Materials Science
Hydride formation and phase separation in palladium nanoparticles from a transferable atomic cluster expansion potential
Minaam Qamar, Apinya Ngoipala, Matous Mrovec et al. (+2 more)
The palladium-hydrogen system is a prototype for hydrogen-metal interactions and underpins technologies such as hydrogen storage, catalysis and purification. Yet its nanoscale behaviour – where surface and interface energetics, elastic coherency strain and size-dependent thermodynamics govern phase separation – has eluded accurate atomistic simulation. Empirical potentials misrepresent the energetics of interstitial hydrogen, while existing machine-learning models are restricted to bulk phases at low-hydrogen environments. Here we introduce an atomic cluster expansion (ACE) for Pd-H that reproduces formation energies,
phonon spectra, elastic constants, hydrogen migration barriers and surface adsorption with near-DFT accuracy, benchmarked directly against
neutron-scattering, high-pressure and
lattice-expansion experiments. Its near-linear scaling and CPU efficiency make molecular dynamics of PdH$_x$ nanoparticles exceeding 28,000 atoms ($\sim$12 nm in diameter) tractable over nanosecond timescales. These simulations resolve, at the atomic scale, the kinetic separation of $\alpha$- and $\beta$-PdH$_x$ into a core-shell architecture, reproduce the experimentally observed size dependence of the
lattice parameter, and uncover a pronounced hydrogen-induced lowering of the nanoparticle melting temperature. The potential brings experimentally relevant scales of metal-hydride dynamics within quantitative reach.
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All authors Minaam Qamar, Apinya Ngoipala, Matous Mrovec, Matthias Vandichel, Ralf Drautz
Materials Science
Group theory of Raman effect in magnetic materials
Rui-Chun Xiao, Xue Liu, Yuxuan Jiang et al. (+5 more)
Despite the wealth of experimental observations on Raman scattering in
magnetic materials, the underlying selection rules have remained largely unexplored. In this work, we use Onsager reciprocity relation, other than the conventional corepresentation method, to deal with the mathematical structures of Raman tensors in
magnetic groups. Using this approach, we generate Raman tensor tables for all
magnetic point groups, and present a comprehensive understanding of the Raman selection rules in
magnetic materials with direct product representations method. Our theoretical and numerical results match previous experiments well, and resolve a recent puzzle in the Raman spectroscopy of CrSBr. Moreover, we identify a common but overlooked phenomenon: the magneto-Raman vector can be orthogonal to the
magnetic moment direction. Our method and associated Raman tensor tables will be helpful for the Raman studies in both experimental and theoretical domains.
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All authors Rui-Chun Xiao, Xue Liu, Yuxuan Jiang, Hang Zhou, Zi-Hao Feng, Jie Hou, Xiangru Kong, Yujun Zhang
Fluid Dynamics
Studies of PHP with CASCO code and its experimental validation
Vadim Nikolayev, Slaven Bajić, Guillaume Boudier et al. (+5 more)
We discuss here two major issues related to the steady functioning of the pulsating (oscillating) heat pipe (PHP): the effect of the surface properties and stopovers. They are studied with the CASCO simulation software (Code Avancé de Simulation du Caloduc Oscillant: Advanced PHP Simulation Code in French) version 4. Its experimental validation against two different prototypes is presented. The first is used also to study the effect of the nucleation barrier (the wall superheating necessary for the bubble nucleation) that reflects the wall wettability and roughness. An optimal value of the nucleation barrier is found where the thermal resistance achieves a minimum for a given evaporator power. The functioning regime is continuous showing pressure waves propagating along all the PHP channel. The stopover regime is observed both for small and large barriers. The second experimental setup (PHP Smart Loop) is used to study the stopover regime. It is found that it is characterized by a chaotically repeating sequence of fast pressure growth (corresponding to oscillations) followed by a slower pressure decay during a stopover. The decrease of the thermal resistance with heating load is explained by a decrease of the stopover time caused by a faster
liquid film shrinking.
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All authors Vadim Nikolayev, Slaven Bajić, Guillaume Boudier, Eric Blondé, Typhaine Coquard, Mauro Abela, Mauro Mameli, Sauro Filippeschi
Astrophysics of Galaxies
A Unified Ionization Framework for the Spectroscopic Diversity of Tidal Disruption Events
Lars L. Thomsen, Lixin Dai, Daniel Kasen et al. (+4 more)
Optical
tidal disruption events (TDEs) exhibit extremely broad emission lines ($\approx 10^3$-$10^4~{\rm km~s^{-1}}$) and are observationally classified into four spectroscopic types: H-dominated, He-dominated, H+He, and featureless. The prevalent H+He class often displays Bowen fluorescence lines (notably \niii~and \oiii), features that are rarely observed in active
galactic nuclei and whose origin has remained poorly understood. We present the first unified radiative transfer framework that reproduces all four TDE spectroscopic classes using simulations of optically thick, outflowing envelopes with
solar composition. Our models successfully capture both the continuum properties and key spectral features, including strong \ha, \heii~and Bowen emissions. We demonstrate that the spectroscopic diversity of TDEs is primarily governed by the gas ionization state, controlled by the ratio of injected luminosity to envelope mass. As the ionization level decreases, the observed sequence of spectroscopic classes emerges naturally, transitioning from featureless to He-dominated, to Bowen-dominated, and finally to H-dominated spectra. We further show that electron scattering in the optically thick
outflow is the dominant mechanism responsible for the extreme line widths, linking line profiles directly to the physical properties of the wind. The model also explains the observed correlations with luminosity, black hole mass, and the relative stability of spectral classifications during TDE
evolution. This work establishes a unified physical framework for TDE spectroscopy, providing new insight into the emission mechanisms, energetics, and
outflow structure of these transient events, and offering a practical pathway for interpreting and fitting observed spectra.
