Quantum Physics · Cross-listed from cs.CR
Operational Roles of QRNG-Derived Quantum Entropy in Bitcoin Proof-of-Work Architectures
Ricardo Fernandes da Silva and Paulo Vitor Batista Santos
Replacing classical
entropy with QRNG output does not change honest Bitcoin PoW success probability when candidate headers remain distinct. The original contribution of this paper is a reproducible
benchmark that locates and measures the operational value of
quantum entropy in hybrid
quantum-classical mining infrastructure through two scheduler-level observables, the
entropy-efficiency factor $\eta$ and the reboot-diversity index $\rho$. Monte Carlo and scheduler simulations with confidence intervals show parity for competent deterministic and strong-classical baselines, while QRNG value emerges in assurance-oriented scenarios involving correlated restart faults, namespace reuse, and
entropy provenance. The study is therefore positioned as a simulation-based validation framework rather than as a device-level QRNG demonstration; hardware-in-the-loop validation with recorded or live QRNG streams is identified as the next experimental step.
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Chemical Physics
Measurements of Diffusion Coefficients of CO$_{2}$ in 1-Butanol with a New Laminar Jet Apparatus and PFG-NMR, Pointing to Interfacial Mass Transfer Effects
Oliver Großmann, Sarah Mross, Jens Wagner et al. (+3 more)
A novel laminar jet apparatus (LJA) was constructed for precise gas-
liquid mass transfer measurements up to 12 bar, significantly extending the technique's operating window. It was applied to carbon dioxide + 1-butanol between 283 K and 333 K. Corresponding measurements were performed using pulsed field gradient NMR spectroscopy (PFG-NMR), which does not involve interfacial mass transfer. Fick
diffusion coefficients from LJA and self-
diffusion coefficients from PFG-NMR were compared in the limit of infinite dilution, where both must coincide. Both methods show consistent trends, but LJA data are systematically lower. Experimental errors cannot explain the deviations. We therefore hypothesize an additional gas-
liquid interfacial mass transfer resistance. PCP-SAFT combined with density gradient theory predicts high CO$_{2}$ enrichment at the interface, and the deviations correlate with this enrichment. Whether such an interfacial resistance exists and is caused by enrichment remains to be established in future studies.
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All authors Oliver Großmann, Sarah Mross, Jens Wagner, Kerstin Munnemann, Fabian Jirasek, Hans Hasse
Materials Science
Cross-Layer Anomalous Hall Transport driven by Néel-Vector rotating in the Altermagnet candidate V2Te2O
Yanan Pan, W. Z. Zhuo, Pan Gao et al. (+7 more)
In van der Waals (vdW) materials, weak interlayer coupling generally suppresses vertical dispersion, reinforcing the conventional paradigm that in-plane transport dominates over cross-layer channels. Here, using first-principles calculations and
magnetic symmetry analyses, we uncover a
giant,
symmetry-unlocked cross-layer anomalous
Hall conductivity (AHC) in the vdW altermagnet V2Te2O. In the
magnetic ground state with Neel vector N//z, horizontal mirror
symmetry protects a
spin-polarized nodal chain near the
Fermi level and strictly enforces zero anomalous
Hall response. Tilting the Neel vector explicitly breaks this mirror protection, allowing
spin-orbit coupling to gap the nodal chain and activate a sharp cross-layer
Hall response. When the Neel vector is rotated into the in-plane configuration (N//x), cross-layer orbital hybridization generates intensive Berry
curvature hotspots, boosting the cross-layer component of AHC {\sigma}_{yz} to approximately 255 S/cm, which exceeds in-plane component {\sigma}_{xy} by nearly two orders of magnitude. Furthermore, varying the azimuthal angle systematically redistributes the anomalous
Hall response, enabling full directional control of transverse transport. Our findings demonstrate a highly sensitive cross-layer anomalous
Hall switch activated by low-barrier
spin canting, offering promising avenues for directional tensor selection and low-power multi-axial vdW spintronics.
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All authors Yanan Pan, W. Z. Zhuo, Pan Gao, Ziyu Zhou, Junqing Xu, Lijie Shao, Damin Meng, Weiwei Chen, Zhongjun Li, Ye Yang
Materials Science
A locally ab initio computational framework for arbitrary incommensurate materials interfaces
Drake Niedzielski and Tomás A. Arias
Incommensurate materials interfaces constitute a broad and technologically important class of systems, yet their lack of shared periodicity limits predictive and computationally efficient first-principles electronic-structure methods. Here we introduce a scalable computational framework for constructing locally ab initio electronic
Hamiltonians for arbitrary materials interfaces. Our approach exploits the nearsightedness of Wannier
Hamiltonian matrix elements, enabling their systematic extrapolation and interpolation across interlayer registries. This strategy yields transferable
Hamiltonians that retain first-principles accuracy while bypassing the need for prohibitively large commensurate supercells or Moiré approximations. We validate the framework on quasicrystalline 30{\deg} twisted
bilayer graphene, reproducing experimentally observed spectral features including mirrored Dirac cones and minigaps at avoided crossings arising from generalized interlayer scattering. We further predict quasiperiodic flat-band states in experimentally accessible doping regimes. By enabling predictive electronic-structure calculations across structurally incommensurate interfaces, this framework establishes a practical route to first-principles exploration of emergent interfacial phenomena.
