Astrophysics of Galaxies
A Decade-Scale Ionization Echo of Black-Hole Accretion in Galactic Nuclei
Wei-Jian Guo, Shuo Zhai, Chen Hu et al. (+16 more)
Circumnuclear structures in active
galactic nuclei respond to
accretion variability over different spatial and temporal scales, but whether compact narrow-line gas responds on decade timescales has not been systematically established. We use repeat Sloan Digital Sky Survey and Dark Energy Spectroscopic Instrument spectroscopy of 473 variability-selected
galactic nuclei with evidence for recent
nuclear brightening. We identify 19 sources whose narrow [O III] $\lambda5007$ flux increased by more than a factor of two over rest-frame baselines of 12.0-20.4 yr, which we term narrow-line ionization echoes (NIEs). In equal-weight stacked spectra, [O III] increased by $229\pm22\%$, while lower-ionization lines remained nearly unchanged or declined, indicating an ionization-dependent response rather than uniform spectral rescaling. The NIE hosts also moved coherently toward higher excitation in optical diagnostic diagrams, with mean increases of $0.46\pm0.18$ dex in $\log([\mathrm{O III}]/\mathrm{H}\beta)$ and $0.58\pm0.13$ dex in $\log([\mathrm{O III}]/[\mathrm{O II}])$. Photoionization models reproduce this
evolution with a higher ionization parameter and a harder AGN-like ionizing spectrum at fixed gas abundance. For 13 sources with well-defined mid-infrared outbursts, the integrated W1+W2 excess energy correlates strongly with the absolute [O III] luminosity change ($r=0.87$), linking the
dust and narrow-line responses to the same
nuclear event. The mid-infrared timescale and spectroscopic baseline constrain the variable [O III]-emitting gas to characteristic scales of 1.5-5.2 pc. Compact narrow-line gas therefore appears to form an intermediate, decade-scale response layer between the infrared
dust echo and the long-lived extended narrow-line region.
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All authors Wei-Jian Guo, Shuo Zhai, Chen Hu, David M. Alexander, Bin Luo, Pu Du, Matthew J. Temple, Leah K. Morabito, Feige Wang, Jinyi Yang, Victoria A. Fawcett, Swayamtrupta Panda, Claire L. Greenwell, Yan-Rong Li, Cheng Cheng, Shengxiu Sun, Zhi-Qiang Chen, Alessandro Marconi, Jian-Min Wang
Chemical Physics
General Time-Dependent Surface Flux for Multiple Ionization and Fragmentation of Molecules. I: General Theory
Stefanos Carlström and Serguei Patchkovskii
We introduce a method for efficiently computing multiple photofragmentation of atoms and molecules into photoelectrons and
nuclear fragments. The method is a generalization of the time-dependent surface flux originally introduced for single and double photoionization.
Solar and Stellar Astrophysics
Photometric and Spectroscopic Study of Young Stellar Objects in IC 1848E Region
Shubham Yadav, Neelam Panwar, Lalita Sharma et al. (+1 more)
We present a comprehensive analysis combining multi-epoch mid-infrared (MIR) photometric and optical spectroscopic observations of young
stellar candidates associated with elongated, elephant trunk-like structures (ETLSs) in the IC 1848E
star-forming region. A sample of 15 candidate YSOs, initially identified by Chauhan et al. (2011), was investigated using multi-epoch NEOWISE $W1$ and $W2$ photometry to characterize their variability properties. After imposing stringent positional and photometric quality constraints, a final set of eight robust YSOs was retained and classified into three variability categories: non-variable, secular, and
stochastic. One source,
Star #9, exhibits a pronounced curved variability in the MIR light-curve and color-magnitude domains, indicative of systematic
evolution of its circumstellar disk and/or
accretion processes. Optical spectroscopic data for this object show strong H$\alpha$ emission and prominent forbidden lines, providing clear evidence of active mass
accretion and
outflow phenomena. The combined photometric and spectroscopic diagnostics establish a close link between infrared variability, circumstellar disk
evolution, and
accretion-driven activity in YSOs associated with ETLSs in IC 1848E.
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All authors Shubham Yadav, Neelam Panwar, Lalita Sharma, C. Rishi
Quantum Physics
Quantum simulation of the Heisenberg XXZ model on a Rydberg atom array
Matthias Werner and Artur García-Sáez
A major application of analog
quantum hardware is
quantum simulation, where a system evolves over time according to a given
Hamiltonian. One challenge when implementing the
Hamiltonian on a programmable
quantum simulator is the availability of distinct coupling types, many of which go beyond the conventional ZZ-couplings found in Ising
Hamiltonians that are naturally implemented by various platforms. In prior work, we have developed a method based on domain wall encoding to simulate one-dimensional
spin chains using only Ising
Hamiltonians, which would otherwise require XX+YY-couplings as well. Here, we implement the method on a commercially accessible Rydberg atom
quantum device, and simulate the time
evolution of the Heisenberg XXZ model with various anisotropies. We successfully probe the XY and Ising phases of the model and reproduce the qualitative behavior of several one- and two-body observables in both phases, as well as at the critical point. Our work augments the toolbox to simulate canonical
quantum many-body systems on analog
quantum simulators.