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All authors Lars L. Thomsen, Lixin Dai, Daniel Kasen, Enrico Ramirez-Ruiz, Panos Charalampopoulos, Giorgos Leloudas, Brenna Mockler
High Energy Physics (Phenomenology)
Electromagnetic form factors of the $\mathbf{\Omega}$ baryon: space-like structure and time-like extrapolation
L. Albino, B. Almeida-Zamora, A. Bashir et al. (+3 more)
We calculate the elastic electromagnetic multipole form factors of the $\Omega^-$
baryon using a
symmetry-preserving vector$\,\otimes\,$vector contact interaction in rainbow–ladder truncation and a Poincaré-covariant
quark–diquark Faddeev equation. A conserved electromagnetic current yields the electric monopole,
magnetic dipole, electric quadrupole, and
magnetic octupole form factors. We examine their sensitivity to a phenomenological transverse dressed-
quark anomalous
magnetic moment (AMM). The
magnetic and higher multipoles show the strongest dependence, whereas the AMM contribution is progressively suppressed with increasing momentum transfer. The calculated
magnetic moment is larger in magnitude than the experimental value, and a positive AMM contribution increases this discrepancy, exposing a limitation of the present truncation. We also construct a model-dependent time-like extrapolation of the space-like results, motivated by their asymptotic behavior, and use it to evaluate the effective form factor measured in $e^+e^-\to\Omega^-\bar{\Omega}^+$. The extrapolation describes the broad trend at larger energies but does not incorporate resonances, final-state interactions, unitarity cuts, or the complex phase structure required near threshold.
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All authors L. Albino, B. Almeida-Zamora, A. Bashir, J.J. Cobos-Martínez, K. Raya, J. Segovia
Fluid Dynamics
A field-equation semi-local transformation for compressible wall turbulence
Zifei Yin and Jing Wang
Compressibility and wall heat transfer change the inner scaling of wall
turbulence through the mean density and viscosity fields. Most semi-local transformations are applied after a wall-normal profile has been selected. Here the transformed coordinate and transformed velocity are defined by wall-anchored field equations before any profile is extracted. Wall density and friction velocity enter as boundary data for auxiliary field equations; the resulting reference density and friction velocity, together with the local density and viscosity, set the viscous scaling in the wall layer. The local logarithmic density contrast is introduced as a bounded correction to the coordinate-stretching factor. For weak density variation the corrected stretch follows the local inverse kinematic-viscosity variation, while the bounded form limits the influence of finite density contrasts. The transformed coordinate $Y^+$ and transformed velocity $\bm{U}^+$ are obtained from field equations using the corrected stretching and the mean viscous shear. In the constant-property limit the density contrast vanishes, $Y^+$ reduces to the ordinary wall coordinate and each transformed velocity component reduces to the conventional mean velocity component in wall units. For channel flows, the field equations are solved with wall boundary data and the extracted profiles retain their own wall origins. A cooled shock/boundary-layer interaction examines the response when the wall density and friction velocity vary in the streamwise direction. Across the cooled high-speed boundary layers considered here, the bounded density correction narrows the inner- and buffer-layer profile spread...
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Materials Science
Crystal Shape and Lattice Deformation in Powder Diffraction
Matteo Leoni and Alberto Leonardi
Accurate modelling of diffraction peak shapes is essential for extracting microstructural information from nanocrystalline materials. Common-volume functions are widely used to describe finite-size and shape broadening in powder diffraction, but analytical expressions are available only for a limited set of ideal geometries. Here, we introduce a generalized
Fourier-based framework in which
crystal-domain shape deformation,
lattice deformation, and relative shape-
lattice misorientation are treated as independently refinable tensor operations within a unified formalism. The approach enables continuous affine transformations of both
crystal shape and
lattice base while preserving analytical evaluation of directional
Fourier coefficients. As a result, complex particle shapes, anisotropic deformations, and arbitrary relative orientations between shape and
lattice can be modelled within a single reciprocal- and real-space framework, including coupled shape-
lattice transformations not accessible using conventional powder diffraction line-profile methods. The formalism can be applied to individual diffraction peaks, full powder patterns, and total-scattering shape corrections. Validation against virtual scattering experiment data demonstrates that
crystal size, shape,
lattice deformation, and relative shape-
lattice orientation can be simultaneously recovered with high accuracy.
