Mesoscale and Nanoscale Physics
Daniel Erkensten, Katarzyna Sadecka, Marie-Christin Heißenbüttel et al. (+2 more)
Two-dimensional
magnetic semiconductors provide a unique platform for exploring the interplay between charge,
lattice,
spin, and light. The strong Coulomb interaction combined with long-range
magnetic order enables efficient coupling between
excitons and both
lattice vibrations and
spin excitations, thereby strongly influencing
exciton dynamics and transport in these materials. Here, we develop a microscopic many-body theory of
exciton–
phonon and
exciton–
magnon interactions in mono- and
bilayer CrSBr. We demonstrate that the quasi-one-dimensional character of
excitons in CrSBr gives rise to strongly anisotropic
exciton–
phonon and
exciton–
magnon scattering, resulting in direction-dependent
diffusion coefficients. Furthermore, we identify a distinct temperature dependence originating from one-
phonon and two-
magnon scattering processes, providing characteristic signatures of the underlying microscopic interactions. Our work establishes a microscopic framework for understanding
exciton transport in
magnetic van der Waals
semiconductors and provides guidance for future optical spectroscopy and
exciton transport experiments.
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All authors Daniel Erkensten, Katarzyna Sadecka, Marie-Christin Heißenbüttel, Thorsten Deilmann, Ermin Malic
High Energy Physics (Phenomenology)
Leptogenesis and Planck-scale black hole remnants in a Pati-Salam cosmology
Arnab Chaudhuri, Erdenebulgan Lkhagvadorj and Satyabrata Mahapatra
We study leptogenesis and Planck-scale remnant dark matter from
primordial black hole (PBH) evaporation in a minimal Pati-Salam cosmology, with the gauge
symmetry broken before inflation so that
magnetic monopoles are diluted away. A singlet inflaton with a near-inflection potential enhances the
curvature power spectrum on small scales, producing a narrow black hole population that briefly dominates the energy density. The Pati-Salam
embedding ties the right-handed
neutrino masses to the SU(2)_R breaking scale, and cosmological consistency forces both the scalar-sector Yukawa coupling and the heavy
neutrino mass well below that scale. Two regimes emerge, depending on whether the black holes are hot enough to emit the lightest right-handed
neutrino. Lighter PBHs drive non-thermal leptogenesis, while heavier ones require a thermal asymmetry and also affect it through
entropy dilution. If
quantum gravitational backreaction halts evaporation at the Planck scale, each PBH leaves a stable remnant whose present abundance scales as the inverse five-halves power of the initial mass. Suppressing remnants requires heavier black holes, but the lighter PBHs needed for non-thermal leptogenesis overproduce remnant dark matter. Thus, remnant dark matter and non-thermal leptogenesis are mutually exclusive. When the thermal contribution is included, a single initial PBH mass near 10^6 g accommodates the observed dark matter abundance, the heavy
neutrino mass required by the
baryon asymmetry, and the Pati-Salam breaking scale. The scenario predicts a
stochastic gravitational wave background from Poisson fluctuations of the black hole distribution, within reach of future experiments, alongside high-frequency graviton emission constrained by future measurements of the effective number of relativistic species.
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High Energy Astrophysical Phenomena
Core-collapse supernovae 2022prr, 2023ucy, and 2024ljc in the luminous infrared galaxy NGC 6745
K. K. Matilainen, E. Kankare, T. Nagao et al. (+19 more)
The core-collapse
supernovae (CCSNe) 2022prr, 2023ucy, and 2024ljc exploded within the central regions of the nearby luminous infrared
galaxy (LIRG) NGC6745. We present our follow-up data with the aim to characterise the spectrophotometric
evolution of these CCSNe, determine their host-
galaxy extinction, and to define their physical nature. The presented spectrophotometric data set covers the optical and near-infrared region for our three
supernovae (SNe). The data are analysed and compared to other hydrogen-rich CCSNe, and a host-
galaxy extinction value Av is derived based on broadband photometry for each of the targets. A spectral energy distribution (SED) for the host
galaxy is constructed, and a combination of different
galactic components are fitted to the SED to estimate the intrinsic CCSN rate and the age of the starburst of NGC6745. 2022prr is a SN2009ip-like event, whose light curve
evolution consists of two consecutive luminous events A and B with peak magnitudes of Mr = -14.8 and -18.3 mag, respectively. The high degree of V and R-band polarisation (P=2.8%) near maximum light suggests interaction with highly aspherical circumstellar material. The spectral
evolution of the SN is dominated by narrow Balmer emission lines, which have a complex
evolution over time. 2022prr joins the growing sample of SN2009ip-like events that show early `flash ionisation' features of CIII, NIII, and HeII. 2023ucy is found to be a normal Type IIP SN. However, 2024ljc is a rapidly evolving Type IIb SN with a post-maximum r-band decline of roughly 3.2 mag by +41 d whereas normal IIb SNe decline typically by 1.5+/-0.3 mag during the same timescale. While the events exploded in a LIRG, the SNe are obscured by only moderate V-band host extinctions ranging from 0 to 1 mag. Based on the SED modelling we estimate an age of the host starburst to be 40Myr, and the intrinsic CCSN rate to be 0.4+/-0.1 SN/year.
