Statistical Mechanics
Classical dipolar Heisenberg models on the Archimedean and Laves lattices
Josep Batle
We study classical Heisenberg
spins interacting through the dipole–dipole interaction on the eleven Archimedean and eight Laves planar
lattices at canonical geometry, which reduce to fifteen distinct vertex sets. For each
lattice we compute the
Fourier-space interaction
matrix $\Am(\bk)$, extract the Luttinger–Tisza ordering wave vector $\bk_{0}$, determine the classical ground state by unconstrained minimization on the commensurate
magnetic cell, and evaluate the linearized
spin-wave dispersion $\varepsilon_{i}(\bk)$ along the high-
symmetry path of the (
magnetic) Brillouin zone together with the Holstein–Primakoff moment reduction. The ground states fall into three classes: five are collinear, two are non-collinear at angles commensurate with the
lattice symmetry, and eight cant at transcendental angles, which we determine to thirty digits. Across the family, failure of the Luttinger–Tisza strong condition coincides exactly with the appearance of incommensurate canting, with no exceptions in either direction. Truncating the interaction range shows that whether a
lattice cants is fixed by the local coordination geometry, whereas the value of the canting angle is set by the long-range tail. The
quantum corrections are governed by the
magnon spectrum through the size of the
magnetic basis and are uncorrelated with frustration, so that the frustration and fluctuation classifications are independent; the corner-sharing
lattices host the narrowest low-energy branches. The results constitute a spectral atlas of dipolar Heisenberg systems on the full family of $1$-uniform planar tilings and their duals, and provide predictions for inelastic
neutron scattering in materials whose
magnetic ions occupy Archimedean or Laves
lattices, and for artificial arrays of dipolar-coupled nanomagnets.
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Mesoscale and Nanoscale Physics
Graphene-enabled dynamic H-J switching of dipole-dipole coupling
Michael McFadden and Robert Bennett
Environmental modification of dipole interactions has long been explored in energy transport. Here we consider the effects of a tunable
graphene monolayer upon nearly H-type or J-type molecular aggregates, concentrating on the inversion of one type of coupling to the other. Modelling the
graphene as being deposited on a metallic substrate, we find that as the surface conductivity of the
graphene is varied, there is a corresponding change in the parameter region over which coupling inversion is predicted. This provides a route towards observing the predicted coupling inversion in a real system by dynamically changing the surface conductivity during a single run of an experiment.
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Chemical Physics
Enumerating Chemical Structures, Stereoisomers, and Stereogenic Units with Analytic Combinatorics
Casper Asbjørn Eriksen and Daniel Merkle
The enumeration of chemical structures traditionally relies on graph- and group-theoretic techniques, including Pólya theory, in order to account for stereochemical
symmetries. These methods require bespoke derivations and methods for each molecular family of interest, and quickly become very intricate for nontrivial classes. In this work, we demonstrate that analytic combinatorics provides a unifying, highly extensible, and relatively simple framework for enumeration problems. Using the symbolic method, we show that classical counting problems, such as the enumeration of acyclic alkanes and other hydrocarbon families, can be naturally solved via concise combinatorial specifications of the class of interest. We first demonstrate the simplicity of this approach by replicating existing results in this framework, requiring significantly less work than previously necessary, and then extend these ideas to more complex problems, counting broader classes of molecules accounting for both tetrahedral and E/Z stereoisomerism, counting the distribution of stereogenic units, and enumerating achiral and meso compounds. All results are made reproducible through CombOL, our open-source software package which automates the translation of combinatorial specifications into generating functions using the symbolic method, and performs both univariate and multivariate enumeration.
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General Relativity and Quantum Cosmology
Parameter Space, Realistic Matter, and Universal Relations in Bose–Einstein Condensate Dark Stars
M. Ilyas
We study slowly rotating Bose–Einstein condensate (BEC) dark
stars by solving the Tolman–Oppenheimer–Volkoff, Hartle dipole, and Postnikov–Hinderer equations together for a polytropic equation of state with a Lee–Huang–Yang correction of strength $\zeta$~\citep{Panotopoulos2026}. A continuous scan of $\zeta$ from 0 to 1.5 shows the mean-field-to-corrected transition is smooth, with no hidden structure at intermediate values. Scanning the underlying
boson parameters $(m,a_s)$ more broadly, we find that a $2\,M_\odot$ maximum-mass bound and a GW170817-like
tidal bound $\Lambda_{1.4}\lesssim800$ cannot be satisfied simultaneously anywhere in this equation-of-state class. The $I$-Love universal relation holds to $0.13\%$ across twelve $(m,a_s,\zeta)$ models, and the $\zeta=0$ and $\zeta=1$ sequences sit on opposite sides of the master curve by a consistent, non-random offset. Applied without modification to realistic
nuclear matter (SLy, APR4), the same solver reproduces published maximum masses to within $1\%$; applied to self-bound MIT-bag
quark matter it gives the expected mass–radius shape; and once extended to a two-fluid
baryon-plus-dark-matter formalism, it shows that the maximum mass of a hybrid
star is not a monotonic function of the central dark-matter fraction. Pooling $I$-Love sequences across
nuclear, hybrid, and BEC dark-
star models, we find they collapse onto a single curve to within about $5\%$, while self-bound
quark stars sit far off it, departing by up to $90\%$.
