Quantum Physics
Quantum Resources and Performance in the Initialization-Free Bernstein-Vazirani Algorithm
Haesol Han, Alexander Streltsov and Soojoon Lee
Naseri et al. [Phys. Rev. A 106, 062429 (2022); arXiv:2205.13610] studied which
quantum resources in initial states are essential for the probabilistic Bernstein-Vazirani (BV)
algorithm, defining its performance as the optimal average success probability over all measurements. In this work, we consider a variant of BV
algorithm, which is called the initialization-free (IF) BV
algorithm, in which an arbitrary ancilla state as the oracle register is allowed, to improve the performance. We derive an explicit formula for the performance of the probabilistic IF-BV
algorithm and obtain a necessary and sufficient condition for an initial state to achieve maximal performance. We further prove that, under a suitable ordering assumption on the coefficients of the initial state, the probabilistic IF-BV
algorithm outperforms the standard probabilistic BV
algorithm.
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Statistical Mechanics
Identifying Non-Ideal Reaction-Diffusion Systems Unable to Maintain Diffusion Out-of-Equilibrium
Francesco Avanzini, Timur Aslyamov and Massimiliano Esposito
We develop a general method, based on the construction of a kinetic potential serving as a Lyapunov function, to establish when
diffusion necessarily equilibrates in non-ideal reaction-
diffusion systems under arbitrary driving by autonomous homogeneous chemostats. This equilibration of
diffusion implies vanishing
diffusion currents and homogeneous chemical potentials, while reactions can remain far from
equilibrium. Using this method, we generalize the results of J. Chem. Phys. 161, 174108 (2024) by relaxing some of the underlying assumptions. Specifically, we show that
diffusion equilibrates in reaction-
diffusion systems whose chemical reaction network is either pseudo-detailed balanced, with reaction fluxes controlled by the stoichiometry of reactants and products, or complex balanced, with reaction fluxes controlled only by the stoichiometry of the reactants. These different constraints on the reaction fluxes are shown to originate from the distinct stoichiometric properties of the two classes of networks.
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Strongly Correlated Electrons
Bose Einstein Condensation of Magnons in BaCuSi$_{2}$O$_{6}$: An experimental perspective
Marcelo Jaime and Franziska Weickert
Han Purple, a pigment first obtained in ancient China, is one of the earliest known synthetic pigments. Also naturally occurring, as a mineral, it is known as colinowensite (Cwn). Its chemical formula is BaCuSi$_{2}$O$_{6}$, and its structure is a layered cyclosilicate in which
magnetic Cu$^{2+}$ ions (S = 1/2) form dimers arranged on a square
lattice, making it also the first known synthetic metal dimer compound. Most interesting
magnetic properties arise from a strong intradimer
spin coupling, accompanied by weaker interdimer interactions within and between Cu-dimer layers. In zero or small
magnetic fields, BaCuSi$_{2}$O$_{6}$ remains a
quantum paramagnet. However, under high
magnetic fields between 23 and 49 Tesla – about a million times stronger than Earth's
magnetic field – it undergoes
magnetic ordering at subliquid Helium temperatures into an almost ideal easy-plane (XY)
antiferromagnetic state regarded as a realization of a Bose-Einstein condensate of
magnons. Within this experimentally accessible field range, BaCuSi$_{2}$O$_{6}$ serves as an extraordinary playground for testing predictions of
quantum many-body physics.
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High Energy Astrophysical Phenomena
The problem of escape: a missing bit in the theory of the origin of cosmic rays
P. Blasi and E. Amato
The escape of
cosmic rays from their sources, as well as from the region surrounding a source, or from the
galaxy hosting the sources, is a non-linear process that involves a complex chain of events, often overlooked. On the other hand, these phenomena are responsible for setting the maximum energy in accelerators, shaping the source spectra and determining the conditions for escape from the
galaxy hosting the sources, a process that is usually modeled by imposing ad hoc boundary conditions in our equations. Here we discuss some of these phenomena and how they affect the spectra of
cosmic rays measured at the Earth.
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Astrophysics of Galaxies
A Face-on View of Interstellar Dust in the Galactic Plane
Lin Zhang, Bingqiu Chen, Fei Qin et al. (+3 more)
Interstellar
dust is a fundamental component of the Milky Way, influencing
star formation,
galactic evolution, and observations across the electromagnetic spectrum. Using red clump
stars selected from near- and mid-infrared photometry, together with
stellar catalogs from previous studies, we construct
dust density maps of the
Galactic plane ({$|Z|<25$}\,pc) covering the full $360^\circ$ in longitude and reaching distances up to $7$\,kpc. By applying a U-Net convolutional neural network to invert the line-of-sight extinction distribution, we obtain
dust density maps at resolutions of $10$, $50$, and $100$\,pc, which reveal detailed structures including spiral arms, inter-arm spurs, and
giant cavities. The
dust distribution in the
Galactic plane exhibits a morphology closely resembling that of the so-called Phantom
galaxy M74. The derived exponential scale length of the
Galactic dust disk is $2.90$\,kpc, slightly larger than that of the
stellar thin disk. Our publicly available
dust maps provide a new
benchmark for extinction correction, studies of
Galactic structure, and the investigation of the interplay between
star formation and the interstellar medium.