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High Energy Physics (Phenomenology)
Fluctuations and correlations of conserved charges in the Polyakov chiral SU(3) quark mean field model
Dhananjay Singh and Arvind Kumar
We compute generalized susceptibilities of conserved charges in the Polyakov
chiral SU(3)
quark mean field (PCQMF) model with the
fermion vacuum term. At $\mu_B = 0$ MeV, the calculation covers the diagonal $\chi_n^{B,Q,S}$ through eighth order and all twelve independent fourth-order off-diagonal correlators. Extending to finite $\mu_B$ at $\mu_Q = \mu_S = 0$, we compute $\chi_n^B$ through eighth order, $\chi_n^{Q,S}$ through fourth order, the second-order off-diagonals, all twelve fourth-order off-diagonal correlators, and the odd-order
baryon susceptibilities $\chi_1^B$, $\chi_3^B$, $\chi_5^B$. The calculation includes the
vacuum term (vac=1) and is repeated for an independently refitted no-sea variant (vac=0). At $\mu_B = 0$ MeV, the
chiral pseudocritical temperature is $T_{\mathrm{pc}} = 170.5$ MeV (vac=1) and $166.4$ MeV (vac=0), while the Polyakov-loop deconfinement temperature is $T_{\mathrm{dec}} = 144.4$ MeV (vac=1) and $146.6$ MeV (vac=0). In vac=1, the derivative $-d\Delta_{l,s}/dT$ of the subtracted
chiral condensate develops an inflection near $T_{\mathrm{dec}}$. Higher derivative orders resolve the
chiral-deconfinement splitting as twin maxima in $\chi_4^B$ and $\chi_6^Q$, twin minima in $\chi_8^B$ and $\chi_8^Q$, and multiple zero crossings in $\chi_6^B$. Among the fourth-order off-diagonal correlators, vac=1 amplitudes exceed vac=0 in the BQ channel across the
chiral crossover. The BS, QS, and mixed BQS components peak near the strange-melting temperature, where vac=0 dominates. Along $T_{\mathrm{pc}}(\mu_B)$, the kurtosis ratio $R_{42}^B \equiv \chi_4^B/\chi_2^B$ of vac=1 crosses zero at $\mu_B/T_{\mathrm{pc}} \approx 2.15$, while vac=0 stays positive across the full range. The higher-order ratios $R_{51}^B \equiv \chi_5^B/\chi_1^B$ and $R_{62}^B \equiv \chi_6^B/\chi_2^B$ start negative in vac=1 and grow more negative as $\mu_B$ increases.
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Instrumentation and Detectors
High-Efficiency Broadband Mid-Infrared Absorption in Asymmetrically Matched Metallic Meanders: Development of Ti40V60 Alloy based LEKIDs for Mid-Far IR
Shilpam Sharma, Shekhar Chandra Pandey, Anudeep Singh et al. (+3 more)
Fast, highly sensitive, and broadband detectors operating in the mid-to-far-infrared (MIR-FIR) spectral region are essential for applications ranging from astrophysics to time-resolved spectroscopy using laboratory-based sources and beamlines at Infrared Free-Electron
Laser (IR-FEL) facilities. Conventional Lumped Element Kinetic Inductance Detectors (LEKID) achieve high optical efficiency using resonant quarter wavelength ({\lambda}/4) backshort cavities. However, this cavity-based approach is inherently narrowband and becomes optomechanically challenging at the mid to far infrared (MIR-FIR) wavelengths. Here, we present a completely backshort-free LEKID absorber architecture that achieves broadband absorption exceeding 50%. The meander absorbers were fabricated from a superconducting Ti-V
alloy and characterized using IR radiation from the IR-FEL at RRCAT, India. By illuminating through the silicon substrate and matching the meander's sheet resistance to the silicon substrate's wave impedance, the front-side reflection is strongly suppressed. Simultaneously, the sub-wavelength periodicity of the dense meander inhibits propagating transmission into free space via evanescent wave confinement. This combined mechanism drives efficient Ohmic dissipation within the metallic meander, yielding an experimental absorption efficiency ranging from 50% to 90% across the 12.5-30 micrometer wavelength range. The cavity-free design greatly simplifies the fabrication of the focal plane array while providing the broadband response required for next-generation detectors. To assess the suitability of the Ti40V60
alloy as an active superconducting detector material, a test LEKID resonator was also designed, fabricated, and experimentally characterized.
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All authors Shilpam Sharma, Shekhar Chandra Pandey, Anudeep Singh, Shankar Lal, R. S. Saini, M. K. Chattopadhyay
Quantum Physics
Energy Transport in Randomly Coupled Quantum Systems: A Perturbative Approach
Tingfei Li and Runyu Chen
We study energy transport between two
quantum systems coupled through a random interaction. The central feature of our approach is to model the coupling as a Gaussian random
matrix, which enables a simple and systematic perturbative expansion. In the large-$N$ limit, we derive explicit expressions for the energy transfer rate and heat conductance up to second order in the coupling strength. Using spectral methods and diagrammatic expansions, we obtain the leading- and next-to-leading-order contributions to the energy transfer rate. We illustrate our results through explicit calculations for Gaussian, constant, semicircular, and Gamma densities of states.
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Quantum Physics
Range-controlled entanglement in Lindbladian skin states of monitored fermions
Gianluca Passarelli, Angelo Russomanno, Davide Rossini et al. (+1 more)
Reservoir engineering can stabilize states inaccessible to
unitary dynamics. Directed particle-conserving dissipation creates Lindbladian skin states, where Pauli exclusion turns edge accumulation into a many-body density imbalance. In a monitored
fermion chain with tunable hopping range, we identify, within a Gaussian trajectory approximation, two finite-size scaling regimes: short-range hopping is consistent with complete skin accumulation and area-law
entanglement, whereas sufficiently long-range hopping produces a finite bulk tail and effective algebraic sub-volume-law
entanglement. Dissipation and coherent hopping thus jointly control skin localization and
quantum entanglement, highlighting their close interconnection.
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All authors Gianluca Passarelli, Angelo Russomanno, Davide Rossini, Procolo Lucignano
Space Physics
Are the Parker and Focused Transport Equations Equivalent for Galactic Cosmic Ray Modulation?
