Fluid Dynamics · Cross-listed from math.AP
On the impact of clusters of rigid balls on the motion of a viscous fluid
Marco Bravin, Eduard Feireisl, Arnab Roy et al. (+1 more)
We develop a new approach to the problem of the motion of a large number of rigid bodies immersed in a viscous fluid. The leading idea is the concept of cluster - a collection of individual rigid objects that may be grouped or even connected in such a way that their collective impact on the bulk motion of the system is similar to that of a single body. The applications of the new approach include: 1. Improving the critical value of the number of balls of small radius such that their cloud has no impact on the limit system represented by the incompressible Navier–Stokes equations. 2. The balls follow the fluid flow in the asymptotic limit of vanishing radius and increasing number even if a gravitational force is imposed.
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All authors Marco Bravin, Eduard Feireisl, Arnab Roy, Arghir Zarnescu
Soft Condensed Matter
The hydrodynamic Euler-elastica: shape transitions in the dynamical buckling of elastic filaments in Stokes flow
Clément Moreau, Laetitia Giraldi and Hermes Bloomfield-Gadêlha
The buckling of elastic filaments in viscous fluids, ubiquitous in biological systems like flagella, microtubules, and DNA, has long been described by the static Euler-elastica. Yet, when such filaments buckle dynamically, their shapes defy static predictions, exhibiting complex, unpredictable behaviours. Here, we use a coarse-grained numerical model to explore the long-timescale dynamics of filament buckling in Stokes flow, revealing three distinct morphological regimes, termed flip, loop, and
knot. The dominance of each regime is primarily governed by the dimensionless buckling number $\mathrm{Bu}$.
Fourier analysis shows that these transitions between shape regimes arise from competition between the first three
curvature modes, with high-order modes decay fitting an exponential law. In some parameter ranges, distinct shapes coexist for close initial conditions, indicating deterministic sensitivity to small perturbations. These findings bridge static and dynamic buckling theories, with implications for biological propulsion and the design of microscale slender swimmers.
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Astrophysics of Galaxies
The size of the HI disk across different environments: isolated, compact groups, clusters, and pairs
R. Ianjamasimanana, L. Verdes-Montenegro, K. M. Hess et al. (+8 more)
The 21 cm line of atomic hydrogen (HI) is a sensitive tracer of the outer disk of
galaxies, where environmental signatures are most apparent. The relative extent of HI disks compared to optical disks ($D_{\rm HI}$ vs $D_{25}$) is thought to provide a quantitative measure of such imprint, yet systematic comparisons between extreme environments remain scarce. We quantify the relative extent of HI disks in Hickson Compact Groups (HCGs) and in the Analysis of the interstellar Medium in Isolated
GAlaxies (AMIGA) sample, using AMIGA as a control sample that captures secular
evolution with minimal external influence. We calculate HI diameters by directly fitting an ellipse to the $1\,M_{\odot}\,{\rm pc}^{-2}$ iso-density contour. Because $D_{\rm HI}$ and $D_{25}$ are nonlinearly related, we avoid the traditional $D_{\rm HI}/D_{25}$ ratio, which carries a size-dependent bias, and instead quantify truncation as the residual from the isolated-
galaxy $D_{\rm HI}$-$D_{25}$ baseline, which we establish for AMIGA via
Bayesian analysis. The full analysis is provided as a reproducible Python package and Snakemake workflow. HCG
galaxies lie systematically below the isolated-
galaxy baseline in the $D_{\rm HI}$-$D_{25}$ plane. When members with HI nondetections are included as upper limits, HCGs have HI disks at least ~71% smaller than expected for isolated
galaxies of the same optical diameter. The truncation increases monotonically along the HCG evolutionary sequence, from Phase 1 to Phase 3. A comparison with literature samples places HCGs at the most-truncated end, statistically indistinguishable from the Virgo cluster sample (VIVA). Compared to AMIGA, HI disks are typically smaller relative to the optical disk in loose groups, compact groups, and cluster infall/field environments, and are most strongly truncated in HCGs and in the Virgo cluster sample.
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All authors R. Ianjamasimanana, L. Verdes-Montenegro, K. M. Hess, P. Kamphuis, M. G. Jones, J. Garrido, S. H. A. Rajohnson, A. Sorgho, B. Namumba, S. Sánchez-Expósito, M. Korsaga
Quantum Physics
Host-guest Crystal Engineering Tailors the Room Temperature Spin Dynamics in Molecular Quantum Devices
Ziqiu Huang, Angus Cowley-Semple, Irena Nevjestic et al. (+5 more)
Molecular materials that enable coherent control over an electron's
spin state at room temperature are promising candidates for
quantum technologies, including
quantum sensors and ultra-low noise microwave amplifiers, known as masers. Host-guest molecular
crystals enable independent control of
spin-active guests and their local environments to enhance molecular
spin properties and so improve device performance. Using electron paramagnetic resonance and optically-detected
magnetic resonance, we demonstrate the ability to tune triplet population, depopulation, and
spin-
lattice relaxation by modulating host-dependent
lattice rigidity and vibrational coupling to significantly reduce the operating requirements for building useful masers. Importantly, the most rigid host, picene, reveals the ability to slow
spin-
lattice relaxation without lengthening triplet lifetime, though at the cost of strain-induced line width broadening and reduced triplet
spin polarisation. We also find that deuteration reduces the triplet resonance line width and vibrationally-mediated triplet depopulation. Consequently, we find that perdeuterated pentacene in perdeuterated p-terphenyl is the most viable candidate for building a continuous wave maser. This work demonstrates host-guest engineering as an important and practical method for tuning the
spin-dependent performance of room-temperature molecular
quantum technologies.