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General Relativity and Quantum Cosmology
A Unified Treatment of the Self-Force Problem
Beka Modrekiladze, Ira Z. Rothstein and Jordan Wilson-Gerow
This paper introduces formalism, based on worldline effective field theory, which allows one to systematically calculate the gravitational self-force on a compact object immersed in an environment with non-vanishing stress energy. Using the closed time path integral we present a universal effective action that can be used to calculate the equations of motion of a compact object due to its interaction with the environment to any order in the relevant expansion parameters, the relative importance of which depends upon the choice of environment. We show that the leading order equations of motion can be universally written in terms of the retarded two-point function of the stress-energy tensor for the environment. The resulting action can be used to calculate both dissipative (dynamical friction) and conservative forces in a completely relativistic fashion. We demonstrate the utility of the result by calculating the dissipative force due to
dust, an inviscid fluid, and a coherent field. Our results agree with those previously derived in the literature. We furthermore show that the famous “Coulomb Log" found by Chandrasekhar should be interpreted as a renormalization group log due to a UV divergence that renormalizes the dissipative part of the in-in action. We then prove that this log is universal in the Newtonian limit in that its value is universal, for a generic class of environments and trajectories. This log is the leading log in an RG flow in the dissipative action that has yet to be explored.
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Data Analysis and Statistics
A Probability Model for Pentagonal Prism Dice Rolls
Paul R. Hurst and J. Naleo Hyde
In the realm of probability theory and game design, the study of dice probabilities plays a crucial role. The featured dice are usually fair, so their probabilities can be predicted without rolling the dice. Pentagonal prismatic dice are not fair. Hence, the probabilities are more complicated. Our mathematical model is naturally derived from both the
geometric properties of the dice and empirical evidence. Dice of varying sizes but with constant volume were designed. Using a 3D printer with 100 percent infill, the dice were printed and prepared. A machine that simulates dropping dice through a dice tower onto a hard surface was used to obtain about 41,000 results. From these data, a statistical model was constructed that gives probabilities of dice with varying height-to-radius ratios. The formula for the model is based on the centroid solid angle, but with two adjustment parameters due to varying energy and other requirements to transition between different resting aspects. Within the range of height-to-radius ratios tested, the data are within reasonable statistical error of the model.
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Instrumentation and Methods for Astrophysics
Lynx2030 Science Analysis Group: Final Report
Lynx2030 Science Analysis Group: Simon R. Bandler, Laura W. Brenneman, Nico Cappelluti et al. (+50 more)
The Lynx2030 Science Analysis Group (SAG) was convened to reassess the scientific goals and technical drivers of the Lynx mission concept amid a rapidly evolving astrophysics landscape. Building on the original Lynx Concept Study, the SAG examined how recent discoveries, emerging facilities, and advances in instrumentation influence the scientific opportunities for a next-generation flagship X-ray observatory. Through focused working groups, the SAG investigated the scientific impact of enhanced capabilities: (i) improved angular resolution, (ii) broader bandpass coverage, (iii) an enhanced microcalorimeter, (iv) new capabilities and observing modes, and (v) larger fields of view. Across a broad range of topics, from the formation of the first black holes and the
evolution of
galaxies to the
baryon cycle, compact objects,
stellar explosions, multi-messenger astrophysics, and the dynamic high-energy Universe, the SAG finds that the scientific motivation for a Lynx-class observatory remains compelling and, in many areas, has significantly strengthened over the past decade, prominently through JWST's discovery of the "Little Red Dots", likely massive accreting black holes in infant
galaxies whose nature is fundamentally an X-ray question. This report shows that modest extensions beyond the original Lynx design reference mission can unlock transformative science while preserving the observatory's core architecture. Powerful current and future facilities such as Roman, Rubin, JWST, SKA, ngVLA, LISA, and NewAthena highlight the unique role a high-angular-resolution, high-throughput X-ray observatory would play in the multi-wavelength and multi-messenger ecosystem of the 2030s and beyond. The findings of the Lynx2030 SAG confirm Lynx's central
vision: an unprecedented view of the hot and energetic Universe, enabling discoveries that will define high-energy astrophysics in the coming decades.