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Earth and Planetary Astrophysics
Gravitational instability in planet-forming discs
Cristiano Longarini and Giuseppe Lodato
During the earliest phases of
star and
planet formation, a young
star is surrounded by a disc that can become gravitationally unstable. Indeed, if the protoplanetary disc is sufficiently massive, its self-
gravity triggers the formation of large scale spiral arms, transporting angular momentum, trapping solid particles and, potentially, collapsing to form sub-
stellar companions. In this paper, we review the theoretical and observational advances in the study of gravitational instability in protoplanetary discs over the last 10 years, since the advent of ALMA. These developments have transformed our understanding of gravitational instability, moving beyond its historical role as a theoretical mechanism for
giant planet formation toward a physically rich framework that can be directly tested against high-resolution observations.
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Mesoscale and Nanoscale Physics
Engineering Giant Thermoelectric Performance through Electrode-Coupling Geometry and Magnetic Flux in Quasiperiodic Su-Schrieffer-Heeger Rings
Sridhar, Souvik Roy and Malay Bandyopadhyay
We investigate coherent thermoelectric transport in
magnetic-flux-threaded quasiperiodic Su-Schrieffer-Heeger (SSH) rings with engineered multi-site electrode couplings using the nonequilibrium Green's function formalism within the Landauer-Büttiker framework. We demonstrate that the electrode-coupling geometry serves as a powerful control parameter for tailoring
quantum interference, thereby reshaping the transmission spectrum and thermoelectric response. In the absence of
magnetic flux, the trivial dimerized phase ($t_1>t_2$) exhibits the highest thermoelectric efficiency, with asymmetric coupling producing a substantially larger figure of merit than the symmetric geometry.
Magnetic flux further reconstructs the transmission spectrum through Aharonov-Bohm interference, driving a crossover of the optimal thermoelectric regime from the trivial to the topological dimerized phase. Under optimal flux conditions, the thermoelectric figure of merit reaches $ZT \approx 12$ for symmetric coupling and is dramatically enhanced to $ZT \approx 90$ for asymmetric coupling through enhanced energy filtering and suppressed electronic thermal transport. We further establish a clear correlation between the enhancement of thermoelectric efficiency and the violation of the Wiedemann-Franz law. Our results demonstrate that the combined interplay of quasiperiodicity,
topology,
magnetic flux, and electrode-coupling geometry provides a versatile strategy for engineering high-performance coherent thermoelectric devices.
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Materials Science
Generalized Helicity-Dependent Magnetization Switching via Substrate Phonons
F.G.N. Fennema, H. Damas, H. Yoshikawa et al. (+3 more)
Coherent excitation of circularly-polarized substrate
phonons can drive deterministic reversal of magnetization in an adjacent
magnetic layer. However, the extent to which this substrate-mediated mechanism can be generalized across different materials remains unresolved. Here, we measure and compare the spectral dependence of helicity-dependent magnetization reversal in
magnetic GdFeCo layers grown on a diverse set of diamagnetic substrates. Switching is observed for all investigated substrates, spanning six point groups and several infrared-active transverse-optical
phonon symmetries. While the switching spectra broadly overlap with the Reststrahlen bands, their maxima are systematically shifted to wavelengths shorter than the corresponding transverse-optical
phonon resonances. This spectral mismatch shows that substrate absorption alone does not determine the switching efficiency. Transfer-
matrix calculations show that strong absorption concentrates energy deposition near the substrate interface, providing a possible source of local heating that could suppress magnetization reversal. Our results reveal the broad applicability of substrate-mediated phononic switching while showing that its efficiency is governed by the full optical response of the
heterostructure rather than substrate absorption alone.
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All authors F.G.N. Fennema, H. Damas, H. Yoshikawa, A. Tsukamoto, C.S. Davies, A. Kirilyuk
Quantum Physics
Impact of Data Loss in Postprocessing on Training and Inference of Quantum Neural Networks
Soraya V. Panambalom, Edoardo Altamura, Nick Chancellor et al. (+1 more)
As
quantum hardware scales to larger devices, the classical software layers that interface with it must evolve in step. Postprocessing routines developed and tested primarily in simulator settings can encode assumptions that no longer hold on utility-scale devices, leading to data loss that can be difficult to detect from high-level model outputs alone. We present a case study of SamplerQNN, the sampling-based
quantum neural network class in the Qiskit Machine Learning library. Here, the postprocessing method applies a filter that assumes measurement bit-strings are in virtual
qubit space. On our
quantum hardware runs, where bit-strings span over 100 physical
qubits, this filter led to the loss of 85 to 99.6% of valid measurement shots, depending on the transpiler's
qubit placement. The resulting probability vector is unnormalised, allowing distorted prediction and loss values to propagate through the model without an API-level warning. We demonstrate the impact across five experiments on two IBM backends: for inference, accuracy drops from 0.94 to 0.39 on the same raw measurements; for training, the loss signal is compressed by 22 to 27$\times$, substantially reducing the sensitivity of the optimiser to the objective landscape. The behaviour arises in all released versions of the library (0.8.4 to 0.9.0). We implemented a layout-based marginalisation fix, merged into the GitHub codebase as Pull Request \#1041, that makes SamplerQNN postprocessing forward-compatible with current and upcoming hardware.