J. P. van den Berg, N. E. Engelbrecht and R. D. Strauss
The Parker transport equation (TPE) has been the equation of choice for the past 60 years in studies of
galactic cosmic ray (GCR) modulation. Conversely, the focused TPE describes the same processes on a more fundamental level than the Parker TPE by modelling an anisotropic distribution rather than an isotropic one. It is usually assumed that the Parker TPE is valid for modelling GCRs, but the two TPEs have not been tested against each other in this context. We conduct a first-of-its-kind comparison of these TPEs without particle drifts to test whether they produce the same results under identical
diffusion conditions. A new model for
protons during
solar minimum conditions is developed to numerically solve the TPEs using
stochastic differential equations. The TPEs are designed to be as consistent as possible for
diffusion by normalising the pitch-angle-dependent
diffusion coefficients (DCs) used in the focused TPE to the isotropic DCs used in the Parker TPE. The Parker TPE overestimates the GCR intensity at Earth's orbit for low energies by ~30%, and by ~40% over the poles. This stems from a small first-order anisotropy caused by particle fluxes over the poles. Particles gain easier access to the inner heliosphere by streaming in over the poles, where pitch-angle scattering is generally weaker, and the
magnetic field is typically less wound. The focused TPE also yields nearly identical results for different pitch-angle dependencies of the DCs. The description of particle streaming and weak pitch-angle scattering as effective parallel
diffusion in the Parker TPE makes it overly diffusive. This suggests that DCs derived from fitting the Parker TPE to observations are likely underestimated. Furthermore, GCR spectral and anisotropy data alone cannot distinguish between scattering theories with similar mean free paths but different pitch-angle dependencies.
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Statistical Mechanics
Control transition in a temporally random classical spin chain
Elisha Shmalo, J. H. Pixley, Manas Kulkarni et al. (+2 more)
We theoretically explore a phase transition between controlled and chaotic dynamics in a classical
spin chain model subject to chaotic
Hamiltonian dynamics and a contractive "control map", which alternate in time. The control map drives the system toward a target configuration that is an unstable fixed point under the chaotic dynamics. When the control is strong enough, the target configuration is the globally attracting stable fixed point of the dynamics; for weaker control, the many-body dynamics remains chaotic for almost all initial states. The phase transition between controlled and chaotic phases has a mixed character: As the transition is approached from the chaotic phase, the fraction of the
spins that are far from the target configuration goes continuously to zero, and there are diverging spatial and temporal correlation lengths; however, the leading Lyapunov exponent is discontinuous across the transition, jumping from a positive value in the chaotic phase to a negative value in the controlled phase. We present evidence that this transition is in the same universality class as directed percolation in the presence of temporal randomness, a universality class for which we obtain results that are consistent with the dynamical Harris criterion but do not saturate the bound.
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All authors Elisha Shmalo, J. H. Pixley, Manas Kulkarni, Sarang Gopalakrishnan, David A. Huse
Geophysics
Satellite gravity constraints on inner core viscosity and LLVPs density anomalies
Yachong An, Hao Ding, Fred D. Richards et al. (+3 more)
Constraining the physical properties of Earth's deep interior, particularly the viscosity of the solid inner core and the density structure of large low-velocity provinces (LLVPs), remains a major challenge in geophysics. Here we develop a unified dynamical framework that combines mantle-inner core gravitational coupling (MICG) with torsional oscillations in the fluid outer core and show that their interaction can produce a distinct and testable geodetic signature. Guided by this prediction, we analyze satellite
gravity observations together with independent corrections for surface mass variability. We identify a robust approximately 6-year signal in the Stokes coefficient Delta S22, while no corresponding stationary signal is detected in Delta C22. A signal with the same periodicity is independently detected in length-of-day variations (Delta LOD), and the two signals exhibit a near anti-phase relationship. Interpreting this coupled signature within the proposed framework allows us to constrain the inner core viscosity to approximately 4.6 (+/- 1.8) x 10^16 Pa s and the equatorial relief of the inner core boundary to a semi-axis difference of about 200 +/- 70 m. The inversion further indicates mean density anomalies of +5.5 (+/- 0.6) per mil at the base of LLVPs. These results indicate that satellite gravimetry provides a direct observational window into deep-Earth dynamics and the physical properties of Earth's deep interior.
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All authors Yachong An, Hao Ding, Fred D. Richards, Weiping Jiang, Jiancheng Li, Wenbin Shen
Nuclear Theory
Global Ab initio Neutrino Mass Limits from Neutrinoless Double-Beta Decay
T. Shickele, L. Jokiniemi, A. Belley et al. (+1 more)
We present global limits for Majorana
neutrino masses by combining latest results from neutrinoless double-beta ($0\nu\beta\beta$) decay searches and ab initio
nuclear theory. Limits are derived in a
Bayesian framework utilizing likelihood functions from a suite of $0\nu\beta\beta$-decay experiments in conjunction with
nuclear matrix elements calculated from
nuclear and electroweak forces derived from
chiral effective field theory and implemented in the in-medium similarity renormalization group many-body approach. In contrast to
nuclear models, ab initio results indicate that the current generation of $0\nu\beta\beta$-decay experiments have likely not yet reached sensitivities required to probe the mass regime allowed by
neutrino-oscillation data, where the combined bounds are notably stronger than those given by individual experiments. Finally, from predicted sensitivities of next-generation searches, we show that, while no one individual experiment fully covers the inverted mass ordering, this can be achieved from combined contributions from the four key isotopes: $^{76}$Ge, $^{100}$Mo, $^{130}$Te, and $^{136}$Xe.
