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Physics

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Tuesday 4 August

Astrophysics of Galaxies

Chemical Abundances and Globular Clusters of Milky Way Dwarf Galaxies

Baitian Tang, Shihui Lin, Ruoyun Huang et al. (+5 more)

We present an overview of our ongoing GASTRONOMI project, which investigates the coevolution of the Milky Way (MW), its satellite dwarf galaxies, and their star clusters through chemo-dynamical analysis. We derive precise chemical abundances for stars in five classical dwarf galaxies, which reveal mass-dependent chemical evolution, particularly in alpha elements, such as [Si/Fe]. A distinct dichotomy in [Al/Fe] is found between metal-rich ([Fe/H]>-1.5) stars formed in-situ in the MW and those originating in dwarf galaxies. Star clusters act as sensitive environmental probes. The presence of multiple populations correlates with galactic evolution, and nitrogen-rich stars in Fornax are likely relics of disrupted globular clusters (GCs). We developed a chemical classification for Galactic GCs, isolating primordial populations by their low [Al/Fe]. This places in-situ and accreted GCs in distinct regions of the [Al/Fe]-[Fe/H] plane, providing a new tool to reconstruct the Galaxy's accretion history.
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All authors Baitian Tang, Shihui Lin, Ruoyun Huang, Cheng Xu, Jose G. Fernandez-Trincado, Doug Geisler, Chengyuan Li, Zhiqiang Yan

Plasma Physics

Radiation reaction in the classical relativistic Størmer problem

Francisco S. N. Lobo and Tiberiu Harko

We extend the classical relativistic Størmer problem by incorporating radiation reaction through the Landau–Lifshitz formulation, thereby providing a self-consistent description of dissipative charged-particle motion in a static dipole magnetic field. We derive the complete dimensionless equations and distinguish them from a reduced drag-only model that preserves the exact energy-loss law while omitting directional effects associated with magnetic field gradients. For planar motion, the reduced system yields exact instantaneous evolution laws for the particle energy and canonical angular momentum, together with averaged transport equations for regular bound librations. When the motion is constrained to the instantaneous circular branch, the secular evolution can be integrated in closed form and approaches a simple large-radius power law. This analytical solution provides a useful benchmark, although the circular branch is radially unstable and therefore does not describe generic nearby trajectories. Numerical integrations further illustrate the nonuniform dissipative deformation of planar rosette-like orbits. In three dimensions, the complete Landau–Lifshitz force produces local exponential damping of small vertical perturbations, with the leading contribution arising from the field-gradient term absent from the reduced model. These exact, averaged, conditional, and local results establish a controlled analytical framework for studying radiation-driven phase-space transport in strongly inhomogeneous magnetic fields and provide a foundation for future global simulations, kinetic descriptions, and calculations of the associated electromagnetic emission.
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Materials Science

Bias Tunable Transport Modulation and Gas Selectivity in Layered BiOI: A DFT NEGF Study

Jemal Yimer Damte, Jiří Houška, Pavel Baroch et al. (+1 more)

Understanding the interplay between adsorption energetics and charge-transport modulation is essential for the rational design of low-power and bias-tunable gas sensors. Here, we present a comprehensive first-principles study of gas selectivity in layered bismuth oxyiodide (BiOI) by integrating density functional theory with nonequilibrium Green's function transport calculations. The adsorption and bias-dependent transport responses toward NO2, NH3, CO2, and representative volatile organic compounds are systematically examined. While NH3 and NO2 exhibit strong chemisorption and localized electronic perturbations, CO2 interacts through weak physisorption, demonstrating that adsorption strength alone does not determine sensing performance. Instead, the evolution of transmission channels near the Fermi level governs the sensing response. Bias-dependent calculations reveal an electrically tunable sensitivity hierarchy, in which weakly adsorbed CO2 preserves conductive pathways and exhibits pronounced low-bias sensitivity despite minimal charge transfer. Recovery-time analysis further highlights the trade-off between transport modulation and reversibility for strongly adsorbed species. These results establish a transport-centered selectivity framework for layered BiOI and provide mechanistic insight into electric-field-controlled gas sensing under ambient conditions.
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All authors Jemal Yimer Damte, Jiří Houška, Pavel Baroch, Xue Yong

Quantum Physics

Single-molecule strong optomechanical regimes in SERS via hybrid plasmonic cavities

Miguel Á. Martínez-García, Johannes Feist and Diego Martín-Cano

We identify enhanced strong coherent Surface-Enhanced Raman Scattering (SERS) interactions facilitated by hybridized metallo-dielectric cavities with a resonant fluorescent molecule. By illuminating a detuned electronic transition near saturation via a narrowband hybrid plasmonic mode, we observe enhanced splittings in the Stokes and anti-Stokes spectra, revealing strong optomechanical coupling and nonlinear vibrational modifications at intensities far below irreversible SERS damage thresholds. We compute the second-order photon correlations that allows identifying the nonclassical character associated to these strong optomechanical interactions and SERS configurations that enables them to optically characterize the anharmonic character of the vibrational modes.
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Solar and Stellar Astrophysics

The double white dwarf merger model for the progenitors of SN 2021yfj-like events

Dongdong Liu, Chengyuan Wu, Takashi J. Moriya et al. (+4 more)