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Mesoscale and Nanoscale Physics
Exciton switching and tunable exciton-phonon coupling in Oxygen doped ZnO nanorods
Aiswarya Rath, Kalyan Ghosh and Pratap K Sahoo
Self ion doping in ZnO nanorods offers a powerful route to dynamically control excitonic states and light matter interactions. Here, vertically aligned hexagonal ZnO nanorods were irradiated with 250 keV oxygen ions to establish a direct link between irradiation induced defects and excitonic and optical responses. Increasing ion fluence progressively quenches the near band edge emission at 380 nm, leading to a complete
exciton OFF state, while thermal annealing restores the emission, yielding a reversible
exciton OFF or ON response. This switching originates from defect mediated modification and thermal recovery of excitonic states. The defect band emission, between 400 to 750 nm, exhibits quasi periodic whispering gallery mode like resonances that are progressively suppressed as irradiation alters nanorod geometry and optical confinement. Low-temperature photoluminescence resolves D0X, FX 1LO, and FX 2LO transitions, whose temperature
evolution follows the Bose Einstein model. The non-monotonic variation of excition
phonon coupling strength reveals a competition among irradiation induced defects,
lattice distortion, and
exciton localization in determining
exciton phonon coupling. These results establish Oxygen ion irradiation as a means to simultaneously engineer excitonic switching,
exciton phonon interactions, and optical resonances, providing a pathway toward defect programmable ZnO nanophotonic and optoelectronic devices.
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Quantum Physics
Measurement-Efficient Differentiable Quantum Architecture Search for Combinatorial Optimization
Lukas Theißinger, Thore Gerlach and Christian Bauckhage
Differentiable
quantum architecture search (DQAS) is a promising framework for the automated design of
quantum circuits, particularly for variational
quantum optimization
algorithms. However, its practical deployment on
quantum hardware is limited by the large number of
circuit measurements required during optimization, making hardware execution costly. In this work, we show that for a broad class of combinatorial optimization problems and commonly used rotational gate parameterizations, the measurement cost of DQAS can be significantly reduced without changing the optimization objective. We derive the proposed measurement reduction scheme theoretically and validate it experimentally on 3-SAT and MaxCut
benchmark problems. Our approach reduces the requested gradient measurement cost by about 39 to 41% while introducing only negligible classical post-processing overhead, lowering the practical cost of executing DQAS on
quantum hardware.
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Lattice Field Theory
Finite-size scaling analysis of three dimensional Z(2) and O(2) spin models with non-vanishing symmetry breaking parameter
Jishnu Goswami, Frithjof Karsch and Sabarnya Mitra
We present results from a detailed finite-size scaling analysis of the $3$-$d$, $Z(2)$ and $O(2)$
spin models in an external field $H$. Using high statistics Monte Carlo data, we obtain the leading finite-size scaling correction to the infinite volume scaling functions. We show that these corrections are proportional to $\widetilde{z}_L^2=1/(H L^{3/(1+1/\delta))})^{2}$. This provides the parametric form for finite-size corrections to bulk thermodynamic observables as well as the pseudo-critical temperatures determined at non-vanishing $H$. In particular, it allows to eliminate systematic errors in the analysis of the
chiral phase transition temperature in (2+1)-
flavor QCD, that arose from the previously not well-controlled ansatz for infinite volume extrapolations. We also establish the validity range of this leading order correction and point out that there are significant differences between the $3$-$d$, $O(2)$ and $Z(2)$ universality classes.
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High Energy Physics (Theory)
Maximally symmetric black holes with torsion in Lovelock gravity
B. Cvetković and D. Simić
We analyze the existence of static black hole solutions with maximally symmetric horizons and nontrivial torsion in five-dimensional Lovelock
gravity. For each
symmetry class, we obtain a black hole solution characterized by two independent constants. We also determine the conserved charges associated with these solutions.
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Quantum Physics
Binary Optimization of Measurement Groupings for Quantum Energy Estimation
Isaac L. Huidobro-Meezs and Rodrigo A. Vargas-Hernández
Repeated measurements can dominate the resources required for
quantum energy estimation, making the choice of which Pauli observables to measure together a central optimization problem for variational
quantum algorithms. We formulate fully commuting measurement grouping as a classical binary optimization problem based on clique selection and construct non-overlapping groups using mixed-integer linear programming (MILP). For a
benchmark of molecular
Hamiltonians, groupings optimized with approximate covariances reduce the non-overlapping measurement requirement $\varepsilon^2M$ by $51.8\%$ on average relative to sorted insertion (SI). Using the MILP groups to initialize iterative coefficient splitting (ICS), denoted MILP-ICS, yields an average $24.3\%$ reduction relative to ICS initialized from SI (SI-ICS). The optimized groups also transfer across nearby molecular geometries while preserving substantial measurement savings. We further introduce O-clique, which directly optimizes overlapping commuting supports through candidate-clique selection and coefficient profiles. Although O-clique provides only modest additional reductions beyond MILP-ICS, it reduces the measurement requirement by $27.3\%$ on average relative to SI-ICS with 100 iterations, despite using only five final coefficient refinement iterations, indicating improved support quality. Finally, we extend the comparison to
Fermi–Hubbard, Kitaev–Heisenberg–$\Gamma$, and XYZ
lattice Hamiltonians, where MILP-based groupings substantially outperform the corresponding SI-based strategies. Together, these results show that variance-informed optimization of measurement-group structure can substantially reduce sampling costs across molecular and
lattice Hamiltonians, with optimized non-overlapping groups providing strong, transferable initializations and direct overlapping optimization offering further gains.
