Computational Physics · Cross-listed from cs.LG
Latent PDE mapping for efficient physics-informed learning across geometries with limited data
Ingvild Askim Adde, Mary M. Maleckar and Gabriel Balaban
In this study, we introduce latent PDE mapping, a broadly applicable physics-informed learning technique designed to enable efficient
geometric generalization with sparse training data. Latent PDE mapping pulls back geometry-specific PDE residuals and boundary conditions to a predefined latent geometry via the deformation gradient, thereby enabling the automated calculation of geometry-consistent shape gradients that are missing in conventional physics-informed machine learning formulations. We demonstrate the utility of latent PDE mapping in solving the anisotropic Aliev-Panfilov PDE of cardiac electrophysiology using both physics-informed neural networks and physics-informed deep operator networks. The Aliev-Panfilov PDE serves as a challenging exemplar: a nonlinear, time-dependent PDE
benchmark with sharp gradients that are expensive to capture using traditional numerical solvers. To represent the limited data regime, we train the networks using just fifteen
geometric samples drawn from parameterized distributions in two and three spatial dimensions. While modest improvements appear for geometries parameterized by affine and shear deformations, latent PDE mapping demonstrates significant benefits on select
geometric families, achieving a factor ~4-6 reduction in mean relative L2 error. Furthermore, our results show that the computational cost of applying latent PDE mapping was modest during network training, and negligible at inference. Taken together, our study highlights how latent PDE mapping facilitates the creation of generalizable physics-informed machine learning models from limited sets of training geometries.
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Astrophysics of Galaxies
When Two Worlds Collide: How Collisions Between Silicate and Carbonaceous Nanograins can Drive Complex Chemistry
Alexandros Kyriazis, Albert Rimola and Stefan T. Bromley
Our overall objective is to determine how collision velocity governs the interactions between silicate and carbonaceous nanograins. We aim to: i) identify collisional regimes capable of producing mixed silicate-carbonaceous grains and/or chemically complex molecular species, and ii) quantify fragmentation threshold velocities related to
dust destruction. We performed molecular dynamics simulations employing a machine-learning force field to model head-on collisions between silicate and carbonaceous nanograins of comparable masses. Collision velocities span 1 - 11 km/sec. For all collisions, we tracked the extent of grain-grain mixing and the formation of molecular fragments. We identified four velocity regimes: 1) <1.5 km/sec, where grains bounce off one another, 2) 1.5-3.5 km/sec, where sticking between the grains starts to occur, 3) 3.5-7.5 km/sec, where grains tend to aggregate and form inter-grain chemical bonds, yielding stable mixed grains, and 4) >7.5 km/sec, where fragmentation dominates. The latter regime produces CO as the main product, along with hydrocarbons, complex organic molecules, molecular silicates, and mixed carbonaceous-silicate clusters. The fragmentation threshold velocity for these collisions is approximately 7.5 km/sec. We show that collision velocities govern both the physical and chemical outcomes of silicate-carbonaceous nanograin interactions. In the fragmentation regime, collisions provide a viable pathway for generating mixed grains and a wide range of molecular species, many of which have been observationally detected. Here, we provide a simple credible mechanism linking the physics of grain processing with observed complex interstellar chemistry.
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Fluid Dynamics
Bubble bursting in a sessile droplet
U. J. Gutiérrez-Hernández, B. Muñoz-Sánchez, A. Agúndez-Cruz et al. (+3 more)
We analyzed experimentally and numerically the bursting of a bubble within a sessile droplet. Our experiments show that both sessile droplet
curvature and confinement enhance the energy focusing. In the low-viscosity regime, this effect results in thinner, faster Worthington jets. In the high-viscosity regime, droplets are ejected for values of the Laplace number (the Reynolds number based on the visco-capillary velocity) smaller than the threshold for a bubble in an infinite
liquid bath. This is probably the major result of the present work. Numerical simulations show the critical role of the additional pressure gradient arising from the
curvature of the sessile droplet interface. The resulting force drives the
liquid towards the bottom of the cavity, compressing it and accelerating jet formation. In the low-viscosity limit, the bottom of the cavity becomes smoother before jet ejection. This effect resembles the energy-focusing enhancement that occurs in an infinite
liquid bath at the critical Laplace number, where short-wavelength waves are damped by viscosity.
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All authors U. J. Gutiérrez-Hernández, B. Muñoz-Sánchez, A. Agúndez-Cruz, J. M. Montanero, D. Fernández Rivas, M. G. Cabezas
Statistical Mechanics
An Experimental Scheme for Testing Molecular Rectification with Only Micrometer-Scale Fabrication Requirements
Jiantang Jiang
In our previous work, we proposed a theoretical model capable of inducing sustained directed transport without consuming information or external energy. However, the experimental verification schemes proposed previously were technically challenging, and the model has therefore not yet been experimentally tested. In this work, we propose a greatly simplified experimental design. By introducing hydrophilic functional groups onto the tip of a gold needle through surface modification and pressing the needle against one of two
liquid-vapor interfaces, the compressed interface is maintained at a higher ionic concentration than the other interface, thereby sustaining a concentration difference between them. This design reduces the fabrication requirement from the nanometer scale to the micrometer scale, substantially lowering experimental complexity and facilitating experimental examination of the proposed mechanism.
