Medical Physics
Slice-Profile-Enabled Phase Distribution Graphs for MRI Simulation
Snawar Hussain, Daniel C. Hoinkiss, Jörn Huber et al. (+2 more)
MRI simulation often separates two descriptions that are both essential for realistic sequence analysis: Bloch dynamics for waveform-resolved radiofrequency (RF) excitation, and phase-graph methods for coherence-pathway
evolution. Extended Phase Graph (EPG) models provide pathway tracking, and Phase–Distribution Graphs (PDG) extend this idea to spatially resolved $k$-space simulation, but existing PDG formulations rely on hard-pulse RF mixing that is order-local: the RF pulse mixes $F_n^+$, $F_n^-$, and $Z_n$ at a fixed coherence order $n$, without coupling different $k_z$ orders. This work introduces a unified Bloch-resolved PDG framework for slice-profile-aware MRI simulation. A scanner-rasterized sequence is partitioned into RF-sensitive Bloch spans and non-RF phase-graph spans. For each unique RF span, Bloch dynamics are solved on a slice grid to obtain a spatially varying propagator $R(z)$. Its
Fourier coefficients $\mathcal{R}_{\Delta}$, indexed by slice-order offset $\Delta$, are compiled into the PDG state graph as sparse cross-order coupling in $k_z$. Graph growth is controlled by retaining the dominant
Fourier coefficients and
pruning low-contribution PDG states. This retains PDG pathway history and voxel-wise image formation while incorporating shaped slice-selective and off-resonant RF behavior. Experiments show close agreement with direct one-dimensional Bloch slice-profile
evolution through repeated excitations, while retaining only a few hundred active PDG states. Image simulations further illustrate slice-position dependence, fat-suppression behavior, measured three-dimensional $B_0$ field maps, and comparison with scanner data. The proposed framework enables sequence-consistent simulation and signal formation understanding in regimes where RF physics, spatial encoding, object heterogeneity, and echo-pathway formation interact.
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All authors Snawar Hussain, Daniel C. Hoinkiss, Jörn Huber, Vincent Kuhlen, Matthias Günther
Mesoscale and Nanoscale Physics
Strain-Induced Tuning of Third-Harmonic Generation in Monolayer Black Phosphorene
Yan Meng, Kainan Chang, Wei Song et al. (+3 more)
Based on the tight-binding model and the
semiconductor Bloch equations, this work systematically reveals the microscopic mechanism of strain engineering in turning of third-harmonic generation (THG) in monolayer black phosphorene (BP). % The results show that under strain-free conditions, monolayer BP exhibits significant in-plane anisotropy, and its dominant susceptibility component reaches a maximum of $\chi^{(3);xxxx} = 1.8 \times 10^{-17} \, \text{m}^2/\text{V}^2$, agreeing well with the experimental results. % By applying uniaxial and biaxial strains along the armchair ($x$), zigzag ($y$), and out-of-plane ($z$) directions, we find that the THG response presents strong direction dependence and unique spectral shifting behaviors: in-plane compressive strain and out-of-plane tensile strain both significantly enhance the THG conductivity and induce a
redshift, whereas in-plane tensile strain and out-of-plane compression lead to suppression and a blueshift, with the tuning efficiency following the order of $z > y > x$. The microscopic origin of these phenomena is identified as the synergistic modulation of the bandgap and Berry connection by strain. % Furthermore, the synergistic or competitive effects of biaxial strain further enrich the manipulation of THG signals. % Strain engineering can serve as an effective strategy for dynamically controlling nonlinear optical processes in two-dimensional materials, and it also lays a theoretical foundation for the development of high-performance reconfigurable infrared photonic devices.
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All authors Yan Meng, Kainan Chang, Wei Song, Yuwei Shan, Jin Luo Cheng, Luxia Wang
High Energy Astrophysical Phenomena
GRB 250706B/C: Insight-HXMT Discovery of a High-Luminosity Burst as a Candidate for Fallback-Regulated Accretion in the Prompt Emission
Chen-Wei Wang, R. Moradi, Shao-Lin Xiong et al. (+15 more)
Fallback
accretion in collapsar models is often associated with underluminous gamma-ray bursts (GRBs), leading to the widespread view that fallback-fed engines may be intrinsically inefficient at producing high-luminosity events. In this Letter, we present GRB 250706B/C, a luminous long GRB observed by Insight-HXMT that exhibits an unusual combination of extreme short-timescale variability and coherent large-scale temporal
evolution. The
prompt emission contains at least 79 resolved pulses and a minimum variability timescale of $\sim11$ ms. The pulse widths are nearly independent of
photon energy and span a broad distribution with a median FWHM of $\sim0.30$ s, while the waiting times between adjacent pulses have a median of $\sim0.38$ s. The
prompt-emission envelope exhibits a prolonged rise described by $F(t)\propto (t-t_0)^{0.47\pm0.01}$ followed by a rapid decline. Despite substantial pulse-to-pulse fluctuations, neither the pulse widths nor the waiting times show significant secular
evolution during the main emission episode. These features indicate the coexistence of two distinct temporal components, including a slow evolving rising luminosity envelope and rapid
stochastic variability. Such behavior is consistent with scenarios in which a time-dependent engine-feeding history regulates the large-scale emission while internal dissipation within the relativistic
outflow produces the pulse structure. Within this context, GRB~250706B/C may represent a fallback-fed collapsar operating on a high-luminosity branch, suggesting that fallback itself does not necessarily limit the luminosity scale of GRBs.