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All authors Ziqiu Huang, Angus Cowley-Semple, Irena Nevjestic, Yifan Yu, Mark Oxborrow, Sam L. Bayliss, Sarah K. Mann, Max Attwood
Other Condensed Matter
Quantitative Theory for the Amplitude of Fluorescence Quantum Beats from Geminate Triplet-Pair Fusion
Zachary Rex, Bách Phạm Xuân, Gerald Curran III et al. (+1 more)
We derive the amplitude of
quantum-beats in the fluorescence from geminate triplet-
exciton fusion in rubrene and tetracene from the full set of parameters that characterize triplet
exciton dynamics. We find that the amplitude depends on the fission time in tetracene, but does not do so in rubrene, where it is determined by the dimensionality of triplet transport. Kinetic Monte Carlo simulations reproduce the experimental data in both materials, for a fission time of the order of 200 ps and isotropic triplet transport int tetracene, and for a triplet hopping time along the herringbone axis of 250 ps and anisotropic transport in rubrene.
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All authors Zachary Rex, Bách Phạm Xuân, Gerald Curran III, Ivan Biaggio
Soft Condensed Matter
String Model Predicts Relaxation in Sheared Glass-Forming Liquids
Zi-Long Wang, Qi-Lu Yuan, Yun-Jiang Wang et al. (+4 more)
Understanding how structural relaxation evolves from
equilibrium to nonequilibrium conditions remains a central problem in glass physics. Using simulations of model glass formers under steady shear, we show that the String Model, which links stringlike cooperative rearrangements to relaxation in
equilibrium glass-forming
liquids, predicts the structural relaxation time across the full range of temperatures and shear rates investigated without additional nonequilibrium fitting parameters, when combined with a shear-dependent effective temperature that is captured by a generalized fluctuation-dissipation relation. These results indicate that
equilibrium and nonequilibrium relaxation are governed by the same underlying cooperative mechanism, but they occur under different effective thermodynamic conditions under steady shear. More broadly, our study provides a unified microscopic description of thermal and mechanically driven dynamics in glass-forming
liquids.
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All authors Zi-Long Wang, Qi-Lu Yuan, Yun-Jiang Wang, Jack F. Douglas, Matteo Baggioli, Zhao-Yan Sun, Wen-Sheng Xu
High Energy Physics (Theory)
A unified expansion of Einstein's gravity
Arkachur Bhattacharya and Pushkar Soni
Non-Lorentzian theories of
gravity, most common of which are Galilean and Carrollian
gravity, arise from General relativity under suitable scalings. General relativity can be obtained by gauging the Poincaré
algebra. A convenient formulation of non-Lorentzian
gravity follows the contraction of the Poincaré
algebra in the tangent space to its non-Lorentzian counterparts, e.g. Galilean and Carrollian
algebras. In existing literature, different non-Lorentzian theories of
gravity have been addressed separately. In this paper, we introduce a single unified framework of expansion to address all these different theories. We show that different scalings can be unified into a single covariant form parametrized by $(s,n)$, alongside the contraction parameter $\epsilon$. Keeping these parameters unfixed in the limit $\epsilon \to 0$ defines a $\textit{unified flat geometry}$ and its $\textit{unified algebra}$, which reduces to a specific non-Lorentzian geometry for a particular choice of $s$ and $n$. Using this setup in the tangent space, we systematically expand the Einstein-
Hilbert action in even powers of $\epsilon$, which we call a $\textit{unified expansion}$ of Einstein's
gravity, whose leading-order theory is fixed by $(s,n)$. This reproduces various classes of gravitational theories, including Einstein
gravity (the trivial case), Galilean
gravity, Carroll
gravity, all of which can be extracted from this expansion. Using the expansion, we then formulate String Carroll (SC)
gravity, where the local metric has two vanishing
eigenvalues. The near-horizon region of generic non-extremal black holes has been recently shown to be a SC geometry. By considering explicit examples, we confirm that these near-horizon geometries constitute solutions of SC
gravity, paving the way of understanding physics near the horizon of generic black holes in terms of SC
gravity.