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Exactly Solvable and Integrable Systems · Cross-listed from math.CO
Mersenne Representation, the Conolly Sequence, and Soliton Profiles over Finite Fields
Fumitaka Yura
We study the canonical skew-binary representation of nonnegative integers, whose positional weights are the Mersenne numbers \(2^{k}-1\), and its decomposition into the binary and nonbinary sides. The nonbinary values, arranged in increasing order, form the OEIS sequence A055938, and their successor structure gives a direct proof of the relation with the OEIS sequence A080578 that is recorded as conjectural in the OEIS entry for A080578. The resulting formulas show that the Conolly sequence describes both sides of the decomposition: a shifted Conolly sequence is the counting function of the binary side, while the same sequence gives the increasing enumeration of the nonbinary side. We then develop the parent map, truncation blocks, truncation remainders, and the Mersenne tau function associated with this representation. The parent map is conjugate to deletion of the lowest digit. Differences of the Mersenne tau rows recover the parent iterates and the counting function, and they give formulas for digit reconstruction and for a diagonal tau defect. Finally, we revisit a known finite-depth one-
soliton family of the finite-field BBS. The Mersenne combinatorics is used directly to reconstruct a global integer-valued traveling-wave profile and to prove an integer window-counting
theorem. Reduction modulo \(3\) yields the corresponding finite-field traveling-wave solutions. We also construct an integer-valued traveling-wave tau function whose front values are given by the Mersenne tau rows. The resulting construction shows how the combinatorics of a number representation can enter directly into the reconstruction of solutions of an integrable system.
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Quantum Physics
Maximal Fisher Budget Forces Blind Directions in Bipartite Collective SU(d) Metrology
Tariq Aziz, Naeem Akhtar, Dong Wang et al. (+1 more)
For pure two-qudit probes used in a single fixed setting to estimate a common SU(d) transformation, maximal total Fisher sensitivity and full local identifiability are mutually exclusive. We derive exact identities that determine the trace of the
quantum Fisher information
matrix from two measurable probe properties: exchange
symmetry and collective polarization. Every maximizer is exchange symmetric and maximally entangled. Its Fisher
matrix has equal sensitivity in every visible direction, while $d(d-1)/2$ generator directions are blind. More generally, weak compatibility, defined by vanishing mean generator commutators, forces at least $\lfloor d/2\rfloor$ blind directions for every pure bipartite probe. A probe-defined antiunitary invariant classifies the complete Fisher spectrum at maximal
entanglement, and approaches to the optimum that preserve exchange
symmetry have a divergent Holevo cost. The bipartite obstruction is sharp in particle number: for $N\geq 3$, generalized GHZ probes can satisfy weak compatibility, attain the corresponding $N$-partite Fisher trace bound, and retain full local identifiability. Hence, Fisher sensitivity, weak compatibility, identifiability, and attainable precision are distinct resources in
quantum metrology with noncommuting generators.
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All authors Tariq Aziz, Naeem Akhtar, Dong Wang, Augusto Smerzi
High Energy Physics (Experiment)
Cross-section measurements of boosted Higgs boson production in final states with pairs of hadronically decaying $\tau$-leptons with the ATLAS experiment
ATLAS Collaboration
Cross section measurements of high-Lorentz boosted
Higgs boson production in final states with pairs of hadronically decaying $\tau$-
leptons are presented. The analysis is based on the full Run 2 data sample of
proton-
proton collisions at a centre-of-mass energy of $\sqrt{s} = 13$ TeV, corresponding to an integrated luminosity of 140 $\mathrm{fb}^{-1}$, and a partial Run 3 data sample at $\sqrt{s} = 13.6$ TeV with an integrated luminosity of 162 $\mathrm{fb}^{-1}$ collected in 2022-2024 with the ATLAS experiment. The analysis extends the sensitivity of previous $H \to \tau\tau$ measurements to
Higgs boson transverse momenta above 300 GeV by reconstructing $\tau$-
lepton pairs produced with a small separation in large radius jets. The standard reconstruction of hadronic $\tau$-
leptons has limited efficiency in this phase space, requiring dedicated boosted di-$\tau$ reconstruction and identification techniques, combined with multivariate analysis methods, to extract the signal. For
Higgs boson transverse momenta above 300 GeV, results are presented for both inclusive and differential cross-sections. Within the simplified template cross-section framework, differential cross-section measurements in
Higgs boson transverse momentum for
gluon-
gluon fusion production are provided, together with an inclusive cross-section measurement for vector-
boson fusion production. For the inclusive measurement, the analysis yields an observed (expected) significance of 3.8 (3.3) standard deviations over the background-only hypothesis, providing evidence of
Higgs boson production in the boosted regime of the di-$\tau$ final state.
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Computational Physics
Producing a complete nuclear data library for adjoint Monte Carlo simulations
Paul Rovel, Coline Larmier, Davide Mancusi et al. (+1 more)
Radiation shielding applications related to reactor design typically involve situations where the source region (the core) is much larger than the detector region (a dosimeter). In such cases, the efficiency of Monte Carlo simulation might be significantly increased by solving the adjoint transport equation: adjoint particles are born from the detector, undergo adjoint ('reversed') flights and collisions, and accumulate their tallies in the source region. A key prerequisite to sample the adjoint collision events is the preparation of adjoint
nuclear data. In this work, we propose a general method able to handle the diversity of
nuclear reactions available in modern
neutron data evaluations, and ultimately create a full adjoint
nuclear data library. This is a stepping stone in view of implementing adjoint sampling schemes in TRIPOLI-5 __ , the next-generation Monte Carlo code developed by CEA and ASNR. We validate this strategy based on a relevant continuous energy
benchmark configuration involving mixtures of heavy and light nuclides, and we compare our results to those obtained by standard forward Monte Carlo simulations.