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All authors T. Shickele, L. Jokiniemi, A. Belley, J. D. Holt
Astrophysics of Galaxies
Disentangling chemical evolution histories with phylogenetic trees
Rebeca Canales, Paula Jofré, Claudia Aguilera-Gómez et al. (+6 more)
Chemical abundances encode the fossil record of
galaxy evolution in a complex and diverse way that requires innovative approaches to reconstruct
galactic histories. We investigate the power of using phylogenetic methods to disentangle different evolutionary pathways in analytical chemical
evolution models. We ran 1024 one-zone chemical
evolution models using flexCE. The resulting chemical abundances are combined with those of two fiducial models, mw-fid and dw-fid, and then used both to determine which combinations produce two-branched phylogenetic trees, as well as how purely these trees split the two input models. We used random forests and Shapley analysis to predict which model combinations return well-separated trees and explain which input parameters are most important for this. We also studied the abundance patterns, as well as
star formation rates, mass accumulation, and branch lengths. We found that {\eta}, the mass-loading
outflow parameter in flexCE, had the largest impact in separating models into separate branches, due to its importance in driving the chemical enrichment rates and total abundances.
Star formation rates and mass accumulation had some impact on {\eta}, but no direct relation between these quantities and the abundances was found. We also found that branches connected through the most metal rich tips in our trees, which is opposite to how phylogenetic trees connect in biological systems. Phylogenetic trees help to reconstruct histories when there is information that is inherited between generations, which is the case of the chemical elements in
galaxy evolution. Branch
topologies can provide information about the rates of evolutionary change of the various populations, and the connection between branches also contains information about their shared history. This work brings us a step further understanding
galaxy evolution through cross-disciplinary research.
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All authors Rebeca Canales, Paula Jofré, Claudia Aguilera-Gómez, Payel Das, Robert Yates, Theosamuele Signor, Patricia Tissera, Xia Hua, Robert Foley
Adaptation and Self-Organizing Systems
Towards personalised intervention: A causal-dynamical framework to determine psychological treatment trajectories
Lourens Waldorp, Titus Mürtz, Anita Jansen et al. (+1 more)
For approximately half of the individuals receiving mental health care, the results are suboptimal, even when treatments align with evidence-based guidelines. These limited effects may partly stem from how clinical decisions on treatment focus are made in mental health care. Typically, treatment strategy is guided by the diagnostic classification combined with the individualized case conceptualization. While standard, this approach may fall short for several reasons such as biases on the part of both the patient and therapist, and treatment guidelines being based on average effects that may not (exactly) suit the individual patient. To address these challenges, we propose a novel framework that reduces biases in clinical decision-making and makes it genuinely possible to tailor treatment focus to the individual patient. This framework involves (a) constructing causal graphs and estimating causal effects from intensively collected, longitudinal patient data, (b) simulating new time series based upon the causal relationships, and (c) using these simulations to identify the most effective treatment focus for the individual patient. By simulating and comparing different intervention strategies and examining both the estimated individual's responsiveness and its long-term effectiveness, this approach may generate useful insights to guide treatment focus and strategy, which can lead to a significant improvement of treatment outcomes in mental health care.
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All authors Lourens Waldorp, Titus Mürtz, Anita Jansen, Jonas Haslbeck
Mesoscale and Nanoscale Physics
Unconventional incommensurate epitaxy of superconducting FeSe films on SrTiO$_3$
M. Klement, K. M. Fijalkowski, M. Kamp et al. (+2 more)
We present a combined X-ray diffraction and transmission electron microscopy study of superconducting FeSe/FeTe multilayers grown by molecular beam epitaxy on SrTiO$_3$(001) substrates. While X-ray diffraction confirms perfect in-plane epitaxial
alignment between FeSe, FeTe, and the substrate, scanning transmission electron microscopy reveals a surprising lack of atomic registry at the FeSe/SrTiO$_3$ interface. Instead of adapting to the substrate
lattice, FeSe retains its own in-plane
lattice spacing. A periodic lateral shift between the atomic positions of FeSe and SrTiO$_3$ is observed, with a registry recurrence length that matches the
lattice mismatch determined by X-ray diffraction. No misfit dislocations or other relaxation features are detected at the interface. This coexistence of directional
alignment and registry-free growth suggests an unconventional regime of epitaxy in which crystallographic orientation is maintained without atomic matching. The findings offer insight into strain accommodation in layered systems and may have implications for interface engineering in Fe-based
superconductors.
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All authors M. Klement, K. M. Fijalkowski, M. Kamp, C. Gould, L. W. Molenkamp
Materials Science
Layer-parity-defined surface polarization in Nb$_3$Cl$_8$ for excitonic modulation at van der Waals interfaces
Xinyue Huang, Hansheng Xu, Yuchen Gao et al. (+10 more)
The intrinsic
symmetry breaking in the breathing kagome
lattice of layered Nb$_3$Cl$_8$ provides a unique mechanism for realizing electrically polar surfaces. In each monolayer, the trimerization of Nb atoms breaks inversion and mirror
symmetries, generating an out-of-plane electric dipole. The AB-stacked $\alpha$ phase arranges adjacent layer dipoles antiferroelectrically, leaving the uncompensated surface polarization strictly governed by layer parity. Here, using atomic force microscopy operated in Kelvin probe force microscopy mode, we directly visualize layer-dependent polarization states in exfoliated Nb$_3$Cl$_8$ flakes and resolve a pronounced odd-even oscillation of the surface electrostatic potential. Beyond this parity-locked antiferroelectric order, we further identify intralayer polar domains in which local atomic reconstructions of the breathing kagome network reverse the out-of-plane dipole of the surface layer, producing ferroelectric-like stacking configurations. By interfacing monolayer MoSe$_2$ with Nb$_3$Cl$_8$, we demonstrate that these surface-polarization textures effectively modulate adjacent excitonic emission through domain-dependent interfacial band
alignment and charge transfer. Our findings establish Nb$_3$Cl$_8$ as an intrinsic layer-polarized van der Waals platform and show that layer parity provides powerful structural degree of freedom for programming excitonic and optoelectronic responses at van der Waals interfaces.