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All authors Lin Zhang, Bingqiu Chen, Fei Qin, Guangxing Li, Haibo Yuan, Yi Ren
Solar and Stellar Astrophysics
Investigating white-light flare mechanisms via the Paschen jump using high-resolution continuum observations from the Swedish 1-m Solar Telescope
Sascha Ornig, Luc Rouppe van der Voort, Mats Carlsson et al. (+4 more)
The continuum is understood to contain a large portion of the energy emitted by a
solar flare. The optical continuum, known as white light (WL), is particularly relevant since it may be observed by ground-based instruments. We measured the WL enhancements short- and longward of the Paschen jump in order to gain insights into the possible mechanism(s) behind the creation of these increases in our two case studies. We took measurements from the Swedish 1-m
Solar Telescope of the pseudo-continuum around the Ca II 8542 Å line as well as the true continuum around the K I 7699 Å and the Fe I 6173 Å line, providing us with observations on both sides of the Paschen jump. We observe WL enhancements of over 40% against the dark (pen-) umbral background in both
flares. The WL excess in
flare 1 is co-temporal with the derivative of the GOES soft X-ray and hard X-ray (HXR) measurements from the Advanced Space-based
Solar Observatory (ASO-S), and the
flare is compatible with the Neupert effect. For
flare 2, a preceding smaller
flare may be the cause of the temporal discrepancy. Signatures of chromospheric evaporation and condensation are found in the WL area for both
flares. The ratio of intensities blueward and redward of the Paschen jump in
flare 1 is below one for most WL pixels. This is in disagreement with the accepted WL formation mechanisms. We believe this is a consequence of the Ca II 8542 Å pseudo-continuum being affected by line wing opacity changes. The co-temporality of WL and HXR enhancements suggests that the WL emission enhancements in
flare 1 (and parts of
flare 2) are a result of direct electron precipitation. We conclude that more reliable continuum measurements free of any nearby line influence are necessary in order to obtain conclusive evidence for the formation mechanism(s) behind optical continuum enhancements from such analysis as presented in this work.
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All authors Sascha Ornig, Luc Rouppe van der Voort, Mats Carlsson, Carlos José Díaz Baso, Eilif Sommer Øyre, Ignasi Josep Soler Poquet, Aline Rangøy Brunvoll
High Energy Physics (Phenomenology)
Anisotropic electron scattering and Migdal effect in semiconductor detectors
Aula Al-Adulrazzaq, Paolo Settembri, Sebastian Sassi et al. (+4 more)
Cryogenic
semiconductor detectors are widely used in dark matter direct detection. Electronic excitations in these materials can be caused either by direct dark matter electron scattering events, or indirectly via dark matter
nuclear scattering events. For
nuclear scattering of light dark matter, the event rate is enhanced due to an inelastic process known as the Migdal effect. Both the electron
recoils and the Migdal effect in
semiconductors depend on the dielectric function of the target material via the so-called energy loss function (ELF). In the standard approach found in the literature, the ELF is approximated as isotropic to simplify the calculation of the event rate. We introduce a practical method for computing the event rate for a general anisotropic ELF. We find that the daily modulation of the Migdal rate arises solely due to the quadrupole component of the ELF, whereas in electron scattering all spherical harmonic components affect the rate. We apply the formalism to study the daily modulation in silicon and gallium arsenide detectors.
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All authors Aula Al-Adulrazzaq, Paolo Settembri, Sebastian Sassi, Federico Giannessi, Gianni Profeta, Matti Heikinheimo, Kimmo Tuominen
Optics
Engineering Disordered Many-particle Plasmonic Nanoclusters for Wafer-scale Uniform and Giant Electromagnetic Field Enhancement
Minjun Kim, Vasanthan Devaraj, Hyeon-Seok Seo et al. (+6 more)
Scalable plasmonic technologies face a critical trade-off: few-body architectures offer high enhancement but are sensitive to fabrication flaws, while scalable methods like solid-state dewetting yield large, low-enhancement gaps. We introduce a paradigm shift using a many-body plasmonic architecture inspired by statistical mechanics. By moving toward the continuum limit (N>>1), local
geometric variations are statistically averaged out, effectively decoupling optical performance from microscopic disorder. We implement this concept via a lithography- and etching-free, multi-step dewetting strategy, creating wafer-scale nanoclusters. This process strategically forms a robust many-body system by introducing numerous small satellite nanoparticles between larger particles. Crucially, this design achieves a high collective enhancement that surpasses even optimized few-body systems, despite having larger individual gaps. Under optimized conditions, these substrates exhibit a surface-enhanced Raman scattering enhancement factor approaching 4 x 108 with unprecedented reproducibility (RSD of ~10%). This scalable, low-cost concept establishes a practical route toward reproducible wafer-scale nanophotonic platforms for sensing, spectroscopy, and
quantum technologies.