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All authors Paul Rovel, Coline Larmier, Davide Mancusi, Andrea Zoia
Applied Physics
Universal scaling of electrochemical information transfer at solid-liquid interfaces
Eikichi Kimura, Ashutosh Rathi, Saki Tsuchiya et al. (+6 more)
Electrochemical potentials at solid-
liquid interfaces govern diverse chemical and energy conversion processes; however, the extent to which their electrochemical influence extends into the solid remains unclear. Here, we show that the maximum accessible electrochemical information is governed by a single dimensionless screening parameter $u$, defined as the ratio of the effective electrostatic separation between the interface and probe to the electrostatic propagation length in the solid. The maximum Fisher information follows a universal inverse-square scaling with this parameter. This relation identifies electrostatic screening as a fundamental constraint on information transfer across solid-
liquid interfaces and provides quantitative design principles for interfacial electrochemical sensing.
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All authors Eikichi Kimura, Ashutosh Rathi, Saki Tsuchiya, El Mustapha Mansouri, Sara Mandić, Kristi Kanya Saikia, Keisuke Oshimi, Masazumi Fujiwara, Keigo Arai
Physics and Society
How large should academic departments be?
Jan Bachmann, Lisette Espín-Noboa, Fariba Karimi et al. (+3 more)
Academic departments are the primary unit of scholarship and education at universities, and they vary vastly in their sizes. However, the consequences and natural dynamics of department size are poorly understood. Small departments face disproportionate teaching and administrative overhead per faculty member, while large ones face coordination costs and thematic incoherence. Here, we characterize and model the dynamics of academic department sizes using $14,000$ U.S.-based departments in eight academic domains. Across all domains, similar broad-tailed distributions reveal a common size range from 4 to 23 faculty members, widening across domains at its upper border. Annual size-dependent closure risks and growth rates indicate that stability is greatest in this size range: below it, small departments either close or grow quickly; within it, closure risk is low and sizes stabilize; above it, large departments can persist, with marginal attrition and minimal closure risk. An analytically tractable model of size-dependent coagulation and fragmentation, informed only by the aggregated size distribution, reproduces department dynamics across the full size range. Rescaling each domain by its most stable size reveals a common regression toward the stable range across most domains. Our results establish academic departments as organizations with natural size dynamics defined by a grow-or-close pattern for the smallest departments, and a weak pressure against unlimited growth for the largest.
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All authors Jan Bachmann, Lisette Espín-Noboa, Fariba Karimi, Daniel B. Larremore, Gerardo Iñiguez, Aaron Clauset
Earth and Planetary Astrophysics
Information content on Venusian aerosols in VIRTIS-M infrared data
Jaime Reyes-Guerrero, Santiago Pérez-Hoyos and Itziar Garate-Lopez
Venus presents a complex cloud structure with aerosol particles of different sizes located mainly between 48 km and 70 km in altitude. However, the number of free parameters that can describe such a cloud structure is usually overwhelming, and a number of simplified parameterizations are commonly assumed. In this work, we re-analyze the information content on aerosol vertical distribution provided by the nightside infrared data collected by VIRTIS instrument onboard Venus Express. Starting from Haus et al. (2013) aerosol vertical distribution description, we use the archNEMESIS radiative transfer code and
retrieval suite together with the
Bayesian inference tool Multinest to compute the evidence supporting different models based on alternative choices of model parameters. This study analyzes locations at three different regions: mid-latitudes, the so-called cold collar, and the South Polar
Vortex. We use a data cube that covers all of these regions simultaneously and additional observations distributed throughout the Venus Express mission. We find that these observations provide significant information about the peak particle number density, base altitude and layer thickness of aerosol modes 2, 2' and 3 when individual parameters are retrieved - a more informative description than the scaling `mode factors' often used in similar
retrievals. Including mode 1 in our models, however, does not provide a significant increase of
Bayesian evidence. Our retrieved cloud and temperature profiles are in general agreement with previous studies, although we find higher cloud tops in the South Polar
Vortex locations. This initial computing effort provides an optimal parameterization that will allow us to study in greater detail the instantaneous horizontal cloud and temperature structure from the entire VIRTIS-M infrared database, which we will discuss in a forthcoming paper.
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Materials Science
From Amorphous to Amorphous-Crystalline Mixed-Phase Boron Nitride: Evolution of the Thermal and Elastic Properties
Jiaqi Yang, Thomas Souvignet, Onurcan Kaya et al. (+11 more)
Amorphous boron nitride (aBN) is a promising dielectric and protective coating, yet its nanoscale heat dissipation and elastic response remain poorly quantified. Here we synthesize a variety of BN thin films by borazine-based chemical vapor deposition (800-1000 C) and study the temperature-driven structural transition from fully amorphous networks to mixed amorphous-crystalline films with embedded BN nanocrystallites.Frequency-domain thermoreflectance data show an ultralow, thickness-dependent cross-plane thermal conductivity for aBN (kout < 0.5 W m-1 K-1 for 10-40 nm), which increases systematically with crystalline order up to 1.5 W m-1 K-1. Micro-Brillouin light scattering and finite-element modelling reveal a concomitant stiffening, with Young's modulus rising from 7.5 +/- 0.7 GPa (800 C) to 53 +/- 5 GPa (1000 C). Green-Kubo molecular dynamics simulations rationalize these trends via bonding
topology and vibrational transport, and highlight how oxygen, hydrogen and carbon
impurities and composition provide practical knobs to further tune the thermal and mechanical responses in BN films for improving nano-electronics, interconnects and coating applications.