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All authors Lynx2030 Science Analysis Group: Simon R. Bandler, Laura W. Brenneman, Nico Cappelluti, Daniel Castro, Steven R. Ehlert, W. Peter Maksym, Fabio Pacucci, Scott W. Randall, Grant R. Tremblay, John ZuHone, Steven W. Allen, Antara R. Basu-Zych, Akos Bogdan, Joel N. Bregman, Tamta Burduli, Thomas Connor, Sanskriti Das, Casey DeRoo, Stephen DiKerby, Paul A. Draghis, Martin Elvis, Giuseppina Fabbiano, Ralf K. Heilmann, Jimmy A. Irwin, Amruta Jaodand, Margarita Karovska, Vinay L. Kashyap, Anthony A. Kerr, Caroline Kilbourne, Ralph Kraft, Jiangtao Li, Labani Mallick, Herman L. Marshall, Michael L. McCollough, Anna Ogorzałek, Frederik Paerels, Daniel Patnaude, Paul Plucinsky, David Pooley, Frederick S. Porter, Daniele Rogantini, Roger Romani, Helen R. Russell, Kazuhiro Sakai, Mark Schattenburg, Dan A. Schwartz, Malgorzata Sobolewska, Paolo Soffitta, Alexey Vikhlinin, Daniel R. Wilkins, Scott Wolk, Ka-Wah Wong, Irina Zhuravleva
Chaotic Dynamics
Fuzzy local reduced order models (fl-ROMs)
Antonio Colanera and Luca Magri
Nonlinear dynamical systems often evolve on low-dimensional
manifolds with intricate geometry, making them difficult to approximate with a single global reduced-order model (ROM). To address this, we previously introduced quantized local reduced-order models (ql-ROMs), which partition the solution
manifold into $K$ clusters and construct local ROMs around the corresponding centroids. In the sharp formulation, discontinuous switching between clusters can induce discontinuities, spurious oscillations, and loss of accuracy near cluster boundaries. Here, we propose a fuzzy extension of ql-ROMs based on fuzzy c-means clustering. The resulting fuzzy local ROM (fl-ROM) advances all local reduced states in parallel and combines their predictions through continuous membership weights, yielding a smooth partition-of-unity coupling of the local dynamics. We also introduce a pseudo-
Bayesian information criterion to guide the selection of the number of clusters in the fuzzy setting. The methodology is assessed on the two-dimensional Kuramoto-Sivashinsky equation in periodic, travelling-wave-like, quasi-periodic, and chaotic regimes. In all cases, the local ROMs outperform the global ROM, while the fl-ROM provides smoother and generally more accurate predictions than the sharp formulation. In the chaotic regime, where long-time trajectory tracking is inherently limited, the fl-ROM achieves the best compromise between short-time predictive accuracy and long-term statistics. These results show that fl-ROM provides an effective, robust, and interpretable framework for reduced-order modeling of nonlinear dynamical systems with regime transitions and complex attractor geometry.
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General Physics
Bianchi Type I Space -Time Geometry of the Universe with Time Dependent G and $\Lambda$ Within the Framework of General Relativity: Observational Aspects
S. Kotambkar, G. K. Goswami, R. Kelkar et al. (+1 more)
Inspired by the latest progress in the hunt of acceptable cosmological model of the universe, present paper is devoted to explore a mathematical model of the universe having initial anisotropy and with accelerated
evolution that attains isotropic character. We have considered a widely accepted anisotropic Bianchi type I space-time geometry of the universe to explore a physically viable model. To find an acceptable model, we adopted a
hyperbolic form for the scale factor as $ a(t)= \left( sinh bt \right)^{\frac{1}{n}} $ and a relation $ \Lambda=\Lambda_0 \frac{\ddot{a}}{a}$. The model parameters are constrained by $ \chi^2$ minimization techniques. Using 35 CC measurements we obtain present day expansion rate $H_0= 65.715 Km/S/Mpc$ and the value of $ n= 1.3024$. Further to estimate the local uncertainties of the best fit parameter, we calculate covariance from the Jacobin of the normalized residuals. The corresponding 1 $\sigma$ uncertainties are $ H_0=65.715 \pm 2.392 Km/S/Mpc$ and $n= 1.3024 \pm 0.0842$. The physical and dynamical behaviour of present model has been discussed by a graphical representation of cosmological parameters. The observational constraints on the expansion history are found to be consistent with a present accelerated phase and a transition from deceleration to acceleration at an intermediate
redshift. The corresponding
evolution of the derived cosmological quantities is also investigated within the adopted model.
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All authors S. Kotambkar, G. K. Goswami, R. Kelkar, G.P. Singh
General Physics
Influence of Generalized Ghost Dark Energy on Wormhole Geometry
Soubhik Paramanik, Anamika Kotal and Ujjal Debnath
This article presents a wormhole solution constructed from a generalized ghost dark energy (GGDE) source in general relativity. At first, a brief review of GGDE is presented along with the necessary mathematical frameworks. We employed the Markov Chain Monte Carlo (MCMC) technique to constrain the free parameters of the model using the CC+BAO, $Pantheon^+$, and their combined
datasets. Furthermore, the Akaike Information Criterion (AIC) and
Bayesian Information Criterion (BIC) were used to statistically assess the model's performance and determine its level of acceptance. Next, the basics of wormhole geometries along with the thin-shell formalism are explained in detail. After that, three different wormhole solutions associated with three different choices of the
redshift function are presented ,and their various
geometric properties as well as energy conditions are studied graphically. Finally, the stability of these thin–shell structures is examined analytically as well as graphically by studying the associated effective potential.
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Mesoscale and Nanoscale Physics
Coherent phononic frequency combs in ferroelectric CMOS oxides
Jinghan Gao, Shruti Mishra, Yilin Kou et al. (+3 more)
Modern electronic systems require tens of clock and carrier frequencies, each synthesized by a dedicated phase-locked loop from a shared reference, imposing routing, power and synchronization burdens that grow with every domain. Optical frequency combs solved this problem in photonics, whereas electronics has lacked an equivalent source in its native radiofrequency domain. Here we report broadband phononic frequency combs in ferroelectric hafnia-zirconia nanoelectromechanical resonators built from complementary metal-
oxide-
semiconductor (CMOS)
oxides. Lithographically defined detuning of a 2:1 internal resonance selects the generation mechanism: two-tone-seeded wave mixing yields more than 170 lines distributed over two octaves, with mutual coherence verified for representative pump and generated lines, whereas an autonomous
Hopf route yields hierarchical combs of more than 200 lines through
torus and period-doubling dynamics, in agreement with slow-flow bifurcation theory.