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All authors Chen-Wei Wang, R. Moradi, Shao-Lin Xiong, Shuang-Nan Zhang, Zheng-Hang Yu, Wen-Jun Tan, Hao-Xuan Guo, Xiao-Bo Li, Cheng-Kui Li, Jia-Cong Liu, Xing-Hao Luo, Yang-Zhao Ren, Yue Wang, Sheng-Lun Xie, Wang-Chen Xue, Yuan-Zao Xue, Peng Zhang, Chao Zheng
Solar and Stellar Astrophysics
Predictability of a solar flare in May 2024 using observational data-driven MHD simulations
Takafumi Kaneko
We examined the applicability of observational data-driven magnetohydrodynamic (MHD) simulations to
flare prediction. The target event was the X1.6
flare that occurred in NOAA AR 13663 at 02:22 UT on 3 May 2024. We employed a velocity-driven model, in which the photospheric velocity field was derived from the time-series magnetograms to use as the boundary input. The simulation showed a rapid increase in both thermal and kinetic energy density around the actual onset time and location of the X1.6
flare. We revealed that the
flare was triggered by two-step reconnection, in which the initial tether-cutting reconnection facilitated the subsequent breakout reconnection. We further examined whether the
flare could be reproduced when the boundary input was stopped prior to the actual
flare onset time, assuming the situation in which the
flare must be predicted using the data before it actually occurs. When the photospheric
magnetic field was fixed more than 1 hour before the actual
flare onset time, the
flare was not reproduced in the simulations. In contrast, when the photospheric velocity field at the final observation time was incorporated to infer the subsequent
magnetic evolution, the prediction lead time could be extended beyond 1 hour. On the other hand, quantitative prediction of the magnitude of
flares remains a subject for future study.
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Optics
Absolute Length Sensing in a Long-Baseline, High-Finesse Optical Cavity
Todd Kozlowski, Henry Frädrich and Aaron D. Spector
The relative phase between two
lasers in transmission of an optical cavity can be used to continuously measure its absolute length with sub-micron precision. The first
laser is kept on resonance with the cavity, while a second
laser is phase-locked to the first with a frequency separation equal to an integer multiple of the cavity's initial free spectral range. As the free spectral range frequency changes due to cavity length changes, the second
laser detunes slightly from resonance and gains an additional phase offset in transmission of the cavity. The cavity length changes can be calibrated in terms of this phase offset. This technique is applied to a high-finesse optical cavity with a length of 123 meters, transforming it into a strainmeter with nanostrain sensitivity to long-term and transient seismic events. We report absolute length changes associated with anthropogenic noise, a distant earthquake, and the diurnal and semidiurnal earth tides.
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Instrumentation and Methods for Astrophysics · Cross-listed from cs.CV
Semi-supervised Source Detection in Astronomical Images: New Benchmark and Strong Baseline
Longhan Feng, Zihuang Cao, Ali Luo et al. (+5 more)
Source detection in modern observational astronomy is a cornerstone for localizing and identifying
stellar sources accurately. It is crucial for studies such as
stellar population synthesis and cosmological parameter estimation. However, the characteristics of astronomical images, including high density, the effect of point spread functions and low signal-to-noise ratios, significantly challenge the latest advanced object detectors. Besides, fully-supervised detection methods are hardly practical, due to the significant difficulty in annotating dense, small, and faint sources in astronomical images. To tackle the scarcity of astronomical
datasets, we introduce a new comprehensive
benchmark (LAMOST-DET), comprising 18,400 astronomical images and 728,898 source instances. Upon the
dataset, we further devise a novel semi-supervised learning framework coined Nova Teacher, capable of detecting dense sources effectively given sparse annotations. It integrates source light enhancement module, confidence-guided pseudo-supervision, and cross-view complementary mining in a dual-teacher paradigm. Extensive experiments on LAMOST-DET show that, Nova Teacher consistently improves previous competitors by 4.04% and 5.22% mAP under two semi-supervised settings. Additionally, our method competes against other detectors on a natural image
dataset, validating its generalization ability to various scenarios. The source code is available at https://github.com/AcWiz/NovaTeacher.