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All authors Soraya V. Panambalom, Edoardo Altamura, Nick Chancellor, Jonte R. Hance
Materials Science
Influence of dislocation density on the tribological response in oxides: case study on SrTiO3
Chukwudalu Okafor, Oliver Preuß, Thomas Chudoba et al. (+6 more)
Most ceramics suffer from brittle surface damage and cracking when small particles slide across the surface under low load. Microscratching tests are a useful technique to mimic this loading scenario while retaining the material's deformation history; however, the impact of pre-seeded dislocations, which can significantly facilitate plastic deformation, has not been explored in ceramics. Here, the influence of mechanically seeded dislocations on the microscratching response of
oxides is investigated using a model perovskite, SrTiO3. First, various dislocation densities over four orders of magnitude are introduced via room-temperature cyclic Brinell indenter scratching. Subsequently, load-ramped microscratching tests are performed within the pristine and dislocation-seeded regions using a nominally 30 {\mu}m spherical diamond tip. On the reference pristine surface, we observe a clear transition from elastic to elasto-plastic deformation, followed by median/radial cracking at higher loads. In contrast, pre-seeded dislocations, accompanied by residual compressive stresses, suppress elastic deformation and lead to median/radial crack shortening and subsequent transition to a partial cone crack. The subsurface cracks are characterized by 3D Nano-CT. The changes in crack geometry, with and without dislocations, were described using the Lawn-Evans-Marshall and Lawn-Wiederhorn-Roberts models. These findings provide direct evidence of dislocation-regulated near-surface damage tolerance, with general applicability to other plastically deformable
oxides.
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All authors Chukwudalu Okafor, Oliver Preuß, Thomas Chudoba, Ujjval Bansal, Daniela Exner, Konrad Priszokovich, Yanfei Gao, Christoph Kirchlechner, Xufei Fang
Cosmology and Nongalactic Astrophysics
Supernovae Unite: Combining Pantheon+ and DES-SN5YR
Ryan Camilleri, Jaemyoung Lee, Tamara Davis et al. (+21 more)
We present the Hubble diagram and cosmological constraints resulting from the combination of the Pantheon+ and DES-SN5YR
supernova (SN) samples, which we refer to as Unite. Unite updates Pantheon+, including methodology improvements that the DES sample enabled, and adds the new SN from the DES survey. This represents the most comprehensive and internally consistent SN Ia
dataset available, consisting of 2884 likely type Ia
supernovae. This work features consistent SN Ia modelling, sample selection, and bias corrections. We also redetermine host-
galaxy stellar masses for over 98% of the sample using a consistent framework. Using Unite alone, for a flat universe with a cosmological constant (Flat-$\Lambda$CDM), we find $\Omega_{\rm m} = 0.310^{+0.012}_{-0.011}$. We further present constraints using the Unite sample combined with
Cosmic Microwave Background and both DES and DESI
Baryon Acoustic Oscillation data. We find strong evidence of tension between CMB measurements and the combined BAO and
supernova datasets when fitting a model with constant dark energy equation of state ($w$), which is alleviated when allowing $w$ to vary with time. For a flat universe with dark energy that has a time-evolving equation of state parametrized by $w_0$ and $w_a$ we find $(\Omega_{\rm m},w_0,w_a) = (0.305\pm0.004,-0.861^{+0.044}_{-0.042},-0.60^{+0.17}_{-0.19})$ with a dark energy Figure of Merit of 315. This corresponds to a $\sim30\%$ reduction in the area of the $w_0-w_a$ confidence region relative to previous constraints from the combination of DES Y6, DESI-DR2, and CMB data (arXiv:2605.27221). The
Bayesian evidence indicates only weak preference for time evolving dark energy, whereas frequentist analyses yield a preference over Flat-$\Lambda$CDM at a significance of $3.3\sigma$ ($3.1\sigma$) when using the maximum $\textit{a posteriori}$ probability (maximum likelihood).
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All authors Ryan Camilleri, Jaemyoung Lee, Tamara Davis, David Rubin, Paul Shah, Dan Scolnic, Chris Lidman, Brodie Popovic, Koby Grech, Maria Vincenzi, Dillon Brout, Maria Acevedo, Patrick Armstrong, Bruce Bassett, Keith Bechtol, Rebecca Chen, Herman Diehl, Josh Frieman, Lluís Galbany, Anais Möller, Masao Sako, Bruno Sánchez, Mark Sullivan, Brad Tucker
Optics
Bounds on Propagation Constants in Dielectric Gratings
Ehsan Faghihifar
We establish analytical bounds on the normalized longitudinal propagation constants $\beta=k_z/k_0$ of modes in lossless dielectric diffraction gratings. If $\epsilon_{\max}$ denotes the maximum relative permittivity, we show that regular modes ($\beta^2\in\mathbb{R}$) satisfy $\beta^2\le\epsilon_{\max}$ despite the lack of a scalar dispersion relation. We further show that the so-called ghost modes ($\beta^2\notin\mathbb{R}$), admitted by the non-Hermitian nature of the associated eigenproblem, satisfy $|\mathrm{Re}(\beta)|\le\sqrt{\epsilon_{\max}}/2$. Both bounds are obtained directly from the
Fourier-series formulation of the fully coupled vectorial eigenproblem.