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All authors Minjun Kim, Vasanthan Devaraj, Hyeon-Seok Seo, Seongjae Eom, Jeong-Su Lee, Donghan Lee, Min Yong Jeon, Thomas Zentgraf, Jong-Min Lee
General Relativity and Quantum Cosmology
Solving Hamiltonian Constraint Equation with Physics-Informed Neural Networks
Yu-Chen Zhou, Hao Ma, Zhoujian Cao et al. (+6 more)
Numerical relativity (NR), solving Einstein equation numerically, plays an important role in source modelling for gravitational wave astronomy. Traditional methods for NR including finite difference method, spectral method and finite element method have been well developed. But newly developed neural network methods for partial differential equations (PDE) have not been well studied yet for NR. We present a Physics-Informed Neural Network (PINN) method to solve the
Hamiltonian constraint equation for binary black hole (BBH) initial data in NR. This equation is a highly non-linear
elliptic PDE, posing significant challenges for conventional PINN approaches. To overcome these difficulties, we introduce a set of new techniques. We show that our PINN together with these techniques can successfully solve the
Hamiltonian constraint equation for generic BBH systems. Validation against the traditional results demonstrates the high accuracy and robustness of our method, revealing the immense potential of constructing a PINN-based initial data solution to all BBH systems for NR.
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All authors Yu-Chen Zhou, Hao Ma, Zhoujian Cao, Tailin Wu, Hong-Bo Jin, Xuefeng Feng, Shuanglin Huang, Zhi-Chao Zhao, Yue-Liang Wu
High Energy Physics (Phenomenology)
Separating energy scales in hadron scattering
S.M. Troshin and N.E. Tyurin
We discuss energy scales in soft
hadron scattering and their separation: the one relevant to the region where the total cross–sections increase starts and another one related to the asymptotic region. The latter is most sensitive to the unitarity effects and the former one — to the gross features of absorption of the initial wave due to multyparticle production. Transition from the shadow to reflective scattering sets a relation between the two energy scales.
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General Relativity and Quantum Cosmology · Cross-listed from math.DG
Charged parallel spinors and applications to mass–charge inequalities
Simon Raulot
We investigate the equality case of the
spin positive mass
theorem with charge in the Riemannian setting. This leads naturally to the notion of charged parallel spinor, which plays a central role in the analysis of extremal charged
manifolds. As an application, we characterize the equality case of the mass–charge inequality in terms of the extremal Reissner–Nordström geometry for asymptotically flat
manifolds with connected boundary and for
manifolds with a single asymptotically cylindrical end.
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Solar and Stellar Astrophysics
TESS light curves and surface activity in two low-mass eclipsing binaries: NSVS 01031772 and 2MASS J04100497+2931023
Marek Wolf, Ladislav Šmelcer, Hana Kučáková et al. (+7 more)
The VRIC light curves were regularly measured for two eclipsing binaries, NSVS 01031772 and 2MASS J04100497+2931023 as part of our long-term observational project to study low-mass eclipsing binaries with a short orbital period and surface activity. The solution of the TESS light curves in PHOEBE results in a detached configuration. Absolute parameters of all components were improved: for N103: M1 = 0.5475 +/- 0.0035 M\sun, R1 = 0.5297 +/- 0.0035 R\sun, M2 = 0.5038 +/- 0.0040 M\sun, R2 = 0.5217 +/- 0.0035 R\sun, for 2M0410: M1 = 0.639 +/- 0.045 M\sun, R1 = 0.655 +/- 0.035 R\sun, M2 = 0.609 +/- 0.045 M\sun, R2 = 0.631 +/- 0.035 R\sun, where the temperatures of the primary components were adopted according to previous studies. The spectral type of the primary components was confirmed to be M4 and K5, and the mass ratio was derived as q = 0.920 +/- 0.003 or 0.952 +/- 0.010, respectively. We propose the presence of a third body in these systems: in the case of N103, a companion with a minimal mass of 50 MJup, orbiting the eclipsing pair with a period of about 19 years, and in 2M0410 a third body with a minimal mass of about 0.1 M\sun and a short orbital period of about 2.1 years. For N103, the hierarchical structure (2+1)+1 of a possible quadruple system was tested, but its stability was not proven. The characteristics and statistics of the
flare events and dark regions on the surface of the components were estimated on the basis of the TESS and our own data. For N103, a mean frequency of
flares of one per 40 hours was determined. In the case of 2M0410, practically no
flares were detected.