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Astrophysics of Galaxies
Changing-look Active Galactic Nuclei from the Dark Energy Spectroscopic Instrument. VII. Testing Disk-Corona Diagnostics with eROSITA
Wei-Jian Guo, Shuo Zhai, Zhu-Heng Yao et al. (+3 more)
Changing-look active
galactic nuclei (CL-AGN) have been proposed to follow an X-ray-binary-like, V-shaped relation between the optical/ultraviolet-to-X-ray spectral slope, $\alpha_{\rm OX}$, and the Eddington ratio, $\lambda_{\rm Edd}\equiv L_{\rm bol}/L_{\rm Edd}$. We test this interpretation using CL-AGN selected from the Dark Energy Spectroscopic Instrument (DESI) and control samples matched to the eROSITA all-sky survey (eRASS). We find that the apparent positive correlation between $\alpha_{\rm OX}$ and the optical-continuum-based Eddington ratio, $\lambda_{\rm Edd,opt}$, is not unique to CL-AGN, but also appears in matched non-changing-look samples. In broad-H$\alpha$ AGN, our main statistical sample, this structure is largely driven by the known dependence of $\alpha_{\rm OX}$ on ultraviolet luminosity and by the covariance between the rest-frame 2500 Angstrom luminosity, $L_{2500}$, the black-hole mass, $M_{\rm BH}$, and $\lambda_{\rm Edd,opt}$. When an X-ray-based Eddington ratio is used instead, the relation reverses sign because the X-ray luminosity, $L_X$, enters the two axes with opposite signs. An apparent $\alpha_{\rm OX}$-Eddington-ratio V-shape can therefore be induced by the luminosity
estimator and is not a standalone
accretion-state diagnostic. As a complementary test, we examine the eRASS effective
photon index, $\Gamma_{\rm eff}$, inferred from catalogue band fluxes. In broad-line AGN, it shows a weak positive association with the X-ray-independent optical Eddington ratio. However, the weaker hard-band trend depends on the null model and does not isolate coronal softening. These results motivate further X-ray spectroscopy, combined with independently estimated Eddington ratios, to test for intrinsic changes in the disk-corona system.
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All authors Wei-Jian Guo, Shuo Zhai, Zhu-Heng Yao, Huaqing Cheng, Jingwei Hu, Jun-Jie Jin
Instrumentation and Detectors
Neural network-based timewalk correction for the Timepix4 ASIC
David Bacher, Kazu Akiba, Martin van Beuzekom et al. (+7 more)
Timewalk corrections of hybrid pixel detectors conventionally employ heuristic fits performed independently in bins of the relevant input variables. This requires both an explicit functional ansatz and binning scheme, as well as densely populated calibration data whose required size grows rapidly as further input variables are added. This paper presents a timewalk correction for the Timepix4 readout chip based on a compact feed-forward neural network (NN), which learns the dependence directly from the input variables without requiring an explicit functional ansatz or binning. The NN is compared against the fit-based baseline using data from the Timepix4 beam
telescope at the CERN SPS in 2025, with $100\,\mathrm{\mu m}$ and $300\,\mathrm{\mu m}$ thick planar sensors. Both methods parameterise the timewalk correction as a function of the measured charge and reconstructed intrapixel impact position. With only 20 % of the calibration data, the NN already achieves the same asymptotic time resolutions as the fit-based baseline: $180\,\mathrm{ps}$ and $300\,\mathrm{ps}$ for the two thicknesses, respectively.
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All authors David Bacher, Kazu Akiba, Martin van Beuzekom, Victor Coco, Raphael Dumps, Tim Evans, Kevin Heijhoff, Malcolm John, Edgar Lemos Cid, Tommaso Pajero
Chemical Physics
LLM-Assisted Generation of Transparent, Open-Source Multiphysics Models of Electrochemical Devices
Sebastian Castro, Maya F. Schuchert, Spencer A. McCluskey et al. (+2 more)
Multiphysics continuum models are powerful tools for studying electrochemical devices, enabling in silico reactor design and resolution of local pH, potential, and concentration fields that govern device performance but are difficult to measure experimentally. However, constructing such models requires substantial numerical expertise or reliance on proprietary software. Here, we show that frontier large
language model
agents can remove this implementation burden while keeping the underlying physics under researcher control. Using one-dimensional electrochemical CO2 reduction to CO in a porous gas
diffusion electrode as a test case, we develop a machine-readable, human-specified modeling harness containing governing equations, parameters, numerical methods, logical build stages, and human-verifiable checkpoints. From this specification, the
agent reproducibly constructs complete multiphysics models in open-source Julia. Independently built models, including fully autonomous
agent-built models, agree with an equivalent COMSOL implementation to within 0.7% of the peak CO partial current density, and with one another to within 0.04%. Systematically planted errors demonstrate the importance of explicit specifications for reproducibility and reveal the
agent's capabilities and limitations in debugging model physics. This framework establishes a more transparent approach to multiphysics modeling in which physical descriptions and governing equations, rather than specialized code, become the primary inputs for computational model development.
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All authors Sebastian Castro, Maya F. Schuchert, Spencer A. McCluskey, Eric W. Lees, Justin C. Bui
Fluid Dynamics · Cross-listed from cs.LG
PoreML: A Data-Driven Framework for Learning Multiphase Flow in Porous Media
Chunyang Wang, Mingrui Zhang, Yuyan Zhang et al. (+5 more)
Multiphase flow in porous microstructures is central to CO$_2$ storage, fuel-
cell operation, and flip-chip packaging. Predicting these flows remains challenging because wettability and complex pore geometry govern the nonlinear
evolution of fluid interfaces. Machine learning holds substantial promise for advancing the field, but progress is constrained by scarce time-resolved 3D
datasets and a lack of a unified workflow for training and evaluating models. To fill this critical gap, we introduce PoreML, an open-source framework unifying data generation, model training, and evaluation grounded in pore-scale physics. The framework comprises three core components. (a) A modern GPU-native
lattice Boltzmann solver, validated against analytical solutions and published experiments, enables reproducible data generation. (b) A 3.3 TB
dataset contains 560 simulation runs and 158,546 stored time steps across four application-driven scenarios. These trajectories span synthetic structures and geometries derived from micro-CT scans of real materials, covering diverse wetting conditions and viscosity ratios. (c) A unified learning framework evaluates one-step prediction and autoregressive rollouts. Its domain-specific evaluation protocols assess predictive accuracy and physical consistency. We evaluate five models of diverse architecture under these protocols. Two complementary challenges assess transfer to larger domains and from synthetic to micro-CT-derived structures. PoreML provides a shared foundation for machine-learning research on multiphase flow in porous media, with the aim of empowering the community to develop reliable predictive models and advance the field.