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All authors Jiaqi Yang, Thomas Souvignet, Onurcan Kaya, Peng Xiao, Emigdio Chavez-Angel, Daniel Capolat Palomar, Zuzanna Ewa Kaczmarska, Bartlomiej Graczykowski, Javier Rodriguez Viejo, Clivia M. Sotomayor Torres, Catherine Marichy, Catherine Journet, Stephan Roche, Marianna Sledzinska
Earth and Planetary Astrophysics
First results of a continuous monitoring campaign of the PLATO Southern field
Thomas Granzer, Jorg Weingrill, Klaus G. Strassmeier et al. (+1 more)
The BMK10k project started as an ancillary project to the PLATO ESA mission, dedicated to photometrically monitor the PLATO Southern field, to help with source confusion, and to mitigate the problem of false-positive
exoplanet detections. Planned as a long-term project, the BMK10k should see an operational time-scale in the order of a decade, well above the proposed PLATO operational phase. Thus, BMK10k may help resolving single- event transit issues detected with PLATO and may be in the unique situation to transit-detect cold Jupiters in
solar-system analogues, which would help in understanding
exoplanet orbit
alignments.
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All authors Thomas Granzer, Jorg Weingrill, Klaus G. Strassmeier, Arto Jarvinen
Chemical Physics
Reactivity of Ambident Nucleophiles in Magnetic Fields: a Combined Conceptual DFT and Current-DFT Study
Bang C. Huynh, Meilani Wibowo-Teale, Andrew M. Wibowo-Teale et al. (+2 more)
The influence of strong external
magnetic fields (up to $0.30\,B_0$) on the electronic structure and reactivity of ambident nucleophiles is investigated using the nitrite and thiocyanate anions as prototypical examples. To capture
magnetic-field-induced changes in reactivity, current-density-functional theory (current-DFT) calculations are interpreted through conceptual density-functional theory (conceptual DFT) descriptors, namely global hardness and local softness via Fukui functions, focusing on the
evolution of the electronic structure and associated properties with increasing field strength in different orientations. By extending our previous adiabatic treatment of molecules to include higher-
spin states, in analogy with earlier work on atoms, and by considering the
symmetry properties of relevant
quantum-chemical quantities within full
magnetic groups using the QSym$^2$ framework, we uncover substantial
magnetic-field-induced modulations of both molecular polarity and the shape of the Fukui function. Despite these modulations, the ambident nucleophilicity of both $(\textrm{NO}_2)^-$ and $\textrm{SCN}^-$ is largely preserved, as is the preference for attack by soft electrophiles at the sulfur end of $\textrm{SCN}^-$. At higher field strengths, however, the Fukui functions become increasingly diffuse, reflecting the growing importance of external
magnetic interactions relative to internal electrostatic forces. The resulting redistribution of local reactivity not only predicts reaction pathways with unexpected geometries but also raises the possibility that regioselectivity may become progressively less well-defined in the strong-field regime.
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All authors Bang C. Huynh, Meilani Wibowo-Teale, Andrew M. Wibowo-Teale, Frank De Proft, Paul Geerlings
Strongly Correlated Electrons
GHz non-reciprocal optical conductivity in hematite ($\alpha$-$\text{Fe}_2\text{O}_3$)
Peng Rao, Johannes Gröbmeyer, P. Peter Stavropoulos et al. (+5 more)
We study the non-reciprocal properties of the iron
oxide $\alpha$-Fe$_2$O$_3$ (hematite) in the canted easy-plane
antiferromagnetic phase, specifically in the GHz to THz frequency range. First, using the the microscopic
spin Hamiltonian, we obtain the correct classical ground state where the canting is induced by the Dzyaloshinskii-Moriya interactions (DMI). The
magnon spectrum is simulated using linear
spin wave theory. We then compute the polarizability and the sub-gap optical conductivities using linear response. We find that the conductivity tensor contains frequency peaks at the zero momentum
magnon gaps of order $0.1~$meV which can be tuned by the DMI and on-site anisotropic
spin interactions. Furthermore, we show that the canting-induced net
magnetic moment $\mathbf{m}$ represents a measure for the effective time-reversal-
symmetry breaking and non-reciprocity of the system: a finite $\mathbf{m}$ results in a non-zero
Hall conductivity. Finally, we discuss the prospective application of hematite in non-reciprocal circulator design, by computing the non-reciprocal circulator transmission amplitude using the conductivities as input.