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All authors Marek Wolf, Ladislav Šmelcer, Hana Kučáková, Alžběta Oplištilová, Petr Zasche, František Bílek, Andrej Mudray, Tomáš Hynek, Miloslav Zejda, Kamil Hornoch
Quantum Physics
QUBO Modeling of Module Learning With Errors: Stability and Scaling in Post-Quantum Cryptography
Ruturaj Khamitkar, Durga Pritam Suggisetti, Soujanya Chatti et al. (+2 more)
Lattice-based post-
quantum cryptography relies on the hardness of the Learning With Errors (LWE) and Module Learning With Errors (MLWE) problems. This work introduces a constructive framework for encoding small MLWE instances as Quadratic Unconstrained Binary Optimization (QUBO) models suitable for
quantum annealing. The formulation jointly represents secret coefficients and explicit error variables within a unified binary optimization structure, enabling their simultaneous recovery from the ground-state solution. Beyond the encoding, we develop a stability analysis of the resulting optimization landscape under additive perturbations. We show that the admissible noise region forms a convex polytope defined by competing candidate secrets, and establish an equivalent characterization in terms of the QUBO energy gap between the optimal and second-best solutions. Numerical experiments on low-dimensional
benchmark instances using exact simulation demonstrate correct recovery of both secret and discretized error vectors, and confirm consistency between
geometric stability regions and energy-gap behavior. We further quantify the scaling of logical variables and
embedding overhead with increasing MLWE dimensions to assess feasibility on
quantum annealing architectures. The results establish a systematic connection between MLWE problems and
quantum optimization while providing a framework for analyzing robustness properties of QUBO formulations. Although current
quantum annealing hardware remains insufficient for cryptographically relevant parameters, the proposed methodology offers a structured basis for studying
lattice-based problems in
quantum optimization settings without implying a practical threat to standardized post-
quantum schemes.
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All authors Ruturaj Khamitkar, Durga Pritam Suggisetti, Soujanya Chatti, Varsha Sambhaje, Durga Dasari
High Energy Astrophysical Phenomena
Two fluid CFL strange quark stars with scalar dark matter: critical mass and mass gap implications
J. Sedaghat, G. H. Bordbar, M. Haghighat et al. (+1 more)
We investigate the structure of strange
quark stars (SQSs) in the color–
flavor–locked (CFL) phase in the presence of scalar bosonic dark matter within a two–fluid formalism employing perturbative QCD. By considering different dark matter masses and varying the pairing gap $\Delta$ and {the central dark matter pressure fraction} $f_r$, we analyze the impact of dark matter on the structural properties of SQSs, including the maximum gravitational mass $M_{\mathrm{TOV}}$, the ratio of dark matter to strange-
quark-matter radii $R_{\mathrm{DM}}/R_{\mathrm{SQM}}$, and the dimensionless
tidal deformability $\Lambda$. We further examine the compatibility of the resulting mass–radius relations with the recent NICER measurements of compact
stars. Within the parameter space considered in this study, we find that $M_{\mathrm{TOV}}$ exhibits a non-monotonic dependence on the dark matter mass, with a critical value beyond which $M_{\mathrm{TOV}}$ decreases. We also show that some pure CFL strange
quark star configurations, particularly those associated with very stiff EOSs and larger maximum masses, may not simultaneously remain compatible with the $\Lambda$ range inferred from GW170817 while occupying the lower mass–gap region. In contrast, the inclusion of dark matter allows two-fluid CFL strange
quark star configurations to reproduce the observed properties of massive compact objects in the lower mass–gap region, such as the secondary component of GW190814, while remaining qualitatively compatible with the $\Lambda$ range inferred from GW170817. We note, however, that the GW170817 constraints were originally inferred within single-fluid compact-
star frameworks and therefore provide only {qualitative guidance} for the present two-fluid
halo configurations. Our results suggest that exotic compact-
star configurations may populate part of the conventionally defined lower mass–gap region.
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All authors J. Sedaghat, G. H. Bordbar, M. Haghighat, S. M. Zebarjad
High Energy Astrophysical Phenomena
Identifying a circum-jet southern ring counterpart to the northern jet of the Crab Nebula
Noam Soker
I analyze images of the Crab Nebula core-collapse
supernova (CCSN) remnant in light of recent three-dimensional hydrodynamical simulations of the jittering-jets explosion mechanism (JJEM) and identify a southern ring opposite to the northern jet, which I attribute to a counterjet. The Crab Nebula is known for its point-symmetric morphology of seven pairs of bays and a pair of two filaments, but no pairs of two jets or their direct outcomes, like ears and rings, have been identified. I identify a ring in visible and infrared images of the Crab Nebula opposite to the prominent northern jet. Recent hydrodynamical simulations of the JJEM show that jets that explode CCSNe can form such circum-jet rings. I, therefore, attribute the shaping of the southern ring to a southern jet, a counter jet to the northern jet, both of which participated in the explosion of the Crab Nebula in the framework of the JJEM.
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Materials Science
High temperature ferromagnetism in epitaxial monolayers of Co-doped Fe5GeTe2
Jules Courtin, Fatima Ibrahim, Davide Benettin et al. (+14 more)
Magnetic van der Waals materials have mainly been investigated in their bulk form or as few-layers flakes. Due to the challenges in producing atomically thin films, only a few have been isolated as monolayers, which typically exhibit long-range
magnetic order below 150 K. In this work, we use molecular beam epitaxy to synthesize Co-doped Fe5GeTe2, achieving precise control over both thickness and composition. We demonstrate ferromagnetism well above room temperature in multilayer samples and present clear evidence of
ferromagnetic ordering in monolayers up to $\sim$200 K. The changes in Curie temperature and
magnetic anisotropy with composition exhibit similar trends in both monolayers and thicker films, indicating that the
magnetic properties are primarily governed by intralayer
magnetic interactions. Through element-specific X-ray
magnetic circular dichroism and density functional theory, we identify the substitution site of Co dopants and reveal the mechanism behind the Curie temperature enhancement induced by Co doping. Our findings suggest that, despite their weak
magnetic moment, Co dopants strengthen the
magnetic moments on neighboring Fe atoms and enhance the intralayer
ferromagnetic exchange interactions.