Context. Recently, a new class of supernovae with prominent narrow emission features of Si, S and Ar has been reported, i.e. SN 2021yfj-like events (SNe Ien). Their progenitor origin is still unknown. It has been suggested that a massive CO WD may evolve into a Si/S-rich WD when accreting He-rich matter at a high mass-transfer rate. If the He companion subsequently evolves into another more massive WD, the merger of this double WD system can generate Si/S-rich CSM through tidal stripping. Following the SN explosion, the interaction between the SN ejecta and the Si/S-rich CSM could produce the Si, S, and Ar emission lines characteristic of SN 2021yfj-like events. Aims. In this work, we aim to determine the initial parameter space of WD+He star systems that can lead to SN 2021yfj-like events via the double WD merger scenario, and to quantify their theoretical Galactic birthrate and delay-time distributions. Methods. We perform detailed binary evolution simulations of a large number of semidetached WD+He star systems to obtain the parameter space that leads to the formation of Si/S-rich WDs and subsequent double WD mergers. We then use binary population synthesis to calculate the Galactic birthrate and delay-time distribution of such events. Results. For the formation of SN 2021yfj-like events, we found that the initial CO WD and He companion masses must lie in the ranges of 1.0-1.2 M_sun and 2.2-2.5 M_sun, respectively. The derived merger rate for this scenario is ~(2.6-4.4)x10^-5 yr^-1 with delay times longer than 450 Myr, which is about 1% of the observed SN Ia rate. Conclusions. We suggest that the double WD merger scenario involving a Si/S-rich WD originating from a CO WD+He star system, represents a significant and competitive model for SN 2021yfj-like events, underscoring the need for further observations of similar events coupled with relevant theoretical investigations.
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All authors Dongdong Liu, Chengyuan Wu, Takashi J. Moriya, Jiawen Ning, Zhengwei Liu, Zhanwen Han, Bo Wang

Solar and Stellar Astrophysics

Electron transport in a radiation-dominated plasma Application to solar corona brightenings

Roland Duclous, Vladimir Tikhonchuk, Marina Leboulanger et al. (+3 more)

Bremsstrahlung scattering of fast electrons on ions can be enhanced by the microwave radiation present in the solar corona. It can account for the electron diffusive transport along magnetic loops and high precipitation rates. This process can also dominate the transport of thermal electrons confined in such loops. The influence of stimulated Bremsstrahlung scattering on the electron transport is studied, with focus on the return current induced by the fast electron population trapped in magnetic loops. Overall, transport coefficients are reevaluated in the radiation-dominated plasma, characterized by the stimulated action of radiation on the Bremsstrahlung electron-ion collision, down to thermal velocities. We develop a theoretical framework for electron transport driven by a large bandwidth, bright low-frequency part of the photon spectrum and compute a set of radiation-enhanced transport coefficients. UV, XEUV and hard X-ray signals from flares, evidencing anomalous resistivity, thermal conduction inhibition and high precipitation rates of fast electrons, are reinterpreted. The anomalous resistivity due to stimulated Bremsstrahlung scattering is found to dominate the classical resistivity in flares. The runaway effect due to Coulomb collisions is suppressed. Thermal conduction is inhibited compared to the Spitzer conduction, in agreement with coronal seismology of slow-mode waves. Stimulated Bremsstrahlung scattering is found to be a key collisional process in flaring events. It can explain the above loop-top hard X-ray signal due to the fast electrons, and the measured electrical conductivity due to the thermal electrons. As a perspective, the corresponding transport coefficients can be used in radiation MHD codes. The radiation model could also be applied to stimulate large-angle electron scattering in the kinetic or hybrid models used to study the solar corona.
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All authors Roland Duclous, Vladimir Tikhonchuk, Marina Leboulanger, Xavier Blanc, Allan-Sacha Brun, Antoine Strugarek

Optics

High resolution meta-stereomicroscope based on birefringent meta-optics

Liheng Yan, Haowen Liang, Emiliano R. Martins et al. (+5 more)

Achieving both high lateral and high depth resolution is a longstanding goal in stereomicroscopy. Although meta-optics have revolutionized lens design by alleviating the physical constraints of conventional optical architectures, existing metalens-assisted stereomicroscopes still suffer from field of view (FOV) mismatch between meta-optical and conventional optical components in stereomicroscopes, thereby limiting their imaging performance. Here, we show that this mismatch can be fundamentally eliminated through a fully meta-optical architecture. The integrated system enables flexible control of numerical aperture and magnification with larger depth of field (DOF) and FOV than those of the metalens-assisted stereomicroscopes. Experimentally, we achieve an integrated meta-stereomicroscope with a lateral resolution of 435 nm, surpassing the performance of previously reported stereomicroscopes. Empowered by a stereo neural network, the system enables straightforward reconstruction of high-resolution three-dimensional surface morphology with a depth resolution of 1026 nm, demonstrating the capability to simultaneously achieve high lateral and depth resolution imaging. This integrated architecture operates in both transmission and reflection modes for biomedical imaging and industrial inspection, highlighting its broad applicability for real-time observation across biomedical and industrial scenarios.
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All authors Liheng Yan, Haowen Liang, Emiliano R. Martins, Yikun Liu, Tao Li, Thomas F. Krauss, Juntao Li, Xue-Hua Wang

Astrophysics of Galaxies

Binary Constraints on the Origin of Nitrogen-rich Field Stars

Liao Yang, Baitian Tang, José G.Fernández-Trincado et al. (+4 more)