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All authors Peng Rao, Johannes Gröbmeyer, P. Peter Stavropoulos, Alexander Mook, Matthias Althammer, Hans Huebl, Alexander Holleitner, Johannes Knolle
High Energy Astrophysical Phenomena
Observation of Wobbling and Precessing Jet Signatures in Gamma-Ray Emission from Blazar PKS 1424-41
Ajay Sharma and Debanjan Bose
We report a clear observational evidence for jet precession and nutation manifested in the gamma-ray emissions of the blazar PKS 1424$-$41. An analysis of $\sim$16 yr of
Fermi-LAT observations reveals three distinct and superimposed quasi-periodic oscillations (QPOs), with characteristic timescales of $\sim$5.26 yr, $\sim$0.96 yr and $\sim$1.3 yr. The longer timescale is detected with a local significance of $\sim 4.1\sigma$ ($99.9958\%$ confidence) and a global significance of $\sim 2.45\sigma$ ($98.5714\%$ confidence). The shorter timescales ($\sim 0.96$ yr and $\sim 1.3$ yr) both show local significances exceeding $3\sigma$. To interpret the origin of these modulations, we examine two physically motivated scenarios: Lense-Thirring precession of a misaligned
accretion disk and orbital-driven jet precession in a binary supermassive black hole (BSBH) system. We model the gamma-ray variability using a compound framework that incorporates jet precession together with intrinsic jet rotation (nutation), which successfully reproduces the observed year-like QPOs. Our results indicate that the long-term, persistent $\sim$5.26 yr oscillation is most consistent with a BSBH origin, while the shorter year-like QPO modulation can be naturally attributed to rotation or wobbling of the jet axis. If PKS 1424$-$41 hosts a supermassive black hole binary, it represents a promising target for future space-borne gravitational-wave observatories such as the
Laser Interferometer Space
Antenna (LISA), providing an independent probe of supermassive black hole binaries.
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Fluid Dynamics
Integral relations for the skin-friction coefficients and other quantities of annular flows
Pierre Ricco
Integral identities relating the skin-friction coefficients and the Reynolds shear stresses in annular cylindrical flows are derived. In the pressure-driven case, an identity for the radial location of the maximum streamwise velocity is obtained and, in the cylinder-driven case, an identity for the bulk velocity is found. The formulas are used to analyse existing numerical and experimental data and simplify to classical channel-flow and pipe-flow identities in the limiting cases of vanishingly small and infinitely large radius ratios.
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Earth and Planetary Astrophysics
Dust characterization of the HD 163296 disk with high-resolution multi-wavelength ALMA observations
Kiyoaki Doi, Myriam Benisty, Akimasa Kataoka et al. (+10 more)
Context.
Planets form through the growth and accumulation of
dust grains in protoplanetary disks. Characterizing
dust properties such as size, surface density, and temperature is key to understanding
planet formation. Aims. We characterize the
dust properties of the protoplanetary disk around HD 163296 by performing spectral energy distribution (SED) fitting of multi-wavelength high-resolution observations. Methods. We present new high-resolution ALMA Band 9 (0.45 mm) observations, which are sensitive to the temperature. We performed SED fitting at a common resolution of 0.066 arcsec using these new Band 9 observations along with archival ALMA Band 3, 4, 6, and 7 observations. We compared the fitted results with VLA observations and explored multiple
dust models with different optical constants and porosities. Results. The Band 9 image shows the central disk, two rings at 0.67 and 1.00 arcsec, and outer extended emission previously seen at other wavelengths. At higher frequencies, the rings appear wider, the gaps appear shallower, and the extended emission appears brighter, which can be explained by optical-depth effects and/or size segregation. We characterized the
dust properties, including temperature, surface density, and
dust size, for each
dust model. However, the inferred
dust properties are dependent on the
dust model, and the ALMA data alone do not allow us to determine which
dust model is preferred. We identified the DSHARP Zubko (porous) model as the preferred model based on VLA profiles and physical and observational constraints. The outer ring temperature is lower than predicted by a passively irradiated disk model, suggesting shadowing by the inner ring. Although the surface density and
dust size depend on the
dust model, the preferred model indicates that the central disk, both rings, and the extended disk each contain more than a few Earth masses of
dust.
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All authors Kiyoaki Doi, Myriam Benisty, Akimasa Kataoka, Haochang Jiang, Francesco Zagaria, Hauyu Baobab Liu, Carsten Dominik, Ryo Tazaki, Takahiro Ueda, Tomohiro C. Yoshida, Takashi Tsukagoshi, Yoshihide Yamato, Ryuta Orihara
Materials Science
Mechanical mapping of thin elastic films and living cells with spherical tip atomic force microscopy probes at large indentations
Gabriel Gomila, Mauricio Cano, Beatriz Cantero et al. (+7 more)
An analytical model to quantify large indentation force curves acquired on elastic thin films and living
cells with spherical tip Atomic Force Microscopy (AFM) probes is presented. The model accounts for the bottom effect in the whole indentation range and overcomes the limitations of Sneddon's and Hertz's contact models, which are valid for semi-infinite thick samples, and of paraboloid tip models with bottom effect correction (BEC) that are applicable to spherical tips only for relatively small indentations. The model is experimentally validated with force volume measurements on polyacrylamide (PAA) hydrogel thin films, where an excellent agreement is obtained. The accurate correction of the bottom effect demonstrates that the intrinsic Young's modulus of PAA thin films increases for thickness below a critical value (~15 um). The model also shows excellent agreement with force curves acquired on live macrophages, providing accurate Young's modulus values for these very soft
cells (E~200 Pa). Young's modulus values extracted with the proposed model significantly differ from those obtained from Sneddon's or paraboloid models with BEC, whose values deviate by 100% and -25%, respectively. Results show the potential of the proposed model for analysing force curve measurements with spherical tips at large indentations on thin film elastic materials and living
cells at the micro and nanoscale.