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All authors Jules Courtin, Fatima Ibrahim, Davide Benettin, Djordje Dosenovic, Roberto Sant, Pâmella Vasconcelos Borges Pinho, Vincent Polewczyk, Alain Marty, Isabelle G de Moraes, Matthieu Jamet, Denis Jalabert, Fadi Choueikani, Philippe Ohresser, N. B. Brookes, Hanako Okuno, Mairbek Chshiev, Frédéric Bonell
Quantum Physics
Universal quantum cloning beyond noncontextual theory
Min Namkung and Hyang-Tag Lim
Quantum theory fundamentally forbids the perfect copying of an arbitrary unknown
quantum state, according to a principle known as the no-cloning
theorem. Nevertheless, it is possible to construct a deterministic
quantum map that produces multiple approximate copies of an unknown
quantum state. This task is referred to as universal
quantum cloning, further facilitating numerous
quantum technologies such as
quantum cryptography and
quantum communication. In this work, we theoretically verify that the universal
quantum cloning cannot be realized within a noncontextual theory, highlighting its intrinsically nonclassical nature. Our verification first {focuses on revealing that} $1\rightarrow2$ cloning scenario {is fully contextual}, and {further covers general examples to observe the contextual behavior of} $N\rightarrow M$ scenario. We believe that our results regarding
quantum cloning serve a key role for understanding both
quantum foundation and application.
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Statistical Mechanics
The Ramsey community number as a renormalization-group crossing
Alexei Vazquez
The Ramsey community number $r_k$ is the smallest size at which a network is better described by communities than by none, under a
Bayesian detection rule. On the diamond hierarchical
lattice we show that $r_k$ is an exact renormalization-group crossing: the block-model sufficient statistics obey a linear map with
eigenvalues $\{bs,b\}$, the degree-corrected evidence density flows to $\ln K$ at a community fixed point, and $r_k$ is the generation at which the running evidence clears the detection threshold. Degree correction advances detection by two generations. We derive $r_k(b,s;q)$ in closed form for the whole family. Finally, placing on the
lattice the Reichardt–Bornholdt community
Hamiltonian – whose ground state is the partition itself – we find an exact community-ordered phase: below the
ferromagnetic critical temperature the two hubs lock into opposite communities for any resolution $\gamma>0$, a staggered order that persists as $n\to\infty$. Allowing each nested sub-community its own label, the optimal partition is a hierarchy of $q_{\rm opt}\sim\sqrt{n}$ communities, so the number of Potts states that best describes the network grows with the network. This hierarchy orders thermally level by level, through a cascade of first-order transitions whose temperatures fall as $1/\ln q$, so every stable level persists as $n\to\infty$: the emergent partition is detectable, optimal, and thermodynamically ordered.
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Disordered Systems and Neural Networks
Electron-Phonon Dephasing in Ultrathin Disordered Films: From Power Laws to Diagnostic Maps
Eugeniy Yu. Beliayev
Electron-
phonon dephasing in ultrathin disordered metallic films is often summarized by a power law, $\tau_{e-ph}^{-1}=AT^p$. However, thin metals,
alloys, and superconducting films exhibit effective exponents close to 2, 3, and 4, as well as intermediate nonuniversal values. We argue that in ultrathin supported films, the exponent should be treated not as a universal material constant, but as a crossover observable. Its interpretation requires several coordinates: the clean-to-dirty parameter $q_T l$,
phonon confinement and film-substrate acoustic coupling, and the microscopic character of disorder. The diagnostic picture is illustrated using Ar-ion-irradiated Au films as a controlled-disorder series. In these films, the fitted electron-
phonon exponent remains near $p\simeq 2$ for low values of the pure-dirty crossover temperature $T_{tr}\simeq \hbar s/(k_B l)$ and increases toward $p\simeq 2.8$ as disorder increases. At the same time, the prefactor trend indicates suppression of electron-
phonon scattering with decreasing mean free path, consistent with dirty-limit weakening rather than static-disorder enhancement. The persistence of $p<4$ points to the role of thin-film or film-substrate
phonon effects. The resulting diagnostic map provides a compact framework for comparing electron-
phonon dephasing data in ultrathin disordered films.