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General Relativity and Quantum Cosmology
Biases in Tests of General Relativity from Microlensed Gravitational-Wave Signals
Anirban Kopty, Apratim Ganguly, N. V. Krishnendu et al. (+1 more)
Gravitational-wave (GW) observations of compact binary mergers enable precision tests of general relativity (GR) in the strong-field regime, but their reliability depends on accurate waveform modeling. Unmodeled physical effects can induce systematic biases that mimic deviations from GR. Here we study the impact of GW microlensing on standard LIGO-Virgo-KAGRA tests of GR using GW150914-like simulated signals lensed by isolated point-mass objects with masses in the range $10-10^{5}M_\odot$. We perform
Bayesian parameter estimation with unlensed waveform templates and quantify biases in parameterized tests, modified dispersion relation tests, the inspiral-merger-ringdown consistency test (IMRCT) and the meta-IMRCT framework. To compare these tests with a common discriminator, we introduce a unified GR-deviation significance statistic based on the GR
quantile, applicable to both one- and multi-dimensional deviation parameters. We find that microlensing-induced waveform distortions can produce significant false deviations from GR, reaching $\sim4\sigma$ in one-dimensional tests and $\sim4.5\sigma$ in two-dimensional consistency tests, despite the injected signals being fully GR-compatible. These false deviations arise mainly in the wave-optics regime, where diffraction induces frequency-dependent amplitude and phase modulations, while signals in the long-wavelength and
geometric-optics regimes remain largely consistent with GR. We also find that the significance of these apparent deviations does not correlate strongly with microlensing detectability as measured by Bayes factors, showing that GR tests probe waveform projections not captured by global
lensing diagnostics. Our results establish wave-optics gravitational
lensing as an important astrophysical systematic for present and future precision tests of GR and highlight the need to model propagation effects in next-generation GW analyses.
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All authors Anirban Kopty, Apratim Ganguly, N. V. Krishnendu, Anuj Mishra
Materials Science
Valley polarization, Rashba interaction, and weak altermagnetism in inversion-asymmetric MnPS$_\text{3}|$WS$_\text{2}$ van der Waals heterostructures
Purba Dutta, Soumajyoti Bid and Nirmal Ganguli
The deliberate breaking of inversion ($\mathcal{P}$)
symmetry in antiferromagnets has recently emerged as an effective means to induce various features, such as the emergence of Berry
curvature,
spin-valley locking, magnetoelectric coupling, and the transition from conventional antiferromagnetism to altermagnetism. Conversely, in non-
magnetic systems, inversion
symmetry breaking in the presence of strong
spin-orbit interaction (SOI) gives rise to momentum-dependent
spin splitting via the Rashba effect, enabling tunable
spin polarization through external electric fields. Motivated by recent advances in two-dimensional materials, we perform first-principles calculations based on density functional theory to investigate the van der Waals (vdW)
heterostructure formed by a $\mathcal{P}$-symmetric MnPS$_3$ monolayer and a WS$_2$ monolayer. We demonstrate that the interface hosts a rich interplay of emergent phenomena, including an altermagnetic phase, Rashba
spin splitting,
spin-valley locking, and valley polarization. Our results demonstrate that the
heterostructure exhibits semiconducting behavior with a direct band gap of approximately 1.65~eV and a type-I band
alignment. Remarkably, the electronic structure and band
alignment can be effectively tuned between type-I and type-II regimes via an external electric field and in-plane biaxial strain. Furthermore, field-induced modulation enables strong control over the altermagnetic phase and the valley splitting. These findings establish the proposed vdW
heterostructure as a highly tunable platform with significant potential for spintronic and valleytronic applications.
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Disordered Systems and Neural Networks
Nanowire networks' interconnection graphs from their photomicrographs
Javier Tau Anzoátegui, Juan Ignacio Diaz Schneider, Eduardo D. Martínez et al. (+3 more)
Self-assemblies of tunable units are being intensively studied as physical systems with signal-processing capabilities. Specifically, silver nanowire networks (AgNWNs) have demonstrated accumulation, non-linearity, and
memory retention with multiple timescales, features that enable a wide variety of neuromorphic implementations. In this study, we aim to extract the interconnection scheme to analyze the experimentally obtained network architecture and, eventually, use it as input to a previously developed simulation platform. By post-processing photomicrographs of AgNWN, we present a pipeline optimized to extract the interconnection diagram, recognizing the intersections formed among the nanowires, to determine the associated graph for each physical sample. A graph is a collection of nodes and edges whose properties can be associated with different electrical responses. It is thus possible to study graphs' metrics, such as the degree distribution, community size, clustering coefficient, and path-length, to compare the experimental assemblies' attributes to those of topological models of reference. Small-world, modular, and scale-free are well-known structures in the field of mathematical graphs. By analyzing the degree distribution, the adjacency
matrices, among other useful representation means, the experimental assemblies reveal similarities to both small-world and modular
topologies. All the mentioned analyses were conducted considering the interconnection scheme obtained from zenithal-view optical images, which overestimates the number of NWs' interconnections (due to the impossibility of distinguishing real junctions from spurious cross-points between vertically displaced NWs). For that reason, this communication also studies the impact of artificially removing junctions from the resulting graphs on the previously calculated clustering coefficient and path length.
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All authors Javier Tau Anzoátegui, Juan Ignacio Diaz Schneider, Eduardo D. Martínez, Pablo Levy, Oscar Filevich, Cynthia P. Quinteros
Medical Physics
Sensitivity of silicon-to-water dose conversion and Bragg-peak metrics to stopping-power datasets in proton dosimetry
F. Matias, J. M. B. Shorto, P. de Vera et al. (+5 more)
Accurate
proton dosimetry requires consistent stopping-power data for detector-to-water conversion and Monte Carlo radiation transport. We quantify the sensitivity of water-to-silicon stopping-power ratios, converted dose-to-water distributions, and Bragg-peak metrics to the stopping-power
dataset for a 67.5 MeV pristine
proton beam in water. PHITS simulations used SRIM-2013, PSTAR/NIST, ATIMA, and TDDFT-Penn stopping powers up to 10 MeV, together with a common SBETHE-based extension at higher energies. The water-to-silicon stopping-power ratio showed relative entrance-to-distal variations of 17.40%$-$22.10%. Conversion of normalized PTW silicon-diode percentage-depth-ionization data yielded relative percentage-depth-dose curves with a common maximum at 36.86 mm, consistent with the experimental Bragg-peak depth of (36.81 $\pm$ 0.15) mm. The converted curves were approximately 3% below the reference throughout the entrance and plateau regions, while deviations of up to 2.1% occurred near the Bragg peak. Direct PHITS calculations predicted Bragg-peak depths of 36.575$-$36.675 mm; only the TDDFT-Penn result lay within the quoted experimental uncertainty. These results show that stopping-power treatment affects the magnitude of the converted dose more strongly than the Bragg-peak position does, and that it should be harmonized or explicitly included in uncertainty budgets for
proton-beam calibration, commissioning, quality assurance, and Monte Carlo validation.