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All authors K. K. Matilainen, E. Kankare, T. Nagao, T. Reynolds, A. Efstathiou, S. Mattila, C. R. Angus, A. Reguitti, Y.-Z. Cai, M. Fraser, L. Galbany, M. González-Bañuelos, C. P. Gutiérrez, T. Kangas, T. L. Killestein, T. Kravtsov, P. Lundqvist, S. Moran, A. Pastorello, A. Popowicz, I. Salmaso, M. Stritzinger
Quantum Physics
Floquet physics from quantized light-matter interaction: geometric phases, gauge consistency, and entanglement
Beatriz Pérez-González, Sigmund Kohler and Mónica Benito
Floquet engineering and cavity
quantum electrodynamics represent two complementary descriptions of light-matter interaction, yet their precise connection beyond the small-coupling regime remains subtle. Here, by representing the cavity field in a large-
photon-number phase basis, we show that the time-dependent Schrödinger equation of a classically driven system emerges directly from the fully quantized problem, without replacing the field by a classical trajectory or assuming a mean-field decoupling. This establishes a one-to-one correspondence between quasienergies and
photon-sector-shifted
quantum energies, while providing a direct
quantum interpretation of the Floquet mean energy and Anandan phase. Because gauge invariance is exactly preserved at the level of the
quantum Hamiltonian, the
quantum-to-classical correspondence remains valid beyond perturbative and small-coupling regimes. We further show that light–matter
entanglement is encoded in matter–harmonic correlations of the corresponding Floquet mode, thus identifying a semiclassical limit in which Floquet physics emerges without requiring the
quantum field itself to approach a coherent classical state.
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Fluid Dynamics
A multi-scale approach for wall-bounded WCSPH–RANS simulations
Feng Wang, Nikolaus Adams and Xiangyu Hu
Achieving sufficient near-wall resolution remains challenging for wall-bounded
turbulence simulations using weakly compressible smoothed particle hydrodynamics (WCSPH), as local particle refinement imposes restrictive time-step requirements. This work proposes a multi-scale near-wall approach within the Reynolds-averaged Navier–Stokes (RANS) framework to improve near-wall predictions without refining the SPH particle distribution. A local one-dimensional sublayer solver based on the simplified steady $k$–$\omega$ equations is coupled with each wall-adjacent fluid particle. A local flow-rate constraint and a friction-velocity-based iteration scheme are developed to close and solve the sublayer system, while a two-way shear-stress coupling with local feedback improves consistency between the two scales. The proposed approach is evaluated using turbulent straight-channel flows over a wide range of Reynolds numbers and a wavy-channel flow involving separation and recirculation. The results demonstrate improved near-wall velocity, turbulent kinetic energy and friction-coefficient predictions, satisfactory convergence, and good agreement with reference solutions. In particular, the approach improves the convergence of near-wall predictions where conventional wall treatments struggle to provide consistent results, and agrees closely with reference solutions at Reynolds numbers as high as $8.0 \times 10^{7}$ without near-wall particle refinement. For separated flow, convergence comparable to that of locally refined finite-volume simulations is obtained using an approximately uniform particle distribution. These improvements are achieved with limited computational overhead, supporting the application of particle-based methods to engineering flows involving wall-bounded
turbulence.
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High Energy Astrophysical Phenomena
Beyond Disk Truncation: X-ray Reverberation Signatures of an Outflowing Corona
Ke Qin, Bei You, Adam Ingram et al. (+1 more)
The corona in black hole X-ray binaries (BHXRBs) is likely dynamic during outbursts. A mildly relativistic outflowing corona has been proposed to explain hard spectra, weak disk reflection, and the higher than expected polarization degree observed in the hard state of X-ray binaries. In this work, we investigate the spectral and timing effects of coronal
outflow using Monte Carlo radiative-transfer simulations. The model consists of a geometrically thin, optically thick truncated disk and an ellipsoidal corona with a prescribed bulk
outflow velocity. We calculate the Comptonized continuum, the disk reflection component, and the lag-frequency spectra for different
outflow velocities and disk truncation radii. We find that increasing the
outflow velocity reduces the reflection fraction through relativistic beaming, because fewer Comptonized
photons irradiate the disk. For $\beta \lesssim 0.5$, the high-frequency soft lag is only weakly affected by the
outflow velocity, whereas increasing the disk truncation radius shifts the zero-crossing frequency($\nu_0$) to substantially lower frequencies. Thus, timing properties can help distinguish the coronal-
outflow scenario from the disk-truncation scenario. We further apply the model to MAXI J1820+070 and find that its unusual $R-\Gamma$ anti-correlation during the plateau phase is qualitatively consistent with a contracting corona accompanied by increasing bulk velocity. Disk recession alone would predict the opposite
evolution of $\nu_0$ under the assumptions of our model. Future polarization calculations will provide an additional test of extended outflowing-corona models.
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All authors Ke Qin, Bei You, Adam Ingram, Barbara De Marco
Superconductivity
Universal Dzyaloshinski-Moriya interaction dictates pairing in unconventional superconductor families
Baishun Yang, Yida Chu, Xuelei Sui et al. (+3 more)
The collinear-
antiferromagnetic spin-fluctuation paradigm has long guided unconventional superconductivity research, yet fails to reconcile the noncollinear
spin phenomena observed across cuprates, iron-based
superconductors, and nickelates. Using extensive first-principles calculations and unbiased large-scale DMRG simulations, we show that Dzyaloshinski-Moriya interaction (DMI)-arising from local inversion-
symmetry breaking-is a common ingredient across these families. This DMI unifies hallmark observations in parent compounds-incommensurate orders,
spin-wave gaps, and noncollinear textures. Under hole doping, strong DMI drives
spin vortices to merge with pi-shifted hole stripes, forming hybrid
vortex-hole stripe phases. These phases stabilize charge order while supporting, not suppressing, superconductivity. By contrast, under electron doping, these
vortices pin holes and suppress long-range superconductivity. Our results establish DMI as a unifying link between noncollinear magnetism and superconductivity, identifying hole-strip-
vortex coupling as a microscopic pairing engine. Given that DMI is common across major
superconductor families, these findings challenge the prevailing pairing mechanism and offer an experimentally testable roadmap for materials optimization.