Geometric scaling extends comb generation across 0.44 GHz to 2.1 GHz. Heterodyne measurements, analyzed using the modified Allan deviation (MDEV), establish a two-timescale law. The mechanism governs short-term stability: seeded combs inherit the white-phase-noise scaling of their pumps, whereas autonomous combs acquire the phase
diffusion of a free-running oscillator, with the one-second MDEV increasing from 1e-11 to 1e-8. The material governs long-term stability: in air and without active thermal control, the temperature-compensated stack suppresses the random-walk drift that dominates uncompensated resonators. These results establish mechanism- and material-level design rules for operating a single resonator as chip-scale frequency infrastructure, from multi-clock generation to radiofrequency parallel processing.
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All authors Jinghan Gao, Shruti Mishra, Yilin Kou, S M Enamul Hoque Yousuf, Hanna Cho, Roozbeh Tabrizian
Materials Science
Giant staggered Dzyaloshinskii-Moriya vectors emerged in synthetic antiferromagnets with spatially alternating stress
Yuuga Iwata, Kensuke Hayashi, Reiju Furumaki et al. (+3 more)
Dzyaloshinskii-Moriya (DM) interaction is a source of
chiral magnetic physics, and it manifests microstructural
symmetry which could link to exotic
magnetic and electronic properties such as altermagnetism. For a new paradigm in magnetism and spintronics, it is crucial to have control on the DM interaction as well as ordering of the DM vectors which characterize the DM interaction. Here, we report on a strong interlayer DM interaction emerged in Co/Ru
magnetic superlattices whose structural
symmetry is unambiguously broken by alternating mechanical strains developed using the peculiar technique of our stress mechanism. Moreover, theoretical analyses reveal that our
magnetic superlattices host a staggered order of the DM vectors. Our results indicate that the spatially varying strains with our breakthrough technique are quite effective in breaking the
symmetry of the system and prove that it can control the DM interaction strength as well as the DM vector order.
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All authors Yuuga Iwata, Kensuke Hayashi, Reiju Furumaki, Satoshi Iihama, Masahiro Sato, Takahiro Moriyama
High Energy Astrophysical Phenomena
Anomalous horizontal track-like events at the HAWC observatory: candidate neutrino-induced charged leptons from the Pico de Orizaba volcano
Hermes León Vargas and Andrés Sandoval
Two track-like events with exceptionally large charge deposits, pointing back to the region of maximum overburden ($>18$ km.w.e.) of the Pico de Orizaba volcano, were reported by the HAWC Collaboration in a search for Earth-skimming
neutrinos. Using exclusively published information, including the published Monte Carlo charge distributions and the scattered-
muon background model, we show that these events are kinematically inconsistent with all identified backgrounds. A conservative energy-conservation bound places the in-tank energy deposit of the candidates above $\approx$190–210~GeV, with a worst-case minimum of 122–136~GeV, in either case exceeding the 100~GeV maximum of the scattered-
muon background model. Calibration systematics derived from the published simulations act unidirectionally, pushing the implied deposits into the multi-TeV regime. Direct atmospheric
muons require $E_\mu \gtrsim 0.67$~PeV to penetrate the overburden and contribute $4.5\times10^{-5}$ expected events ($\lesssim 10^{-3}$ under the largest possible
prompt-charm flux); collinear
muon bundles are excluded by five independent arguments. Conversely, the
neutrino hypothesis predicts identifiable events precisely in the observed charge window ($10^{3}$–$10^{4}$ photoelectrons) and in the highest-overburden analysis region, both observed. The two track-like events imply a rate that exceeds the conventional atmospheric
neutrino flux expectation at the 2.1–2.5$\sigma$ level. The charges of the observed candidates require an emerging
lepton above about 20~TeV; the published calibration does not bound the energy from above. These would constitute the first
neutrino candidates detected in Mexico and the first obtained with the Earth-skimming volcano technique.
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High Energy Astrophysical Phenomena
A Self-Sustaining Black Hole Engine Powered by the Tidal Disruptions of Stars
James Guillochon and Avi Loeb
Tidal disruption events (TDEs) strongly prefer host
galaxies undergoing, or recovering from, a burst of
star formation, implying that a rare minority of
galaxy types produces most events. The required per-
galaxy rates, as high as $10^{-2}$ gal$^{-1}$ yr$^{-1}$, are hard to achieve through
stellar relaxation alone. Molecular clouds surrounding
nuclear clusters help set the relaxation rate, offering a path to higher rates. We show that (post-)starburst
galaxies, whose nearby prototypes contain large molecular gas reservoirs, are likely in a self-sustaining cycle: an enhanced disruption rate compresses the surrounding clouds through momentum injected by the unbound debris, the denser clouds compress the cluster, and the cluster disrupts
stars faster still. The runaway is arrested only when
stars begin to collide. Solving for the steady state, the rate saturates at $1.4\times10^{-2}(M_{\rm h}/10^{6}M_\odot)^{-0.84}$ yr$^{-1}$, two orders of magnitude above the canonical rate at $10^{6}M_\odot$, with a normalization uncertain by a further two orders of magnitude through the
stellar collision rate. Three independent requirements — that
tidal debris outweigh AGN feedback, that the molecular clouds fit within the disk that holds them, and that the cusp be no denser than observed
nuclei — bound the flattening of the
stellar cusp to $0.18 \lesssim f_\ast \lesssim 0.25$. Because no engine can run below a threshold black hole mass, holes seeded beneath it stay dark until
accretion carries them across, switching on after $\sim 1$ Gyr and offering a natural explanation for the late peak recently measured in the TDE delay time distribution. The
nucleus is buried under $A_V \simeq 50$ whatever its geometry, so most such disruptions should be hidden from optical surveys and emerge instead in the infrared.