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Mathematical Physics · Cross-listed from math.RA
Extending Structures for $n$-Lie Algebras
Tao Zhang
Motivated by the Casas-Loday-Pirashvili maps concerning representations of $n$-Leibniz
algebras, we give an intrinsic characterization of the
cohomology of $n$-Lie
algebras with coefficient in a representation space $V$. We investigated the
cohomology theory of $n$-Lie
algebras in three different ways:
cohomology theory of Leibniz
algebras, infinitesimal deformation and abelian extension. In the main part of this paper, we solve the extending problems for $n$-Lie
algebras. A necessary and sufficient unified-product criterion is obtained. The case of crossed products, sparse non-abelian extensions, matched pairs are studied as special cases. We also investigate the factorizations, deformation maps, and complements problem for $n$-Lie
algebras. An appendix removes the general non-reduced unified product with all intermediate mixed components.
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Statistical Mechanics
Tensor-Network Inference in a Field-Coupled XY Model for Portfolio Allocation
Kartikeya Chowdhry and G Subrahmanya V.R.K. Rao
We apply tensor-network methods to a field-coupled XY model for long-only portfolio construction. Daily return statistics set asset-specific fields and correlation couplings. Correlation distance, four-point Gromov hyperbolicity, and Ward clustering are used to construct a sparse interaction path. A
Fourier-Bessel expansion maps the continuous angular partition function to a finite-current tensor network; bottom-up and top-down contractions then give the one-site marginals and
equilibrium cosine scores. A softmax map converts these scores into positive, fully invested portfolio weights. We study five equity
markets over continuous ranges of inverse temperature beta and concentration gamma, and compare selected parameter pairs with long-only Markowitz frontiers and standard
benchmarks. The same-sample comparisons demonstrate a tractable route from financial time series to network-adjusted allocations; predictive trading performance is outside their scope.
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Quantum Physics
Qlippy: A Retrieval-Augmented GenAI Assistant for Reproducible Quantum Workflows and Experiment Tracking
Mahee Gamage and Vlad Stirbu
Quantum software development is iterative and error-prone. Noisy hardware and repeated re-execution make experiment tracking, provenance, and reproducibility essential, yet these practices are hard to adopt because of tooling complexity and the specialized knowledge they demand. General-purpose
language models can help but tend to hallucinate and lack grounding in domain-specific tooling. We present Qlippy, a
retrieval-augmented GenAI assistant embedded in the development environment that grounds its responses in a curated corpus of
quantum-software-engineering knowledge. Qlippy explains reproducibility and provenance concepts in context and augments existing Qiskit programs with MLflow-based experiment tracking aligned to the QProv schema. By separating knowledge from model parameters, grounding gives explicit control over the scope and provenance of the assistant's responses and reduces reliance on model scale, which points toward low-cost,
privacy-preserving local deployment.
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High Energy Astrophysical Phenomena
Nonstationary Stochastic Timing Signatures in the Prompt Gamma-Ray Light Curve of GRB 170817A
Lin Xie and Dahai Yan
We investigate time-dependent
stochastic structure in the weak
prompt gamma-ray emission of GRB 170817A using change-point and deep-kernel Gaussian-process (GP) models. The analysis is based on the 10-300 keV
Fermi/GBM light curve with 0.10 s time resolution. Two change-point configurations identify similar covariance transitions at 0.269 and 0.237 s after the gravitational-wave merger, with 10-90% transition widths of 0.441 and 0.393 s, respectively. At the representative gate-defined boundary of t_tr = 0.27 s, all four fixed-split assignments yield positive evidence gains over the full-exposure stationary Matern-3/2 reference. The largest gain is Delta ln Z_split = 5.72 +/- 0.16 for the Matern-3/2 to Matern-3/2 assignment, while the gate-matched damped random walk (DRW) to Matern-3/2 assignment gives Delta ln Z_split = 5.50 +/- 0.16. The fixed-split comparison therefore supports segment-specific covariance
evolution without requiring a change of covariance family. The deep-kernel models recover localized time-deformation features peaking at 1.65 and 1.75 s after the merger for DRW and Matern-3/2 base kernels, respectively. Their offsets from the adopted gamma-ray onset at 1.74 s are -0.09 and +0.01 s, both within the 0.10 s sampling resolution. The full-band timing features remain stable when the bin width is changed from 0.10 to 0.12 s, whereas energy subdivision produces larger shifts in gate locations than in warp peaks. Residual diagnostics show that the models reproduce the dominant temporal structure, although localized residual dependence remains. We interpret the gate-defined covariance transition and the localized time-deformation feature as model-dependent phenomenological timing diagnostics. Further simulation calibration and count-level modelling are needed to assess the statistical robustness and physical origin of the recovered nonstationary structure.