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All authors Gabriel Gomila, Mauricio Cano, Beatriz Cantero, Sophie Strawbridge, Lara Aiassa, Loris Rizzello, Giuseppe Battaglia, Eleni Dalaka, Jordi Comelles, Annalisa Calò
High Energy Physics (Phenomenology)
Resolving Lorentz-Violating New Physics at ESSnuSB Using High-Statistics Complementarity with T2HK
Himanshu Bora, Debajyoti Dutta, Monjowara Khatun et al. (+1 more)
A primary objective for next-generation long-baseline
neutrino facilities is the search for Planck-scale Lorentz Invariance Violation (LIV). In this work, we explore the capabilities of the proposed ESSnuSB and T2HK experiments to constrain isotropic, CPT-violating LIV parameters ($a_{\alpha\beta}$). The modifications to oscillation probabilities induced by these LIV parameters can introduce parameter degeneracies with the atmospheric mixing angle $\theta_{23}$ and the Dirac CP-violating phase $\delta_{CP}$, which can potentially result in incorrect determination of the said standard oscillation parameters if we do not account for LIV effects. Through detailed GLoBES simulations, we find that while the second-oscillation-maximum configuration of ESSnuSB yields good constraints on the exact phase of $\delta_{CP}$, its intrinsic
neutrino-antineutrino statistical asymmetry persistently leads to wrong octant fake solutions for $\theta_{23}$. By synergizing ESSnuSB's 360 km and 540 km baselines with the complementary, high-statistics measurements from first-maximum configuration of the T2HK's 295 km baseline, we show that the degeneracies are resolved for most LIV parameters. Our analysis reflects how complementarity between ESSnuSB and T2HK provides an effective, matter-independent framework to break LIV-induced degeneracies and establish bounds on Planck-scale LIV physics.
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All authors Himanshu Bora, Debajyoti Dutta, Monjowara Khatun, Abinash Medhi
Mesoscale and Nanoscale Physics
Levitated nano-trampoline resonators for magnetic field sensing
Xianfeng Chen, Nirmala Raj, Matthew R. Chua et al. (+7 more)
Levitated systems and high-$Q$ membrane nanomechanical resonators have achieved exceptional sensitivity in precision sensing, but functionalizing such resonators for practical applications without degrading their low dissipation remains challenging. Here, we combine diamagnetic levitation with a high-$Q$ nanomechanical resonator to realize a high-precision magnetometer for sensing weak oscillating
magnetic fields. A macroscopic diamagnetically levitated graphite plate acts as a free-floating proof mass that couples strongly to
magnetic fields, converting them into mechanical motion that is resonantly amplified by a low-dissipation nano-trampoline resonator. Operating at room temperature and without
magnetic shielding, we achieve a peak
magnetic-field sensitivity of $4.5\, \mathrm{pT}/\sqrt{\mathrm{Hz}}$ using a resonator with a mechanical quality factor of $Q=6\times10^{6}$ at $443\, \mathrm{kHz}$. The system sensitivity is limited by thermomechanical noise. With further improvements in mechanical $Q$, this hybrid levitated platform offers a pathway toward femtotesla-level AC
magnetic-field sensing, establishing diamagnetically levitated nanomechanical resonators as a new class of high-sensitivity magnetometers at room temperature.
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All authors Xianfeng Chen, Nirmala Raj, Matthew R. Chua, Yi Fan Chen, Chenyue Gu, Minxing Xu, Young-Wook Cho, Syed M. Assad, Lu Ding, Ping Koy Lam
Soft Condensed Matter
Geometric Renormalization and a Chirality Threshold in Recursively Coiled Filaments
Hiroyuki Shima
Repeated coiling creates a filament hierarchy. We formulate helicalization as an iterated map acting on an arbitrary rod compliance, rather than homogenizing one prescribed construction. A marginal Jordan mode yields an outer-radius inverse-square stiffness class, while pitch disorder creates a Lyapunov threshold between amplified and screened extension–twist response. An exact finite-level rate distinguishes representative amplified and screened cases by level three; direct three-dimensional beam calculations validate the response through level four and convergence through level five.
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Quantum Physics
Molecular chiral discrimination through symmetry-breaking spin dynamics
Tianyu Xie, Yucheng Hao, Mingzhe Liu et al. (+7 more)
Molecular chirality plays a crucial role in physics, chemistry, life sciences and pharmacology. Nowadays, the
chiral discrimination and control at the single-molecule level is urgently needed to reveal the origin of the chirality-relevant phenomena by recovering the information disturbed by the ensemble averaging. The method of
magnetic resonance (MR), as one of powerful tools for structure analysis, is blind to the molecular chirality in the absence of a
chiral reagent. Here we propose and experimentally demonstrate a direct MR-based method for determining the chirality at the single-molecule level through constructing the
symmetry-breaking dynamics of nearby
nuclear spins. In principle, the mirror asymmetry of two enantiomers in real space is manifested by breaking the joint
symmetry of the mirror reflection and time reversal in
spin space under
spin dynamics. Experimentally, two enantiomers are indistinguishable from the dynamics of strongly-coupled but unpolarized
nuclear spins, but diverge evidently in the dynamical results that break the field-inversion
symmetry after
spins are polarized. Our method and results will benefit the study of chirality-induced properties in the fields of chemistry and biology.