Recent JWST observations have revealed galaxies with unusually high N/O ratios, suggesting that nitrogen enrichment may be common in intense star-forming environments in the early Universe. In the Milky Way, nitrogen-rich(N-rich) stars in the Galactic field have long served as probes of early Galaxy formation and globular cluster enrichment. However, the identification of binaries among these stars raises the possibility that binary mass transfer could contribute to their origin. In this work, we utilize multi-epoch radial velocities and element abundances from APOGEE DR17 to constrain their formation sites. Among 266 N-rich field stars, 33 exhibit radial velocity variations of $\Delta {\rm RV} > 1\,{\rm km/s}$, including 10 robust spectroscopic binaries identified using the $F_2$ statistic within a well-sampled subset of 46 stars. The resulting close-binary fraction ($21.7\pm6.1\%$) is statistically indistinguishable from that of chemically normal field stars ($18.1\pm0.6\%$), showing no evidence of the excess expected from AGB binary pollution. This is further supported by the absence of correlation between [N/Fe] and [Ce/Fe] and the lack of [C/Fe] enhancement. Crucially, we detect an anti-correlation between binary fraction and [Al/Fe], with strongly Al-enhanced stars ($[\mathrm{Al/Fe}] \gtrsim 0.5$) exhibiting a reduced binary fraction ($< 10\%$). This trend serves as a dynamical fingerprint of high-density environments, consistent with the efficient disruption of binaries via three-body interactions in GC cores. Our results do not support binary mass transfer as the dominant formation channel for N-rich field stars; they are predominantly GC escapees that retain the dynamical memory of their dense birth sites.
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All authors Liao Yang, Baitian Tang, José G.Fernández-Trincado, Chengyuan Li, Long Wang, Dengkai Jiang, Bo Ma

Computational Physics

A Unified Graph Neural Network Framework for Non-Equilibrium Carrier and Lattice Dynamics Driven by Electric Fields

Jia-Wen Li, Sheng Meng, Xinghua Shi et al. (+2 more)

Finite-temperature simulations of electric-field-driven dynamics need a unified description of interatomic interactions, local electronic states, and configuration-dependent electric responses. First-principles simulations remain scale-limited, whereas conventional machine-learning potentials lack electric-field effects. Recent machine-learning frameworks have incorporated electric-field response or atom-resolved electronic-state information, but rarely both within a single framework. Here, we develop an electric-field-response graph neural network (EFR-GNN) that predicts energies, forces, Born effective charge tensors, atom-resolved charges and magnetic moments, and supports long-time field-driven molecular dynamics with atom-resolved tracking of localized electronic states. In hole-doped MgO, static fields rectify thermally activated hole-polaron hopping through a forward–backward asymmetry quantified by a nearest-neighbor model. In GaAs, resonant terahertz excitation generates a coherent $\Gamma$-point transverse-optical phonon with dephasing consistent with experiment, while opposite helicities reverse its rotation. In superionic $\alpha$-AgI, it reproduces temperature-dependent Ag$^+$ mobility and collective field-driven ionic drift. Together, EFR-GNN offers an approach to finite-temperature simulations of field-driven atomic and localized-carrier dynamics.
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All authors Jia-Wen Li, Sheng Meng, Xinghua Shi, Jin Zhang, Wei-Hai Fang

Materials Science

AccelNet: Exact backward-compatible acceleration of polynomial angular descriptors through Cartesian moment factorization

Yuki Nagai

We present AccelNet, an exact, backward-compatible method for accelerating existing trained aenet and n2p2 neural-network potentials without retraining. For angular terms with separable one-neighbor weights and a finite polynomial dependence on $\cos \theta$, the method exploits their hidden finite-rank structure to replace explicit neighbor-pair loops by one-neighbor Cartesian moments. AccelNet reads models trained with either package and reproduces their descriptors, energies, and analytic forces to floating-point roundoff. We verified this equivalence for H$_2$O and TiO$_2$ models and tested the resulting potentials in LAMMPS molecular-dynamics simulations. The implementation, model-conversion tools, and LAMMPS interfaces are released as open-source software. AccelNet also enables GPU-accelerated molecular dynamics with existing aenet and n2p2 potentials. Moment evaluation achieves speedups of up to 10.9 on a CPU and 15.8 on a GPU relative to direct evaluation within AccelNet. The implementation, model-conversion tools, and LAMMPS interfaces are released as open-source software.
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Other Condensed Matter

Topological properties and phase diagram of the triangular Hofstadter model with staggered flux

Qi Gao and Wei Chen

We study the topological properties and phase diagram of the triangular Hofstadter model with staggered flux in adjacent triangles in this work. This lattice can be used to describe the low energy physics of the twisted bilayer transition metal dichalcogenides (TMD) in a certain range of the electric displacement field between the two layers. We show that the Hofstadter spectrum of this model is generally asymmetric except at specific staggered flux $3\phi= \pi/2 \mod {\pi}$ due to an additional P symmetry at such $\phi$. Breaking the translation symmetry by dimerization lifts the P symmetry and results in rich topological phases in the system. The dimerized model with different rational external magnetic flux ${\Phi}_B = 2\pi p/q$ has phase diagram with the following common features. For even q, the dimerized model generally has three gapped regimes. The one with small dimerization has finite Chern number and the other two have zero Chern number. For odd q, the model is gapped with zero Chern number at any finite dimerization. For both q even and odd, the two regimes with zero Chern number can be further characterized by the inversion symmetry of the parametrized one-dimensional chains of the system at \phi = 0 \mod \pi/3$, and one regime is topologically non-trivial and the other is trivial. Our results may be tested in twisted bilayer TMD with weak interaction or cold atom systems in optical lattice or photonic crystals achieved in recent experiments.
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Quantum Physics

Analysis of Superradiance-Based Quantum Metrology under Independent Markovian Pure Dephasing

Yasunari Sakuma, Yuichiro Matsuzaki, Hoi-Kwan Lau et al. (+1 more)

