulation nuisance gain adds no inference-time cost, and the gain posterior returns the prior. The bias survives, and exact gain-marginalized nested sampling shows the flow capturing at most 0.163 of its gain constraint (continuous-prior convention) at high counts. Marginalization over posited calibration nuisances is the working defence for X-ray SBI at catalog scale; no check we ran supplies a warning.

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Optics

Bright Emission from Dark Sources in Hyperbolic Media

Evgenii E. Narimanov

Hyperbolic media enable ultra-strong light-matter interactions through their extreme field localization and small mode volumes, but low-loss realizations are fundamentally limited to the mid-infrared, owing to the long lifetimes of optical phonons in high-quality crystals. Here we show that bright emitters operating at visible or near-infrared frequencies can be used to generate radiation in this regime by inducing mid-infrared population dynamics, thereby creating a source in the hyperbolic frequency band without a corresponding dipole transition. We demonstrate that even a source with vanishing dipole and higher multipole moments - strictly non-radiating in any isotropic medium - becomes radiatively active in a hyperbolic environment. This enables visible and near-infrared control of light-matter interactions in polaritonic hyperbolic materials, establishing a new low-loss solid-state quantum optics platform.

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Plasma Physics

On modeling energetic electrons in laser fusion plasmas

Wallace Manheimer

It has been known for decades that laser fusion can be, and often is plagued by the production of energetic electrons.produced either by a instability or by the production of energetic electrons, produced either by an instability or by the energetic tail of a Maxwellian distribution. Despite more than 25 years of a variety of efforts, there is still no generally accepted way to address this issue. This work hopes to advance the progress by developing a Fokker Planck model which is simple enough to be used at every time step of a rad-hydro simulation, and accurate enough to be useful. It makes several approximations, the main one being that the percentage of these energetic electrons is small. Recent experiments confirm this so far that this is the case for plasmas subject to a laser plasma instability. Hence energetic electons interact with the background plasma, but not with each other. This work makes no attempt to solve for the entire electron distribution function. It makes a variety of tohter approximations to solve the resulting Fokker Planck equation. This rather elngthy report both summarizes the author's work with the NRL group, and presents new advances since the termination of the NRL laser fusion project. An important tentative conclusion is that energetic electrons may not be such a big problem for laser fusion.

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Quantum Physics

Enhanced Sensitivity near a Quantum Exceptional Point in the Absence of Engineered Dissipation

Réouven Assouly, Harry Hanlim Kang, Aziza Almanakly et al. (+8 more)

Non-Hermitian systems exhibit phenomena absent from Hermitian systems, including exceptional points (EPs), at which two or more eigenvectors coalesce. Conventional implementations rely on gain and loss, which strongly limit quantum coherence. Here, following a proposal by Wang and Clerk (PRA 2019), we realize a closed four-mode quantum system that emulates the dynamics of a PT dimer - two coupled resonators with balanced gain and loss - without engineered dissipation. The four modes are implemented as harmonics of a superconducting coplanar-waveguide resonator, with parametric couplings engineered using a current-pumped SNAIL. We use this device as a sensor for small variations in the PT dimer coupling strength. From signal-to-noise-ratio measurements, we observe enhanced sensitivity near the EP in a non-quantum-limited regime.

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All authors Réouven Assouly, Harry Hanlim Kang, Aziza Almanakly, Michael A. Gingras, Bethany M. Niedzielski, Hannah Stickler, Mollie E. Schwartz, Kyle Serniak, Max Hays, Jeffrey A. Grover, William D. Oliver

Quantum Physics

Readout-Induced Leakage in Superconducting Circuits with Nonlinear Couplings

Sumeru Hazra, Wei Dai, Daniel K. Weiss et al. (+3 more)