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All authors Tianyu Xie, Yucheng Hao, Mingzhe Liu, Mengqi Wang, Shaoyi Xu, Zhiyuan Zhao, Chang-Kui Duan, Ya Wang, Fazhan Shi, Jiangfeng Du
Chemical Physics
Putting PASPT2 on a Firmer Basis
Chunzhang Liu, Ning Zhang and Wenjian Liu
The recently proposed partial-active-space (PAS) multi-state second-order perturbation theory (PASPT2) [Precis. Chem. 4, 997 (2026)] features connected amplitudes and a connected, closed intermediate
Hamiltonian. Despite these hallmarks, PASPT2 (denoted as PASPT2H from now on) is not strictly size-extensive, as originally thought (and numerically confirmed), albeit strictly size-consistent. Nevertheless, PASPT2 is near-extensive for the states with major projections on the chosen PAS $\mathcal{M}_0$. This becomes more transparent upon introducing PASPT2X, a strictly size-extensive variant. Compared with the intruder-prone PASPT2X, the intruder-free PASPT2H merely neglects the second-order corrections that are important only for those states with major projections on the orthogonal complement $\mathcal{R}_X$ of $\mathcal{M}_0$ within the closed space $\mathcal{M}_X$ ($=\mathcal{M}_0\oplus\mathcal{R}_X$); however, such states are not supported by the chosen finite one-particle basis set. The weak violation of size-extensivity is therefore numerically insignificant for the target states supported by $\mathcal{M}_0$, reinforcing the theoretical basis of PASPT2H.
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Mesoscale and Nanoscale Physics
Fractional parametric resonance in spintronic diodes
Andrea Grimaldi, Denys Slobodianiuk, Eleonora Raimondo et al. (+7 more)
Parametric pumping is a powerful tool for the excitation, amplification, and processing of oscillations and waves of different nature. In general, parametric resonance can occur when the pumping frequency $f_p$ and eigenfrequency of a linear mode (or wave) $f_0$ satisfy the relation $f_p$=2$f_0$/n (n=1,2,3,...). While such parametric resonance is well known in mechanical, superconductive, and
quantum systems, in
magnetic and spintronic systems only the lowest (n=1) parametric resonance at double the
spin wave mode frequency $f_p$=2$f_0$ was thoroughly studied and explored. Here, using a theoretical analysis based on both micromagnetic simulations and an analytical model, we show the emergence of resonances at fractional frequencies $f_p$=2$f_0$/n (with n>10) in spintronic diodes driven by the simultaneous action of ac
spin-transfer torque (STT, current densities < $10^6$ A/cm2) and voltage-controlled
magnetic anisotropy (VCMA, effective anisotropy fields < 50 mT). The analytical model shows that parametric magnetization dynamics is irreducible to the standard Mathieu model of a parametric oscillator and demonstrates the crucial role of VCMA-driven mode frequency modulation: together with parametric coupling, it results in higher-order odd (n=3,5,7,...) fractional resonances, observed above certain VCMA pumping threshold, while simultaneous action with linear STT drive produces thresholdless even (n=4,6,8,...) resonances. This higher-order parametric dynamics is not restricted to VCMA pumping and opens new directions for the application of spintronic diodes for nonlinear signal processing and electromagnetic energy harvesting.
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All authors Andrea Grimaldi, Denys Slobodianiuk, Eleonora Raimondo, Raghav Sharma, Anna Giordano, Mario Carpentieri, Hyunsoo Yang, Riccardo Tomasello, Roman Verba, Giovanni Finocchio
Optics
Field-driven nonlinear metasurface: self-adaptive transition between high-selectivity transmission and broadband shielding
Yuan Xu, Hanqing Liu, Shangjing Xi et al. (+4 more)
The escalating complexity of electromagnetic (EM) environment is posing a significant challenge to the reliability of modern electronic information systems. To address the need for the spatial EM safety of electronic devices, we present a field-driven nonlinear metasurface (NMS) that enables effective protection against out-of-band interference and in-band high-intensity radiation. By constructing a reconfigurable hybrid coupling
topology and mapping it to the metasurface geometry, the proposed NMS achieves a self-adaptive transition between its transmission and shielding mode depending on the incident power. The experimental results are in good agreement with theoretical analysis and full-wave simulation. We obtain a highly selective passband with roll-off rate larger than 20.6dB/GHz and a broadband shielding with shielding effectiveness exceeding 23.6dB and 60% bandwidth, demonstrating a significantly enhanced performance relative to the literature. Our findings establish a promising route toward comprehensive EM protection on
radio frequency front-end systems.
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All authors Yuan Xu, Hanqing Liu, Shangjing Xi, Xiaodi Zhang, Yanqing Cheng, Wenye Ji, Peiguo Liu
Quantum Physics
Mitigating Capacitive Loading Enables Fast Two-Qubit Gates in Highly Connected Fluxonium Quantum Processors
Quan Guan, Guo Xuan Chan, Xu Dou et al. (+2 more)
Fluxonium
qubits combine long coherence times with strong anharmonicity, making them attractive for scalable superconducting
quantum processors. Recent experiments have demonstrated high-fidelity two-
qubit gates and multi-
qubit entanglement in one-dimensional and connectivity-four fluxonium processors, motivating their extension to highly connected two-dimensional (2D) architectures. A central challenge in this extension is to achieve strong coupling to multiple
circuit elements while preserving the finite capacitance budget of fluxonium
qubits, which constrains the attainable
qubit-
qubit effective coupling strength and, consequently, two-
qubit gate performance. Here, we establish a unified theoretical framework that identifies the connectivity-dependent upper bound on capacitive coupling and quantifies its reduction by distinct parasitic-capacitance channels, applicable across both fluxonium and transmon regimes. We show that pad-to-ground loading is primarily geometry limited and can be substantially suppressed through
qubit-pad engineering, whereas inter-pad loading is ultimately constrained by parasitic capacitances of Josephson junctions and Josephson junction arrays. Building on these insights, we formulate practical design principles and numerically demonstrate two-
qubit gates as fast as 27 ns and leakage-induced infidelity below $10^{-3}$ under representative fabrication variations in 2D fluxonium architectures. These results establish a quantitative framework for understanding and mitigating capacitive loading, suggesting that it does not impose a fundamental performance limit on highly connected fluxonium processors.