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All authors Baishun Yang, Yida Chu, Xuelei Sui, Haiqing Lin, Shijie Hu, Bing Huang
Optics
Symmetry Properties of Bound States in the Continuum in Hexagonal Lattice Photonic Crystal Slabs
Rhys Jones and Sang Soon Oh
Bound states in the continuum (BICs) within photonic
crystal (PhC) cavities realise the full confinement of light despite lying within the continuum of radiation modes. While their diverse practical applications has attracted considerable research interest, developing the fundamental understanding of BICs is important for the design of future devices. This paper uses a group theoretical approach to determine the basis functions of the irreducible representations (irreps) of a PhC with the
symmetry of the $C_{6v}$ space group, from which the spatial distribution of the electromagnetic fields within the cavity can be determined. Furthermore, the reflection parity of the electric field and a $k \cdot p$ perturbation theory approach are used to determine the far-field polarisation of each irrep. The $k \cdot p$ perturbation explains why the $E_2$ irrep has a topological charge of $-2$, as well as showing that a topological charge does not necessarily indicate the presence of a BIC. Additionally, it is found that the quality factor of the modes do not necessarily scale as $Q \propto 1/|k|^{2|q|}$, but are instead dependent on the coupling to the radiative mode in the $k \cdot p$ perturbation, which is determined from the
symmetry of each irrep.
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Superconductivity
Collective excitation-mediated transport in nanoscale Josephson junctions that exhibit quantum confinement
Zhengyuan Liu, Sebastian Scherb, Werner M.J. van Weerdenburg et al. (+3 more)
Quantum confinement can strongly modify transport through Josephson junctions. Here, we study local tunneling transport through nanoscale Josephson junction stacks in the Coulomb blockade regime, where the metallic layers exhibit strong vertical
quantum confinement. We find that quasiparticle transport is strongly enhanced by a collective excitation mode intrinsic to the junction and localized in the isolated metallic overlayer. We quantify both the collective-mode energy and the Coulomb gap and show that both exhibit strong layer-dependent modulation, consistent with the modulation of the underlying
quantum well states. We further investigate how the collective excitation responds to various perturbations, including mechanical motion and an applied
magnetic field. Our results suggest that this collective mode is sensitive to quasiparticles near the
Fermi level and may therefore provide an indirect probe of the superconducting state.
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All authors Zhengyuan Liu, Sebastian Scherb, Werner M.J. van Weerdenburg, Daniel Wegner, Nadine Hauptmann, Alexander A. Khajetoorians
Statistical Mechanics
Self-avoiding trails in two and three dimensions
Xiaodi Su, Zongzheng Zhou and Qianqian Wu
The self-avoiding trail is an important variant of the self-avoiding walk. In this work, we employ an irreversible Markov chain Monte Carlo
algorithm, together with the reversible Berretti-Sokal
algorithm for comparison, to simulate self-avoiding trails on the square and simple cubic
lattices with periodic boundary conditions. Based on finite-size analyses of the unwrapped end-to-end distance and the Binder ratio, we accurately estimate the critical points on the simple cubic and square
lattices to be 0.206\,376\,9(2) and 0.367\,561\,1(1), respectively, improving the precision of previous best estimates by factors of 500 and 70. At the estimated critical point of the simple cubic
lattice, we numerically demonstrate that both the critical scaling behaviors of various quantities and the length distributions of self-avoiding trails and walks are consistent with each other. Our accurate numerical results are attributed to the efficiency of the irreversible
algorithm, whose advantage over the reversible
algorithm is even more pronounced for the self-avoiding trail model than for the self-avoiding walk model.
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Earth and Planetary Astrophysics
Some challenges for the long-term survival of Naiad, Neptune's innermost moon
Harrison Agrusa, Matija Ćuk, David Nesvorný et al. (+1 more)
The Naiad-Thalassa 73:69 mean-motion resonance implies these moons have co-existed for $\gtrsim$1 Gyr, raising the question of how they survived to the present day. We examine three challenges to Naiad's long-term survival:
tidal disruption, heliocentric bombardment, and runaway collisional erosion by planetocentric debris. We constrain Naiad's internal strength requirements from its nominal density and shape, compute present-day impact rates on Neptune's inner moons from heliocentric bombardment, and use $N$-body simulations to model the fate of ejecta produced by non-disruptive impacts. First, Naiad's nominal density of ${\sim}0.8\text{ g cm}^{-3}$ and elongated shape suggest it cannot be held together by self-
gravity alone, implying a cohesive strength of $\gtrsim10$ kPa to avoid
tidal disruption, although this constraint is relaxed if Naiad has a higher density of ${\gtrsim}1.3\text{ g cm}^{-3}$. Second, we show that Naiad may have been disrupted in the last 1 Gyr by heliocentric bombardment, although this depends sensitively on the size-frequency distribution of Kuiper Belt objects at small sizes and on Naiad's catastrophic disruption threshold, both of which are poorly constrained. Third, and most notably, we find that even small, non-disruptive impacts can trigger runaway collisional erosion by planetocentric debris on extremely short timescales. Avoiding this “sesquinary catastrophe” requires that Naiad has a collisional strength of at least several MPa, which is difficult to reconcile with being a reaccumulated “rubble pile”, leftover from the capture of Triton and the subsequent cataclysm of Neptune's
primordial satellite system. Together, these results suggest that Naiad may be a physically unusual object among small ring-moons – possibly a largely coherent, monolithic fragment – and that our understanding of Neptune's inner satellite system leaves much to be explained.
