Atomic Physics · Cross-listed from cond-mat.quant-gas
Second excited state of ${}^4\mathrm{He}$ tetramer
A. Deltuva
The four-
boson universality suggests the existence of the second excited tetramer state in a system of cold ${}^4\mathrm{He}$ atoms. It is not bound but could be seen as a resonance in the atom-trimer scattering. This process is rigorously calculated using the momentum-space transition operator framework with two realistic interatomic potentials. The $S$-wave phase shift and cross section show a resonant behavior below the excited trimer threshold, but there are sizable nonresonant contributions from $P$ and $D$ waves as well. The position and width of the resonant state is determined, and for the latter significant finite-range effects are found.
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Optics
Theoretical description of interface states in a tetragonal lattice of bianisotropic resonators
Alina D. Rozenblit and Nikita A. Olekhno
In the present paper, we construct a theoretical description of a three-dimensional photonic structure in the form of a tetragonal
lattice of bianisotropic resonators applying a dyadic Green's function approach. By representing the resonators as point electric and
magnetic dipoles, we obtain the Bloch
Hamiltonians for the approximations considering the interactions between the nearest, next-nearest, and next-to-next-nearest resonators, and construct the corresponding real-space tight-binding models. We analyze the band diagrams, spatial structure of the eigenmodes, and their localization, revealing quadratic degeneracies in the vicinity of high-
symmetry points in the absence of bianisotropy and the emergence of in-gap states localized at a domain wall upon the introduction of bianisotropy. Finally, we compare the theoretical results with full-wave numerical simulations for an array of bianisotropic resonators.
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Optics
Coherent Perfect Tunneling at Exceptional Points via Directional Degeneracy
Huayang Cai and Bishuang Chen
Coherent perfect tunneling in the presence of loss and asymmetry remains a fundamental challenge in wave transport, a universal problem across optics, acoustics, and
quantum mechanics. Here we demonstrate coherent perfect tunneling at an exceptional point in a passive one-dimensional waveguide cascade with three coupled interfaces. Using a waveguide-invariant scattering framework, we show that the suppression of a selected output channel originates from a directional scattering degeneracy rather than from resonance or absorption collapse. This exceptional-point condition emerges when interference between boundary-induced feedback loops promotes a simple zero of the scattering response to a second-order degeneracy. As a direct consequence, fixed coherent excitation produces a robust quartic leakage law within a transparency-dominated tunneling window. These results establish directional degeneracy as a general mechanism for loss-tolerant tunneling enabled by exceptional points across a broad class of wave systems.
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Atomic Physics · Cross-listed from quant-ph
Realization of a cavity-coupled Rydberg array
Jacopo De Santis, Balázs Dura-Kovács, Mehmet Öncü et al. (+3 more)
Scalable
quantum computers and
quantum networks require the combination of
quantum processing nodes with efficient light-matter interfaces to distribute
quantum information in local or long-distance
quantum networks. Neutral-atom arrays have both been coupled to Rydberg states to enable high-fidelity
quantum gates in universal processing architectures, and to optical cavities to realize interfaces to
photons. However, combining these two capabilities and coupling atom arrays to highly excited Rydberg states in the mode of an optical cavity has been an outstanding challenge. Here we present a novel cavity-coupled Rydberg array that achieves this long-standing goal. We prepare, detect, and control individual atoms in a scalable optical tweezer array, couple them strongly to the optical mode of a high-finesse optical cavity and excite them in a controlled way to Rydberg states. We show that high-cooperativity coupling to an optical cavity – demonstrated via the dispersive shift of the resonance of the cavity in presence of the atoms – and strong Rydberg interactions – demonstrated via the collective enhancement of Rydberg coupling in the atomic array – can be achieved in our setup at the same spatial location. Our presented experimental platform opens the path to several new directions, including the realization of
quantum network nodes,
quantum simulation of long-range interacting, open
quantum systems and photonic-state engineering leveraging high-fidelity Rydberg control.
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All authors Jacopo De Santis, Balázs Dura-Kovács, Mehmet Öncü, Adrien Bouscal, Dimitrios Vasileiadis, Johannes Zeiher
Atomic Physics · Cross-listed from cond-mat.quant-gas
Protocols for a many-body phase microscope: From coherences and d-wave superconductivity to Green's functions
Christof Weitenberg, Luca Asteria, Ola Carlsson et al. (+2 more)
Quantum gas microscopes probe
quantum many-body
lattice states via projective measurements in the occupation basis, enabling access to various density and
spin correlations. Phase information, however, cannot be directly obtained in these setups. Recent experiments went beyond this by measuring local current operators and local phase fluctuations. Here we propose how
Fourier-space manipulation in a matter-wave microscope allows access to various long-range off-diagonal correlators in experimentally realistic settings, realizing a many-body phase microscope. We demonstrate in particular how the fermionic d-wave superconducting order parameter in arbitrary Hubbard-type models, the non-equal time Green's function yielding the spectral function, or the hidden order of composite
bosons in a fractional Chern
insulator can be directly measured. Our results show the great potential of matter-wave microscopy for accessing exotic correlators including phases and coherences and characterizing intriguing
quantum many-body states.