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Quantum Physics
On the entropy of a pseudo-density matrix
James Fullwood and Boyu Yang
The pseudo-density
matrix (PDM) formalism naturally extends the notion of density operator to the spatiotemporal domain. While PDMs are Hermitian and of unit trace, they admit negative
eigenvalues when encoding temporal correlations unattainable for spacelike separated systems. Consequently, there have been various approaches to extending the von~Neumann
entropy—which is only defined for positive operators—to PDMs. Here, we prove that there exists a unique extension of the von~Neumann
entropy functional to Hermitian
matrices of unit trace satisfying two simple assumptions:
unitary invariance and strong additivity with respect to affine combinations within the interval $[-1,1]$, which we prove contains the
eigenvalues of a PDM. We also prove that this unique extension of von~Neumann
entropy to PDMs is subadditive for single
qubit dynamics, and we analyze its behavior in a number of examples.
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High Energy Physics (Theory)
Action-angle variables and phase space formulation of Hermitian matrix models
Arghya Chattopadhyay
We develop a phase space description of large $N$ Hermitian one
matrix models directly from the recursions satisfied by the orthogonal
polynomials. In the one-cut phase, the recursion
lattice naturally gives rise to a semiclassical action-angle pair, which can be mapped canonically to
eigenvalue and momentum variables. We show that the resulting momentum profile is determined by the density of zeros of the orthogonal
polynomials, and that the same phase space structure is reproduced from the Wigner transform of the Christoffel-Darboux projector and from the planar spectral curve. The Gaussian model provides a simple consistency check of the proposal. We then extend the construction to the symmetric quartic two-cut phase, where a period-two Jacobi recursion produces two Bloch bands and two disconnected phase space components with actions given by the partial 't Hooft couplings. Finally, we outline the finite-gap generalization appropriate to multicut phases.
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Optics
First-return statistics and the point-spread function of a Henyey-Greenstein random walk - a far-field stable law
Claude Zeller and Robert Cordery
A particle launched normally into a half space, scattering by the Henyey-Greenstein (HG) phase function, exits after a first-return time whose count of flights n approaches the distribution-free Sparre Andersen exponent, f(n) ~ n^{-3/2}, with an amplitude fixed by the launch rather than by the
theorem. Conditioned on n, and past a correlation-set transient, the lateral exit position is Gaussian with variance proportional to n, a scaling we test directly. Subordinating that Gaussian displacement to the one-sided 1/2-stable first-return time gives, in the
diffusion limit, an isotropic 1-stable scaling limit: the far tail of the point-spread function (PSF) for a normally incident pencil beam is the two-dimensional Cauchy tail p(r) ~ r^{-3}, the large-radius limit of the half-space Poisson kernel. The index alpha = 1 is the product of the central limit
theorem and the distribution-free first-return exponent, so no phase function admitting the same
diffusion limit - finite step variance, short-range angular correlation - can move it. Absorption weights each path by exp(-mu_a L) in its total length L, truncating the subordinator and producing the screened radial structure (mu_eff + 1/r) exp(-mu_eff r)/r^2 carried by each source term of the Farrell-Patterson-Wilson (1992)
diffusion dipole; the finite-depth two-source dipole is not derived here. Keeping the launch-depth factor that the tail calculation discards continues the same kernel into a finite core of radius 1.7 l*, with no additional fitted parameter. A scale-dependent index alpha_eff from the empirical characteristic function tracks the similarity parameter gamma, separating phase functions matched in g_1 by 0.15-0.22 near one transport mean free path. Results are Monte Carlo at g = 0 to 0.9 with up to 10^6 walkers.
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Earth and Planetary Astrophysics
Magnitude of stable iron isotope fractionation limited by multiple stages of terrestrial core formation
Gabriel Nathan and Seth A. Jacobson
One proposed mechanism for generating iron isotopic differences between planetary mantles and chondrites is metal-silicate equilibration during terrestrial core formation. Prior studies of this isotopic fractionation effect employ single-stage core formation models that are inconsistent with reproducing the siderophile element budget of the Earth's mantle. Here, we model iron isotopic
evolution of the Earth's mantle in a multistage core formation scenario that is consistent with dynamic models of
planet formation and reproduces the geochemistry of the bulk silicate Earth, specifically the refractory moderately siderophile elements. We find that multiple stages of core formation rebalance the fractionating effect of metal-silicate equilibration for the iron isotopic system, comparable to or smaller than typical analytical uncertainties in mantle rocks. Ultimately, this rebalancing effect - coupled with
stochastic accretion and differentiation histories which further complicate planetary formation processes - makes it unlikely that isotopic fractionation during metal-silicate equilibration is the primary mechanism responsible for the iron isotopic composition of the Earth's mantle.