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All authors Xinyue Huang, Hansheng Xu, Yuchen Gao, Yushen Zhou, Zhijie Ma, Kenji Watanabe, Takashi Taniguchi, Zuxin Chen, Jianqi Huang, Jianpeng Liu, Teng Yang, Youguo Shi, Yu Ye
Mesoscale and Nanoscale Physics
Non-Bloch band theory of boundary-controlled magnon edge modes in an antiferromagnetic chain
Suman Debnath, Sonu Verma, Rohit Mukherjee et al. (+1 more)
We define a winding number within the Non-Bloch band theory framework that captures the emergence of
magnon edge modes in a one-dimensional
antiferromagnetic spin chain, even when the conventional Bloch winding number is trivial. Within linear
spin-wave theory,
magnon excitations are governed by a non-Hermitian dynamic
matrix, despite the underlying
Hamiltonian being Hermitian. The
symmetry classification of this
matrix yields a trivial bulk invariant, however, finite systems exhibit boundary-localized modes, signaling a breakdown of the conventional bulk-boundary correspondence. We further show that these edge modes can be controlled via boundary perturbations. By tuning the boundary potential, the modes can be driven into or out of the bulk spectrum. To resolve the bulk-boundary mismatch, we develop a non-Bloch framework based on a generalized Brillouin zone and a winding number that correctly predicts the presence of edge states. Our results establish boundary-controlled topological transitions that are experimentally accessible through local Zeeman fields or modified edge anisotropy in
antiferromagnetic van der Waals nanostructures.
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All authors Suman Debnath, Sonu Verma, Rohit Mukherjee, Arijit Kundu
Soft Condensed Matter
Ivan I. Smalyukh and Mykola Tasinkevych
In soft condensed matter,
curvature does more than simply distort an ordered medium: it helps select defect structures, redistribute elastic stress, bias chirality, and guide self-assembly. This review examines how curved, multiply connected, and knotted boundaries in
liquid-
crystal colloids and confined nematics generate topological defects and localized solitonic textures, and how these structures mediate interactions between mesoscale building blocks. We introduce a unifying framework based on genus, Euler characteristic, anchoring, and chirality, and use it to discuss spherical, handlebody, and boundary-bearing colloids, together with droplets and
polymer-dispersed nematics of nontrivial
topology. Particular emphasis is placed on the interplay of geometry and
topology in determining boojums, disclination loops, hedgehog charges, and linked and knotted defect structures. We then turn to
chiral systems hosting skyrmions, torons, hopfions, and related localized textures, highlighting how chirality and confinement stabilize three-dimensional topological states. Finally, we discuss how these concepts translate into design principles for controlled self-assembly, templating, and functional composite materials. More broadly, we argue that
liquid-
crystal colloids and confined nematics provide experimentally accessible model systems in which
curvature,
topology, and chirality can be harnessed as programmable tools for designing organized soft matter.
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Mathematical Physics · Cross-listed from math.DG
Jet Bundles as Higher-Order Polarised $k$-Contact Manifolds
Javier de Lucas
We prove that the Cartan distribution $C^r_\pi$ on the jet bundle $J^r\pi$, for $\pi:E\rightarrow Q$, is an $N^r_\pi$-contact distribution, where $N^r_\pi$ is the corank of $C^r_\pi$. In other words, $C^r_\pi$ has non-degenerate distributional
curvature, and admits, locally, a complementary distribution spanned by $N^r_\pi$ commuting infinitesimal
symmetries. Consequently, there exists around every point of $J^r\pi$ an open $U\subset J^r\pi$ and an $R^{N^r_\pi}$-valued one-form $\eta\in\Omega^1(U,R^{N^r_\pi})$ such that $\ker\eta= C^r_\pi|_U$ and $\ker\eta\oplus\ker d\eta=TU$. This recovers the canonical structure of $J^r\pi$, algebraic Spencer contractions, and other mathematical entities in a simple unifying manner while providing a local
Hamiltonian structure and other advantages. We will call a
manifold endowed with a k-contact distribution a k-contact
manifold. New types of polarisations for k-contact distributions lead to our main recognition
theorem, which shows that a polarised k-contact distribution is locally equivalent to a Cartan distribution precisely when its polarisation is of jet type. This characterises finite-order jet geometry as polarised $N_\pi^r$-contact geometry of jet type. Moreover, the highest-order vertical polarisation, holonomic submanifolds, characteristics for Lie
symmetries and their brackets, and other structures are reconstructed and generalised via k-contact geometry. Solutions of PDEs become polarised Legendrian submanifolds, jet prolongations are polarised k-contact Legendrian prolongations, etc. Our k-contact formalism gives a common
language for constructions that are awkward in a single jet presentation, and extends jet geometry to new problems. Our techniques provide new general reduction methods for PDEs retrieving standard and non-local reductions as particular cases, and are applied to PDEs.