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High Energy Astrophysical Phenomena
Unveiling the Local Environment of FRB 20220912A: Sub-arcsecond $4-26$ GHz Radio Continuum Mapping
Yash Bhusare, Yogesh Maan, Mohit Bhardwaj et al. (+4 more)
The local environments of repeating fast
radio bursts (FRBs) provide critical clues to their progenitors. While some active repeaters (e.g., FRB~20121102A, FRB~20190520B) are embedded in compact persistent
radio sources (PRS), others appear to reside in cleaner environments. We present a high-resolution, multi-frequency (4$-$26 GHz) continuum study of the hyperactive repeater FRB 20220912A using the Karl G. Jansky Very Large Array (VLA). We report the discovery of a previously unknown
radio source distinct from the compact PRSs seen in other FRBs, spatially coincident with the FRB position and offset by $\approx 300$~mas ($\approx 450$~pc) from the host
galaxy's center. The absence of continuum emission in archival milliarcsecond-resolution VLBI observations indicates that the source is resolved out, ruling out a hyper-compact ($< 1$~pc) central-engine-powered origin. We constrain the physical diameter of the emitting region between 75~pc and 190~pc. We further demonstrate that the source is characterized by a steep non-thermal spectral index ($\alpha \approx -0.73$) and a remarkably high
star-formation rate surface density $\Sigma_{\text{SFR}} \gtrsim 13~M_{\odot}~\text{yr}^{-1}~\text{kpc}^{-2}$. We argue that this emission is best explained as a compact
star-forming region within the host
galaxy. This association with a site of ongoing
star formation provides strong observational support for the hypothesis that young magnetars, formed after the deaths of massive
stars, are the progenitors of at least some repeating FRBs.
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All authors Yash Bhusare, Yogesh Maan, Mohit Bhardwaj, Thomas C. Abbott, Yuxin Dong, Danté M. Hewitt, Afrokk Khan
Strongly Correlated Electrons
CE-antiferromagnetic electronic structure in LaSr$_2$Mn$_2$O$_7$ revealed by micro-focused angle-resolved photoemission spectroscopy and tight-binding models
Yasutaka Sawata, Yudai Hirai, Rintaro Miyabayashi et al. (+7 more)
We have investigated the electronic structure of LaSr$_2$Mn$_2$O$_7$ in the CE-type
antiferromagnetic (CE-AFM) state below the Néel temperature using micro-focused angle-resolved photoemission spectroscopy ($\mu$-ARPES) and tight-binding models. In agreement with the tight-binding calculations, we found a dispersive intensity around the X point in the $\mu$-ARPES spectra, where the A-type
antiferromagnetic (A-AFM) phase has no bands experimentally and theoretically, demonstrating that we have successfully captured the signatures of the CE-AFM band structure for the first time. Many observed features can be explained by the CE-AFM tight-binding bands, although some of them and the overall near-
Fermi level intensity mapping can be explained by the A-AFM band structure. This indicates that the CE-AFM domain size would be no larger than the beam footprint size of a $\sim\!20$~{\textmu}m scale.
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All authors Yasutaka Sawata, Yudai Hirai, Rintaro Miyabayashi, Goro Shibata, Hideki Kuwahara, Miho Kitamura, Koji Horiba, Kenichi Ozawa, Noriaki Hamada, Tomohiko Saitoh
Materials Science
Modelling the mean inner potential of alloyed and strained materials
Marco Schowalter, Peer Kruse and Andreas Rosenauer
In this publication, we study the influence of strain and alloying on the mean inner potential (MIP) using density functional theory (DFT) within an augmented plane waves plus local orbitals basis set. Two major effects have been identified allowing to model the influence of strain and alloying on the mean inner potential with a reasonable accuracy. First, alloying for constant volume results in a linear relationship between the MIP and the concentration. Second, the MIP scales with changes in volume as we already pointed out in an earlier publication (M. Schowalter, D. Lamoen, A. Rosenauer, P. Kruse, and D. Gerthsen, Appl. Phys. Lett. 85, 4938-4940 (2004)). Specifically, a linear relationship between MIP and concentration x was found for AlGaAs (nearly no change in
lattice parameter), whereas InGaP and GeSi (volume changes with concentration x) exhibits a clear bowing. The bowing can be modeled by taking the rescaling of the MIP with the varying volume additionally into account. The rescaling could be also used to model the dependence of the MIP on strained binary
cells and the density dependence of e.g. amorphous materials.
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Materials Science
Orientation-resolved ultrafast spin reorientation dynamics in ferrimagnetic DyCo$_5$
Johanna Richter, Martin Hennecke, Martin Schmidbauer et al. (+3 more)
Under quasi-static conditions, ferrimagnetic DyCo$_5$ thin films exhibit a thermally induced
spin-reorientation transition, in which the
equilibrium magnetization changes from an out-of-plane to an in-plane orientation, mostly as a result of the competing
magnetic anisotropy contributions of the Dy $4f$ rare-earth and Co $3d$ transition-metal sublattices. While this
equilibrium transition has been studied, it remains an open question whether such a reorientation can be triggered on ultrafast timescales using femtosecond
laser excitation. In this work, we investigate the ultrafast
spin-reorientation dynamics in DyCo$_5$. The time-dependent orientation of the magnetization vector following femtosecond
laser excitation is quantified by combining polar with transverse magneto-optical Kerr effect (MOKE) measurements in the extreme ultraviolet spectral range, which are sensitive to the out-of-plane and in-plane magnetization component, respectively. Both techniques are implemented at the Co M$_{3,2}$ resonance and are complemented by visible-light MOKE measurements. This combined approach allows us to resolve the canting of the magnetization from an out-of-plane toward an in-plane orientation and to determine the characteristic timescales of the transient
spin-reorientation process.