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All authors Longhan Feng, Zihuang Cao, Ali Luo, Yuanhao Guo, Shuilian Yao, Yixin Guo, Qi Jia, Yu Liu
Quantum Physics
Satellite-Based Quantum Communication: Performance Evaluation of Discrete-Variable Quantum Key Distribution Protocols
Muskan
Quantum Key Distribution (QKD) has emerged as a fundamentally secure approach to communication in the era of
quantum computing, offering protection against threats posed to classical cryptographic schemes such as RSA and Diffie-Hellman. This thesis presents a comprehensive performance analysis of satellite-based QKD protocols, focusing on both prepare-and-measure and
entanglement-based schemes under realistic atmospheric and operational conditions. The study begins by introducing the theoretical foundations of
quantum communication, including
qubits,
entanglement, and
quantum entropy, and motivates the need for satellite-based QKD to overcome the distance limitations of fiber-based systems. Subsequently, the thesis evaluates four prominent QKD protocols-BB84, B92, BBM92, and E91-using a circular beam propagation model that incorporates atmospheric effects such as diffraction,
turbulence, attenuation, and pointing errors, along with environmental noise contributions for uplink and downlink. Comparative numerical simulations reveal that protocol performance is strongly influenced by channel asymmetries, beam propagation characteristics, and noise, providing guidance on optimal protocol selection for low Earth orbit (LEO) satellite links. The research further investigates high-dimensional (HD) QKD protocols, specifically HD-BB84 and HD-Extended B92, using the
elliptic-beam approximation to account for
turbulence-induced distortions for both uplink and downlink. Simulations under vary ing system dimensions, weather conditions, and zenith angles demonstrate that HD-BB84 achieves higher key rates, superior noise tolerance, and more favorable probability distributions of the key rate compared to HD-Extended B92, highlighting the advantages of high-dimensional encoding for robust satellite-based QKD.
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Instrumentation and Detectors
An investigation of fast simulation techniques for pion showers using kernel density estimators with the CALICE AHCAL Technological Prototype
CALICE Collaboration: A. Wilhahn, J. Utehs, Z. Ghafoor et al. (+28 more)
In this article, the development and investigation of fast
hadron shower simulation methods is presented. A test beam
dataset has been recorded in 2018 at CERN with the AHCAL Technological Prototype of the CALICE Collaboration, where the calorimeter prototype was exposed to electron,
muon, and negatively charged pion beams of various initial energies. The pion shower
dataset, covering energies between 10 GeV and 200 GeV, has been used to develop a data-driven fast simulation
algorithm of the AHCAL response to pion showers. The resulting shower model demonstrates excellent agreement with measured shower observables. In addition, a method for simulating pion showers at arbitrary energies is introduced, based upon interpolation between simulated showers at neighbouring beam energies.
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All authors CALICE Collaboration: A. Wilhahn, J. Utehs, Z. Ghafoor, G. Eigen, S. Lai, O. Bach, E. Brianne, K. Gadow, D. Heuchel, K. Krüger, J. Kvasnicka, A. Laudrain, O. Pinto, M. Reinecke, F. Sefkow, M. De Silva, E. Garutti, G. Kasieczka, S. Martens, J. Rolph, F. Hummer, F. Simon, A. Brogna, V. Büscher, L. Masetti, A. Rosmanitz, C. Schmitt, Q. Weitzel, W. Ootani, T. Suehara, A. Irles
Soft Condensed Matter
Evaluation of nonlinear optical coefficients in uniformly aligned dioxane-based ferroelectric nematic liquid crystals using second harmonic generation
Hirokazu Kamifuji, Jigen Furukawa, Kazuma Nakajima et al. (+3 more)
Ferroelectric nematic
liquid crystals (FNLCs) are promising soft platforms for nonlinear optics, but quantitative determination of their second-order nonlinear optical coefficients has been hindered by limited
alignment control. Here, polarization-resolved second-harmonic generation (SHG) measurements on a uniformly aligned dioxane-based FNLC, combined with Jones-
matrix simulations, enable determination of all principal tensor components. The resulting tensor is consistent with the expected $C_{\infty v}$ and Kleinman
symmetries, while the measured coefficients cannot be explained by a simple sum of molecular first hyperpolarizabilities. These results provide a quantitative basis for understanding nonlinear optical responses and guiding the design of FNLC-based nonlinear optical materials and devices.
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All authors Hirokazu Kamifuji, Jigen Furukawa, Kazuma Nakajima, Hirotsugu Kikuchi, Kenjiro Fukuda, Masanori Ozaki
Cosmology and Nongalactic Astrophysics
Optimising ultra-light dark matter searches with ground-based interferometers
Paola C. M. Delgado, Ornella J. Piccinni and Federico R. Urban
Ultra-light dark matter fields induce nearly monochromatic signals in gravitational-wave detectors through their coupling to the Standard Model. Their spectral morphology exhibits features caused by sidereal modulation that, for frequencies below $\sim 30~$Hz, enable discrimination between
spin-1 and
spin-2 ultra-light dark matter signals, provided sufficient signal-to-noise ratio. In the context of LIGO–Virgo–KAGRA search techniques, we show that incorporating these spectral features can improve current excess-power constraints at low frequencies by up to $\sim36\%$. Additionally, we propose an optimised implementation of the cross-correlation statistics within the Band-Sampled-Data framework, enhancing the sensitivity of cross-correlation searches across nearly the entire frequency range, reaching up to $\sim42\%$ at low frequencies and $\sim35\%$ at high frequencies.