Recently, a DC magnetometry protocol utilizing $N$-spin-ensemble superradiance was proposed. This method physically amplifies the acquired signal, suppressing estimation errors from measurement noise and achieving $\mathcal{O}(1/N)$ precision scaling when measurement noise dominates quantum fluctuations. However, quantum metrology is generally vulnerable to independent Markovian pure dephasing. For instance, the scaling of Greenberger-Horne-Zeilinger (GHZ) state-based magnetometry deteriorates from $\mathcal{O}(1/N)$ to $\mathcal{O}(1/\sqrt{N})$. Although pure dephasing likely degrades superradiant sensing, its quantitative impact remains unclear. Here, we investigate the effect of independent Markovian pure dephasing on this protocol using numerical simulations and mean-field analysis. We demonstrate that, in the large-$N$ limit, the estimation error increase is limited to a constant factor. This sharply contrasts with GHZ-state-based sensing, where the error increases by a factor of $\sqrt{N}$. Our analytical solutions elucidate the physical origin of this robustness qualitatively. These findings establish the high robustness of superradiance-based DC magnetometry against independent Markovian pure dephasing.
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All authors Yasunari Sakuma, Yuichiro Matsuzaki, Hoi-Kwan Lau, Junko Ishi-Hayase

Nuclear Experiment

Measurement of forward jet suppression in Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$$ TeV with the ATLAS detector

ATLAS Collaboration

Inclusive jet production is measured with the ATLAS detector at the LHC at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV in Pb+Pb and $pp$ collisions, using data samples corresponding to integrated luminosities of 1.72 nb$^{-1}$ and 255 pb$^{-1}$, respectively. The jet nuclear modification factor, $R_{\mathrm{AA}}$, is reported for anti-$k_t$ jets with radius parameter $R=0.4$ in the forward-rapidity intervals $2.8<|y|<3.2$ and $3.2<|y|<3.6$, probing transverse momenta $p_\mathrm{T}>74$ GeV. The observed $R_{\mathrm{AA}}$ values show a significant suppression of jet yields in Pb+Pb collisions relative to those measured in $pp$ collisions. The suppression increases monotonically from peripheral to central collisions and exhibits a mild jet $p_\mathrm{T}$ dependence. A comparison with previous ATLAS measurements indicates stronger jet suppression in the $2.8<|y|<3.2$ region than in the $|y| < 2.8$ region. In the $3.2<|y|<3.6$ region, the precision of the measurement does not allow a conclusive comparison with the $|y|<2.8$ region. These results constitute the first measurement of inclusive jet suppression at forward rapidity in heavy-ion collisions and provide new constraints on flavor, geometric, and medium-density dependence of parton energy loss.
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High Energy Physics (Phenomenology)

Unraveling weak radiative hyperon decays with broken flavor symmetry

Kaiwen Chen, Lin Qiu, Jin Sun et al. (+2 more)

We present a broken $SU(3)$ flavor analysis of weak radiative decays of spin-1/2 hyperons, incorporating current-current and electromagnetic-penguin contributions as well as charge- and mass-insertion effects. Six independent reduced amplitudes describe all decay channels, while a minimal relation between the parity-conserving and parity-violating form factors reduces to eight free parameters. A global fit to the ten available observables yields $\chi^2/\mathrm{d.o.f.}=0.98$ and accommodates the large negative asymmetry in $\Sigma^+\to p\gamma$. The resulting nonzero effective form factor $g_{b_8}$ provides a possible flavor-symmetry realization of the parity-violating amplitude while remaining compatible with Hara's theorem, which constrains the current-current contribution in the exact symmetry limit. Our analysis favors a sizable negative value of $\alpha_\gamma(\Xi^- \to \Sigma^- \gamma)$, which differs from the current experimental result by approximately $1.3\sigma$. Future precision measurements of this observable will provide a decisive test of this prediction.
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All authors Kaiwen Chen, Lin Qiu, Jin Sun, Zhi-Peng Xing, Ruilin Zhu

Optics

Valley polarization driven by two-color circular fields from a strong-field tunneling perspective

Rui E.F. Silva, Olga Smirnova, Misha Ivanov et al. (+1 more)

Valley polarization in hexagonal materials driven by the form of the lightwave and its orientation relative to the lattice, rather than solely by the helicity of the driver, has recently been demonstrated both theoretically and experimentally. This has extended valley control to the non-resonant, sub-cycle regime and to inversion-symmetric materials. One interpretation of this field-orientation-dependent valley polarization is that the laser-dressed, cycle-averaged band structure obtained from a Floquet-type approach is modified so as to lift the degeneracy between the valleys. Here, we derive a complementary explanation based on strong-field tunneling dynamics. We show that the effective valley gap at the dominant injection times depends on the orientation of the field relative to the lattice through the trigonal-warping term of the low-energy dispersion. We derive general expressions for co- and counter-rotating $\omega+N\omega$ fields and show that the leading orientation-dependent contribution survives the cycle average only for field configurations compatible with the threefold lattice symmetry, most notably counter-rotating $\omega+2\omega$ and co-rotating $\omega+4\omega$ fields.
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All authors Rui E.F. Silva, Olga Smirnova, Misha Ivanov, Álvaro Jiménez-Galán

Atmospheric and Oceanic Physics

Experimental validation of an open-source low-cost single-camera 6-DOF tracking of floating-body motion in wave tanks

Herman Martens Meyer, Paul Fromont, Øystein Lande et al. (+1 more)