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All authors Johanna Richter, Martin Hennecke, Martin Schmidbauer, Ilie Radu, Clemens von Korff Schmising, Stefan Eisebitt
Optics
Exact flat bands in a 3D photonic crystal
Kin Hung Fung, Yan-Long Chen, C. T. Chan et al. (+1 more)
Photonic flat bands are hard to engineer because Maxwell's equations are vectorial: transversality obstructs the localized scalar-like bases that generate destructive-interference flat bands in tight-binding models. We show that a three-dimensional metallic network of dipolar cavities joined by waveguide channels–a fully vectorial photonic
crystal belonging to space group No. 224–hosts an exact scalar sector, carrying exact flat bands. The twelve-band vector problem contains one self-adaptive radial dipole axis per site whose projection is exactly the scalar four-band
Hamiltonian of the same network. A microwave-scale coupled-dipole calculation confirms this scalar-vectorial duality. The result is a
symmetry-based design rule for scalar-like flat bands in reciprocal vector media.
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All authors Kin Hung Fung, Yan-Long Chen, C. T. Chan, Qinghua Guo
Quantum Physics
High-Precision Method for Characterizing Degree of Collimation and Beam Quality for Application in Cold Atom Gravimeter System
Nawaz Sarif Mallick, Anju and Aishik Acharya
Highly collimated
laser beam with excellent spatial quality is essential for
quantum sensing experiments, where even small residual beam divergence can accumulate over distance and introduce significant systematic errors. In this article, we present the design and detailed characterization of a high precision
laser beam collimator developed for a cold-atom Gravimeter system, capable of producing an expanded
laser beam with a diameter of 16 mm while achieving microradian level collimation accuracy through a five-degree-of-freedom (5-DOF) adjustment mechanism. The beam quality is evaluated using an ISO11146 compliant beam propagation measurement combined with Gaussian beam analysis to extract key parameters, including the beam waist, divergence angle, Rayleigh length, and beam quality factor $M^{2}$. The measured divergence angles of 0.006{\deg} (105 micro-radian) along the $x$ axis and 0.007{\deg} (122 micro-radian) along the $y$ axis confirm stable and well controlled collimation over long propagation distances. The demonstrated collimation architecture and characterization methodology provide a robust and scalable solution for cold-atom Gravimetry and other precision optical applications that require stable, high quality
laser beams maintained over extended distances.
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Chemical Physics
Direct Analytical Evaluation of Electron-Impact Excitation Cross Sections via Multiconfigurational Binary Encounter Approach: Applications to Benzene and Naphthalene
Kaoru Yamazaki
We present a multiconfigurational binary-encounter (MC-BE) framework for direct analytical evaluation of electron-impact electronic-excitation cross sections for dipole-allowed transitions from ab initio excited-state data. The method combines the threshold-modified Mott-Massey (TMMM) approximation with binary-encounter (BE/BE$f$) scaling. The effective binding energy in the BE/BE$f$ prefactor is obtained from amplitude-weighted occupied-orbital contributions computed by linear-response time-dependent density functional theory (LR-TDDFT), without system-specific fitting parameters. For benzene, MC-BE/TMMM cross sections for the dominant $1{}^{1}\!E_{\mathrm{1u}}$ ($\pi\!\to\!\pi^{\ast}$) band agree well with experiment at incident energies $T=10$-$20$ eV and improve on the Schwinger multichannel/truncated configuration-interaction singles results of Falkowski et al. [J. Chem. Phys. 159, 194301 (2023)] for this band and energy range. For naphthalene, the calculated total excitation cross section reproduces the onset and principal maximum of the gas-phase apparent fluorescence cross section, used as an emission-based proxy under dipole-dominated conditions, without empirical energy shifts or intensity scaling. Analytic peak-position and peak-height expressions, parameterized by $r=\langle B\rangle/\Delta E$, show that typical valence excitations peak at incident energies $T\simeq 1.5$-$1.6\Delta E$ with substantial BE attenuation, providing a diagnostic for relating measured cross-section profiles to excitation energies. Although demonstrated with LR-TDDFT, the framework is transferable to other excited-state theories that provide compatible amplitudes and well-defined orbital energies. These results support MC-BE/TMMM as a practical, inexpensive route for modeling electron-impact excitation of polyatomic molecules with finite oscillator strength.
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Optics
Refractive-index tomography of opaque tissue from its own backscattered light
Tran Dinh Hoang, Jaecheol Cho, Thi Van Anh Nguyen et al. (+9 more)
The refractive index (RI) is an intrinsic, label-free marker of a living
cell's dry mass and subcellular morphology, and hence of its physiological state. Its three-dimensional (3D) reconstruction has become a powerful way to study
cells and tissues in their native state, spanning
cell growth, drug response and disease diagnosis. Yet this capability rests on a fundamental constraint: the RI can be recovered only from light transmitted through the specimen, which demands optical access to both sides. The
cells that matter most – those within thick tissues, intact organs and living animals – are therefore out of reach. A tissue, however, can illuminate its own
cells from behind: light backscattered by intrinsic tissue structures beneath a
cell carries the same transmission information a microscope would collect from the far side. Here we develop a divide-and-conquer inverse-scattering framework that recovers this transmission from the backscattering and reconstructs a
cell's 3D RI. We demonstrate label-free, quantitative imaging of
cells within an engineered tissue, and a living mouse through its intact skull, where we further quantify the dry mass of individual osteocytes in vivo. By removing the need for two-sided access, this reflection-only approach extends RI
tomography into living tissue, enabling non-destructive, longitudinal imaging of
cells in their native environment.