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Materials Science
The impact of interfacial chemistry on the band offset of GaAs/Ga$_2$O$_3$ heterostructures
Sofia Apergi, Alfredo Pasquarello, Charles Cornet et al. (+1 more)
Ga$_2$O$_3$/GaAs heterojunctions are emerging as promising candidates for next-generation power electronics, photonics, and energy devices, leveraging the high breakdown voltage and thermal stability of Ga$_2$O$_3$ alongside the mature technology, high hole mobility, and higher refractive index of GaAs. The efficiency of these devices depends strongly on the band
alignment between the two materials, however both type-I and type-II
alignment have been reported in the literature for these
heterostructures. To address this ambiguity, we use hybrid density functional theory to systematically investigate the band
alignment at GaAs/Ga$_2$O$_3$ interfaces, focusing on the role of interface chemistry. By considering Ga-O-, As-, and As-O-rich interfaces both in amorphous and crystalline Ga$_2$O$_3$ phases, we demonstrate that interface stoichiometry determines the
alignment type: Ga-O-rich interfaces exhibit type-II
alignment with large valence band offsets (~3.1 eV), while As-rich and As-O-rich interfaces favor type-I
alignment with reduced offsets (~2.3-2.6 eV). These trends are attributed to interface dipole formation driven by bonding configuration. Our findings provide insight into the relationship between chemistry and band
alignment in GaAs/Ga$_2$O$_3$
heterostructures, enabling targeted optimization for specific device applications.
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All authors Sofia Apergi, Alfredo Pasquarello, Charles Cornet, Laurent Pedesseau
High Energy Physics (Phenomenology)
Meson-nucleus bound states with neural-network quantum states
Wei-Lin Wu, Liang-Zhen Wen and Shi-Lin Zhu
We present the first systematic calculations of $\phi$-, $\eta_c$-, and $J/\psi$-
nucleus ground states up to mass number $A{=}12$ based on the HAL QCD
meson-nucleon potentials at near-physical point. The $(A{+}1)$-body Schrödinger equation is solved with a neural-network variational Monte Carlo framework, generalized to incorporate mesonic degrees of freedom. Benchmarking on light
nuclei from $^2$H to $^{12}$C yields ground-state energies consistent with the experiment.
Meson-
nucleus bound states emerge at $A\ge2$ for $\phi$, $A\ge4$ for $J/\psi$, and $A\ge6$ for $\eta_c$. The $\phi$-
nucleus systems exhibit the strongest binding, with binding energies reaching tens of MeV. The $J/\psi$-
nucleus and $\eta_c$-
nucleus systems are weakly bound at the few-MeV and sub-MeV scale, respectively. The binding energy per nucleon deepens nearly linearly with $A$ for charmonium systems, whereas the $\phi$-
nucleus system exhibits a non-monotonic behavior peaking at $^4$He—a distinctive hallmark of the short-range and strongly attractive $\phi N$ interaction. The
meson compresses the nucleon distribution relative to the parent
nucleus, and evolves from a
halo configuration to one embedded inside the
nucleus with increasing $A$. Our results provide predictions for future experimental searches, and establish a quantitative bridge between
lattice QCD
meson-nucleon interactions and the emergent many-body phenomena in
meson-
nucleus bound states.
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Medical Physics · Cross-listed from cs.CV
A practical probabilistic framework for deformable image registration uncertainty in radiotherapy dose propagation
Stefan Heldmann, Sven Kuckertz, Nasim Givehchi et al. (+4 more)
Deformable image registration (DIR) is widely used in radiotherapy for dose propagation and accumulation, but uncertainty in the underlying deformation can substantially affect clinically relevant dose estimates. We present a practical probabilistic framework for propagating DIR uncertainty to voxel-wise dose statistics and dose-volume histograms (DVHs). The method models the mapped correspondence at each voxel as a random variable governed by a transparent local certainty map that can be defined by simple safety margins, structure-boundary mismatch, or structure-wise conservative uncertainty values. This yields interpretable quantities such as dose probabilities, expected dose, confidence bounds, and induced DVH envelopes. The framework is designed to remain lightweight and interpretable: it avoids complex biomechanical or ensemble-based uncertainty models and instead emphasizes simple parameterization, computational feasibility, and transparent dose metrics. We further introduce a structure-guided in/out strategy as an optional refinement that restricts mapping probabilities to anatomically plausible target regions. The approach is demonstrated on a prostate radiotherapy case study and used to compare different certainty-map strategies and probability kernels. The experiments show that the certainty-map design has a stronger effect on resulting dose and DVH uncertainty bounds than the specific kernel choice, while the additional benefit of the in/out strategy is case-dependent and modest in the present example. Overall, the proposed framework provides a transparent way to incorporate DIR uncertainty into radiotherapy dose assessment and to study how modelling choices affect propagated dose metrics.
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All authors Stefan Heldmann, Sven Kuckertz, Nasim Givehchi, Thomas Coradi, Mikel Byrne, Ben Archibald-Heeren, Nils Papenberg
Solar and Stellar Astrophysics
A consistency check for the calibration of 5303Å solar coronal emission line observations with Aditya-L1/VELC
V. Muthu Priyal, R. Ramesh, Jagdev Singh et al. (+2 more)
We carried out radiometric calibration of the Visible Emission Line Coronagraph (VELC) onboard Aditya-L1 at 5303Å using observations of the Sun itself, a novel approach compared to the calibration using bright
stars in the other currently operational space
solar coronagraphs. The measured VELC detector count corresponding to the center of Sun's disk is ${\approx}(1.70{\pm}0.12){\times}10^{8}\, \rm sec^{-1}{\AA}^{-1}$, which relates to Sun's flux at 1\,AU in 5303Å, ${\approx}3.0456{\times}10^{6}\, \rm {erg\,sec^{-1} cm^{-2} {\AA}^{-1}}$. We verified the above calibration using observations of the bright
star Sirius-A whose estimated flux at 1\,AU in 5303Å is ${\approx}1.44{\times}10^{-8}\,\mathrm{erg\,sec^{-1} cm^{-2} \AA^{-1}}$. The expected detector count with VELC in this case is ${\approx}19{\pm}1.4\, \rm sec^{-1}{\AA}^{-1}$, and the measured count is ${\approx}23{\pm}0.4\, \rm sec^{-1}{\AA}^{-1}$. The reasonable agreement between the expected and observed values for Sirius-A in this initial consistency check after two years of observations with VELC, indicates that measurements of coronal brightness at 5303Å with the VELC and its conversion into absolute physical units using observations of the Sun disk light are in order. Using the Sirius-A observations we measured the point spread function (PSF) of the VELC in its 5303Å channel also. Its full width at half maximum (FWHM) is ${\approx}3.8^{\prime\prime}$.