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Fluid Dynamics
NeuralFlowNet: Towards Data-Free Physics-Informed Neural Network Solutions of Navier-Stokes Equations Across Low and High Reynolds Numbers
Jayanga T. Samarasinghe, Luis De la Fuente and Laura V. Alvarez
Physics-informed neural networks (PINNs) have emerged as a compelling pathway toward trustworthy artificial-intelligence-based computational fluid dynamics (CFD) by
embedding governing equations directly into the learning process. Many existing AI flow models require large simulation or experimental
datasets and often remain problem-specific, limiting their generalization and physical reliability. Data-free PINN frameworks offer an alternative by learning flow solutions from the Navier-Stokes equations and prescribed boundary conditions, potentially reducing dependence on expensive CFD
datasets while retaining physical consistency. However, traditional PINN frameworks have struggled at high Reynolds numbers, limiting their application in CFD. In this work, we present NeuralFlowNet, a data-free, physics-informed proof-of-concept framework designed to solve steady Navier-Stokes problems across low- to high-Reynolds-number conditions. We describe the proposed methodological framework and demonstrate its applicability using
benchmark problems with increasing physical and
geometric complexity. The results demonstrate that NeuralFlowNet can accurately recover steady flow fields across a broad Reynolds-number range, including cases with strong pressure gradients, without training on external flow-field data and while maintaining good agreement with reference numerical solutions. These findings establish NeuralFlowNet as a reliable framework for future testing of unsteady and more complex simulations and could provide a basis for developing trustworthy and efficient AI solvers for high-Reynolds-number fluid dynamics.
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Mesoscale and Nanoscale Physics
Chiral Tubular Magnonic Crystals with Periodic Dzyaloshinskii–Moriya Interaction
P. Contreras-Gallardo, J. Flores-Farias, B. Mimica-Figari et al. (+3 more)
We introduce a
chiral tubular magnonic
crystal formed by a
ferromagnetic nanotube with a periodically modulated interfacial Dzyaloshinskii–Moriya interaction (DMI). Using a plane-wave formalism adapted to the cylindrical geometry, we calculate the
spin-wave band structure including exchange, nonlocal dipolar coupling, and interfacial DMI. We show that the tubular geometry qualitatively modifies the role of periodic DMI compared with planar
chiral magnonic
crystals. Besides producing the usual nonreciprocal frequency shift,
curvature converts part of the interfacial DMI into an effective anisotropy-like internal field. This creates a sign-dependent frequency landscape along the tube, so that DMI-covered regions can act either as potential wells or barriers for the lowest-frequency modes. As a result, flat and weakly dispersive bands appear in both Damon–Eshbach-like and backward-volume-like configurations, with the latter having no direct counterpart in planar systems. Our results identify periodically engineered DMI in nanotubes as a route for controlling nonreciprocal
spin waves, localized modes, and flat magnonic bands in curved architectures.
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All authors P. Contreras-Gallardo, J. Flores-Farias, B. Mimica-Figari, V. Puliafito, P. Landeros, R. A. Gallardo
Instrumentation and Methods for Astrophysics
Pre-shipment optical characterization of the SCALES instrument
Isabel J. Kain, Reni Kupke, Daren Dillon et al. (+31 more)
The Slicer Combined with an Array of Lenslets for
Exoplanet Spectroscopy (SCALES) instrument is a 1-5 micron imager and 2-5 micron integral field spectrograph, currently being commissioned on the Keck II
Telescope. SCALES is optimized for
exoplanet high-contrast imaging and spectroscopic characterization, and will be sensitive to older, colder
exoplanets than existing instrumentation. The 12.3" x 12.3" imaging channel is designed to replicate the capabilities of NIRC2, and the low (R~35-200, 2.2" x 2.2" FOV) and medium (R~2500-5000, 0.36" x 0.34" FOV) spectral resolution modes offer new capabilities compared to existing Keck instrumentation. We present preliminary optical performance results from laboratory testing and commissioning of SCALES.
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All authors Isabel J. Kain, Reni Kupke, Daren Dillon, R. Deno Stelter, Rosalie McGurk, Gwendolin Weber-Stover, Athira Unni, Marc Kassis, Scott Lilley, Peyton Benac, Mackenzie Lach, Arun Surya, Amirul Hasan, Ravinder Banyal, Raquel Martinez, Nicholas MacDonald, Will Deich, Aaron Hunter, Emily Plume, Michael Gonzales, Cristian Rodriguez, Arjun Kumar, Cyril Bourgenot, Paul Whiteg, Juergen Schmollg, James Wells, Spencer Davies, David Bramall, Dimitri Mawet, Olivier Absil, Michael Fitzgerald, Eric Wang, Steph Sallum, Andrew Skemer
Mathematical Physics
Pseudorandomness and Diffraction
David Damanik and Nicolae Strungaru
Pseudorandom structures are structures that behave like random ones, without necessarily being random themselves. It is a prominent, and evidently very difficult,
conjecture that $$ V(n) = \lambda \cos \Big( 2 \pi \Big( x_1 + n x_2 + \frac{n(n-1)}{2} \alpha \Big) \Big) $$ is pseudorandom from a Schrödinger operator perspective in that the Schrödinger operator in $\ell^2(\mathbb{Z})$ with potential $V$ displays Anderson localization, that is, pure point spectrum with exponentially decaying eigenfunctions for almost all parameter values — the same spectral features as those produced by random potentials. We show that $V$ is pseudorandom in terms of its diffraction properties, that is, the associated diffraction measure is purely absolutely continuous for all $\lambda \not= 0$, all irrational $\alpha$, and all $x_1,x_2$ — which is the case as well for the random case. Our result gives further evidence for the
conjecture in the Schrödinger case and it elucidates the apparent dual behavior of Schrödinger spectral measures and diffraction measures.