Accurately measuring motion of floating structures in experimental settings is both important and non-trivial. In this paper, we present a single-camera, 6-degree-of-freedom motion-tracking system that is both low-cost and simple to set up for an experimental campaign. The system uses fiducial markers and open-source computer vision tools to estimate the positions and orientations of multi-marker geometries and track them. We validate the accuracy and limitations on a precisely controlled linear actuator with static, regular, and irregular motion. The performance is quantified depending on both the camera-to-marker distance and direction of motion relative to the camera plane. Additionally, we present a practical use case for our system in a wave tank. Although the motion direction perpendicular to the camera plane shows the highest errors, the system achieves sub-millimeter accuracy at short and moderate camera-to-marker distances. For the irregular motion validation, the best cases reproduced the displacements with an RMSE of approximately 0.5 mm. Overall, the results indicate that low-cost single-camera fiducial-marker tracking can provide sufficiently accurate, non-intrusive motion measurements for a range of hydrodynamic laboratory experiments.
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All authors Herman Martens Meyer, Paul Fromont, Øystein Lande, Atle Jensen

Plasma Physics

Generation of dense relativistic electron beams via vortex laser-driven self-generated magnetic pinching

Mingxuan Wei, Fengyu Sun, Zhongpeng Li et al. (+21 more)

In multi-petawatt laser plasma accelerators, achieving high-density relativistic electron beams is typically accompanied by large transverse divergence, limiting the attainable effective electron density needed for high-flux interaction regimes relevant to laboratory astrophysics. Here we report experimental demonstration of self-generated magnetic pinching (SMP), a collective mechanism that actively regulates transverse beam dynamics using a Laguerre-Gaussian laser at strong relativistic intensity (~8 x 10^19 W/cm^2) interacting with an underdense plasma. The electron beam evolves from a two-lobe high-charge injection structure into a compressed, high-density profile, yielding a threefold reduction in divergence and nearly an order-of-magnitude enhancement in effective beam density compared with a Gaussian driver. Particle-in-cell simulations agree with the experimental observations and reveal that a self-generated azimuthal magnetic field governs the electron dynamics within the SMP regime, which is defined by the forming condition S = 0.717 l a0 [ne(10^18 cm^-3)]^-3/4 = 1, where l, a0, and ne are topological charge, laser amplitude, and plasma density, respectively. A transient kick from a dense inner sheath electron population drives collective magnetic pinching, transforming an initially separated electron distribution into a compressed and well-collimated beam. For higher-power laser systems, the forming condition can be extended to higher plasma densities and larger orbital angular momentum modes, potentially enabling electron beams with charges exceeding several nC and effective densities above 10^19 cm^-3. This mechanism provides a route to overcoming transverse expansion and enhancing rare interaction processes relevant to high-flux particle sources.
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All authors Mingxuan Wei, Fengyu Sun, Zhongpeng Li, Xichen Hu, Huiting Ma, Guangwei Lu, Zhuofan Zhang, Lijie Cui, Qijin Zhang, Mengjiao Wang, Weijun Zhou, Qian Zhao, Wenqing Wei, Yi Xu, Zongxin Zhang, Jiayi Qian, Jiacheng Zhu, Xiaoyan Liang, Min Chen, Wenpeng Wang, Jian-Xing Li, Wenchao Yan, Yuxin Leng, Jie Zhang

Fluid Dynamics · Cross-listed from math.NA

An asymptotic-preserving adjoint unified gas kinetic scheme for sensitivity analysis

Yue Zhang, Junzhe Cao, Wenpei Long et al. (+1 more)

High-dimensional sensitivity analysis and uncertainty quantification for multiscale gas dynamics, spanning the continuum to rarefied regimes, require computationally efficient and mathematically consistent gradient evaluation. This paper develops a discrete adjoint method for the unified gas-kinetic scheme (UGKS) based on a dual-consistent formulation. The adjoint system is derived directly from the discrete microscopic velocity-distribution equation coupled with the macroscopic-moment compatibility conditions. To resolve the stiff cross-scale coupling, we propose an asymptotic-preserving (AP) adjoint formulation constructed via macroscopic-moment projection and microscopic lifting. Under this framework, the AP adjoint formulation eliminates the stiff collision coupling and removes the collision-time step restriction in the continuum regime. Numerically, a memory-efficient residual-evaluation algorithm that mirrors the forward UGKS cell-vertex data structure is implemented to bypass the memory bottleneck in velocity space. Furthermore, a macroscopic–microscopic predictor–corrector implicit marching scheme is designed to accelerate convergence without solving a globally coupled system. The accuracy, consistency, and robustness of the proposed AP-adjoint scheme are rigorously verified against an independent linearized UGKS solver across a wide range of Knudsen numbers, including lid-driven cavity heat conduction, microchannel thermal creep flow, and hypersonic flow past a circular cylinder.
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All authors Yue Zhang, Junzhe Cao, Wenpei Long, Kun Xu

Cosmology and Nongalactic Astrophysics

The One-Loop Power Spectrum of Fast Radio Burst Dispersion Measures

Haruki Ebina and Martin White

Fast radio burst (FRB) dispersion measures trace free electron column densities and will soon offer a unique probe of low-$z$ baryons. Such measurements can constrain cosmology directly, with the free electrons serving as a new tracer of large-scale structure, and probe the baryonic feedback of galaxies, a leading systematic for weak lensing surveys such as LSST and Euclid. We prepare for both science cases using effective field theory (EFT) and hydrodynamical simulations. We construct the one-loop EFT description of the free-electron auto-spectrum $P_{ee}$ and electron-galaxy cross-spectrum $P_{eg}$, placing FRB dispersion clustering on the same theoretical footing as spectroscopic galaxy analyses, and quantify the FRB densities at which this modeling is useful. We also investigate suitable galaxy samples for cross-correlations, finding that current spectroscopic catalogs provide appropriate redshift range and sufficient density. We validate the model against the FLAMINGO simulations, jointly fitting $P_{ee}$, $P_{eg}$, and $P_{gg}$ for DESI-like samples at $z=0.2$ and 0.5. The model describes all three spectra to $k\sim0.2\,h\,{\rm Mpc}^{-1}$, with an electron linear bias $b_{e,1}\simeq0.92$, higher-order biases consistent with zero, and all parameters stable across feedback variants. Together with the near-perfect electron-matter correlation $r_{em}\simeq1$, this establishes free electrons as nearly unbiased, feedback-robust tracers of matter, supporting a key assumption of FRB-based feedback constraints. These properties make electron clustering an ideal application for Hybrid Effective Field Theory (HEFT), which would extend the modeling reach by a further factor of 2–3. The low-$z$ electron spectrum becomes signal-dominated beyond the linear regime within the first few years of next-generation surveys; the models developed here will be necessary on these timescales.
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Solar and Stellar Astrophysics