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All authors Harrison Agrusa, Matija Ćuk, David Nesvorný, David Minton
High Energy Astrophysical Phenomena
X-ray polarization of the Compton-thin Seyfert galaxy NGC 5506 with IXPE
Daniele Tagliacozzo, Alessandro Leonardo Lai, Andrea Gnarini et al. (+14 more)
We report on the observation of the Compton-thin Seyfert
galaxy NGC~5506 performed with the Imaging X-ray Polarimetry Explorer (IXPE). The observation, with a net observing time of 975~ks, was partly simultaneous with NuSTAR (52~ks) and XMM-Newton (37~ks). Using a simple baseline model with IXPE data only, we find an upper limit on the 2–8~keV polarization fraction at the $99\%$ confidence level: $\Pi<3.1\%$. We then performed a spectropolarimetric analysis combining data from the three X-ray observatories. While pure spectral modeling confirms the presence of both relativistic and cold distant reflection, in addition to the primary continuum power law, their contributions lead to somewhat different constraints on the coronal $\Pi$, depending on the specific assumptions. We also performed Monte Carlo simulations with the radiative transfer code MONK, exploring various coronal geometries. Comparing these results with the IXPE data, and assuming a radially extended corona, as suggested by previous observations of similar sources, the corresponding polarization upper limits require inclination angles below 40{\deg}.
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All authors Daniele Tagliacozzo, Alessandro Leonardo Lai, Andrea Gnarini, Giorgio Matt, Stefano Bianchi, Francesco Ursini, Andrea Marinucci, Alessia Tortosa, Sudip Chakraborty, Federico Ferretti, Vittoria Elvezia Gianolli, Elias Kammoun, Frédéric Marin, Herman Marshall, Riccardo Middei, Romana Mikusincova, Dawoon Kim
High Energy Astrophysical Phenomena
COBALT-BLUE: a fast and accurate model for gravitational self-lensing binary systems
Danny J. Dixon, Adam Ingram, Matthew J. Middleton et al. (+5 more)
We present COBALT-BLUE, a fast public model for the optical light curve of a luminous
star in a non-accreting binary with a compact object. The model includes gravitational self-
lensing, Doppler beaming, ellipsoidal variations, eccentric orbital geometry, and wavelength-dependent limb darkening. In sufficiently edge-on systems, it predicts sharp periodic self-
lensing flares together with phase-locked orbital modulation outside the
flare. We improve upon earlier models by including non-linear limb darkening laws based on
stellar atmosphere simulations to calculate the self-
lensing flare profile. This enables light curves to be self-consistently calculated in multiple wavebands from one set of physical parameters, thus offering the prospect of constraining binary parameters such as compact object mass from photometry alone if multiple self-
lensing flares are observed. We also include the option to utilise simpler limb darkening prescriptions to save computational expense. As a proof of principle, we fit our model to ZTF data of 14 candidate self-
lensing sources. The model describes the
flare morphology well for most candidates, but we find that the best fitting parameters are not physically plausible. We conclude that the observed
flares are most likely
stellar flares and not self-
lensing events. In future, we plan to use the model to systematically search optical survey data for signatures of binary motion.
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All authors Danny J. Dixon, Adam Ingram, Matthew J. Middleton, Adam McMaster, Grzegorz Wiktorowicz, Hugh Dickinson, Allison Crossland, Eric C. Bellm
Earth and Planetary Astrophysics
Amit Reza, Ludmila Carone and Christiane Helling
With the rapid advancement of
telescopes like JWST and Ariel, there is an urgent need for efficient 3D
climate models to interpret observations of
exoplanet atmospheres. Traditional 3D general circulation models (GCMs) are computationally intensive, prompting the development of machine learning (ML) emulators to accelerate simulations. Recent work, such as that by Plaschzug et al. 2026 \cite{plaschzug2026accelerating}, uses a dense neural network (DNN) to predict local gas temperatures and winds from input parameters, including local gas pressure, spatial coordinates (longitude and latitude), and global temperature. However, this model relies on predicting individual temperature values (points) at specific grid points, which can be limited by the resolution and constraints of the training grid. In this work, we investigate a couple of alternative frameworks based on latent-space representations of local gas temperature ($\text{T}_{\text{gas}}$) to obtain a faithful, low-dimensional representation of these profiles. This represents the first step toward developing a latent space regression model, offering a structurally cohesive alternative to the existing point-wise prediction method \cite{plaschzug2026accelerating}. By capturing the optimal
embedding space of atmospheric data, our proposed framework can produce simulated profiles while maintaining computational efficiency, making it suitable for large-scale
exoplanet ensemble studies.