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Mathematical Physics · Cross-listed from math.DS
Many coexisting attractors, a case study of the almost-conservative Hénon map
Corrado Falcolini, Laura Tedeschini-Lalli and James A. Yorke
For dynamical systems in the plane, there can be many periodic attractors coexisting in a bounded region. They become easier to find in systems with small dissipation, which we call “almost-conservative”. We ask what happens when there are many periodic attractors. That is the vague question we start with. For a test study, we chose the Hénon map with a tiny dissipation. We tuned the other parameter to yield a case with 50 attracting periodic orbits. They have a total of 4259 periodic points. We describe how these orbits can be organized into families. In addition to two low-period orbits, the remaining 48 orbits can be classified into three families, which we describe in detail.
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Fluid Dynamics
On the spatial statistics of free-surface turbulence and the complementarity of 'dimples' and 'scars'
Daniel R. Kjellevold, Jørgen R. Aarnes, Omer M. Babiker et al. (+2 more)
The air–water interface governs the exchange of heat and gas between natural water bodies and their surrounding environment.
Turbulence beneath the free surface imprints characteristic features: near-circular depressions (`dimples') and elongated indentations (`scars'). Recent studies have shown that these are linked to sub-surface flow features in a temporal sense. For instance, rapid increases in mean-square surface divergence due to upwelling events, precede dimple count surges. Yet the spatial structure of these connections remains unquantified. We employ spatial statistics to consider the spatial and temporal correlations between dimples and scars and two key velocity-derived fields, surface divergence $\beta=\partial_x u+\partial_y v$ and vertical vorticity $\omega=\partial_x v-\partial_y u$. The dimples and scars are modelled as inhomogeneous Poisson point-processes, with intensity fields driven by the local variance of $\beta$ and $\omega$. Parameters, including spatial support radius $r$ and time lag $\tau$, are estimated by maximum likelihood against six DNS
datasets, quantifying the spatial and temporal connection between dimples, scars, surface divergence and vorticity. Our results demonstrate a clear complementarity: Dimples show strong local connection to the vertical vorticity field but has weak spatial connection with surface divergence and a spatially “global” model is required for dimples to work as
estimators of surface divergence; scars, in a similar but opposite manner, couple locally to surface divergence but globally to the vertical vorticity. The complementarity sheds new light on the way dimples and scars may be used to infer fluxes across the surface, e.g., in remote sensing contexts.
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All authors Daniel R. Kjellevold, Jørgen R. Aarnes, Omer M. Babiker, Simen Å. Ellingsen, Ingelin Steinsland
High Energy Physics (Phenomenology)
Five-flavor $udsc\bar{b}$ molecular pentaquarks from heavy-quark and local hidden gauge symmetries
Ratirat Suntharawirat, Nongnaphat Ponkhuha and Daris Samart
We study a family of genuinely exotic five-
flavor molecular pentaquark states containing the five
quark flavors $u,d,s,c,b$ that form experimentally accessible
hadrons. We construct the
meson-
baryon interaction from the local hidden gauge
symmetry combined with heavy-
quark spin symmetry, following the
chiral unitary description that reproduces the LHCb hidden-charm strange pentaquarks. Heavy-
quark flavor symmetry allows us to obtain the $udsc\bar{b}$ sector by replacing the anti-charm
quark in the
meson with an anti-bottom
quark while keeping the charm
quark in the
baryon. As a result, we obtain ten threshold-associated isoscalar poles with $J^P=1/2^-,3/2^-,5/2^-$ in the range $7.72$ to $7.96$ GeV. They are narrow and organized into heavy-
quark spin multiplets with predicted near-degeneracies. There are four states that overlap with the earlier two-sector study in the literature to about $2$ MeV, which shows that the separate-sector treatment is recovered as a limit of this work. Moreover, we also identify two additional, more deeply bound $B_s\Lambda_c$ and $B_s^{*}\Lambda_c$ poles generated by strong inter-channel coupling because these poles are farther from their dominated thresholds. This is an interesting signal that can be searched for at LHCb in the $B_c\Lambda$ and $B_s^{*}\Lambda_c$ invariant mass spectra.
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Strongly Correlated Electrons
Order parameters and ground-state phase diagram of the interacting topological Su-Schrieffer-Heeger model with extended-range hoppings
Tsz Hin Hui, Pedro D. Sacramento and Wing Chi Yu
Topological
insulators have attracted numerous attentions recent years, where the Su-Schrieffer-Heeger (SSH) model is one of the most studied models. While the interacting version of it has been explored recently, the interplay between interactions and long-range hoppings merit further investigations. In this work, we uncover a rich phase diagram of the interacting SSH model with extended-range hoppings, in which it consists of several topological phases, two novel superconducting-like (SC-like) phases and five distinct charge-density-wave (CDW) phases. We substantiate that the SC-like and two CDW phases are direct consequences of imbalanced interactions and extended-range hoppings. We derive the order parameters (OPs) for each of the phases and verify them in large-system simulations, finding consistency with the
entanglement entropy and the fidelity in capturing the phase transitions. In contrast to the non-interacting case where the favored hoppings are unidirectional in the topological phases, the derived OPs suggest non-unidirectional hoppings are possible under the influence of interactions.