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Materials Science
Energy landscape and dissipation of sliding magnetic rotor arrays
Johannes Krotz and Anton Lüders
Magnetically coupled damped rotational degrees of freedom can give rise to tribological loss when excited by a relative sliding motion, linking friction to the dynamics of
magnetic moments. We analytically investigate such
magnetic friction by studying a recently introduced simplified model for a rigid
magnetic rotor array sliding over a commensurate
magnetic substrate. Here, the array rotors can rotate about an axis perpendicular to the sliding direction and are damped by microscopic shaft friction, while the substrate magnets have a fixed in-plane orientation. The simplified model reduces the collective rotor dynamics of this setup to a set of coupled nonlinear differential equations, which can be studied by the corresponding energy landscape in the quasi-static regime. We find that the parameter plane spanned by layer separation and time can be divided into distinct chambers, in which the structure of the energy landscape remains invariant. Using these chambers, we identify the layer separation intervals corresponding to different dynamical states and recover the emergence of a regime where the moment
alignment alternates globally while exhibiting peak dissipation. Additionally, we derive the leading nontrivial orders of the collective
magnetic friction in the regimes of small and large gaps between the array and the substrate. For the alternating regime, we find that friction can be computed by tracking energy jumps from unstable to stable critical points at the chamber boundaries. These results provide an analytical foundation for the observed dynamics and dissipation in sliding rotor arrays. Because the simplified model is scale-free, our conclusions transfer across a broad range of microscopic and macroscopic length scales.
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Quantum Physics
Exact Haar Statistics of Planar $k$-Purity in Multipartite Quantum Systems
Kourosh Mirsohi
Planar $k$-uniform states have maximally mixed reductions on every $k$-site interval of a ring. We introduce planar $k$-purity—the mean purity of those intervals—as a faithful cost function for this simultaneous constraint. For a Haar-random pure state of $n$ parties with local dimension $p$, the joint purity of two intervals depends only on their overlap. An exhaustive four-replica calculation therefore yields the complete cyclic covariance kernel and a closed variance for every $1\le k\le\lfloor n/2\rfloor$. In the balanced
qubit case, $k=\lfloor n/2\rfloor$ and $N=2^n$, the variance is asymptotic to $20/(3nN^2)$ for even $n$ and $6/(nN^2)$ for odd $n$. A site-factorized permutation representation gives all raw moments and permits exact finite-sum evaluation of the skewness. Fixed-seed simulations validate nonbalanced
qubit and qutrit cases, while balanced-
qubit simulations through $n=10$ validate the parity formulas and finite-size skewness. Balanced planar and absolute balanced purity have the same Haar mean but different fluctuations; the planar variance is approximately $2.83$ times larger at $n=10$. Thus subsystem incidence, although invisible to every one-cut marginal distribution, controls the collective fluctuations of geometrically related cuts. Together with universal attainability and a linear number of interval constraints at balance, this provides a geometry-aware
benchmark for multipartite
entanglement beyond AME existence regimes.
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Biological Physics
Active wetting transition in cell aggregates
MJ Franco-Oñate, Hanno I. Hennighausen and Ricard Alert
During many biological processes,
cell aggregates spread on substrates in a process of active wetting. The existing models of tissue spreading, however, do not explicitly capture the state of partial wetting, in which the
cell aggregate reaches a non-zero contact angle. Here, modeling
cell aggregates as active polar
liquid droplets, we predict a transition between partial and complete wetting. This transition emerges from the competition between tissue surface tension and active traction forces, which is captured in an active Young-Dupré equation. The active wetting transition is discontinuous, and it features a region of parameters in which both partial and complete wetting are possible. Unlike in passive wetting, the transition depends on dynamical parameters such as the tissue viscosity and substrate friction. Finally, adding contractile intercellular active stresses leads to higher contact angles and even full dewetting. Overall, our work predicts an active wetting transition for tissues and it captures the partial wetting states often seen in experiments.
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Chemical Physics
libNLPBE: An Open-Source Python Package for Solving the Non-Linear Poisson-Boltzmann Equation
Jun-Hyeong Kim and Weitao Yang
Solvent environments surrounding a solute can significantly alter its chemical properties. These changes become more prominent in electrolyte solutions, where mobile ions largely influence the solute through electrostatic interactions. A theoretical description of these ionic effects will benefit the design of chemistry performed in electrolyte solutions. As a result, the non-linear Poisson-Boltzmann equation (NLPBE) has emerged as an efficient implicit solvent model for electronic structure calculations to address such effects. However, the limited availability of NLPBE solvers for molecular electronic structure calculations greatly hinders theoretical investigation into the ionic effects. To improve accessibility of the NLPBE, we present libNLPBE, an open-source Python library, that solves the NLPBE for molecular systems in combination with density functional calculations, specifically to obtain electrostatic correction terms arising from the electrolyte solution environment for the Fock
matrix. The library employs the density fitting (DF) approximation to efficiently calculate solute electrostatic potentials. Furthermore, we develop the modified Damped Inexact Newton Multigrid developed by Holst (mDINMH) method for solving the NLPBE. The mDINMH features a symmetric preconditioner for solving the Newton equation, which enables the use of robust multigrid methods designed for symmetric linear operators. In addition, an algebraic multigrid method has been incorporated into the mDINMH to support a broad range of grid points. We also present a GPU-accelerated version of libNLPBE to leverage parallelization efficiency of GPUs.