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All authors V. Muthu Priyal, R. Ramesh, Jagdev Singh, K. Sasikumar Raja, P. Savarimuthu
High Energy Astrophysical Phenomena
Bayesian analysis of the shear modulus in the neutron-star crust
T. Diverrès, G. Montefusco, A. F. Fantina et al. (+1 more)
The elastic properties of the
neutron-
star crust are important for the calculations of crustal modes. In particular, the ability of the crust to support shear stresses has been connected to observations of quasi-periodic oscillations and to crust deformations potentially emitting gravitational waves. In this work, we assess the uncertainties in the shear modulus and shear speed in the
neutron-
star outer and inner crust. To this aim, we performed a
Bayesian analysis of the shear properties of the
neutron-
star crust at zero temperature starting from both a non-informative and a
nuclear-physics-informed prior. For the treatment of inhomogeneous matter in the crust, we relied on the one-component
plasma approximation, with a (semi-)classical treatment of the ions. We show that the use of a
nuclear-physics-informed prior has a non-negligible impact on the prediction of the elastic properties of the crust. The frequency of the fundamental torsional crustal modes we obtain is compatible with the low-frequency range of observed quasi-periodic oscillations, our estimates lying in the interval $\approx 20 - 50$~Hz. Although the different considered priors lead to compatible results, the inclusion of
nuclear-physics experimental information in the prior considerably reduces the uncertainties in the prediction of the elastic properties of the crust, potentially constraining the predicted frequency of the crustal modes.
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All authors T. Diverrès, G. Montefusco, A. F. Fantina, F. Gulminelli
Mesoscale and Nanoscale Physics
Correlation enhanced resistance hysteresis near half filling in MoS2/WSe2 heterobilayer
Yong Chen, Weikang Zhang, Meizhen Huang et al. (+11 more)
Ferroelectricity, typically arising from ionic displacements in noncentrosymmetric
lattices, enabling applications in
memory devices and sensors. Recent advances in two-dimensional materials and van der Waals
heterostructures have revealed novel ferroelectric phenomena, including sliding ferroelectricity and correlation-driven ferroelectricity in moire superlattices. In this work, we fabricate and study a MoS2/WSe2 moire superlattice device exhibiting a high field-effect mobility of 17,650 $cm^2V^{-1}s^{-1}$. Electrical transport measurements reveal correlated insulating states accompanied by a prominent and reproducible resistance hysteresis near half filling. Temperature and displacement field dependence further confirms the correlation-enhanced nature of the hysteresis. Our analysis suggests that displacement field-induced metal-to-
insulator transition at correlated insulating state coupled with interfacial dipoles enables the observed resistance hysteresis. These results establish correlation enhanced resistance hysteresis near half filling in a MoS2/WSe2 heterobilayer, offering opportunities for exploring emergent
quantum phases and device functionalities.
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All authors Yong Chen, Weikang Zhang, Meizhen Huang, Shengling Xiang, Zishu Zhou, Yaqi Ma, Chenxuan Lou, Haoxi Ji, Aoqian Zhang, Yifei Jin, Liheng An, Zefei Wu, Chun Cheng, Ning Wang
General Relativity and Quantum Cosmology
Geodesic structure of the cosmological Levi-Civita spacetimes
Adam Tyc and Martin Zofka
We investigate the implications of the behavior of geodesics in static, cylindrically symmetric spacetimes with a non-zero cosmological constant. We consider the
symmetries of these spacetimes to restrict admissible ranges of the metric parameters and to formulate an intuitively plausible interpretation of the coordinates.
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General Relativity and Quantum Cosmology
Detectability to extreme mass ratio inspirals with alternative space-based detector networks
Chao Zhang and Gang Wang
Extreme mass ratio inspirals (EMRIs) are among the primary targets for space-based gravitational-wave (GW) detectors, providing valuable opportunities to study
stellar-mass compact objects orbiting supermassive black holes (SMBHs) and to probe
gravity in the strong-field regime. As the LISA, TAIJI, and TianQin missions are expected to operate around 2035, joint observations by multiple detectors may provide enhanced measurement capabilities compared to individual missions. In this work, we investigate the detectability and parameter-constraint prospects for EMRIs using global detector networks composed of LISA, TianQin, and two alternative TAIJI orbital configurations. Employing Fisher information
matrix analysis, we find that joint observations improve source localization relative to a standalone LISA mission, with sky-localization uncertainties reduced by up to two orders of magnitude for a one-month observation period. We further find that a three-detector network (LISA-TAIJI-TianQin) operating for one month yields parameter constraints comparable to, and in some cases tighter than, those obtained from a one-year observation by LISA alone. This result indicates that network observations can partially compensate for shorter observation durations in parameter inference. Furthermore, we evaluate measurement uncertainties in concurrent dual-signal scenarios: (i) two EMRIs orbiting the same SMBH and (ii) two EMRIs with identical intrinsic parameters but different sky locations and orientations. The results indicate that differences in the detector responses associated with the source geometries reduce correlations between overlapping signals, allowing the sources to remain distinguishable even for a standalone mission. The inclusion of multiple detector constellations further improves source localization and tightens parameter constraints in these concurrent-source scenarios.
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