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Optics
Compact Optical-Resolution Photoacoustic Microscopy System with Reflective Objective-Based Transducer Integration
Albano Tabacchi, Bhanu Pratap Singh, Michael Jaeger et al. (+5 more)
We present an optical-resolution photoacoustic microscopy (OR-PAM) system designed to overcome key limitations in conventional transducer integration within a compact microscopy configuration, while preserving high optical performance and improving acoustic detection efficiency. The system uses a reflective objective that reduces spatial constraints within the optical pathway, enabling the integration of a large-area PVDF transducer within the optical obscuration zone. The system performance was characterized through spatial resolution analysis,
laser pulse energy measurement at the sample plane, and evaluation of photoacoustic signal dependence on
laser pulse energy. For biological validation, OR-PAM imaging of sections from B16F10 tumors implanted in mice was performed and compared with optical microscopy and H&E stained histological sections. The results demonstrate strong spatial correlation between photoacoustic signal intensity and melanin rich regions, confirming label-free sensitivity to endogenous optical absorbers at 532 nm. This work establishes a compact OR-PAM imaging setup with improved optical-acoustic integration for high resolution biomedical imaging applications, with potential for future extension to multi-wavelength
laser excitation.
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All authors Albano Tabacchi, Bhanu Pratap Singh, Michael Jaeger, Damien Guignet, Mirjam Schenk, Pavel Subochev, Martin Frenz, Andre Stefanov
Materials Science
Metal Halide Perovskite/Chalcohalide Heterojunctions for the Photoinduced Oxidative Coupling of p-substituted Thiophenols
Anna Cabona, Stefano Toso, Alejandro Cortés-Villena et al. (+7 more)
The introduction of a
semiconductor-
semiconductor junction is an effective strategy to enhance the photocatalytic performance of perovskite nanocrystal-based systems. Herein, we optimized the synthesis of CsPbX3/Pb4S3X2 (X= Cl, Br, I) perovskites-chalcohalides
heterostructures, whose band
alignment can be tuned by halide composition. As a proof-of-concept, we evaluated the photooxidative coupling of p-substituted thiophenols at room temperature, under visible-light, air, and without sacrificial electron donor. Notably, CsPbBr3/Pb4S3Br2 achieved up to 94 % selectivity toward disulfide (p-OCH3 thiophenol with a turnover number of 14300) highlighting the crucial role of the type-II heterojunction to promote charge separation and efficient electron delocalization across the junction.
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All authors Anna Cabona, Stefano Toso, Alejandro Cortés-Villena, Ignacio Rosa-Pardo, Mirko Prato, Michele Ferri, Julia Perez-Prieto, Ilka Kriegel, Liberato Manna, Raquel E. Galian
Soft Condensed Matter
Quantitative measurement of fluid inertial effects in confined Brownian motion
Quentin Ferreira, Pablo Palacios-Alonso, Harshit Joshi et al. (+3 more)
The hydrodynamic response of Brownian particles in
liquids is fundamentally altered by inertial forces arising from unsteady momentum transport in the surrounding fluid. These forces are of two distinct types: the added mass and the history effect. While both are well understood in bulk and weakly-confined geometries, under deterministic driving, their respective behaviours under strong confinement and thermal fluctuations remain scarcely addressed, unclear and often entangled together. The goal of the present study is thus to fill this fundamental gap. The confinement-induced variations of the two distinct inertial contributions are separately investigated in the vicinity of a flat, rigid wall, using a combination of broadrange thermal colloidal-probe atomic-force-microscopy experiments, advanced numerical simulations and theoretical arguments. Specifically, the separation of the added-mass and history-force contributions is achieved through their different frequency-scaling signatures within the assumed form of the generalized dissipation coefficient. Our results pave the way towards a complete picture of Brownian motion at interfaces, in the lubrication regime, with direct relevance to nanofluidics and interfacial biophysics.
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All authors Quentin Ferreira, Pablo Palacios-Alonso, Harshit Joshi, Rafael Delgado-Buscalioni, Yacine Amarouchene, Thomas Salez
Materials Science
BSE+ calculations for 2D materials: a unified description of excitons and plasmons
Amalie H. Svaneborg and and Kristian S. Thygesen
The Bethe-Salpeter equation (BSE) accurately describes low-energy optical spectra in materials with strong excitonic effects, but its high computational cost limits the number of electron-hole transitions that can be included. Neglecting high-energy transitions leads to an underestimation of the real part of the dielectric function, often producing a spurious plasmon peak in the BSE electron energy loss spectrum (EELS). The recently introduced BSE+ method addresses this by combining a four-point BSE-like equation for the irreducible polarisability with a two-point Dyson equation that includes the high-energy transitions at the Random Phase Approximation (RPA) level. Here, we present a detailed account of the method, extend it to two-dimensional materials, and apply it to a set of transition metal dichalcogenide monolayers. BSE+ preserves the excitonic features of the BSE at low energies while reproducing the plasmonic structure of the RPA at higher energies, yielding good agreement with experimental EELS data across the full energy range and strongly suppressing the spurious plasmon. BSE+ converges much faster than BSE with respect to the electron-hole basis size, at a comparable computational cost, and is implemented in the GPAW code.