In superconducting circuits, drive-induced unwanted transitions limit the readout power, thereby constraining readout speed and fidelity. When such transitions excite the qubit into leakage states, they produce correlated errors that are particularly harmful for quantum error correction. Native nonlinear qubit-readout resonator coupling is a promising alternative to conventional linear hybridization because it provides intrinsic Purcell protection and stricter selection rules for multiphoton processes. In realistic devices, however, we show that such a coupling alone neither eliminates nor necessarily suppresses drive-induced transitions. Instead, if not appropriately engineered, these couplings often worsen the situation by introducing additional parasitic processes. Moreover, the rates of these unwanted transitions remain sensitive to the choice of readout frequency, regardless of the coupling mechanism. We demonstrate that readout-induced leakage can thus vary by orders of magnitude even when readout frequencies differ by less than ~7%. Our results establish that the benefits of native nonlinear couplings are realized only through informed device design, including the spectral placement of relevant auxiliary modes and elimination of parasitic ones.

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All authors Sumeru Hazra, Wei Dai, Daniel K. Weiss, Pranav D. Parakh, Luigi Frunzio, Michel H. Devoret

Mathematical Physics · Cross-listed from math.SP

Resolvent estimates for one-dimensional Dirac operators with imaginary potentials

Antonio Arnal, Tho Nguyen Duc and Petr Siegl

We investigate massive one-dimensional Dirac operators perturbed by diagonal matrix potentials of the form $i V$ where the function $V$ is real-valued and unbounded at infinity. For such operators we find an $L^2$-realization with non-empty resolvent set using generalized coercivity and Schur complement dominance techniques. In the prototypical Airy-Dirac case $V(x)=x$, $x \in \mathbb{R}$, we derive the precise asymptotic behavior of the resolvent as the spectral parameter tends to infinity and also as the mass $m$ tends to $0$. Finally, we find the asymptotics of the resolvent norm for general potentials $V$ in terms of the Airy-Dirac resolvent, which in particular yields an asymptotic shape of $\varepsilon$-pseudospectral curves and establishes the optimality of the pseudospectral region found in [32].

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Optics

Spectral tailoring of Raman soliton generation via a dispersion-managed fibre Fabry-Pérot resonator

Yiqing Xu, Stuart G. Murdoch, Stéphane Coen et al. (+1 more)

Dissipative Raman solitons in passive Kerr resonators have emerged as a promising route to broadband coherent frequency comb generation. Yet, their centre frequency has so far been mostly fixed near the Raman gain peak (13~THz downshifted from the pump centre frequency in silica-based fibres), constraining spectral coverage and compatibility with standard optical amplifiers. This limitation arises because the frequency shift of Raman solitons that fulfills phase-matching and group-velocity-matching conditions has to fall within the Raman gain band, leaving little room for spectral tuning when using a single conventional optical fibre. Here, we demonstrate that dispersion management of the fibre Fabry-Pérot resonator which allows us to directly shift the soliton centre frequency. By combining two fibres with complementary dispersion profiles, we tailor the resonator's average dispersion to satisfy the phase-matching conditions for soliton formation at a target frequency downshifted by 7.8~THz from a pulsed pump, which is well outside the conventional 13~THz Raman gain band. This allows us to optically amplify the dissipative Raman soliton with a commercial L-band erbium-doped fibre amplifier, and fully characterise its temporal profile via the frequency-resolved optical gating technique.

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All authors Yiqing Xu, Stuart G. Murdoch, Stéphane Coen, Miro Erkintalo

Quantum Physics

Adiabatically-induced Kawaguchi geometry and jerk in quantum-classical systems

Athanasios Chatzistavrakidis, Larisa Jonke and Ryan Requist

Adiabatically eliminating the quantum degrees of freedom in a mixed quantum-classical system produces an effective force in the classical equation of motion. The elimination can be made to any order in the adiabatic parameter, generating a series of higher order forces. By applying a sequence of near-identity unitary transformations to the quantum state, we derive a hierarchy of increasingly accurate effective actions for the classical variables. The third order Euler-Lagrange equation is non-Newtonian as the force depends on the jerk, the third order time derivative of position. We find that the third order terms induce a special kind of Kawaguchi geometry on the space of classical variables. This geometry is characterized by an almost symplectic structure and a differential line element that depends on the acceleration in addition to the velocity. Our results can be used to efficiently capture higher order nonadiabatic effects in molecular dynamics simulations.

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