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Quantum Physics
Hadamard Rigidity of Positive Sojourn Time Distributions for Rotation Coins
Shunya Tamura and Tomoki Yamagami
We study the distribution of the positive sojourn time for a one-dimensional two state
quantum walk, conditioned on return to the origin. Konno showed that, for the Hadamard walk, this conditional distribution is exactly uniform at times divisible by $4$. In this paper, we investigate whether this finite time exact uniformity characterizes the Hadamard coin within the family of rotation coins. For a fixed initial state, we prove that the following three conditions are equivalent for rotation coins: the conditional distribution is exactly uniform at time $8$; the conditional distribution is exactly uniform at every time $4m$ with $m\ge2$; and the coin is the Hadamard coin. Thus, the uniformity phenomenon found by Konno is characterized as a
rigidity phenomenon of the Hadamard coin within the rotation coin family. The proof uses a
matrix-valued generating function for paths returning to the origin. We analyze the algebraic structure arising from an absorbing process on the half line. Finally, by comparing low degree coefficients at time $8$, we show that exact uniformity forces the rotation coin to be the Hadamard coin.
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Mesoscale and Nanoscale Physics
ANT:UI: An interactive 3D tool for preparing ANT.Gaussian molecular junction geometries
A. Martinez-Garcia, J. J. Palacios and C. Sabater
ANT.UI is a Python graphical interface that automates the construction of molecular-junction geometries for NEGF-DFT
quantum transport calculations. Through a real-time 3D viewer, users interactively position electrodes and molecules and generate complete, ready-to-run input files for Gaussian and ANT.Gaussian without manual scripting. Dedicated Pull, Grid, and Rotation assistants further automate electrode-pulling sequences, surface scans, and step-wise rotation studies, with optional geometry-optimisation chaining across each sequence. By replacing a process that previously demanded days of custom scripting with a point-and-click workflow, ANT.UI accelerates research in theoretical molecular electronics and lowers the barrier to entry for new users. The software also exports all constructed geometries in standard XYZ format, allowing direct reuse in molecular dynamics codes or third-party visualization tools without manual reformatting.
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Astrophysics of Galaxies
Corona Australis 151: an extremely young protostar
E. Redaelli, S. Spezzano, P. Caselli et al. (+9 more)
Context. Prestellar cores are the birthplace of
stars and planetary systems, but they are short-lived objects, since the initial stages of dense core
evolution, collapse, and the formation of a protostellar seed are fast. In an effort to build a catalogue of bona-fide prestellar cores in the
Solar neighbourhood, we used APEX observations to identify dynamically evolved cores among dense cores observed with Herschel. One of them, Corona Australis 151, stood out because of its centrally peaked structure, with densities above 1e7cm-3 in the central 500-1000 au, and high deuteration levels (N2D+/N2H+~0.5), suggestive of an evolved, prestellar stage. Aims. Corona Australis 151 appears to be an evolved prestellar core, but the presence of broad wings in some of the detected lines and a tentative 70micron detection with Herschel partially challenges its prestellar stage. We intend to assess its evolutionary stage. Methods. We analyse new ALMA data of the continuum emission and of several line tracers (including typical
outflow tracers) at a resolution of~150-200au, tracing the envelope. Results. We unveil the presence of a compact and young
outflow (projected dynamical age:~500yr), traced by SiO, CO, and H2CO emission. The continuum emission traces an envelope structure of size~1000 au and mass 0.33M_sun(assuming Tdust=20 K). Conclusions. Corona Australis 151 is an extremely young protostar, possibly one of the youngest known in the
Solar neighbourhood, and hence a new laboratory to study the chemical and dynamical
evolution at the dawn of
star formation.
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All authors E. Redaelli, S. Spezzano, P. Caselli, J. Harju, D. Arzoumanian, O. Sipilä, A. Belloche, F. Wyrowski, J. E. Pineda, S. Jensen, Y. Misugi, G. Majerczyk
Quantum Physics
Lindblad Multiproduct Formulas
Niall F. Robertson, Andrea D'Urbano, Anton Dekusar et al. (+11 more)
We introduce Lindblad Multiproduct Formulas: a
quantum error mitigation technique that uses two-dimensional tensor networks contracted with loop-corrected belief propagation. The quantities required to implement the error mitigation scheme that are evaluated with tensor networks can be less computationally expensive to calculate than the expectation values themselves, thus allowing for the possibility of applying our method to certain systems for which tensor network methods may struggle to calculate the observable quantities of interest. The workflow incorporates Clifford rescaling techniques and outputs an estimated error bar. We apply our method to a model of two-dimensional discrete time
crystals studied previously and implement it on $65$
qubits arranged in a $3\!\times\!3$ heavy-hexagonal
topology on the
quantum computer ibm_basquecountry. We show that a GPU implementation of the classical part of our workflow achieves a speedup of up to $5.6\times$.