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Strongly Correlated Electrons
Designing electronic magnetoelectric matter with organic quantum spin trimers
Yuko Hosokoshi, Christopher P. Aoyama, Zhuowei Zhang et al. (+17 more)
Magnetoelectric (ME) phenomena are commonly driven by
spin-
lattice coupling. Here we demonstrate a different route based on frustrated
quantum spin trimers that intrinsically intertwine
magnetic moments and electric dipoles. Using molecular design principles, we realize a weakly coupled
lattice of equilateral $S=1/2$
spin trimers in the organic radical
crystal TNN$\cdot$CH$_3$CN. In this material, correlated electronic fluctuations within each trimer generate electric dipoles, while geometrically frustrated intertrimer interactions organize them into collective ME states. Magnetization, thermodynamic, and dielectric measurements reveal multiple
magnetic-field-induced phases, including the $1/3$-magnetization plateau marked by pronounced dielectric anomalies. Effective low-energy theories and numerical simulations show that these phenomena are driven by electronically generated trimer dipoles whose collective order is stabilized by frustration relief of the intertrimer interactions, establishing a direct connection between
geometric frustration and emergent magnetoelectricity. Our results identify
quantum spin trimers as multifunctional building blocks, providing a bottom-up route for designing correlated ME materials from electronically active
quantum spin clusters.
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All authors Yuko Hosokoshi, Christopher P. Aoyama, Zhuowei Zhang, Toshio Ono, Kosuke Takada, Ayaka Higashiguchi, Seitaro Iisaka, Koudai Yamasaki, Hironori Yamaguchi, Shengzhi Zhang, Mohammad Irfan, Minseong Lee, Eun Sang Choi, Yasuyuki Shimura, Toshiro Sakakibara, Zhiyuan Xie, Hiroki Nakano, Yasu Takano, Cristian D. Batista, Yoshitomo Kamiya
General Relativity and Quantum Cosmology
Static axisymmetric Einstein spaces with a cosmological constant and the limitation of canonical Weyl coordinates
Sheref Nasereldin
The canonical Weyl form for four-dimensional static axisymmetric
vacuum metrics is obtained by identifying the area function of the two Killing orbits with a harmonic coordinate on the twodimensional orbit space. This construction is valid in
Ricci-flat
vacuum, but it is no longer available in Einstein spaces with nonzero cosmological constant. In this paper, we consider the generalized orthogonally transitive static axisymmetric line element and derive the reduced Einstein- $\Lambda$ field equations. We show that the canonical Weyl choice $W=\rho$ is locally admissible if and only if $\Lambda=0$. The Kottler metric gives the simplest explicit example of the resulting equation for the area function. Thus, the statement that "Weyl metrics do not allow $\Lambda \neq 0$ " is precise only when the metric is assumed to be in canonical Weyl coordinates. The issue is not staticity or axisymmetry, but rather the fact that the area function is no longer harmonic.
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Solar and Stellar Astrophysics
Ages and ZAMS spin distribution of stars in detached eclipsing binaries
T. Merle, W. Van Rensbergen, L. Siess et al. (+4 more)
Benchmarking fundamental
stellar properties is essential for calibrating evolutionary models and establishing empirical relationships between mass, radius, luminosity and related
stellar properties. We determine the current ages and initial equatorial velocities at the Zero-Age Main Sequence (ZAMS) for a well-characterized sample of 108 detached main-sequence eclipsing binaries. Evolutionary tracks from the ZAMS to the present are calculated by accounting for
tidal interactions, including meridional circulation, and angular momentum loss via
stellar winds, under the assumption of circular orbits. System ages are derived by identifying the evolutionary stage at which the calculated radii of both
stellar components best match the observed values. While initial velocities for currently synchronized systems cannot be uniquely constrained, as a wide range of initial states naturally converges to synchronisation over time, we are able to determine unique solutions for ZAMS
spin velocities in systems that remain asynchronous today. Our models successfully reproduce observed present-day equatorial velocities with a precision of 1%. Two systems, HD~71636 and V396~Cas, were found to have primaries with initially retrograde
spin at ZAMS. We also find an increasing dispersion of
spin velocities with age. Our results demonstrate that
tidal and evolutionary effects in binary systems actively counteract rotational deceleration from
stellar winds, effectively preventing the substantial
spin-down that typically characterizes the
evolution of isolated single
stars.
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All authors T. Merle, W. Van Rensbergen, L. Siess, J.P. De Greve, K. Jansen, S. Van Eck, G. Van de Steene
High Energy Physics (Theory)
Stress Tensor Deformations in dS/CFT: Mixed Boundary Conditions, Spectrum Flow and Pseudo Entropy
Feng Hao, Hao Ouyang and Xi-Yang Ran
We formulate a semiclassical stress tensor deformation dictionary in the context of the dS/CFT correspondence. Using the metric-flow formulation, we propose that stress tensor deformations of the putative boundary theory are encoded holographically as mixed boundary conditions for the bulk metric at future infinity. The coupled flow equations determine the deformed boundary metric and stress tensor, thereby specifying the source–response relation of the deformed boundary theory. We test the proposal in Kerr-dS$_3$/CFT$_2$, where the conserved charges constructed from the
holographic boundary stress tensor agree exactly with the boundary spectrum obtained from the field-theoretic flow equation, providing a nontrivial consistency check of the dictionary. As an application, we compute the
holographic pseudo
entropy of boundary intervals from complexified geodesic saddles in the deformed Kerr-dS$_3$ geometry, and present explicit results for the $T\bar{T}$ and root-$T\bar{T}$ deformations.