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All authors Chunyang Wang, Mingrui Zhang, Yuyan Zhang, Linqi Zhu, Xin Ju, Edo Sicco Boek, Martin J. Blunt, Gege Wen
Optics
Visibility function and Stokes parameter analysis for non-ideal quarter-wave plates in a polarization contrast scheme
Stepan Kupavskii, Roman Malikov, Sergey Dyakov et al. (+6 more)
The match of the fourth power of the normalized third Stokes parameter for a single non-ideal quarter-wave plate (QWP) and the visibility function of the polarization contrast measured using a polarimetric setup with parallel polarizers and two identical QWPs was examined and observed. The behavior of the Stokes parameters of a single QWP and the visibility function of the polarization contrast scheme were investigated theoretically using the
Fourier-modal method (FMM) and described within the Jones
matrix formalism. This analysis was then generalized to a realistic case, accounting for the transmission anisotropy, phase deviation, and misalignment of optical components from their ideal orientations. An analytical expression for the visibility function of the polarization contrast scheme in terms of the normalized Stokes parameters was derived, along with the asymptotic expansions in terms of small parameters representing the phase deviation, transmission anisotropy, and angular misalignment of the polarization contrast scheme. For the investigated silicon-grating-based QWP, good quantitative agreement between the FMM-calculated fourth power of the normalized third Stokes parameter, and the visibility function (FMM-calculated and experimentally measured) was demonstrated over almost the entire investigated frequency range of 200-700 GHz.
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All authors Stepan Kupavskii, Roman Malikov, Sergey Dyakov, Sergei Tikhodeev, Arseniy Gavrilov, Kirill Dzhikirba, Sofya Andreeva, Igor Kukushkin, Nikolay Gippius
Solar and Stellar Astrophysics
ROSE (Red-giant Oscillations Spectra Estimator): A Modular Machine-Learning Framework for Automated Asteroseismic Characterisation. I. $\nu_{\max}$ and $\Delta\nu$ from TESS
Nipun Ghanghas, Dinil B. Palakkatharappil, Rafael A. Garcia et al. (+1 more)
Space-based photometry from Kepler and TESS has delivered oscillation spectra for hundreds of thousands of red
giants, and PLATO and the Roman
Galactic Bulge Time-Domain Survey will add more. We present ROSE, a modular machine-learning framework for automated asteroseismic characterisation of red
giants, and apply two of its modules to the frequency of maximum oscillation power, $\nu_{\rm max}$, and the large frequency separation, $\Delta\nu$. Each module is a neural network bundled with its own preprocessing transform and output binning, so that each parameter is measured in the representation that displays it most effectively: $\nu_{\rm max}$ from the power-density spectrum, and $\Delta\nu$ from the power spectrum of the power spectrum taken over a window centred on $\nu_{\rm max}$. Both are trained only on synthetic spectra generated at a one-year baseline and both return probability distributions rather than point estimates. This enables us to retrieve asymmetric uncertainty and a reliability index. Validating against held-out synthetic spectra, Kepler spectra at the training resolution and TESS continuous-viewing-zone
giants, we obtain robust dispersions of 1.4, 3.3 and 4.4% in $\nu_{\rm max}$ and 0.35, 0.61 and 1.3% in $\Delta\nu$, with the $\nu_{\rm max}$ uncertainties close to their nominal coverage. The fully automated pipeline was applied to 274,721 TESS red-
giant candidates observed for at least ten sectors, the framework returning reliable $\nu_{\rm max}$ for 56,224
stars and reliable $\Delta\nu$ for 39,939, taking 8 ms per
star. The sample follows $\Delta\nu = 0.278 \nu_{\rm max}^{0.757}$ with a scatter of 6.2%, and the red-clump phase stands out as a distinct overdensity, although neither module is provided an evolutionary label or asked to produce one.
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All authors Nipun Ghanghas, Dinil B. Palakkatharappil, Rafael A. Garcia, Shravan Hanasoge
Earth and Planetary Astrophysics
Two Low-Mass-Ratio Microlensing Planets from High-Magnification Events: KMT-2021-BLG-0247 and MOA-2023-BLG-169
Kansuke Nunota, Andrew Gould, Takahiro Sumi et al. (+56 more)
We present an analysis of two planetary microlensing events, KMT-2021-BLG-0247 and MOA-2023-BLG-169, both of which exhibit high magnifications and low
planet–host mass ratios, but with markedly different levels of parameter constraint. For KMT-2021-BLG-0247, the finite-source effect and microlens parallax are both clearly detected, leading to unusually tight constraints on the physical properties of the lens system. The host mass and lens distance are approximately $M_{\rm L}=0.9\pm0.1\,M_\odot$ and $D_{\rm L}=6.7^{+1.0}_{-0.3}\,\mathrm{kpc}$, respectively, and the
planet mass is $M_{\rm p}=41\pm5\,M_\oplus$. The projected
planet–host separations are $a_\perp=3.4^{+0.7}_{-0.3}\,\mathrm{au}$ and $3.0^{+0.6}_{-0.3}\,\mathrm{au}$ for the wide and close solutions, respectively. In contrast, MOA-2023-BLG-169 involves an extremely faint source, with $I_{S,{\rm OGLE}}=26.73$, such that the light curve permits a broad family of strongly correlated solutions. We therefore construct the physical-parameter likelihood using approximate invariant combinations of the light-curve parameters and supplement it with post-event Euclid/VIS imaging from the Euclid Q2
Galactic Bulge Survey (Beaulieu et al. 2026). The Euclid data reveal a component at the event position with ${\rm VIS}_{\rm AB}=23.05\pm0.09\,{\rm mag}$. Interpreting this component as the combined light from the source and any luminous lens, the resulting posterior gives $M_{\rm L}=0.48^{+0.23}_{-0.17}\,M_\odot$, $D_{\rm L}=3.50^{+2.82}_{-1.20}\,\mathrm{kpc}$, $a_\perp=1.62^{+0.77}_{-0.43}\,\mathrm{au}$, and $M_{\rm p}=143^{+103}_{-63}\,M_\oplus$. MOA-2023-BLG-169 demonstrates that, for an extreme faint-source event, even the event timescale and angular Einstein radius can remain strongly dependent on the
Galactic prior and independent flux constraints.