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All authors F. Matias, J. M. B. Shorto, P. de Vera, R. Garcia-Molina, I. Abril, T. F. Silva, J. Pereira, H. Yoriyaz
Materials Science
Atomically precise triple-step staircase on a vicinal silicon surface: Is it Si(5 5 7), Si(7 7 10) or Si(8 8 11)?
A. N. Chaika, A. Yu. Aladyshkin, V. N. Semenov et al. (+3 more)
Scanning tunneling microscopy studies of periodic arrays of triple steps fabricated on single-crystalline Si(5 5 7) wafers demonstrate several possible atomic structures of consecutive steps and Si(1 1 1) terraces maintaining the same periodicity on micrometer-sized surface areas. Detailed analysis of the atomically resolved data reveals the formation of Si(8 8 11) triple-step staircase with a period of 18b=5.99 nm in projection onto the terrace plane, where b=0.333 nm is the distance between atomic rows for the Si(1 1 1)1x1 surface. Schematic models for several possible configurations of either 7x7 or 5x5-reconstructed terraces and triple steps are proposed.
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All authors A. N. Chaika, A. Yu. Aladyshkin, V. N. Semenov, A. S. Aladyshkina, A. M. Ionov, S. I. Bozhko
General Relativity and Quantum Cosmology
Gravitational Waves as Thermodynamic Shear Excitations in Scalar-Tensor Gravity
David S. Pereira
Can a propagating
spin–2 mode participate in a local thermodynamic process without assigning an autonomous
entropy or a unique local energy to the wave itself? We show that this occurs in Jordan-frame scalar–tensor
gravity, where a timelike scalar gradient defines an internal gravitational thermodynamic medium. Building on the first-order TT deformation–response relation, we identify the local shear power $\mathcal W_\phi=\pi_{ab}^{(\phi)}\sigma^{ab}$ from scalar-frame traction mechanics and show that its leading pure-TT contribution is second order, gauge invariant, and enters the exact scalar-sector energy balance. We further show that the same effective anisotropic stress controls the non-GR tensor damping, so the local thermodynamic exchange is directly encoded in gravitational-wave propagation. In
geometric optics the corresponding ratio of shear work to GR-normalized tensor energy is controlled by the running effective Planck mass, linking the local process to the modified gravitational-wave luminosity distance. Finally, we extend this shear-excitation mechanism to nonminimally coupled scalars, metric $f(R)$
gravity, and viable luminal Horndeski theories, and identify the condition required for the same interpretation in more general tensor sectors.
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Quantum Physics
Feynman Meets Turing: The Curse of Quantum Universality
Yannik N. Böck, Holger Boche and Frank H.P. Fitzek
We consider a formal model of
quantum circuit description
languages (QCDLs) in which semantically meaningful programs correspond to computable
unitary matrices. We show that any semantically universal QCDL – that is, any QCDL able to describe all computable
unitary matrices, which in turn form the set of
matrices we can meaningfully represent on digital hardware – cannot have a semi-decidable set of semantically meaningful descriptions. In particular, no such
language admits a compiler that reliably recognizes all valid program descriptions. This result stands in contrast to classical programming
languages. While compilation in
languages such as C or C++ may itself involve non-terminating computations, the set of semantically meaningful programs remains recursively enumerable, since successful compilation provides a witness of validity. The essential difference lies in the nature of the semantic domains: classical
languages describe partial recursive functions, whereas QCDLs describe total
unitary operators. Our analysis establishes a fundamental limitation of
quantum circuit description
languages and highlights a structural distinction between classical and
quantum models of computation at the level of formal
language theory.
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Optics
Two-color solitons in Kerr third harmonic generation model
Alexey Sukhinin, Curtis Menyuk, Natalia Litchinitser et al. (+2 more)
We investigate two-color, two dimensional spatially localized light modes in a resonant Kerr third-harmonic generation model. Using computational tools, we identify two distinct families of localized states. Unlike the single-component 2D nonlinear Schrödinger equation and previously studied non-resonant two-color systems, the dynamics are not dictated by a universal critical power, but depend on the distribution of power between the harmonics. The "fundamental-dominated" family acts as a "dynamical separatrix" between simultaneous collapse and joint diffraction, whereas the "third-harmonic-dominated" family does not. We further identify resonant collapse events accompanied by strong oscillations of the third harmonic, revealing a collapse mechanism absent from standard Kerr self-focusing.