A Possible Stellar CME Event Associated with a Long-duration Optical Flare on the RS CVn-type Star UX Arietis

Cao Dongtao and Gu Shenghong

Coronal mass ejections (CMEs) are large-scale eruptions of magnetized plasma from stellar coronae, and they are always accompanied by flares. In this study, we present high-resolution spectroscopic observations of a long-duration optical flare on the RS CVn-type star UX Arietis (UX Ari). Around the flare peak, we have detected a far-blueshifted emission component in the H$\alpha$ line profile—a signature of an erupting prominence—indicating a possible stellar CME. After correcting for projection effects, the eruption velocity reaches $\sim -432$ km s$^{-1}$ when assuming radial propagation, significantly exceeding the escape velocity of the primary component ($\approx 304$ km s$^{-1}$). This strongly supports the detection of a stellar CME. The mass of this CME is at least $2.7 \times 10^{20}$ g, and its kinetic energy is $2.5 \times 10^{35}$ erg. The mass value is consistent with the solar flare–CME scaling relation, while its kinetic energy lies below the solar trend. The flare itself released an energy of $4.2 \times 10^{36}$ erg in the H$\alpha$, corresponding to a white-light bolometric energy of roughly $2.8 \times 10^{38}$ erg. Throughout the flaring event, evolving asymmetries in the H$\alpha$ profile reveal complex plasma dynamics.
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Instrumentation and Detectors

Spectacular - A Modular DAQ System for Microdosimetry

Matthias Knopf, Simon Waid, Daniel Radmanovac et al. (+8 more)

Particle therapy using light ions like protons, helium ions or carbon ions enables precise tumor targeting with enhanced biological effectiveness while minimizing damage to healthy tissue. Successful treatment planning depends not only on the absorbed dose but also on quality of the radiation, as quantified by the linear energy transfer (LET). Microdosimetry provides a direct experimental determination of such quantities by measuring the energy deposited per incoming particle in micrometer-sized solid-state detectors representing the relevant biological scales. However, the small signal amplitudes and high particle rates in therapeutic ion beams challenge existing readout systems, which are not sufficiently optimized for reliable operation with respect to pileup and signal-to-noise ratio (SNR). To address this, a modular data acquisition (DAQ) system was developed to accelerate the design of custom readout electronics and sensor characterization in microdosimetry and related spectroscopic applications. Centered around a Xilinx Zynq system-on-chip, it combines real-time processing, high-bandwidth streaming, and high-resolution digitization (16 bit at 100 MSas$^{-1}$) to enable advanced digital signal processing. The platform integrates programmable power supplies, a bias-voltage filter, test-pulse generators, and flexible I/O. Detector and preamplifier front-ends are hosted on interchangeable daugtherboards connected via a standardized interface, allowing different hardware configurations and readout algorithms to be evaluated on the same platform. The Spectacular DAQ system was successfully tested at the MedAustron ion therapy facility with custom charge-sensitive amplifiers and a diamond microdosimeter. First results demonstrate the feasibility and provide a proof-of-concept for potential future applications in clinical practice.
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All authors Matthias Knopf, Simon Waid, Daniel Radmanovac, Sebastian Onder, Richard Thalmeier, Peter Fischer, Stefan Gundacker, Claudio Verona, Edoardo Domenicone, Thomas Bergauer, Albert Hirtl

High Energy Astrophysical Phenomena

One year of broadband radio monitoring of the enigmatic transient GRB 250702B reveals the evolution of the relativistic jet

A. J. Goodwin, James C. A. Miller-Jones, Itai Sfaradi et al. (+18 more)

We present an extensive radio monitoring campaign of the unique extragalactic transient GRB 250702B, associated with unprecedentedly long duration gamma-ray emission, lasting over 3\,hr. Our observations span 0.65-233 GHz from 6-356 d (observer frame) post-discovery. The radio emission shows a smoothly evolving peaked synchrotron spectrum consistent with an adiabatic shock expanding into a stratified ambient medium ($n_e\propto R^{-k}$; $k= 1.5-2$). We detect significant variability in the low frequency ($\leq3$ GHz) light curves which we interpret as interstellar scintillation, placing an approximate bound on the blast wave image size of $1.2\times10^{16}\lesssim R_{\perp} \lesssim 5\times10^{17}$ cm. The temporal evolution of the flux density and critical synchrotron frequencies suggest the shock that powers the radio emission is potentially a wide-angle $\theta_j\gtrsim15$ deg, low Lorentz factor ($\Gamma\lesssim10$) jet, or a narrow $\theta_j\lesssim2$ deg highly relativistic jet. A narrow jet is expected for a stellar-mass black hole engine, such as a helium star merger, and the beaming-corrected kinetic energy in this scenario is consistent with the known distribution for long GRBs ($E_K\sim10^{51}$ erg). The wide-angle jet scenario would instead require a progenitor involving prolonged accretion. We derive and show an intermediate or stellar-mass black hole tidal disruption event are viable possibilities. The beaming-corrected kinetic energy in this scenario is on the low end of the known distribution for relativistic SMBH TDEs ($E_K\sim10^{50}$ erg). We disfavour an SMBH TDE due to lack of compatibility with the observed timescales. The detection of a jet shut off within the next year would favour a WD-IMBH TDE due to the shorter theoretical duration of super-Eddington accretion than the main-sequence TDE channels.
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All authors A. J. Goodwin, James C. A. Miller-Jones, Itai Sfaradi, Andrew Mummery, Raffaella Margutti, Tanmoy Laskar, K. D. Alexander, Yuhan Yao, Arvind Balasubramanian, G. C. Anupama, Edo Berger, Varun Bhalerao, Yvette Cendes, Ryan Chornock, C. T. Christy, D. Eappachen, Tarraneh Eftekhari, Miguel Pérez-Torres, Enrico Ramirez-Ruiz, D. K. Sahu, Sjoert van Velzen