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All authors Kansuke Nunota, Andrew Gould, Takahiro Sumi, Ian A. Bond, Jennifer C. Yee, Valerio Bozza, Fumio Abe, David P. Bennett, Aparna Bhattacharya, Kotaro Daimon, Ryusei Hamada, Yuki Hirao, Takuto Inoue, Stela Ishitani Silva, Shuma Makida, Shota Miyazaki, Yasushi Muraki, Seiya Nakayama, Ryo Ogawa, Ryunosuke Oishi, Greg Olmschenk, Hideaki Ose, Clément Ranc, Nicholas J. Rattenbury, Yuki K. Satoh, Daisuke Suzuki, Takuto Tamaoki, Sean K. Terry, Paul J. Tristram, Chihiro Ueda, Aikaterini Vandorou, Hibiki Yama, Michael D. Albrow, Sun-Ju Chung, Cheongho Han, Kyu-Ha Hwang, Youn Kil Jung, Yoon-Hyun Ryu, In-Gu Shin, Yossi Shvartzvald, Hongjing Yang, Weicheng Zang, Dong-Jin Kim, Chung-Uk Lee, Byeong-Gon Park, Andrzej Udalski, Przemek Mróz, Radosław Poleski, Jan Skowron, Michał K. Szymański, Igor Soszyński, Paweł Pietrukowicz, Szymon Kozłowski, Krzysztof Ulaczyk, Krzysztof A. Rybicki, Patryk Iwanek, Marcin Wrona, Mariusz Gromadzki, Mateusz J. Mróz
Fluid Dynamics
Steady translation of a chemically active viscous drop along a rigid wall
Nikhil Desai and Sébastien Michelin
Chemically active drops release a chemical solute, gradients in whose concentration cause interfacial flows that advect the emitted solute. This non-linear coupling between solute distribution and fluid flow causes the drop to swim via an advective instability, if the system's Peclet number Pe–ratio of advective-to-diffusive solute transport–is larger than a finite threshold. Theoretical analyses often model active drops as diffusiophoresis-driven active particles, primarily to simplify the implementation of boundary conditions at the drop surface. However, physical insights about drop motion that rely on this simplification risk having limited applicability to fluid drops, especially when the drop is interacting chemo-hydrodynamically with its environment. Towards this, we study here the translation of a chemically active viscous drop parallel to a rigid wall, as an example of a common experimental configuration. We consider a propulsion mechanism where the drop swims due to interfacial Marangoni stresses and diffusiophoretic flows, and compare our results to those of the ”isotropic active particle” model, to examine the validity of the latter. Our analysis shows that, for the same confining force, a less viscous drop swims closer to the wall than a more viscous drop. This results in faster swimming, due to stronger concentration gradients driving the drop's motion. It is also shown that for moderate Pe, the swimming speed of the drop depends weakly on its mobility ratio (relative strength of diffusiophoretic and Marangoni flows). This weak dependence provides a quantitative justification for studying diffusiophoresis-driven active particles to infer the motion of Marangoni-stress-driven active drops.
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Chemical Physics · Cross-listed from cs.LG
Physics-Aligned Electronic Ground-State Learning Improves Generalization
Eike S. Eberhard, Xaver Kainz, Viktor Kotsev et al. (+2 more)
Machine-learned interatomic potentials (MLIPs) excel at in-distribution tasks, accelerating drug and material development, yet they struggle to generalize out-of-distribution. We propose to push the cost-accuracy Pareto frontier by designing observable-agnostic electronic ground-state descriptor models (GSMs) with computational costs situated between MLIPs and Kohn-Sham density functional theory (KS-DFT). We align the learning objectives and architectures of GSMs with the governing equations of KS-DFT by enforcing physical constraints and removing optimization pressure on unphysical or irrelevant degrees of freedom. In our size-extrapolation experiments from QM9 to QM40, our combined contributions OrthoNormal-Loss (ON-Loss) and Grassmann Restricted Occupied-Orbital Training (GROOT) reach a 79.1% energy and 83.4% force mean absolute error (MAE) reduction over previous state-of-the-art density GSMs. For
Hamiltonian GSMs, ON-Loss and Residual Optimal-gauge Conditioning-aware KS-Eq. Training (ROCKET) together reduce the energy and force MAEs of the strongest baseline by 99.8% and 95.9%, respectively. Using a self-consistency rejection criterion, we filter out extrapolation errors on QMugs, rejecting fewer than 0.4% of predictions while reaching an energy MAE of 0.07 mHa. Finally, we demonstrate the efficiency of label-free self-consistency fine-tuning, and transfer GSMs to reactive chemistry in Transition1x, reaching energy errors below chemical accuracy.