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All authors Alexey Sukhinin, Curtis Menyuk, Natalia Litchinitser, Jean-Claude Diels, Alejandro B Aceves
Astrophysics of Galaxies
VAR-PZnn: A machine-learning framework for AGN photometric redshifts using color and variability-based features
S. Satheesh-Sheeba, P. Sánchez-Sáez, R. J. Assef et al. (+39 more)
Photometric
redshift estimation for active
galactic nuclei (AGNs) remains a fundamental challenge for current and upcoming large-scale photometric surveys. Traditional spectral energy distribution (SED) fitting suffers from color-
redshift degeneracies, particularly for AGNs whose power-law continua hide the strong spectral features required to anchor
redshift estimates. While AGN variability provides additional constraining power, existing frameworks require multi-band light curves that are not always available. This work presents VAR-PZnn, a fully connected mixture density network that integrates 26 variability features extracted from ZTF g-band light curves with optical photometry from Pan-STARRS1, mid-infrared (MIR) photometry from CatWISE, and, for a subsample, NIR photometry from UKIDSS. The model is trained and tested on 72,728 spectroscopically confirmed AGNs/QSOs spanning 0.01 < z < 4.5 and g-band magnitudes from 17 to 21.5. For the main sample, we achieve \sigma_{NMAD} = 0.058 and an outlier fraction of \eta = 8.2%, which reduces to 5.4% when the 10% of sources with the highest predicted uncertainty are excluded. An ablation study demonstrates that MIR photometry provides the dominant constraint for photo-z accuracy, while variability features serve as a secondary refiner. Using UKIDSS NIR data as a proxy for future synergies between LSST and space-based missions like Euclid and Roman, we obtain \eta = 13.3% without MIR data and \eta = 4.6% when MIR is available. We
benchmark against Low-Resolution Templates (LRT) SED fitting (\eta = 28.7%) and the VAR-PZ framework; applying single-band VAR-PZ priors worsens LRT performance to \eta = 39.4% due to single-band light-curve degeneracies, confirmed via simulations (\eta = 27.6% to 28.1%). This framework provides a scalable approach for the Legacy Survey of Space and Time (LSST).
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All authors S. Satheesh-Sheeba, P. Sánchez-Sáez, R. J. Assef, T. Anguita, R. Shirley, M. Salvato, P. Arévalo, T T. Ananna, F. E. Bauer, C. G. Bornancini, W.N. Brandt, D. De Cicco, M. Espinoza-Ortiz, J. Fagin, M. Fatović, A. W. Graham, H. Guo, L. Hernandez-García, D. Ilić, A. B. Kovačević, P. Lira, A. I. Malz, M. Marculewicz, D. Marsango, C. Mazzucchelli, T. Mkrtchyan, S. Panda, A. Peca, V. Petrecca, B. Rani, C. Ricci, G. T. Richards, R. A. Riffel, A. Rojas-Lilayú, E. Saremi, D. P. Schneider, B. Sotomayor, M. J. Temple, A. Viitanen, I. Yoon, Z. Yu, F. Zou
General Relativity and Quantum Cosmology
Probing f(R) AdS Black Hole via Hawking Evaporation, Shadows and Thermal Fluctuations
Muhammad Israr Aslam, Saira Waheed, Rabia Saleem et al. (+1 more)
The process of Hawking evaporation, shadows and thermal fluctuations are investigated within the fabric of f(R) AdS Black Hole (BH). Specifically, the Hawking evaporation process is analyzed numerically using the Stefan-Boltzmann law. The results indicate that the BH lifetime is always infinite, which means the BH becomes a remnant in the late time. Additionally, the evaporation rate depends on the AdS radius and coupling parameters. We further examined the visual properties of BH shadows observed for various values of the two parameters. The results reveal that the BH shadow radius decreases with $\psi_{0}$, while it increases with $\lambda$. Consequently, we further investigate the infalling
accretion matter in the vicinity of BHs. The results depict that while variations in relevant parameters do influence the central region, the important factor is the change in optical appearance of the bright
photon ring, which is exhibited at the position of the
photon sphere. Next, we discuss many thermodynamical quantities, such as temperature,
entropy, Helmholtz free energy, internal energy, corrected pressure, enthalpy, Gibbs free energy and specific heat and interpret how the variations in $\lambda$ and $\psi_{0}$ impact on the stability and phase transitions of the AdS BHs.
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All authors Muhammad Israr Aslam, Saira Waheed, Rabia Saleem, Nazek Alessa
Soft Condensed Matter
Nonlocal Electrostatic Field Theory from Microscopic Description
Varazdat Stepanyan, Yevgeni Sh. Mamasakhlisov and Armen E. Allahverdyan
The study of electric fields in soft materials converges either to the study of point-like particles (local) in nonlinear theories or to the use of particles with finite sizes in nonlocal linear theories. In this work, we start from the microscopic equations of motion and construct a unified mean field Fokker-Planck equation that describes the non-
equilibrium electrostatics of nonlocal nonlinear systems. We obtain a generalized Poisson-Boltzmann equation for such systems, as well as their electrostatic free energy expression. In the linear approximation, we obtain an anisotropic susceptibility in an isotropic fluid, which allows for local linear response inversion in electrostatics.