Solar and Stellar Astrophysics

Investigating Possible Stellar Coronal Mass Ejections in M-type Dwarfs Using the CARMENES DR1 Spectra

Cao Dongtao and Gu Shenghong

Stellar coronal mass ejections (CMEs) have significant impacts on surrounding exoplanets and stellar evolution. For M-type dwarf stars, hosting close-in habitable zones, frequent and intense stellar CMEs may render their potentially habitable planets uninhabitable. In this study, we used the CARMENES DR1 spectra to investigate potential stellar CMEs in M-type dwarfs by analyzing asymmetric features of the H{\alpha} profiles. Through a comprehensive visual inspection, we identified 61 distinct asymmetric features in the H{\alpha} line profiles across 33 M-type dwarfs. These asymmetries were associated with increased emissions in several chromospheric activity lines, indicating likely connections to flare events. The velocities of these features remain below the escape velocities of the investigated stars, except for one case where an asymmetric feature's maximum velocity approaches the star's escape velocity. While stellar CMEs are one potential explanation, the observed features are also consistent with other flare-related plasma motions. The estimated moving plasma masses range from 10^15 to 10^19 g, with corresponding kinetic energies of 10^29–10^32 erg. Stars with asymmetric H{\alpha} profiles are generally associated with stronger surface-average magnetic field <B> and higher normalized X-ray luminosity log(L_X/L_bol). However, we find no significant correlation between the line asymmetry rate and either <B> or log(L_X/L_bol).
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Strongly Correlated Electrons

Fluctuations of topological charges in two-dimensional classical Heisenberg model through high-temperature and low-temperature expansions

Shan-Chang Tang

It is well known that KT transition in 2d XY model is driven by the binding and unbinding of topological defects, which can be characterized by the fluctuation of topological charges inside a region. We extend the idea into the 2d Heisenberg model and calculate the fluctuation through high-temperature and low-temperature expansion respectively. It is found that the fluctuation of topological charges is proportional to the area of the region at high temperatures while obeys the perimeter law at low temperatures.
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Strongly Correlated Electrons

Contrasting anisotropic electron-phonon-spin coupling in Fe$_{3}$GeTe$_{2}$ and Fe$_{5}$GeTe$_{2}$: A helicity-resolved Raman study

Smrutiranjan Mekap, Jyoti Saini, Andrzej Ptok et al. (+4 more)

Two-dimensional van der Waals ferromagnets Fe$_3$GeTe$ _2$ (F3GT) and Fe$_5$GeTe$_2$ (F5GT) exhibit pronounced magneto-optical responses, which open promising platforms for investigating the interplay among lattice, electronic, and magnetic degrees of freedom. Here, we present a comparative study of optical resonance-induced anisotropic electron-phonon coupling and its association with magnetic ordering in these systems using wavelength- and temperature-dependent helicity-resolved Raman spectroscopy. By resolving the doubly degenerate E modes under left- and right-circularly polarized excitations, we demonstrate that the temperature evolution of the chiral mode splitting ($\Delta f$) does not track the magnetization behavior, indicating that the helicity-dependent Raman response arises not solely from time-reversal symmetry breaking due to magnetic order, but also from spin-orbit-coupled electronic interactions. Notably, in F3GT, the out-of-plane magnetization indirectly governs the in-plane anisotropic electron-phonon coupling under optical resonance, whereas F5GT exhibits static anisotropic interactions. The Fano asymmetry parameter $1/q$ reveals mode- and temperature-dependent coupling strengths between phonons and the electronic continuum, with pronounced angular anisotropy in F3GT but isotropic behavior in F5GT— a consequence of its multiple Fe sites and enhanced interlayer hybridization in the latter. Our results demonstrate the role of crystal structure and magnetic anisotropy in shaping the anisotropically coupled electron-phonon-spin dynamics in these layered metallic ferromagnets, and highlight Fe$_n$GeTe$_2$ as a versatile platform for microscopic insight into chiral light-matter interactions in layered metallic ferromagnets.
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All authors Smrutiranjan Mekap, Jyoti Saini, Andrzej Ptok, Pawan Kumar Srivastava, Changgu Lee, Subhasis Ghosh, Anushree Roy

Chemical Physics

Negative Differential Capacitance from Composition-Dependent Stern Capacitance in a Binary Mixture

Yuki Uematsu

We develop a thermodynamic theory of electric double layers in binary liquid mixtures by allowing the Stern-layer capacitance to depend on the local solvent composition. This coupling produces an additional negative contribution to the inverse differential capacitance. As a result, the surface potential can become a nonmonotonic function of the surface charge density, leading to negative differential capacitance and a voltage-induced first-order transition between two electric-double-layer states. We determine the coexistence condition using a common-tangent construction for the surface-charge-controlled grand potential and obtain phase diagrams in terms of the Stern-capacitance contrast, surface charge density, bulk composition, and surface potential. We also compare the theory with capacitance data for tetrabutylammonium chloride in water/1-propanol mixtures, finding semi-quantitative agreement in the continuous-response regime. These results suggest that solvent exchange inside the Stern layer can strongly control the capacitance and interfacial phase behavior of binary mixtures.
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Quantum Physics