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All authors Eike S. Eberhard, Xaver Kainz, Viktor Kotsev, Abdulrahman Aldossary, Stephan Günnemann
Optics
Sub-shot-noise mid-infrared photothermal measurements using twin beams
Kazuki Hashimoto and Takuro Ideguchi
Mid-infrared photothermal (MIP) measurement probes refractive-index changes induced by mid-infrared (MIR) absorption using visible or near-infrared light and has recently emerged as a powerful modality for MIR spectro-imaging in the life sciences. Reducing measurement noise allows the probe power to be lowered without compromising the signal-to-noise ratio (SNR), thereby mitigating the risk of sample damage. However, even in the absence of classical noise, the SNR of conventional MIP measurements using a classical coherent probe is fundamentally limited by shot noise. Here, we demonstrate sub-shot-noise MIP measurement using twin beams generated through seeded optical parametric amplification. Balanced detection of the twin beams suppresses the noise by more than 5 dB below the shot-noise level established using a coherent beam. As a proof-of-principle demonstration, we measure the MIP signal from
liquid water using balanced twin-beam detection and achieve an SNR enhancement of more than 2 dB over the balanced coherent-beam detection.
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Optics
Thermal Holography with Nonlocal Metasurfaces
Mingze He, Lin Jing, Michele Guizzardi et al. (+7 more)
Thermal radiation and luminescence are among the most ubiquitous sources of light, yet their properties are difficult to engineer due to their incoherent nature. Recent advances in thermal emission control have endowed heat-generated light with spatial and temporal coherence, as well as control over its polarization, by judiciously patterning periodic arrays of nanostructures. However, custom wavefront engineering of incoherent light has remained an open challenge, as it requires not only sufficient spatial and temporal coherence but also arbitrary local phase control, which experimentally translates into sustaining long-range
lattice resonances in aperiodic systems while maintaining their robustness against local phase perturbations. In this work, we address this longstanding limitation and demonstrate programmable vectorial control over the thermal emission wavefront from single-layer aperiodic nonlocal metasurfaces, realized by manipulating local
geometric phases across a collective delocalized resonance. We exemplify the wavefront-shaping capabilities of our approach by demonstrating thermal beam steering,
spin-momentum-locked thermal focusing and the generation of a thermal vectorial hologram, providing custom spatial and spectral control over thermal light. Our platform addresses challenges in thermal emission engineering and provides a route for light generation and control without the need for external coherent sources or bulky setups. Future work may extend this design principle to other incoherent emission systems, such as photo- and electroluminescence.
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All authors Mingze He, Lin Jing, Michele Guizzardi, Shixiong Yin, Martina Riva, Yajun Gao, Shuwei Guo, Adam C. Overvig, Sander A. Mann, Andrea Alù
High Energy Physics (Phenomenology)
An effective macroscopic description of early-stage chemical equilibration in high-energy heavy-ion collisions
Anar Akbarov, Hendrik Roch and Chun Shen
The early stage of high-energy heavy-ion collisions undergoes transient dynamics, evolving non-perturbatively from a
gluon-rich to a chemically equilibrated
quark-
gluon plasma. We develop an effective hydrodynamic approach that casts the microscopic
quark equilibration dynamics as the relaxation
evolution of an effective macroscopic bulk viscous pressure. The
evolution of this effective bulk viscous pressure captures
quark chemical equilibration and the breaking of conformal
symmetry, thereby providing a smooth onset of the
lattice QCD equation of state after a few fm/$c$ in the hydrodynamic
evolution. We investigate phenomenological effects of this macroscopic description on final-state observables in $\mathrm{Pb}+\mathrm{Pb}$, $\mathrm{O}+\mathrm{O}$, and $\mathrm{p}+\mathrm{Pb}$ collisions at the Large
Hadron Collider.
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General Relativity and Quantum Cosmology
Analytic parity-violating greybody factors of a dynamical Chern-Simons black hole
Abhishek Rout
We study the low-frequency scattering of gravitational and pseudoscalar waves off a non-rotating black hole in dynamical Chern-Simons (dCS)
gravity, where the axial (odd-parity) gravitational sector is irreducibly coupled to the dynamical pseudoscalar while the polar sector remains general relativistic. Working to first order in the dimensionless coupling
zeta = (ell_CS/M)^4 and using matched asymptotic expansions, we obtain an exact closed form for the graviton-to-pseudoscalar conversion probability, d_2 = 3(pi^2-9)^2/8, and a high-precision reconstruction, in a proven transcendental basis, of the graviton greybody (absorption) asymmetry, kappa_2 = (21/80) pi^4 + (27/8) pi^2 - 89833/1536, for the quadrupole (ell=2) channel. Both reduce to combinations of pi^4, pi^2, and rational numbers, with no ln2 or odd-
zeta terms in the reconstructed basis; the transmission-phase sector, by contrast, contains an analytically derived
zeta(3)-9/8 static integral, while its overall matching prefactor is identified numerically. The leading reflection-phase asymmetry vanishes, so that no polarization rotation is imprinted on the reflected wave at leading low-frequency order, while a subleading O(omegazeta) asymmetry remains in the transmitted phase. The normalized flux asymmetries are numerically consistent with a 1/(Momega)^2 falloff in the
geometric-optics limit, where the leading remaining flux effect is conversion loss. The matched-asymptotic results are checked against direct two-channel integration, while the one-dimensional integral determining kappa_2 is evaluated to high precision within an analytically controlled transcendental basis. The results provide analytic targets linking dCS parity violation in absorption and mode conversion to the axial/polar quasinormal-mode splitting.