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High Energy Physics (Phenomenology)
Light-front diagnostics in the 't Hooft model: II. Boundary cancellations, ERBL spectral sums, and analyticity of the EMT form factor
Arkadiy I. Syamtomov
A diagonal light-front overlap contains near-forward energy-momentum-tensor (EMT) information but is not itself a local
matrix element. In the large-$N_c$ 't Hooft model we complete the second GPD moment with its ERBL contribution and follow how the two support regions combine. Boundary exponents generate fractional powers and, at $\beta=1/2$, resonant logarithms in the separate terms. We show that these structures cancel, including the interference of the leading and next indicial families. At the resonance, cancellation of the double and single logarithms also yields an inverse-mass-squared residue sum rule; above it, the two regions combine into a finite fourth-order coefficient. The complete EMT form factor is therefore analytic through
curvature order. The ERBL sector leaves the slope unchanged but is essential for
curvature and higher derivatives. We extract stable canonical and heavy
curvatures, estimates with systematic envelopes for the second and third light excitations, and the longitudinal trace radius. The intermediate-state decomposition further shows how constituent mass and excitation redistribute pole strength and generate removable poles and interference zeros.
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Mathematical Physics
Frame Representation of the First-Order Part of the Laplace-Beltrami Operator
A.G.Nuramatov
We investigate the
geometric content of the first-order part of the Laplace–Beltrami operator on an oriented Riemannian
manifold. Relative to an arbitrary local orthonormal frame, the first-order part of the Laplace–Beltrami operator defines a distinguished vector field, whose coefficients are expressed through the Levi–Civita connection forms. The corresponding one-form determines a covariant derivative whose connection factorization removes the first-order part of the Laplace–Beltrami operator and replaces it by a natural scalar potential. The construction is frame dependent. We show that its transformation under local rotations of the orthonormal frame compensates the corresponding variation of the sum-of-squares part, leaving the full Laplace–Beltrami operator invariant. These results reveal the
geometric role of the first-order part of the Laplace–Beltrami operator.
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High Energy Astrophysical Phenomena
Simultaneous radio, optical and X-ray monitoring of hard X-ray selected AGN: a variability study
L. Hernández-García, F. Panessa, D. Williams-Baldwin et al. (+2 more)
AGN emission is intrinsically variable across the electromagnetic spectrum. Mapping the coupling between the
accretion disk, the X-ray corona, and ejection flows is key to understanding the energy flow within the central engine. We characterize the multi-wavelength variability of 14 hard X-ray selected AGN from the INTEGRAL/IBIS catalog in the
radio, optical, and X-ray bands, to determine the coupling between these frequencies and how variability relates to the physical properties of the central engine, with emphasis on the
radio band. We analyzed multi-epoch observations from AMI-LA at 15 GHz, ZTF in the g and r bands, and Swift/XRT over 2018–2020. Variability was quantified using the normalized excess variance, the fractional variability amplitude, and the Mexican Hat filter at 70- and 200-day timescales. We also characterized the
radio-loudness of the sample and evaluated the impact of variability on the Fundamental Plane of black hole activity by comparing time-averaged with strictly simultaneous data. Significant variability is detected in 86% of the sample, with a clear amplitude stratification: the fractional rms amplitude is highest in X-rays, with a median of 30% (11-67%), followed by the optical g and r bands at 19% (2-33%) and 8.5% (0.2-24%), and the
radio band at 10% (4-23%). The Mexican Hat analysis reveals a red-noise power spectrum dominated by long-term fluctuations. The sample follows the expected Fundamental Plane scaling; although individual sources shift within the relation due to
stochastic fluctuations, this dispersion accounts for only ~3% of the total scatter. Our findings support a core-dominated origin for the 15 GHz emission, likely a compact jet base or a magnetized corona, while differences in variability patterns,
radio-loudness, and Fundamental Plane location point toward distinct
accretion/ejection processes and degrees of corona-jet coupling.
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All authors L. Hernández-García, F. Panessa, D. Williams-Baldwin, P. Arévalo, A. M. Muñoz Arancibia
Solar and Stellar Astrophysics
Dynamical friction in stratified stellar envelopes
Damien Gagnier
Dynamical friction prescriptions used for common-envelope and planetary engulfment inspirals often assume a homogeneous medium and/or rectilinear perturber motion. A gravitating object embedded in a
giant-
star envelope instead excites an orbit-scale wake while moving on a curved orbit through a finite, radially stratified medium. We formulate the linear barotropic acoustic response of a weak point perturber on a circular orbit in a hydrostatic, spherically stratified gaseous medium. We apply the formulation to single perturbers in power-law density profiles and
giant-
star envelope models, and to double perturbers in power-law density backgrounds. We find that stratification affects dynamical friction through the global structure of the wake. The radial component is set by the low-order, orbit-scale wake and can strongly differ in amplitude and sign from the homogeneous-medium result. The azimuthal component is also modified by stratification, but in the supersonic regime it retains the Coulomb-logarithmic sensitivity of the homogeneous problem. In double-perturber systems, the companion wake can substantially change the radial force and reduce the azimuthal drag on a given component, but, unlike the perturber's own wake, it has no local Coulomb-logarithmic contribution. For the adopted
giant-
star envelope profiles, the azimuthal drag exerted by the stratified wake gives shorter inspiral times than uniform-medium prescriptions evaluated with the same local background quantities. The formulation provides a flexible tool for computing embedded-perturber wakes in prescribed radial stratifications and is a first step toward computationally efficient, self-consistent models of common-envelope and planetary-engulfment inspirals.