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All authors Niall F. Robertson, Andrea D'Urbano, Anton Dekusar, Max Rossmannek, Eric D. Switzer, James R. Garrison, Nicolas Lorente, Igor Pasichnyk, Paolo D'Alberto, Muhammad Osama, Zachary Streeter, Yasuko Eckert, Constantinos Evangelinos, Sergiy Zhuk
Fluid Dynamics
Fisher Information Dynamics: A Kinematic Framework for Phase Space Ordering with Applications to Shock Layers and Turbulence
Yingchuan Wu
Order here denotes the sharpness of probability-density gradients as quantified by Fisher information, distinct from thermodynamic order parameters. A kinematic framework for phase space ordering is established based on the Fisher information production rate, which possesses a rigorous thermodynamic foundation through the de Bruijn identity, Stam inequality, and dissipation
theorem. A four-term decomposition into isotropic contraction, traceless shear, divergence gradient, and boundary flux is derived from the continuity equation. Extending to the Fokker-Planck equation, the non-positivity of the diffusive dissipation term is proved, with strict negativity for non-uniform densities. A vorticity-independence
theorem shows that purely rotational velocity fields do not alter the order measure, and explicit
geometric sign criteria enable prediction of where order is generated or destroyed. Through exact solutions of the Burgers shock layer, a pointwise identity between compression and divergence-gradient contributions is uncovered, underlying the three-term balance. In two-dimensional incompressible
turbulence, a statistical two-term
equilibrium (vanishing time-averaged production) is established as the null hypothesis: the conservative reference state from which three-dimensional
turbulence departs through
vortex stretching. Variational steady states of the associated Wasserstein gradient flow imply vanishing of the total production rate. This framework provides a diagnostic and predictive tool for analyzing ordering dynamics in non-
equilibrium systems.
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General Relativity and Quantum Cosmology
Probing Dark Matter with Strongly Lensed Binary Black Hole Mergers: Prospects in the Near Future
Koustav N. Maity, Souvik Jana, Ankur Barsode et al. (+2 more)
Gravitational-wave~(GW) transients, strongly lensed by intervening
galaxies and clusters, are expected to constitute a small fraction ($\sim 0.1$-$0.5\%$) of the events detectable by ground-based detectors. A strongly lensed binary black hole (BBH) merger will produce multiple copies of the GW signal arriving at different times at the detector. The abundance and time-delay distribution of these lensed events are sensitive to the mass, density profile, and
redshift distribution of the lens population, and in turn, to the underlying nature of dark matter. Jana et al. (Phys.Rev.Lett. 135 (2025) 11, 111402) recently proposed a method to constrain the masses of warm dark matter (WDM) particles making use of the strongly lensed events detectable by next-generation GW detectors. In this work, we investigate the prospects of constraining the mass of the WDM particle using upcoming observations of the upgraded LIGO-Virgo-KAGRA network. This requires a careful modeling of the detector selection effects. The upcoming fifth observing run (O5) is expected to yield only a modest bound, since only a few lensed pairs are expected at that early stage. By the sixth observing run (O6), we forecast a bound on the WDM particle mass, $m_{\rm wdm}^{-1} \lesssim 0.1$-$0.2\text{keV}^{-1}$ ($m_{\rm wdm} \gtrsim 5$-$10\text{keV}$), which is comparable to the tightest existing astrophysical constraints. Runs beyond O6 will tighten the constraint by roughly an order of magnitude. Strongly lensed GWs therefore offer a complementary, competitive, and independent probe of dark matter.
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All authors Koustav N. Maity, Souvik Jana, Ankur Barsode, Tejaswi Venumadhav, Parameswaran Ajith
Fluid Dynamics
Unveiling wing turbulence dynamics through explainable deep learning
Samuel Molina-Casino, Andrés Cremades, Sergio Hoyas et al. (+3 more)
The three-dimensional organization of coherent structures in the turbulent flow over aircraft wings remains elusive, limiting our ability to reduce fuel consumption. Here, we use explainable artificial intelligence to characterize these structures by predicted flow
evolution rather than classical predefined kinematic criteria. After training a deep neural network to predict the short-term
evolution of the flow, we identify the highest-relevance flow regions using Shapley-value attribution methods. We have found that as the flow decelerates towards the trailing edge, predictive importance shifts from near-wall low-speed structures to three-dimensional pairs of high- and low-speed fluid regions. Matching no single classical structure family, these pairs progressively dominate the dynamically relevant flow. Most stand spanwise side-by-side, enclosing a near-vertical momentum interface with the strongest velocity jump. Their geometry remains invariant in viscous units while their volume expands when approaching separation. Our results reveal a predictive organization that traditional paradigms overlook, opening new ways to control turbulent flows.
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All authors Samuel Molina-Casino, Andrés Cremades, Sergio Hoyas, José I. Cardesa, François Chedevergne, Ricardo Vinuesa
Lattice Field Theory
Accessing the Wess-Zumino-Witten term using Lattice QCD
Fernando Romero-López and Stephen R. Sharpe
The Wess-Zumino-Witten interaction in
chiral perturbation theory is a manifestation of
chiral anomalies. One of its consequences is the presence of a nonvanishing $K \overline K \to \pi^+ \pi^0 \pi^-$ amplitude. We derive the finite-volume formalism that allows one to access this, and related, amplitudes, using the spectra of two and three particles in finite volumes, spectra that can be calculated using
lattice QCD. Specifically, we present the formalism for the systems $K \overline K + 3 \pi$ with $I=0$ and $\pi K + \pi\pi K$ with $I=1/2$ and $3/2$. In addition, we determine the threshold expansions for the $2\leftrightarrow 3$ and $3\leftrightarrow 3$ K
matrices that enter the formalism, and calculate the leading order predictions from
chiral perturbation theory for the coefficients that enter these expansions.