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Astrophysics of Galaxies
Morphology classification for galaxies in the Kilo Degree Survey using a label-efficient self-supervised learning framework
Xu Huang, Rui Li, Liang Gao et al. (+14 more)
Galaxy morphology classification is fundamental to understanding
galaxy formation and
evolution. The advent of large-scale sky surveys has produced an unprecedented volume of
galaxy images, making traditional manual classification impractical. Although supervised deep learning can achieve high accuracy, it requires large labeled
datasets that are time-consuming to construct. In contrast, unsupervised methods often show limited classification performance. To address this limitation, we propose a label-efficient self-supervised learning framework for
galaxy morphology classification. Our method first learns robust morphological representations from 305,583 unlabeled KiDS
galaxy images through contrastive learning, and then trains a classifier using only 5,000 human-labeled images. The classifier separates
galaxies into five categories: elliptical, spiral, lenticular-disk, irregular, and "other." Using a ResNet-50 model with a crop size of 64x64 pixels, our approach achieves an overall test accuracy of up to 91.0% (90.5% +/- 0.2% on average) on the human-classified catalog. The corresponding F1 scores for elliptical, spiral, irregular, lenticular-disk, and "other"
galaxies are 0.96, 0.86, 0.86, 0.95, and 0.92, respectively. We apply this pipeline to the Kilo-Degree Survey Data Release 5 and produce a publicly available morphology catalog of 310,583
galaxies. This is the first morphology catalog for KiDS
galaxies and provides a valuable resource for future studies of
galaxy evolution. Our results show that self-supervised learning can substantially reduce the need for manual labels while maintaining high classification accuracy, making it a promising and scalable approach for automated
galaxy morphology classification in the era of large-scale surveys.
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All authors Xu Huang, Rui Li, Liang Gao, Liqing Chen, Hui Li, Huijun Mu, Hao Su, Fucheng Zhong, Zhenping Yi, Xiaoyue Cao, Ran Li, Haicheng Feng, Nicola N. Napolitano, Yue Dong, Yida Deng, Sihan Li, Kang Jiao
Mathematical Physics · Cross-listed from math.RA
Restricted (Relative) Rota-Baxter operators on restricted Lie algebras and restricted Lie triple systems and related structures
Jon Beristain and Abdenacer Makhlouf
The main purpose of this paper is to define and study the notion of restricted Rota-Baxter operator on restricted Lie
algebras and restricted Lie triple systems. We provide the relevant properties and the usual connections with pre-Lie structures. We show that the operad of pre-Lie triple systems is the splitting of the operad of Lie triple systems. Moreover, we prove that Jacobson identities hold in pre-Lie triple systems in positive characteristic and then introduce the notion of restricted pre-Lie triple system.
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Biological Physics
Signature of mechanically induced cell extrusions in cell size distribution
Ali Tahaei and Marko Popović
How a growing tissue organizes its own homeostatic state is a central question in the physics of living matter. We show that when a growing epithelial sheet counteracts increasing
cell density by mechanically squeezing
cells out of its plane, a homeostatic in-plane pressure emerges as a generalization of a yield stress. We find that in the quasistatic growth limit the homeostatic state is marginally stable, with a pseudogap in the distribution of local distances to the extrusion threshold pressure. Because such mechanically induced extrusions arise from an instability of individual
cells, the pseudogap is imprinted in the distribution of
cell areas. This provides an image-based way to test for presence of mechanically induced extrusions and we identify this signature in the developing wing epithelium of D.~melanogaster. We expect the same principles to apply to confined three-dimensional tissues.
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Cosmology and Nongalactic Astrophysics
Lens Modeling and Cosmological Inference from an Impure Sample of Galaxy-Galaxy Strong Lenses
Philip Holloway, Aprajita Verma, Philip J. Marshall et al. (+7 more)
The start of the Legacy Survey of Space and Time marks a new era for strong
lensing science, where the number of strong lenses identified is expected to increase to $\mathcal{O}(10^5)$. In this paper we use a neural network to determine the precision with which lens parameters can be determined, using realistic simulated LSST lensed systems. We find that the Einstein radius can be measured with a mean precision of $3.7\%$ with calibrated uncertainties accurately reflecting the corresponding measurement error. Based on the performance of current strong lens classifiers, the $\sim 100,000$ detectable strong lenses are expected to be accompanied by a similar or larger number of false positives (non-lenses). In readiness for this we introduce a formalism, termed `
COSMIC-BEAMS', to infer cosmological parameters while accounting for contamination by false positives. As a proof-of-concept, using simulated LSST measurements of the Einstein radii of a realistic and impure sample of photometric lens systems, i.e. those without spectroscopic confirmation, we find that the cosmological parameters $\Omega_m$, $\Omega_\Lambda$, and $w$ can be measured to a precision of $0.1$, $0.03$ and $0.15$ respectively for a $w$CDM cosmology. We demonstrate that unbiased cosmological parameters can be inferred even in strong lens samples contaminated by $50\%$ false positives, and that the photometric
dataset of $100\,000$ strong lenses will provide equivalent $w$-precision to $2500-3500$ spectroscopic systems.
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All authors Philip Holloway, Aprajita Verma, Philip J. Marshall, Padmavathi Venkatraman, Sydney Erickson, Tian Li, Simon Birrer, Steven Dillmann, Thomas E. Collett, the LSST Dark Energy Science Collaboration
Instrumentation and Methods for Astrophysics
Bayesian classification of astronomical spectra with class uncertainties
Simon Barton, Martin Sahlén, Andreas Korn et al. (+1 more)
Context: We developed a probabilistic machine learning method with the aim of performing the O(10)-way classification of low- and high-resolution spectra of
stellar and extragalactic targets for the upcoming 4MOST survey. In fulfilment of the survey requirements, this method should be able to express uncertainty in the input data as well as uncertainty introduced in its prediction. Aims: Four different methods are explored: (1) convolutional neural networks (CNNs), (2) the Dirichlet distribution, (3) Monte Carlo dropout (MCD), (4)
Bayesian neural Networks (BNNs) + variational inference (VI). Training and validation was performed using labelled spectra from the SDSS database and a custom 4MOST mock
dataset. All the methods were compared in terms of the same metrics: accuracy, area under the curve (AUC), expected calibration error (ECE), Shannon
entropy, negative log-likelihood (NLL), Brier score, training time, and inference time. Methods: A CNN with simple architecture and about 20,000 parameters was trained to achieve classification accuracies of 91.5% on SDSS data and 92.8% on 4MOST mock data. The direct Dirichlet prediction and VI models tested provide uncertainties on class membership probabilities, but they confuse classes more often. The MCD on a CNN is found to be the most suitable; it boosts the point-estimate accuracies to 92.6% and 93.9%, while still providing fast training and sufficiently fast inference. Compared to a standard CNN, the method additionally provides well-calibrated uncertainties at marginal extra cost.