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High Energy Astrophysical Phenomena
Detectability of Gravitational-wave counterparts of EP-FXTs observed during the O4b LIGO-Virgo-KAGRA Observing Run
Ansh Chopra, Samuele Ronchini, Biswajit Banerjee et al. (+5 more)
Fast X-ray transients (FXTs) detected by the Einstein Probe mission have emerged as a rapidly growing class of extragalactic transients, whose physical origin remains uncertain. Compact binary coalescence (CBC) systems have been proposed as one possible progenitor for at least a subset of these events, making FXTs promising targets for multi-messenger studies with gravitational-wave (GW) observations. This work presents the first systematic investigation of GW counterparts to FXTs observed by Einstein Probe and assesses the detectability of associated CBC. We focus on FXTs detected during the second half of the fourth observing run (O4b) of the Advanced LIGO-Virgo-KAGRA detector network by searching for temporal coincidences with GW candidates from the fifth Gravitational-Wave Transient Catalog (GWTC-5). We analyze a sample of 47 FXTs, including 11 with measured
redshifts, and assess the significance of the association between FXTs and GW candidates using a ranking statistic. We find no significant GW counterpart associated with any FXT in our sample. In the absence of a detection, we place 90% exclusion-distance constraints under the assumptions of binary
neutron star and
neutron star-black hole progenitor scenarios. For observations with the full LIGO and Virgo detector network, the typical median exclusion distances are $\sim$178 Mpc and $\sim$349 Mpc, respectively. These constraints disfavor a nearby compact-binary merger origin. Longer periods of joint observations by the LVK and Einstein Probe, combined with improved GW detector sensitivity, will enhance the prospects for identifying genuine GW-FXT associations and place tighter constraints on the progenitor scenarios of these events.
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All authors Ansh Chopra, Samuele Ronchini, Biswajit Banerjee, Marica Branchesi, Stefano Ascenzi, Maria Edvige Ravasio, Peter Jonker, Andrew Levan
Quantum Physics
Remote Infrared Absorption Spectroscopy with Undetected Photons
Simon Neves, Fériel Armbruster and Jean-Pierre Wolf
We demonstrate a novel method for remote open-path
Fourier-transform infrared spectroscopy with undetected
photons. Similar to previous
quantum spectroscopy works, a mid-infrared spectrum is reconstructed by detecting a near-infrared radiation only, thus bypassing important limitations of infrared detectors. Our study however relies on the co-propagation of the
photon-pair and the pump-
laser over the same optical path, which allows the probing of the open atmosphere over long distances. By sending the
photons over unprecedented distances of up-to 43.4m in the outdoor atmosphere, we were able to detect butane released in the open-path, as well as natural atmospheric methane, thus demonstrating the first use of infrared spectroscopy with undetected
photons for atmospheric measurements.
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Astrophysics of Galaxies
LoVoCCS. III. Third Generation Pipeline & The Hercules Supercluster
Anthony M. Englert, Shenming Fu, Ian Dell'Antonio et al. (+29 more)
The Local Volume Complete Cluster Survey (LoVoCCS) is a volume-complete survey of over one-hundred nearby ($0.03 < z < 0.12$), X-ray luminous ($L_{500} > 10^{44} \text{ erg s}^{-1}$)
galaxy clusters in the southern sky. Observations for the survey concluded in December 2025, reaching Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) Year 1-2 depth in each field and providing observations with $\lesssim 1"$ seeing for weak
lensing science. In this paper, we present the latest pipeline for reducing observations using the third-generation of the LSST Science Pipelines. We use recent observations of the Hercules Supercluster to validate the pipeline's data-products and conduct an extensive multi-plane weak-
lensing analysis of a $\sim 16 \text{ deg}^2$ complex covering Abell 2147, 2151, 2152, and several additional structures. We confirm that the dynamical mass of the complex is biased due to the dynamical state of Abell 2147, which is consistent with being $\sim 0.2-0.4 \text{ Gyr}$ out-of periapsis, and estimate that the total mass of the supercluster is $8.9^{+1.7}_{-1.4} \times 10^{14}~M_{\odot}$.
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All authors Anthony M. Englert, Shenming Fu, Ian Dell'Antonio, Mohamed H. Abdullah, Shrouk Abdulshafy, Eddie Aljamal, William K. Black, Nicole Chidester, Doug Clowe, M. C. Cooper, Megan Donahue, Zacharias Escalante, August Evrard, Eric Habjan, Soren Helhoski, Binyang Liu, Jacqueline McCleary, Hironao Miyatake, Mireia Montes, Priyamvada Natarajan, Jessica Nelson, Michelle Ntampaka, Elena Pierpaoli, Marc Postman, Rahul Shinde, Jubee Sohn, Fuyuko Tanaka, David Turner, Keiichi Umetsu, Yousuke Utsumi, Ray Wang, Gillian Wilson
High Energy Physics (Theory)
Recursive construction of scalar one-loop integrals in dimensional regularisation
Paul Mork
We derive a novel recursive structure for dimensionally regularised scalar one-loop Feynman integrals based on Schläfli's differential formula for
hyperbolic simplices. The recursion relates the Laurent coefficients in the dimensional regulator $\varepsilon$ of an $N$-point integral to lower-order coefficients of integrals with additional external legs. The construction is seeded by the $\varepsilon=0$ contributions, which admit a
geometric interpretation as volumes of simplices in
hyperbolic space and are known in terms of multiple polylogarithms (MPLs). Iterating the recursion therefore provides a constructive
algorithm for computing arbitrary orders in the $\varepsilon$-expansion of scalar one-loop integrals with arbitrary masses and kinematics, while remaining entirely within the class of MPLs. In particular, this establishes that all coefficients in the Laurent expansion of dimensionally regularised scalar one-loop integrals can be expressed in terms of MPLs. As a first application beyond existing results, we obtain an explicit closed MPL expression for the $\mathcal{O}(\varepsilon)$ coefficient of the scalar hexagon with arbitrary masses and off-shell Euclidean kinematics.