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All authors Quan Guan, Guo Xuan Chan, Xu Dou, Chunqing Deng, Lijing Jin
General Relativity and Quantum Cosmology
Dynamical and Observational Analysis of Generalized Nash's Theory of Gravity
Amin Rezaei Akbarieh, Mohammad Amin Bolouri and Yaghoub Heydarzade
We investigate
cosmic evolution in generalized Nash's theory of
gravity involving the quadratic
Ricci invariant $\chi=R_{\mu\nu}R^{\mu\nu}$. The analysis is divided into two complementary branches. First, we study the power-law family $f(R,\chi)=R^{\alpha}+\beta\chi$ as a reduced autonomous system in a flat FLRW background. Because the adopted variables become singular at the Einstein–
Hilbert limit $\alpha=1$, the phase-space analysis is restricted to $\alpha\neq1$, with $\alpha=2$ used as a representative quadratic
benchmark. This
benchmark contains radiation-like boundary configurations, restricted scaling saddles, and de Sitter-like accelerating endpoints (a stable node away from $\alpha=2$ and non-
hyperbolic at the
benchmark itself), but not a complete regular radiation-to-matter-to-de Sitter sequence. Second, we constrain the regular observational branch $f_{\rm obs}(R,\chi)=R-2\Lambda+\beta\chi$, which reduces exactly to flat $\Lambda$CDM when $\beta\to0$. The Hubble rate is obtained from the reduced $\Lambda$CDM-connected background branch, integrated over $0\le z\le10$ and matched at higher
redshift to a standard radiation+matter+$\Lambda$ background. Using SNe~Ia, BAO, and Planck~2018 compressed CMB distance priors, we find an expansion history very close to $\Lambda$CDM, with the quadratic correction tightly constrained around the nested standard-model limit. The resulting bound on $\beta$ should be interpreted as a background-level constraint within this reduced prescription, not as a perturbation-level viability test of the full higher-derivative theory.
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General Relativity and Quantum Cosmology
Charged Black Holes in Einstein–$U(1)$ Gravity with Letelier–Alencar Cloud of Strings: Thermodynamics and QPO-Based Observational Constraints
B. Eslam Panah, Bidyut Hazarika and Prabwal Phukon
In this study, black hole solutions are derived within the framework of Einstein
gravity, coupled to a $U(1)$ gauge field in the presence of both the Letelier–Alencar cloud of strings and the cosmological constant. Subsequently, the influence of the cloud of strings parameters and the electric charge on the structure of the event horizon is investigated. Conserved and thermodynamic quantities associated with these solutions are computed, and their consistency with the first law of black hole thermodynamics is verified. To assess the thermodynamic behavior of the system, the heat capacity and Gibbs potential are derived, thereby enabling an analysis of local and global stability under variations of the relevant parameters. Finally, the parameters of the proposed black hole solution are constrained via a
Bayesian Markov Chain Monte Carlo (MCMC) analysis, utilizing observational quasi-periodic oscillation (QPO) data derived from
stellar-mass, intermediate-mass, and supermassive black holes.
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Mathematical Physics · Cross-listed from math.NA
No Spectral Invisibility for Dissipative Barrier Truncations in Any Dimension
Matthew J. Colbrook and Marco Marletta
The dissipative barrier method suppresses spectral pollution, but whether it can itself conceal genuine spectral points has remained open. Known as the graveyard problem in computational spectral theory, the higher-dimensional case has remained unresolved for more than a decade. We resolve it for Schrödinger operators in dimensions $d\geq2$; together with the known one-dimensional
theorem, this settles the no-invisibility problem in all dimensions. Let $A=-\Delta+V$ be a Dirichlet Schrödinger operator on a connected open set $\Omega\subseteq\mathbb R^d$ with $V\in L^1_{\mathrm{loc}}(\Omega)$ bounded below, and set $H=A+iS$, where $S\geq0$ and $S\in L^p(\Omega)$, with $1<p<\infty$ for $d=2$ and $d/2\leq p<\infty$ for $d\geq3$. Let $(\Omega_R)_{R>0}$ be a nested family of nonempty connected bounded open sets such that $\Omega_R\nearrow\Omega$ as $R\nearrow+\infty$. Denote by $H_R$ the Dirichlet truncation of $H$ to $\Omega_R$. We prove that every spectral point of $H$ is detected by the truncations: for every $\lambda\in\sigma(H)$ and every neighborhood $U$ of $\lambda$, $\sigma(H_R)\cap U\neq\emptyset$ for sufficiently large $R$. Equivalently, $\sigma(H)\subseteq\liminf_{R\to\infty}\sigma(H_R)$. Thus the barrier method does not trade suppression of spectral pollution for spectral invisibility. No regularity of $\partial\Omega$ is required, and the assumptions reach the critical Sobolev scale. The proof combines compactness of the dissipative form perturbation, Cwikel-type Schatten estimates for Birman–Schwinger operators, generalized strong resolvent convergence, and a reverse Hansmann–Weyl spectral-variation inequality due to Gil'. A two-dimensional numerical example illustrates the absence of spectral invisibility for the truncated dissipative operators.
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