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Plasma Physics
Conservative Charge and Current Deposition on Nonuniform 3D Cylindrical PIC Meshes with Residual Self-Field Diagnostics
Zhe Liu, Zhijun Zhou and Yinjian Zhao
Particle-in-
cell simulations on nonuniform cylindrical meshes require deposition schemes that respect cylindrical metrics while controlling numerical self-fields. This work develops cylindrical-volume-weighted charge and current deposition using nodal control volumes and swept-volume factors on logically structured stretched grids. Uniform-density and controlled-transport tests demonstrate accurate charge recovery, well-controlled current-density errors, and continuity residuals substantially lower than the corresponding current-density errors. Single-particle diagnostics show that charge-transport consistency alone does not ensure self-field cancellation; face-centered electric fields give the smallest residual, whereas
cell-centered and shifted
cell-centered layouts produce larger residuals.
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High Energy Physics (Phenomenology)
The Muon and Tau Electric Dipole Moments in the B-L Supersymmetric Standard Model
Wen-Hui Zhang, Jin-Lei Yang, Zhao-Feng Ge et al. (+2 more)
Recently proposed experiments are expected to significantly improve the measurement sensitivities of the electric dipole moments (EDMs) of
muon ($d_\mu$) and tau ($d_\tau$). Given that theoretical predictions for $d_\mu$ and $d_\tau$ typically surpass those for the electron EDM, this work focuses on studying the contributions from the CP-violating (CPV) effects in the B-L supersymmetric (SUSY) standard model (B-LSSM) to $d_\mu$ and $d_\tau$. After considering the corrections from some two-loop diagrams, the contributions in the B-LSSM to the EDMs of charged
leptons are presented analytically in general forms. The numerical results show that the traditional $\mu$-term in most SUSY models makes dominant contributions to $d_\mu$ and $d_\tau$, while the B-LSSM specific CPV parameters also induce significant effects. It is found that across a substantial region of the B-LSSM parameter space, $d_\mu$ falls well within the projected sensitivity at Phase II of the proposed experiment, and $|d_\tau|$ can reach about $10^{-21}e\cdot\text{cm}$.
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All authors Wen-Hui Zhang, Jin-Lei Yang, Zhao-Feng Ge, Yu-Li Yan, Yin-Jie Zhang
High Energy Physics (Phenomenology)
Constraining DVCS Compton Form Factors Using Lattice QCD informed Neural Network
Yuan-Yuan Huang and Xu Cao
The
lattice QCD calculation of generalized form factors are exploited to determine the subtraction constants through all order dispersion relations of Deeply Virtual Compton Scattering (DVCS). The leading order relation is found to constrain significantly the real part of the Compton Form Factors (CFFs), and the higher order one reduces considerably both the real and imaginary part of CFFs in a global analysis of
proton data. This is realized by a synthesis of the DVCS data and LQCD calculations within a neural network framework, whose architecture is specifically designed for a reliable extrapolation to unmeasured kinematic regime. By leveraging dispersion relations beyond leading order, our framework allows for adding higher moments of generalized parton distributions (GPDs) from LQCD into the extraction of CFFs from DVCS data.
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Materials Science
Artificial Intelligence for Instability in Inorganic Perovskites: From Mechanism Discovery to Engineering Strategies
Xue Zhao, Chuan-Xin Cui, Zi-Hao Xu et al. (+3 more)
Three-dimensional all-inorganic halide perovskites, represented by CsPbX$_3$ (X = Cl, Br, I), have attracted broad interest in photovoltaics, photodetectors, and light-emitting devices because of their outstanding optoelectronic properties. Their practical deployment, however, remains limited by instability under thermal, chemical, optical, and electrical stress. Conventional studies have established important experimental and theoretical foundations, but they still struggle with
multimodal data, coupled degradation pathways, protocol dependence, sparse statistics, and uncertainty quantification. Artificial intelligence (AI) offers a practical route to address these limitations. This review summarizes recent progress in AI-assisted studies of instability in 3D CsPbX$_3$ and organizes the discussion around four linked tasks, including stability discrimination and diagnosis, microscopic mechanism analysis, consequence and reliability modeling, and engineering stability enhancement. We further discuss the main limitations of current methods, especially in data quality, protocol consistency,
benchmark design, interpretability, and transferability across domains. Finally, we outline future directions for the field, including standardized data infrastructures, interpretable cross-scale models, and tighter integration of AI with automated experiments and physics-based modeling. The aim of this review is to provide a coherent and practically useful framework for researchers seeking to use AI to understand, predict, and mitigate instability in inorganic perovskites.