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All authors Tran Dinh Hoang, Jaecheol Cho, Thi Van Anh Nguyen, Eunyoung Seong, Joowon Lim, Jin Hee Hong, Yongwoo Kwon, Jun Wan Kim, Juhee Yang, Seokchan Yoon, Sungsam Kang, Wonshik Choi
Mathematical Physics · Cross-listed from math.AG
Shifted Poisson unfoldings and quantum anomalies
Mauricio Corrêa and Simone Noja
Families of classical field theories often depend on
geometric parameters. A basic question is whether the corresponding classical observables can be compared by flat parallel transport, and whether this comparison survives quantization. We study this problem for families of shifted Poisson structures. To such a family we attach a Poisson transverse controller $\mathbb U_\pi$, a homotopy stabilizer encoding transverse
symmetries which preserve the Poisson Maurer–Cartan element up to coherent homotopy. Its flat splittings are precisely transversal shifted Poisson unfoldings, and they act on vertical
symmetries, Poisson
cohomology and local deformation theory. We then formulate the $\hslash$-adic lifting problem for quantized objects; its degree-two obstruction classes are the transport anomalies. The construction is realized for
star-products, BV observables, factorization
algebras and AKSZ theories. For the Poisson sigma model, anomaly-free quantization of the flat transport makes the Cattaneo–Felder/Kontsevich boundary product horizontal over the parameter space.
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Atomic Physics
Constraints on Yukawa-type New Forces from the Lamb Shift in Muonic Hydrogen and Deuterium
Chung-Chien Huang and Li-Bang Wang
We develop an analytical framework to constrain Yukawa-type fifth-force interactions using the Lamb shift in hydrogen and deuterium. The sixfold coordinate-space integral for the energy shift is transformed into a one-dimensional momentum-space convolution of the atomic form factor and the Yukawa potential, eliminating the need for approximations. This formulation directly incorporates empirical
nuclear charge distributions through their form factors, making the implementation of experimental results straightforward. Applying this method to the latest hydrogen and deuterium spectroscopy data, we derive constraints on the coupling constant $\alpha$ in the interaction range $\lambda \in [10^{-4}, 10^{6}]$~fm. A resonance-like cancellation between the $2s$ and $2p$ orbital shifts is identified at a critical range $\lambda \sim 10^{5}$~fm, where the energy shift vanishes and the constraint on $\alpha$ diverges, marking a transition between attractive and repulsive regimes. The constraints are shown to be independent of the
nuclear charge distribution model. Our results indicate that the transition frequency shifts induced by such new forces lie well below current spectroscopic resolution, establishing spectroscopic precision as the primary bottleneck for probing these interactions.
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Mesoscale and Nanoscale Physics
Interfacial Noncollinear Filtering of Spin Hall Currents
Dan-Yang Han, Zi-An Wang, Hong-Liang Chen et al. (+6 more)
Spin Hall currents generated in nonmagnetic materials are conventionally regarded as bulk responses whose polarization is fixed by
crystal symmetry. This view has motivated the search for intrinsically low-
symmetry spin sources when unconventional
spin polarizations are required. Here we point out that, in realistic
heterostructures, the device-relevant quantity is not the fully
symmetry-averaged bulk
spin Hall current, but the emitted
spin current transmitted across the interface. We therefore establish emitted
spin currents as bulk-interface hybrid responses and propose interfacial noncollinear filtering as a mechanism to bypass the bulk-
symmetry constraint. A low-
symmetry interfacial
spin-orbit field, generally noncollinear with the momentum-resolved
spin polarization of the incident
spin Hall current, imposes
spin-dependent transmission and converts hidden momentum-resolved
spin-polarization components into an observable unconventional emitted
spin current. Using both a rotationally symmetric minimal model and a realistic high-
symmetry Dirac-semimetal model, we show that conventional
spin Hall sources can emit sizable out-of-plane
spin currents when their hidden bulk
spin Hall textures are selectively transmitted by the interfacial
spin-orbit field. Our results reveal that
spin-current polarization emerges from the cooperative action of bulk and interfacial responses, providing a strategy for reprogramming
spin-current polarization in high-efficiency, CMOS-compatible
spin Hall materials without relying on intrinsically low-
symmetry bulk
crystals or external
symmetry-breaking schemes.
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All authors Dan-Yang Han, Zi-An Wang, Hong-Liang Chen, Bo Li, Wen-Jian Lu, Yu-Ping Sun, Liang Liu, Shu-Hui Zhang, Ding-Fu Shao