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High Energy Physics (Theory)
de Sitter and S-folds in type IIB from $\mathcal{N} = 4$ $D = 4$ gauged supergravity
Colin Sterckx
In this paper, we classify the type IIB uplifts of the $\mathcal{N}=4$ $D=4$ pure $\text{SO}(4)$-gauged supergravity admitting a dS$_4$ solution. As for their AdS cousins, the internal geometries of these uplifts consist of two $S^2$ fibred over a Riemann surface $\Sigma$, and are classified by pairs of harmonic functions $h_{1,\,2}$ on $\Sigma$, providing a new family of de Sitter solutions in type IIB. Choosing specific functions $h_{1,\,2}$ on $\Sigma = \mathbb{R} \times I$, we perform an S-fold quotient of the internal space along its non-compact direction. This S-folding allows us to evade the assumptions of the Maldacena-Nunez no-go
theorem and provides a classical de Sitter solution of type IIB supergravity with finite and non-vanishing four-dimensional effective Newton constant.
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Optics
Fabrication-Aware Design of a Hybrid Metasurface-Bragg Mirror for Low-Noise Precision Optics
Mika Gaedtke, Christian Kranhold, Markus Walther et al. (+3 more)
High-reflectivity coatings for precision interferometry must simultaneously minimize optical losses and thermally driven displacement noise. Dielectric Bragg mirrors provide robust high reflectance but rely on thick multilayer coatings, whereas metasurface mirrors provide high reflectance and low noise but are sensitive to fabrication-induced deviations. A fabrication-aware photonic design framework is introduced that combines a resonant single-layer metasurface, an etch-stop layer, an antiresonant spacer, and a reduced Bragg reflector. Fabrication effects, including
geometric tolerances and line-edge roughness, are explicitly considered in the optical design. Full-wave electromagnetic simulations are combined with a truncated-Gaussian Monte Carlo analysis to determine the performance distribution under the assumed fabrication conditions. The ideal metasurface design achieves a modeled non-reflected power of $1-R<10^{-5}$. After roughness-aware reoptimization, the modeled non-reflected power remains below $1.04\cdot10^{-4}$ at $80\%$ fabrication yield. For the cryogenic ETpathfinder gravitational-wave testbed, two Bragg layer pairs reduce the non-reflected power of the complete stack to approximately $6.6\,\mathrm{ppm}$. The estimated thermal displacement-noise amplitude spectral density is $1.97\cdot10^{-20}\,\mathrm{m/\sqrt{Hz}}$ at $100\,\mathrm{Hz}$. The architecture connects fabrication robustness, optical performance, and thermal-noise reduction within a single design framework.
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All authors Mika Gaedtke, Christian Kranhold, Markus Walther, Falk Eilenberger, Stefanie Kroker, Thomas Siefke
Materials Science
Local coordination, structural softening, and polarization-switching energetics in Sc-alloyed GaN
Shailesh Kalal, Gueorgui Kostov Gueorguiev, Martin Magnuson et al. (+8 more)
Sc-alloyed wurtzite nitrides exhibit strongly tunable electromechanical and ferroelectric properties, yet the relationship between their
lattice evolution and local bonding environment remains insufficiently established, particularly in Sc$_x$Ga$_{1-x}$N. Here, we investigate the structural and local bonding
evolution of Sc$_x$Ga$_{1-x}$N across the dilute-to-intermediate composition range by combining X-ray diffraction, Sc K-edge X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS) and first-principles calculations. Sc incorporation produces an anisotropic
lattice expansion and a progressive reduction in the c/a ratio. XANES and EXAFS reveal a concurrent modification of the local environment around Sc, with the effective Sc-N coordination number increasing from 4.1(4) to 4.5(2) and the average Sc-N bond length increasing from 2.045(7) to 2.081(8)Å over x=0.06-0.26. The local response is accompanied by a reduction in the Sc K-edge pre-edge intensity, consistent with a gradual reduction of the local tetrahedral asymmetry. First-principles calculations show that these structural changes are associated with site-selective distortions around Sc and progressive flattening of the structural energy landscape. The calculated intrinsic polarization-switching barrier decreases from 24.2 to 19.0 meV/Å$^3$ with increasing Sc content, while the calculated piezoelectric stress coefficient (e$_{33}$) increases from 0.82 to 1.66~C/m$^2$ and elastic constant (C$_{33}$) decreases from 380 to 227~GPa, resulting in an increase of piezoelectric strain coefficient (d$_{33}$) from 2.99 to 12.46~pC/N. These results show that Sc incorporation progressively modifies the local coordination environment and structural energetics of ScGaN while the long-range wurtzite structure remains preserved over the investigated composition range.