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All authors Simon Barton, Martin Sahlén, Andreas Korn, Christian Glaser
High Energy Physics (Theory)
BMS$_3$ modules from path integrals on the coadjoint orbits
Pujian Mao and Xin-Cheng Mao
In this paper, we provide a systematic construction of
quantum modules associated with coadjoint orbits of asymptotic
symmetry groups through the path integral quantization at one-loop order. In particular, for the orbits with
Hamiltonians unbounded from below, we show that an appropriate choice of integration contour defines a convergent Euclidean half-line path integral. The reference state associate with the orbit is determined by the path integral of the
geometric action on the corresponding coadjoint orbit. The coadjoint module is therefore spanned by the reference state and its descendants. We apply this formalism to the Virasoro and BMS$_3$ groups and derive the coadjoint modules corresponding to all constant orbits. We also compute the characters of all constant Virasoro and BMS$_3$ coadjoint orbits by counting the states within the modules, and the results agree with the corresponding computations from the path integral of the
geometric action with a periodic Euclidean direction.
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Materials Science
Adsorption of Phosgene Gas on Pristine and Noble Metal-Doped B12N12 Nanocages: Insights from Density Functional Theory
Shahariar Chowdhury, Mohammad Abdul Matin, Samiran Bhattacharjee et al. (+1 more)
This study examines phosgene (COCl2) adsorption on pristine and noble metal-doped (Ag, Au, Pd, Pt) B12N12 nanocages using dispersion-corrected density functional theory [B3LYP-D3(BJ)]. Boron-site substitution narrows the HOMO-LUMO gap far more than nitrogen-site substitution (69-82% vs 41-67%) and was adopted throughout. All systems were fully optimized; multiple starting geometries converged to two stable minima per dopant, X-O and X-Cl. Pristine B12N12 binds phosgene weakly (Eads = -12.8 to -24.9 kJ mol^-1). Doping strengthens binding, spanning -14.0 to -60.7 kJ mol^-1 after counterpoise correction, with platinum exhibiting the highest affinity and structural stability. Natural population analysis indicates phosgene donates at most 0.33 e, and QTAIM classifies all cage-adsorbate bond critical points as closed-shell or intermediate, confirming physisorption. Vibrational frequency analysis confirms all structures as true minima and reveals that the adsorption
entropy penalty (59-161 J mol^-1 K^-1) is decisive. Under Grimme's quasi-harmonic approximation, pristine cages fail to bind phosgene (Delta G = +23.8 to +27.9 kJ mol^-1), whereas only Pt-O (Delta G = -8.8 kJ mol^-1) and Pd-O (-7.2 kJ mol^-1) adsorb phosgene spontaneously at 298 K. Transition-state theory indicates rapid room-temperature recovery (tau = 43 ms for Pt-O), while thermodynamic desorption occurs at 69.6 deg C, ensuring a practical regeneration window. Silver-doped cages provide narrow post-adsorption gaps and high electrophilicity but cannot retain phosgene at ambient conditions. Platinum doping is therefore the most effective strategy for reversible phosgene detection using B12N12 nanocages.
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All authors Shahariar Chowdhury, Mohammad Abdul Matin, Samiran Bhattacharjee, Ishtiaque M. Syed
Computational Physics
Perspective on Magnetic Nanoparticle Modeling: Interactions, Timescales and Regimes
Deniz Mostarac, Andrey A. Kuznetsov, Manuel Wolfschwenger et al. (+7 more)
The response of
magnetic nanoparticles (MNPs) to applied
magnetic fields underpins a broad range of biomedical and technological applications. In this Perspective, we review the principal modeling approaches for describing MNP dynamics across different physical regimes, ranging from coarse-grained macrospin descriptions to spatially resolved micromagnetic simulations. Selecting an appropriate model depends on the relevant energy scales and timescales, including those associated with
magnetic anisotropy. We compare the assumptions, computational requirements, and regimes of applicability of the fixed-point-dipole, effective-field, thermal Stoner-Wohlfarth,
diffusion-jump, coupled Landau-Lifshitz-Gilbert, egg, and micromagnetic models. Particular
attention is given to coupling magnetization dynamics with translational and rotational particle motion, hydrodynamic interactions, and long-range dipolar interactions. By relating the relevant physical regimes to the resolution and computational cost of each approach, we provide practical guidance for model selection and outline challenges for predictive multiscale simulations of interacting MNP systems.