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Strongly Correlated Electrons
$J_{1} - J_{2} - \delta$ model on a square lattice: From Altermagnet to Columnar antiferromagnet via quantum disordered phase
Subharthi Paul and Darshan G. Joshi
Altermagnetism in the case of local-moment magnets is characterized by zero net magnetization and splitting of opposite chirality
magnon bands in the absence of any
spin-anisotropic interactions or external field. In this work we investigate the robustness of altermagnets against
quantum fluctuations arising from
magnetic frustration. We consider a Heisenberg model on a square
lattice with two different types of second-neighbor interactions, as in a checkboard pattern, in addition to the nearest-neighbor interaction. This model continuously interpolates between the $J_{1}-J_{2}$ Heisenberg model on the square
lattice and the Heisenberg model on the checkerboard
lattice. For weaker second-neighbor interactions a Néel-type altermagnet phase is realized. On the other hand, for stronger second-neighbor interactions a columnar antiferromagnet emerges. Using linear
spin-wave theory we calculate the
magnon dispersion, order parameter, static and dynamical structure factors for the two
magnetic phases. Further, we show that there is an intermediate
quantum disordered phase separating the two
magnetic phases, which is connected to the one realized in the $J_{1}-J_{2}$ model. The
quantum disordered region is further stabilized as we tune towards the checkerboard
lattice limit.
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High Energy Physics (Experiment)
Measurement of the branching ratio of the $K^{+}\rightarrow\pi^{+}\nu\bar{\nu}$ decay
NA62 Collaboration
The NA62 experiment has measured the branching ratio of the rare decay $K^+\to\pi^+\nu\bar{\nu}$ using data collected in 2023 and 2024 at the CERN SPS, obtaining ${\rm B}_{\rm 2023-2024}(K^+\to\pi^+\nu\bar{\nu}) = \left(7.2^{+2.3}_{-2.1}\right)\times10^{-11}$. With results from data collected between 2016 and 2022, the analysis gives ${\rm B}_{\rm 2016-2024}(K^+\to\pi^+\nu\bar{\nu}) = \left(9.6^{+1.9}_{-1.8}\right)\times10^{-11}$, corresponding to a relative precision of $20\%$. This value is consistent with Standard Model predictions.
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Strongly Correlated Electrons
Multibath Influence Matrices: Universal Scaling from Real-Time Dynamics
Matan Lotem, Michael Sonner, Valentin Link et al. (+2 more)
Diverging timescales are the hallmark of critical dynamics and the bottleneck to their classical and
quantum simulation. To tame this, we compress a spacetime tensor network: temporally into
semigroup influence
matrices and spatially via
matrix-product states. Benchmarking on the two-
impurity Anderson model with its four fermionic species, we compute spectral functions to map the
evolution from a Kondo resonance, across a non-
Fermi-
liquid quantum critical point, and into a gapped singlet phase. Resolving transient through asymptotic dynamics in sudden quenches and Kibble-Zurek ramps, we obtain the universal two-channel-Kondo exponent. Together, these results establish multibath influence
matrices as a practical tool for real-time dynamics in strongly correlated multi-orbital systems.
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All authors Matan Lotem, Michael Sonner, Valentin Link, Alessio Lerose, Dmitry A. Abanin
Quantum Physics
Quantum-Centric Geometry Optimization with Wave-Function-Based Embedding
Danil Kaliakin, Akhil Shajan, Fangchun Liang et al. (+2 more)
The EWF-(FCI,SQD) method, a wave-function-based
embedding approach combining full configuration interaction (FCI) and sample-based
quantum diagonalization (SQD), is a promising new tool for the simulation of molecular systems. However, applications of EWF-(FCI,SQD) have so far been limited to single-point calculations, whereas the study of complex chemical processes requires the ability to explore potential energy surfaces. In this work, we demonstrate geometry optimization with EWF-(FCI,SQD), scaling our simulations to molecules as large as menthone and benzidine within the STO-3G basis set. Without fragmentation, these systems comprise 73 and 82 molecular orbitals respectively, presenting an intractable
Hilbert space for conventional exact or high-level subspace solvers and establishing a clear necessity for fragmentation-based methodologies. The underlying fragment SQD simulations in the EWF-(FCI,SQD) geometry optimizations use up to 70
qubits. The resulting geometries show exceptional accuracy relative to the classical reference, with deviations below 4 picometers.
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All authors Danil Kaliakin, Akhil Shajan, Fangchun Liang, Zhen Li, Kenneth M. Merz Jr