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Statistical Mechanics
Gaussian Scrooge Ensemble from Deep Thermalization in Free-Fermions
Angelo Russotto, Katja Klobas, Pasquale Calabrese et al. (+1 more)
Deep thermalization indicates the emergence of universal ensembles of pure states in a subsystem after measuring its environment. We investigate this phenomenon in a free-
fermion chain using local measurements that preserve Gaussianity and break particle-number conservation. Although the measurement outcomes provide partial information about local conserved charges within a finite subsystem, we argue that this information becomes negligible in the thermodynamic limit. This effective non-revelation underlies the emergence of a fermionic Gaussian Scrooge ensemble, determined by the subsystem's generalized Gibbs ensemble. We construct this universal ensemble directly at the subsystem level and provide numerical evidence that it describes the late-time projected ensemble at finite temperature. Our results extend the description of thermalization in non-interacting integrable systems beyond the reduced density
matrix to universal statistics of conditional pure states.
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All authors Angelo Russotto, Katja Klobas, Pasquale Calabrese, Bruno Bertini
Materials Science
Electronic Structure Descriptors for CO$_2$ Conversion Activity in Perovskite Oxides
Hyo-sun Jin, Jiyeon Kim and Sooran Kim
Electronic structure descriptors have been widely used to rationalize catalytic activity, but their application to CO$_2$-to-CH$_4$ conversion in perovskite
oxides remains relatively limited. Here, we investigate six electronic structure descriptors related to band centers and bandwidths. We find that the unoccupied transition-metal (TM) $3d$-band center, charge-transfer energy, and the ratio of the unoccupied TM $3d$ to occupied O $2p$ bandwidths, $W_{3d}/W_{2p}$, exhibit negative correlations with CH$_4$ activity. These qualitative trends are further quantified using a parametric brute-force searching (BFS) approach to obtain explicit fitting equations. Notably, the selected equations depend only on $W_{3d}/W_{2p}$, providing an electronic structure perspective on the enhanced activity in double perovskites. We apply the selected equation to screen 24 La-based double perovskites. This screening suggests that La$_2$CoGaO$_6$, La$_2$CoAlO$_6$, and Ti-containing compositions are promising candidates. The present approach can help identify descriptor-activity relationships and guide materials screening in perovskite
oxides.
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High Energy Astrophysical Phenomena
A relativistic inflow candidate in a quasar at cosmic noon
Yerong Xu, Xiurui Zhao, Elena Bertola et al. (+14 more)
Cosmic noon ($z\sim2$) marks the peak epoch of
cosmic star formation and black hole
accretion activity, where strong
accretion and
outflows are expected. We report two candidate absorption features in the XMM-Newton spectrum of the
quasar WISEA~J094835.95+432302.6 at $z=1.893$. Two redshifted features occur at rest-frame energies of $\sim4.65$ and $\sim5.75$keV with confidence levels of 99.3% and 94.1%, respectively, estimated from Monte Carlo (MC) simulations considering the look-elsewhere effect. These features can be explained by the Fe XXV/XXVI K-shell transitions from one ultra-fast inflow (UFI) with an apparent velocity of $0.37^{+0.02}_{-0.01}c$. If confirmed by follow-up XMM-Newton observations, these detections would extend reported UFI candidates from the local Universe to
cosmic noon, offering a rare laboratory for black hole
accretion at the peak of their growth.
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All authors Yerong Xu, Xiurui Zhao, Elena Bertola, Valentina Braito, Francesca Civano, Luca Comisso, Luigi Gallo, Vittoria E. Gianolli, Elias Kammoun, Giorgio Lanzuisi, Stefano Marchesi, Mar Mezcua, Ciro Pinto, James N. Reeves, Daniele Rogantini, Núria Torres-Albà, Lizhong Zhang
Quantum Physics
Numerically exact simulation of open quantum networks with strong system-bath couplings using tensor network path integrals
Quentin W. Richter and Moritz Cygorek
Non-Markovian open
quantum networks are among the most challenging problems in
quantum theory, as they suffer from both, the exponentially scaling many-body state space as well as long
memory times when the sites are strongly coupled to structured environments. Recent efforts to address them by combining tensor networks with real-time path integrals, such as TEMPO and process tensors, were however limited to systems with rather weak system-environment couplings because strong couplings lead to large bond dimensions. Here, we devise a tensor network scheme (CTEMPO) resulting in particularly small bond dimensions for single-site problems. We then extend this to a practical scheme to simulate non-Markovian
quantum networks by time-evolving a corresponding comb tensor network. Benchmarking the single-site
algorithm on the
spin-
boson model we find orders-of-magnitude improvement over established methods. The multi-site
algorithm is shown to solve the notoriously difficult problem of the 7-site Fenna-Matthews-Olson photosynthetic complex, whose spectral density contains 62 peaks. We then apply our approach to explore the scaling behavior of the superradiance of up to $N=20$
quantum dots individually coupled to super-Ohmic
phonon baths. Our approach provides a turnkey solution to non-Markovian
quantum networks and is compatible with more general tensor network
topologies.