Factorization of Exclusive-Sum-Of-Products Expressions with Rectangle Covering to Reduce Quantum Circuit Cost

Audrey Hou, Lucia Zhang, Ali Al-Bayaty et al. (+1 more)

The implementation of quantum circuits is currently very expensive, especially due to the usage of large Toffoli gates. Therefore, it is critical to optimize circuit costs by factoring expressions as they become more complex. In the proposed algorithms to factor ESOP expressions, each product term is converted into a cell in a 2D matrix, and optimal factored AND/EXOR solutions are determined using Disjoint and Even-Odd Rectangle covering methods. Two Python programs implementing these algorithms were tested and evaluated using well-known benchmarks. The results showed that both the literal counts used in classical logic circuits as well as the Maslov cost used in quantum circuits was reduced by 20%-95% depending on expression size.
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All authors Audrey Hou, Lucia Zhang, Ali Al-Bayaty, Marek Perkowski

Astrophysics of Galaxies

The mass-dependent interplay of active galacitc nuclei and supernova feedback in shaping the $L_{\rm X}$–$T$ relation of early-type galaxies

Haojie Xia, Feng Yuan, Bocheng Zhu et al. (+4 more)

The observed X-ray luminosity–temperature ($L_{\rm X}$–$T$) relation of hot gas in early-type galaxies deviates significantly from the prediction of purely gravitational heating, providing a key constraint on non-gravitational processes such as supernova (SN) and active galactic nucleus (AGN) feedback. We investigate the physical origin of this relation using high-resolution 3D hydrodynamical simulations with the multiscale AGN-regulated cosmic ecosystem resolver in 3D (MACER3D) framework, which we applied to a dwarf elliptical, a massive elliptical, and a cluster-central galaxy. For comparison, we performed controlled simulations that included AGN winds and SN feedback in isolation, excluding cosmological inflow and environmental effects. The dominant regulation mechanism depends strongly on the halo mass. In the cluster-central case, neither AGN winds nor SN feedback alone can sufficiently suppress the gas density and $L_{\rm X}$. When both are included, their nonlinear coupling suppresses the X-ray emission, producing ($L_{\rm X}$, $T$) values below the observed relation; this discrepancy can be resolved by incorporating AGN jet feedback. In massive elliptical galaxies, the inclusion of AGN feedback brings the model predictions into broad agreement with the observed $L_{\rm X}$–$T$ relation, indicating that AGN feedback dominates SN feedback. At the low-mass end, dwarf galaxy models also follow the observed trend. In this regime, models with either SN or AGN feedback alone predict low $L_{\rm X}$. When both are included, AGN wind-driven transport of SN-enriched gas to intermediate radii enhances the metallicity and radiative cooling, thereby increasing $L_{\rm X}$. This coupled process establishes a fountain-like circulation, in which gas is repeatedly lifted and recycled within the galaxy.
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All authors Haojie Xia, Feng Yuan, Bocheng Zhu, Haoen Zhang, Tingfang Su, Aoyun He, Suoqing Ji

Quantum Physics

Characterizing pairwise swapping capabilities of dense coding channels

Abhishek Muhuri, Nirman Ganguly, Aditi Sen De et al. (+1 more)

We introduce a novel multipartite entanglement-assisted classical communication task, referred to as dense coding swapping, in which legitimate parties collaboratively swap the dense codeability from one communication channel to another through suitable joint unitary operations. Due to the dense coding (DC) exclusion principle, the scheme enhances the dense codeability of a target pair while simultaneously reducing it for a non-target branch in the network. This swapping capability has broader implications, as it may be viewed as a form of process swapping, distinct from resource swapping, while also providing a prevention measure when one of the receivers is compromised. We derive necessary and sufficient conditions, expressed in terms of the Schmidt coefficients, for three-qubit pure states to support DC swapping, while we obtain a sufficient criterion for mixed states using their Bloch correlation parameters. Furthermore, we identify the optimal two-qubit unitary operators capable of realizing the swapping of dense codeability between communication channels. We further examine the tolerance of these eligible states against both colored and white noise, demonstrating the resilience of the proposed task under environmental perturbations. We also show that multipartite states supporting DC swapping require only a small amount of genuine multipartite entanglement and that this requirement decreases with increasing system size.
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All authors Abhishek Muhuri, Nirman Ganguly, Aditi Sen De, Indranil Chakrabarty

Statistical Mechanics

Exact Resonances Are Not Sufficient for Phonon Energy Diffusion

Wei Lin, Yong Zhang and Hong Zhao

Multi-phonon resonance conditions underpin kinetic theories of phonon transport and lattice thermalization. We show that exact resonance matching, nonzero interaction coefficients, and network connectivity do not guarantee persistent energy diffusion. Symmetry-enforced balance relations drive exact-resonant collision currents to nonthermal zero-flux states, producing kinetic arrest from individual resonant sets to connected networks. Complete energy spreading is sustained by quasi-resonances. The thermodynamic and weak-nonlinearity limits do not commute: the leading kinetic behavior is recovered in the former, whereas at fixed finite size the thermalization time diverges through higher-order crossovers as the nonlinearity vanishes. Exact-resonance existence and connectivity are therefore kinematic, not sufficient dynamical, criteria for phonon energy diffusion.
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