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All authors Deniz Mostarac, Andrey A. Kuznetsov, Manuel Wolfschwenger, Santiago Helbig, Claas Abert, Rudolf Weeber, Daniel Baumgarten, Patrick Ilg, Dieter Suess, Sofia Kantorovich
Mesoscale and Nanoscale Physics
Field-free and Sub-ns Magnetization Reversal in Synthetic Anti-ferromagnets using Sequential Spin-Orbit Torque and Spin-Transfer Torque Pulses
Subham Das and Naveen Sisodia
Single free-layer
Magnetic Tunnel Junctions (MTJs) with a perpendicular easy axis driven by
spin currents have demonstrated fast, deterministic switching, non-
volatility, and low-power
memory capabilities when integrated with modern nanoelectronic devices. In this article, we numerically investigate sub-ns and field-free switching characteristics of a p-MTJ with a Synthetic Antiferromagnet (SAF) based free layer structure using sequential sub-ns current pulses of
Spin Orbit Torque (SOT) and
Spin Transfer Torque (STT). While the SOT pulse applied to one layer decreases the transition time by bringing the coupled layers into an in-plane configuration, the subsequent STT pulse on the system determines the switching direction. Various pulse protocols have been investigated for both SOT and STT current amplitude and pulse widths, while also considering the effect of the Reference Layer (RL). While significant regions of deterministic switching events are observed, limitations in SOT, STT parameters are further investigated in presence of thermal fluctuations.
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Strongly Correlated Electrons
Orbital character and photoemission signatures of the A-pocket in infinite-layer nickelates
Leonard M. Verhoff, Michael Seidl, Liang Si et al. (+1 more)
The orbital character of the so-called $A$-pocket in infinite-layer nickelates remains under debate. We investigate bulk NdNiO$_2$ using density-functional theory combined with dynamical mean-field theory and identify the $A$-pocket as a strongly hybridized state with substantial interstitial-$s$, Nd-$d_{xy}$ and Ni-d_${xz/yz}$ contributions. Our angle-resolved photoemission spectroscopy simulations reproduce the main polarization-dependent features measured experimentally. Removing the interstitial-$s$
matrix element leads to a clear disagreement with the measured
Fermi surface maps, even though the interstitial-$s$ contribution is not dominant. Suppressing instead the Nd-d$_{xy}$ or Ni-$_{dxz/yz}$
matrix elements leaves the maps almost unchanged, because these are small at the zone corner. More generally, our results demonstrate that assigning the microscopic origin of spectral features in infinite-layer nickelates requires treating orbital hybridizations and photoemission
matrix elements together.
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All authors Leonard M. Verhoff, Michael Seidl, Liang Si, Karsten Held
Astrophysics of Galaxies
LenNet: Direct Detection and Localization of Strong Gravitational Lenses in Wide-Field Sky Survey Images
Pufan Liu, Hui Li, Ziqi Li et al. (+9 more)
Strong gravitational lenses are invaluable tools for addressing fundamental questions in astrophysics, from the nature of dark matter to the expansion of the universe. While current sky surveys have successfully identified thousands of lens candidates, the search methods employed face a critical challenge. The conventional approach relies on a "crop-and-classify" strategy, where small images are first cut out around billions of potential host
galaxies before being individually classified. This process creates a significant computational and storage bottleneck that is unsustainable for future large-scale surveys. To overcome this limitation, we propose LenNet, an object detection model that identifies lenses directly within large, original survey images. Our method completely bypasses the inefficient cropping step by framing the problem as a direct detection and localization task. We initially train LenNet on simulated data to learn the complex features of gravitational lenses and then use transfer learning to fine-tune the model on a limited set of real, labeled examples from the Kilo-Degree Survey (KiDS). Our experiments show that LenNet performs remarkably well on real survey data, validating its potential as a highly efficient and scalable solution for lens discovery in massive astronomical surveys.
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All authors Pufan Liu, Hui Li, Ziqi Li, Xiaoyue Cao, Rui Li, Hao Su, Ran Li, Nicola R. Napolitano, Léon V. E. Koopmans, Valerio Busillo, Crescenzo Tortora, Liang Gao
Instrumentation and Methods for Astrophysics
Identification of gravitational lenses obscured by foreground light in the KiDS dataset using U-Nets and ResNets
S. Liu, Rui Li, J. Jia et al. (+13 more)
*Context.* Many
lensing images are often obscured by foreground light from the central
galaxies, making them challenging to detect. *Aims.* To address the limitations of previous lens search efforts, particularly for samples with smaller $R_E$ or faint lensed images, we developed a composite convolutional neural network framework that utilizes both U-Net and ResNet architectures for feature extraction and classification. *Methods.* We propose a hybrid search method that combines U-Net and ResNet architectures to enhance the detection of foreground
galaxy-obscured lenses. Our approach consists of two main stages: first, the U-Net model separates the foreground
galaxy light from potential
lensing signals, creating residual images that highlight the
lensing features. Next, the ResNet module performs binary classification on these residual images to detect
lensing signals. *Results.* We evaluated the hybrid search method with real observational data to demonstrate its effectiveness, achieving a recall of 71.5% and a 4.5% false positive rate at a confidence threshold of 0.6. Applying this method to over 638,398
galaxy samples from the Kilo-Degree Survey Data Release 4 and conducting thorough inspections, we identify 88 Class A, 322 Class B, and 1,758 Class C candidates. *Conclusions.* This hybrid approach significantly enhances the completeness of existing strong gravitational
lensing searches and shows great potential for improving future astronomical surveys.