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All authors Xue Zhao, Chuan-Xin Cui, Zi-Hao Xu, Yuan-Long Pang, Jun-Jie Li, Jin-Wu Jiang
Materials Science
Molecular dynamic simulation of multicomponent CoCrFeNiMn high-entropy alloy thin film deposition
Oleksandr I. Kushnerov, Sergey I. Ryabtsev and Valerij F. Bashev
The deposition and growth of a thin CoCrFeMnNi high-
entropy alloy film on an Al(100) substrate were investigated by molecular dynamics simulation. Interatomic interactions were described using a calibrated set of Morse potentials combined with mixing rules for regular solutions. During a 100 ns simulation, 50,000 atoms with an incident energy of 10 eV were deposited, producing a film of about 6.1 nm thickness. The resulting film contains face-centred cubic (FCC), body-centred cubic (BCC), hexagonal close-packed (HCP), and amorphous regions. Analysis of the radial distribution function (RDF) was used to determine nearest-neighbour distances and estimate
lattice parameters for the crystalline phases. The simulated phase composition and structural parameters are in good agreement with available experimental data.
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Chemical Physics
Persistent singlet electronic character in the multiexcitonic triplet-pair state of strongly coupled pentacene singlet fission dimers
Atandrita Bhattacharyya, Namana Venkatareddy, Sanjoy Patra et al. (+5 more)
Singlet fission converts an optically excited singlet state into a
spin-entangled triplet pair state (TT$_1$)$^1$ that can, in principle, yield two free triplets for photovoltaics and/or a polarized high
spin state for
quantum technologies. Synthetically tunable templates suggest that the above photophysics is governed by a subtle but poorly understood interplay of molecular motifs, geometry and structural fluctuations. Here, we investigate the (TT$_1$)$^1$ state in a library of conformationally flexible pentacenic dimers, where a (TT$_1$)$^1$-specific near-IR spectral feature is readily available. Using a suite of polarization-controlled impulsive optical spectroscopies, we find that (TT$_1$)$^1$ formation is specific to planar conformations and is accompanied by large
nuclear reorganization in the (TT$_1$)$^1$ photoproduct. Introducing polarization anisotropy to track the electronic character of the (TT$_1$)$^1$ species, supported by screened configuration interaction based electronic structure theory, we find that significant singlet-triplet electronic mixing is persistent throughout its
evolution. This behavior is universal across diverse bridging motifs and indicates that, once the triplet pair is strongly bound, neither substantial
nuclear reorganization nor structural fluctuations on longer timescales are sufficient to suppress persistent singlet-triplet electronic mixing, such that triplet-pair decorrelation is outcompeted by its decay. Our observations establish polarization-selective pump-probe and anisotropy as a direct optical probe of triplet pair decorrelation, complementary to
spin-selective measurements at longer timescales.
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All authors Atandrita Bhattacharyya, Namana Venkatareddy, Sanjoy Patra, Kanad Majumder, Vithoba Hugar, Satish Patil, Manish Jain, Vivek Tiwari
Applied Physics
Hyperbolic dynamic friction models for viscoelastic sliding and rolling contact
Luigi Romano
This paper considers the sliding and rolling contact between viscoelastic bodies. Combining linear viscoelastic rheologies for bristle-like elements with nonlinear dynamic friction models, and under the assumption of small deformations and displacement gradients, it derives a class of viscoelasto-kinematic equations, formulated as a system of semilinear partial differential equations (PDEs) governing the
evolution of the frictional force, bristle deformations, and internal state variables at the interface between the contacting bodies. The resulting system is analysed mathematically, demonstrating that linear viscoelasticity preserves the
hyperbolic character of the PDE systems typically encountered in rolling contact. The proposed theory is illustrated through representative examples of both sliding and rolling contact, highlighting that these two processes, whilst often treated as distinct, may in fact exhibit closely related underlying dynamics. Overall, the framework provides a general theoretical setting applicable to a broad class of viscoelastic frictional systems.
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Materials Science
Symmetry-Breaking Induced Spin Transport and Magneto-Optical Regulation in 2D Altermagnet Ru2MoSe4
Wenpeng Wang, Hang Shi, Yuping Tian et al. (+2 more)
Two-dimensional (2D) altermagnets (AMs) offer a compelling paradigm for advanced spintronics, yet their fully compensated macroscopic
spin currents inherently limit practical device integration. In this work, using first-principles calculations and theoretical analysis, we demonstrate that the 2D material Ru2MoSe4 hosts AM ground state protected by S4zT
symmetry. Using uniaxial strain modulation and stacking configuration, we show that the monolayer and the AC-stacking
bilayer Ru2MoSe4 host fully
spin-polarized currents, piezomagnetically induced net magnetization, and the magneto-optical Kerr effect. Our findings establish Ru2MoSe4 as a tunable platform, offering a feasible mechanism to simultaneously trigger electrical
spin transport signals and amplify optical readout signatures for next-generation spintronics and valleytronics.
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All authors Wenpeng Wang, Hang Shi, Yuping Tian, Wei-Jiang Gong, Xiangru Kong