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All authors Shailesh Kalal, Gueorgui Kostov Gueorguiev, Martin Magnuson, Edward Ferraz de Almeida Junior, Rohini Sanikop, Sagar Jathar, Per Sandström, Ray-Hua Horng, Jens Birch, Per Eklund, Ching-Lien Hsiao
High Energy Astrophysical Phenomena
The October 2022 flare in OJ 287 and the mass of its primary black hole
Mauri J. Valtonen, Staszek Zola, Manpreet Singh et al. (+21 more)
The bright blazar OJ~287 has demonstrated a sequence of
flares, which are well explained by a quasi-Keplerian orbit model. The
flares are associated with the impact of the secondary on the
accretion disk of the primary. The orbit must precess in order to produce the correct sequence of
flares, and from the precession rate we calculate the mass of the primary. This precession rate gives the mass of the primary $M_{BH} = (18.35\pm0.05) \times 10^9 M_{\odot}$. Two kinds of
flares have been identified: direct
flares from the impacts, and
tidal flares arising from an increased
accretion flow into the jet. The precession rate and the primary black hole mass may be independently determined from both sets of
flares; the
tidal flare of October 2022 was recommended for an intense campaign for this reason. This paper describes these observations over a wide spectral range. We show that the October 2022
flare fits the expectations for a
tidal flare and thus supports the earlier determination of the mass of the binary black hole system in OJ 287. The mass of the primary may also be deduced from secondary indicators such as the correlation with the hydrogen line strength and the black hole mass. These studies require that the mass is above $M_{BH} \sim 10^{10} M_{\odot}$, but do not specify the value more exactly.
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All authors Mauri J. Valtonen, Staszek Zola, Manpreet Singh, Andrei V. Berdyugin, Kari Nilsson, A. Gopakumar, Alok C. Gupta, Tapio Pursimo, Alexandr E. Volvach, Marek Drozdz, Waldemar Ogloza, Rene Hudec, Martin Jelínek, Jan Štrobl, Michal Zejmo, Stefano Ciprini, Daniel E. Reichart, Vladimir V. Kouprianov, Alberto Sadun, Markus Mugrauer, Katsura Matsumoto, Ryo Imazawa, Makoto Uemura, Lankeswar Dey
Quantum Physics
Learning unknown stabilizer codes using product measurements
Heather Leitch, Sri.S.Tirukkovalluri and Yingkai Ouyang
Efficiently characterizing
quantum error correcting codes is a key challenge on the path to fault-tolerant
quantum computation. Stabilizer codes, a central class of such codes, are defined by a set of stabilizer generators. Here, we present an
algorithm that uses random single-
qubit measurements to learn the stabilizer generators of any stabilizer code from $N$ copies of stabilizer states in its codespace, requiring no prior knowledge of the code's structure. This also enables verification that a device implements its intended code. We derive a lower bound on $N$ needed to recover the stabilizer generators with high probability, together with a bound on the
algorithm's overall probability of success. When applied to
quantum low-density parity-check (qLDPC) codes, a leading candidate for practical fault-tolerant architectures, our approach requires a number of states that scales polylogarithmically with $n$, the number of
qubits.
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Optics
Fisher-information retention under local driving in non-Hermitian feed-forward chains
Qingrui Bai, Zhichao Li and Junlong Kou
When local drive hardware is installed before a sensing task is revealed, directional non-Hermitian buildup creates a tradeoff between targeted preparation and spatial coverage. We quantify this tradeoff for stable linear scatterers with proper complex Gaussian output statistics. For parameters encoded in the internal generator, and at fixed coherent internal resource, the drive hardware enters the optimized mean-response Fisher information only through the projector onto the internally reachable subspace, while the preparation Gramian sets the source cost. In an on-resonance feed-forward chain, nested Green-function columns decompose into disjoint port intervals, and the site-local retention factors in each interval sum exactly to unity. Directionality concentrates this unit downstream, so the worst-site retention decays exponentially when one port serves many sites; for $m$ equal intervals, a single probe shared by all tasks has a worst-site retention lower by a further factor $m$ than task-specific reoptimization. Joint source-power and internal-resource constraints connect this fixed-resource law to source-limited preparation. A noisy RLC/VCCS model illustrates the retention law with stored electromagnetic energy, covariance Fisher information, and component disorder. The resulting bounds turn directional buildup into a port-layout criterion: source savings for a selected task are accompanied by a spatial coverage cost for tasks unknown at the hardware-design stage.
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Statistical Mechanics
Anomalous diffusion in porous fractal media
Alexander Iomin and Trifce Sandev
We suggest a model of a diffusive process inside a fractal sponge structure, which is a generalization of the
diffusion processes on a comb and fractal mesh structure. The sponge model is considered as the direct product of Cantor sets. It is shown that the corresponding one-dimensional
diffusion process is governed by a generalized Fokker-Planck equation with a power-law
memory kernel and a position-dependent
diffusion coefficient. That is, the fractal structure of the medium induces
memory effects and heterogeneity in the transport system. The considered model may be of interest to describe anomalous heat transport in porous fractal media.
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