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Mesoscale and Nanoscale Physics
Design and Modeling of the Charge Readout of a SiMOS Quantum Dot with a Single Electron Transistor and CryoCMOS
Adam Quinn, Troy England, Andrew Li et al. (+1 more)
Single electron
spin qubits trapped in SiMOS
quantum dots are a promising technology for scaling to thousand- or million-
qubit systems due to their compatibility with mature CMOS manufacturing processes. A readout system that combines a single electron transistor with a custom cryogenic CMOS amplification and digitization chain offers key advantages by avoiding the use of bulky RF components or room-temperature interconnects. We present design techniques and simulation results for an optimized
qubit-SET cryoCMOS interface, culminating in the design of the QNDR1 ASIC, the first cryogenic readout ASIC designed under the Quandarum project, which targets the development of a many-channel
spin qubit based detector for use in high energy physics.
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All authors Adam Quinn, Troy England, Andrew Li, Sharmila Mustari Nandita
Quantum Physics
Spin-spin effects from non-relativistic limit of Dirac-Pauli-Maxwell Lagrangian
Radmehr Fathi and Nima Khosravi
It is natural to expect that the electromagnetic
spin-
spin interaction has roots in a more fundamental theory:
quantum electrodynamics in this case. To show this, we take the non-relativistic limit of the Dirac-Maxwell Lagrangian, using the Foldy-Wouthuysen transformation and derive the Breit interaction by an alternative approach. By adding the Pauli term (i.e., a higher-order interaction between
spin and the electromagnetic field), we calculate the correction terms to electromagnetic
spin-
spin interactions in the non-relativistic limit. Finally, we study some of the physical effects of these terms regarding
spin-
spin interactions and
spin-
spin entanglements. Accordingly, we provide theoretical estimates that are not yet accessible with current experiments.
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Materials Science
Revealing low-energy surfaces of multinary compounds by controlling surface coordination environments
Weihang Xie, Harshan Reddy Gopidi, Zhengyu Liu et al. (+5 more)
When modeling surfaces of multinary compounds, conventional cleavage planes often cut through strongly bonded polyhedra, resulting in unphysical surface energies. Here, we introduce SALAMI (Symmetric Atomic Layers for Arbitrary Multinary Interfaces), a Python package that generates symmetric, charge-neutral, dipole-free, and low-energy slab models for multinary compounds. SALAMI performs combinatorial searches to selectively remove surface atoms and generate corrugated terminations that preserve optimal coordination environments. We applied this workflow to all symmetrically inequivalent crystallographic orientations with Miller indices up to 2 for two prototypical structures: the solid-state electrolyte Li3PS4 and the transparent conducting
oxide ZnSb2O6. Density functional theory calculations reveal that Li3PS4 must preserve all PS4 units to achieve the minimum surface energy. For ZnSb2O6, low-energy surfaces are achieved by partial undercoordination of surface Sb atoms to SbO5 or SbO4 from the bulk SbO6, depending on the surface orientations. Compared to surface models generated with unconstrained coordination, applying constraints to achieve optimal local coordination environments significantly lowers surface energies, shrinking the volume of the predicted Wulff shape by approximately 20%. Our results demonstrate that meticulous control of local coordination environments is necessary for accurately predicting the surface energetics of multinary compounds.
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All authors Weihang Xie, Harshan Reddy Gopidi, Zhengyu Liu, Romain Claes, Alexander G. Squires, Keith T. Butler, David O. Scanlon, Pieremanuele Canepa
Optics
Defects encode high-dimensional topological information
Yunqi Zhang, Fengjun Li, Runchen Zhang et al. (+13 more)
In polarization fields, Stokes skyrmions are continuous vectorial textures that encode integer-valued topological invariants across real space, enabling robust optical information encoding under complex perturbations. This topological resilience, however, fails when singular points occur where the Stokes vector has no unique limiting value, placing a fundamental constraint on skyrmion-based information manipulation. Here, we show, paradoxically, that the very defects that destroy conventional resilience can become the carriers of topological information. We introduce the resulting structures as Stokes defect skyrmions, in which singular Stokes responses constitute measurable topological degrees of freedom with theoretically minimal size. We design and realize one class of them using all-dielectric metasurfaces that combine arbitrarily controlled distinguished fast-axis singularities with customized retardance profiles. The resulting fields are then described by high-dimensional integer-valued topological tuples, providing theoretically unbounded information capacity at the nanoscale. As a proof-of-concept demonstration, selected tuple components are mapped to represent predefined alphabetic symbols, realizing controlled high-dimensional information representation within a single optical field. Our results establish Stokes defects as functional units for higher-dimensional topological encoding, expanding the role of defects from failure points to engineerable carriers of optical information.
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All authors Yunqi Zhang, Fengjun Li, Runchen Zhang, Zi-Lan Deng, Liangyu Deng, Zhikai Zhou, Ruofu Liu, Zimo Zhao, Yifei Ma, Yuanzhe Xu, Zixuan Wang, Yixuan Zhao, Jize Yan, Honghui He, Xiangping Li, Chao He