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All authors S. Liu, Rui Li, J. Jia, Hui Li, Liqing Chen, Xiaoyue Cao, Zizhao He, Valerio Busillo, Nicola N. Napolitano, Crescenzo Tortora, Fucheng Zhong, Hao Su, Haicheng Feng, Yue Dong, Ran Li, Liang Gao
Astrophysics of Galaxies
KiDS J1447-0149: The first spatially resolved spectroscopy of a relic galaxy beyond the local universe. An old high-dispersion core embedded in a compact rotating stellar structure
Johanna Hartke, Chiara Spiniello, Michele Cappellari et al. (+13 more)
Relic
galaxies are the descendants of high-
redshift compact quiescent systems. We present the first spatially resolved spectroscopic study of J1447-0149, a massive relic at $z=0.21$, observed with MUSE+AO. We characterize its kinematics and
stellar population properties to probe its spatially resolved mass assembly history. We measured
stellar kinematics with sub-kpc bin sizes, covering $\sim 1.4$ effective radii. We then used a coarser three-bin configuration informed by the kinematics to recover the higher-order velocity moments, $[\alpha/{\rm Fe}]$,
stellar age and
metallicity. We reconstructed the
star formation history and computed the degree of relicness (DoR). MUSE data reveal a velocity gradient, showing that J1447-0149 is not purely pressure supported. The velocity-dispersion field displays a central peak, reaching $\sigma_\star=233\pm13\,{\rm km\,s^{-1}}$, substantially larger than previous seeing-limited measurements ($\sigma_{\star} =187 \pm 9\,{\rm km\,s^{-1}}$). The $h_3$–$V_\star$ anti-correlation and mildly positive $h_4$ values support a composite structure, with a rotating
stellar component surrounding a compact dynamically hot core. This central, dispersion-dominated region is also the oldest and most metal-rich component. Its SFH rises rapidly, with the
stellar mass assembled within $\sim2\,{\rm Gyr}$ after the Big Bang, and reaches ${\rm DoR}=0.9^{+0.1}_{-0.2}$. The two outer bins have a DoR value of ${\rm DoR}=0.8\pm0.2$, consistent with the central bin, but possibly indicating slightly longer formation times. Spatially resolved spectroscopy has been crucial to confirm the relic nature of J1447-0149, linking resolved morphology, kinematics, and
stellar populations to constrain the early assembly of its central spheroid and surrounding disk.
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All authors Johanna Hartke, Chiara Spiniello, Michele Cappellari, Davide Bevacqua, Enrico Congiu, Anna Ferré-Mateu, Adriano Poci, Claudia Pulsoni, Magda Arnaboldi, Giuseppe D'Ago, Michalina Maksymowicz-Maciata, Paolo Saracco, Diana Scognamiglio, David A. Simon, Crescenzo Tortora, Petri Väisänen
Materials Science
Material chemical composition impacts on the band alignments: preliminary results on the 3D/2D perovskite interfaces
Philippe Baranek
While hybrid organic-inorganic halide perovskite
solar cells have achieved remarkable certified efficiencies, their widespread industrial and societal adoption is hindered by instabilities against light, heat, and moisture. A strategy to mitigate issues, such as moisture sensitivity, involves depositing 2D perovskites on 3D thin films for passivation, but their precise impact on
cell performance requires detailed understanding. This work employs atomistic first-principles simulation, based on hybrid functionals, to investigate the structural and electronic properties of 2D/3D interfaces. Specifically, it focuses on interfaces formed by (PEA)2PbI4 (PEA = C6H5CH2CH2NH3, as 2D perovskite) and complex 3D perovskites (Cs0.125MA0.14FA0.735Pb(I0.87Br0.13)3, with MA = CH3NH3 and FA = CH(NH2)2) which are ones of the most used perovskites. The approach is based on optimized hybrid functional methods to consistently determine work function (WF), electron affinity, and band offset (EBO) across different layers. Preliminary results demonstrate that WF are strongly dependent on the cleavage and chemical nature of the surfaces. Furthermore, the creation of interfaces significantly impacts macroscopic potential, with a noticeable slope linked to the polarization of the 3D materials due to ionic substitutions. The band
alignment is also highly sensitive to the termination and chemical nature of the perovskites, with valence and conduction EBOs varying from 0.2 to 0.7 eV and of approximately 0.25 eV, respectively. This ongoing work aims to provide a systematic description of these effects, with further investigation into the impact of dimensionality loss on perovskite stability.
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High Energy Astrophysical Phenomena
Wave-particle acceleration during supernova explosions
Zaza N. Osmanov and S.M. Mahajan
We investigate particle acceleration during the early stages of a
supernova explosion via a resonant interaction between electromagnetic waves and
quantum waves associated with particles. For typical progenitor masses of $(8; 12; 20)\times M_s$, we find that this mechanism can accelerate
protons to energies of up to $3\times 10^{14}$ eV. Interestingly, despite the continuously declining luminosity, the particle energy initially increases, reaches a maximum, and subsequently decreases, reflecting the characteristic behavior of the resonant acceleration mechanism.
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High Energy Physics (Experiment)
Axel Gallén, Sarah Ben Abdesselem, Giulia Ripellino et al. (+1 more)
A prospective search for dark
photons decaying into collimated, displaced
muon pairs is presented for the electron-positron stage of the Future Circular
Collider, FCC-ee. Assuming the full luminosity of the
Higgs run at 240 GeV, the study probes a broad range of dark
photon masses and couplings. The signature comprises two jets from a Z
boson decay and two
muon pairs from dark
photons produced in
Higgs decays. A kinematics-based selection achieves zero background while retaining high signal efficiency. Expected limits are set on the
Higgs boson branching ratio to dark
photons as a function of the dark
photon mass and coupling.
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All authors Axel Gallén, Sarah Ben Abdesselem, Giulia Ripellino, Rebeca Gonzalez Suarez