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Quantum Physics · Cross-listed from cs.SE
QuSema: Detecting Silent Bugs in Quantum Libraries via Quantum-knowledge-enhanced Agents
Yujin Song, Kaining Zhang, Qixin Zhang et al. (+3 more)
Quantum libraries are now critical infrastructure for
quantum algorithm development, yet their correctness remains difficult to test. Existing testing techniques mainly rely on failure-based or comparison-based oracles, exposing bugs only when executions fail, violate runtime checks, or disagree with another implementation. Their applicability is limited when suitable execution-based oracles are unavailable, leaving some silent bugs undetected. Such missed bugs can produce incorrect results that propagate into experimental conclusions, simulation studies, and algorithmic designs. Here we present QuSema, an autonomous testing
agent for finding silent bugs in
quantum libraries. QuSema uses constraints from
quantum semantics and documentation as a source-level semantic oracle to assess whether implementation logic can produce invalid outputs from valid inputs. It operates through an agentic loop that repeatedly inspects library API documentation and source code, reasons about the intended behavior of
quantum operations, identifies potential semantic deviations, and validates them by generating executable tests through library APIs. Guided by
quantum-domain
reasoning, QuSema turns high-level behavioral mismatches into concrete, user-triggerable bug reports, enabling it to uncover non-crash defects. We implement QuSema for Qiskit and PennyLane. On a
benchmark of 20 historical silent bugs, QuSema achieves higher mean bug relocation counts than Claude Code and Codex, with the DeepSeek configuration costing less than Claude Code. QuSema also discovers 40 previously unknown bugs confirmed by the developers, including 30 silent bugs.
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All authors Yujin Song, Kaining Zhang, Qixin Zhang, Shuai Wang, Pingchuan Ma, Yuxuan Du
Strongly Correlated Electrons
Mapping Strain and Spatial-Modulation Phase from Local Wave Vectors in Scanning Tunneling Microscopy
Xinze Yang, Sandra Sajan, Maria N. Gastiasoro et al. (+2 more)
Spatially varying
lattice distortions can produce local changes in electronic properties that are obscured by measurements averaging over extended regions. With its atomic-scale spatial resolution, scanning tunneling microscopy (STM) provides, in principle, a means of quantifying such distortions locally. A widely used approach for extracting local strain from STM images is the Lawler–Fujita (LF)
algorithm [Lawler et al., Nature 466, 347 (2010)], which determines the displacement field from the phase of the
lattice modulation and subsequently obtains the strain by differentiation. However, this approach requires two-dimensional phase unwrapping, which can fail in regions where the phase is ill-defined, particularly near topological defects such as edge dislocations. Here, we introduce an alternative approach that circumvents these limitations by directly measuring the local wave vector in real space. We derive the relationship between the local wave vector, strain, and the phase gradient, and show that the local wave vector mapping (LWM)
algorithm remains robust even when the phase itself is ill-defined. This makes the method particularly well suited for imaging the phase-gradient textures associated with
vortices and other topological defects. We
benchmark the
algorithm using simulated data containing known
lattice distortions and artificially generated
vortices. Finally, we apply the method to experimental STM data and resolve the charge density wave (CDW) incommensurabilities,
lattice distortions, and CDW phase
vortices in 4Ha-NbSe2 and 2H-NbSe2. The physical implications of these observations were recently reported by S. Sajan, X. Yang, et al. [arXiv:2607.20335 (2026)]. The program package and the example usage is publicly available at the GitHub: https://github.com/jsntxyang/LocalWavevectorMeasuremnt.
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All authors Xinze Yang, Sandra Sajan, Maria N. Gastiasoro, Miguel M. Ugeda, Eduardo H. da Silva Neto
Quantum Physics
Benchmarking Modular Optimization Strategies for Parameterized Quantum Circuits
Carla Cotea, Stefan Balauca and Andreea Arusoaie
Training parameterized
quantum circuits requires balancing optimization progress with limited evaluation budgets and the statistical uncertainty of near-term
quantum hardware. We present a modular benchmarking framework that separates
quantum search-direction estimation from classical parameter-update rules, allowing their interactions and sensitivities to be examined independently. We evaluate a suite of gradient-based,
stochastic, and derivative-free optimizers across combinatorial optimization using the
Quantum Approximate Optimization
Algorithm (QAOA), supervised
quantum machine learning using Iris classification and a
quantum convolutional neural network (QCNN) for binary MNIST classification, and
quantum chemistry using the variational
quantum eigensolver (VQE) for molecular hydrogen. By separating objective evaluations from sample-
circuit costs under finite-shot simulation and physical execution on a 156-
qubit processor, we compare optimizer behavior across workloads with different parameter counts and measurement requirements. Four selected simulator and hardware case studies report terminal and best observed objectives separately, alongside post-training classifier accuracies. The comparisons include selected MaxCut and hydrogen trajectories and illustrate workload-dependent objective changes and evaluation costs, while the simulator
benchmark compares both peak and mean performance across three seeds. The hardware runs do not establish an optimizer ranking or isolate a causal effect of device noise.
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Mesoscale and Nanoscale Physics
Deterministic Vortex Generation from Coupled Trapped Polariton Condensate Triad
X. Qin, N. Pitanios, S. Dam et al. (+4 more)
We present the deterministic generation and all-optical switching of ternary topologically distinct
vortex states in a triad of trapped
exciton-polariton condensates with direct state readout from momentum-space emission distribution. Tuning the non-resonant pump power controls the sign of the dissipative coupling, selecting between a
ferromagnetic in-phase state and two frustrated states with global phase winding. The zero-winding
ferromagnetic state has unstructured far-field emission at low momenta and forms
vortex-antivortex arrays at the Dirac points, reflecting the C_3v global
symmetry. The two frustrated states of +-2pi winding can be activated on-demand by a control beam and produce different triangular emission patterns selectively localized at the K or K' points. Although all three states share identical real-space emission distributions, their momentum-space photoluminescence profiles distinguish them unambiguously, revealing the chirality without the need for interferometry. This enables on-demand orbital angular momentum control using a pump independent of resonant phase or OAM imprinting, establishing condensate triads as a compact platform for reconfigurable
chiral light generation operating on a ternary logic basis.
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All authors X. Qin, N. Pitanios, S. Dam, S. Betzold, S. Höfling, S.V. Koniakhin, P.G. Savvidis