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All authors Christof Weitenberg, Luca Asteria, Ola Carlsson, Annabelle Bohrdt, Fabian Grusdt
Physics Education
Spreading viscous fluids on a horizontal surface: project-based learning in fluid mechanics
R. Bolaños-Jimenez and P. L. Luque-Escamilla
The spreading of a thin viscous fluid film on a horizontal surface is an interesting problem in fluid mechanics with many practical applications ranging from coating processes to biological systems and environmental flows. It can even be observed in everyday situations, such as syrup spreading on a pancake. We present a project-based learning approach to this problem, in which engineering or physics undergraduates apply classroom knowledge to understand and solve it, using dimensional analysis, experiments, and theoretical modeling. First, a dimensional analysis is conducted to guide the design of the experiment suitable for an undergraduate laboratory or even at home. The problem is then simplified to obtain a mathematical model that accounts for the experimental results. Through this process, students are able to obtain a solution compatible with those published in fluid mechanics journals with minimal supervision from the instructor. This project not only develops important skills but also motivates students by showing that they have the ability to solve complex problems.
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Optics
Variable dose slicer for refractive index engineering in two-photon polymerization
Michal Ziemczonok and Koen Vanmol
In two-
photon polymerization (TPP), the degree of conversion (DC) of the resin has an effect on a broad range of material properties like refractive index (RI) or stiffness. Heterogeneous DC can substitute material doping and multimaterial structures, and outright enable structure designs not possible otherwise. However, obtaining variable DC in the
polymer, typically achieved by implementing a variable exposure dose, is held back due to the lack of software support for fabrication and measurement techniques for validation, adding up to a high barrier of entry. This work presents two major breakthroughs in (3+1)D TPP: design freedom and variable-DC fabrication, that are provided by an open-source slicer, as well as calibration methodology for determination of the RI for any DC. Application examples include grayscale lithography, control over writing direction and trajectories, as well as bio-mimicking microphantoms with carefully engineered 3D RI. Results of the RI calibration demonstrate excellent repeatability, accuracy and stability of variable-DC structures. Supported by in-depth metrological analysis, the goal is to popularize variable DC printing within TPP community and to get more out of the existing TPP systems and workflows. In summary, this work provides a complete toolbox for 3D RI engineering and sets the stage for new inventions enabled by point-wise dose control.
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Chemical Physics · Cross-listed from cond-mat.mtrl-sci
A critical assessment of bonding descriptors for predicting materials properties
Aakash Ashok Naik, Nidal Dhamrait, Katharina Ueltzen et al. (+4 more)
Most machine learning models for materials science rely on descriptors based on materials compositions and structures, even though the chemical bond has been proven to be a valuable concept for predicting materials properties. Over the years, various theoretical frameworks have been developed to characterize bonding in solid-state materials. However, integrating bonding information from these frameworks into machine learning pipelines at scale has been limited by the lack of a systematically generated and validated database. Recent advances in high-throughput bonding analysis workflows have addressed this issue, and our previously computed
Quantum-Chemical Bonding Database for Solid-State Materials was extended to include approximately 13,000 materials. This database is then used to derive a new set of
quantum-chemical bonding descriptors. A systematic assessment is performed using statistical significance tests to evaluate how the inclusion of these descriptors influences the performance of machine-learning models that otherwise rely solely on structure- and composition-derived features. Models are built to predict elastic, vibrational, and thermodynamic properties typically associated with chemical bonding in materials. The results demonstrate that incorporating
quantum-chemical bonding descriptors not only improves predictive performance but also helps identify intuitive expressions for properties such as the projected force constant and
lattice thermal conductivity via symbolic regression.
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All authors Aakash Ashok Naik, Nidal Dhamrait, Katharina Ueltzen, Christina Ertural, Philipp Benner, Gian-Marco Rignanese, Janine George
Fluid Dynamics
Covariant Chu-Kovasznay Decomposition: Resolving Thermodynamic Ambiguity in Compressible Flows
Chanho Park, Gyeongho Gong, Yeachan Kwak et al. (+1 more)
We establish the Covariant Chu–Kovasznay Decomposition (CCKD), a
geometric framework that resolves thermodynamic ambiguity in compressible mode content by formulating the decomposition on the effective acoustic spacetime. Enforcing orthogonality in the covariant Chu energy norm, we show that shock–
turbulence interaction, often treated as a scattering source, is, in the idealized linear, inviscid setting, a near-
unitary (Chu-isometric) scattering map constrained by conservation of covariant Chu-energy flux. In the canonical Shu-Osher problem, CCKD characterizes the shock as a thermo-acoustic lens, mathematically demonstrating that the transfer of
entropy fluctuations into sound follows a
geometric blue-shift ($k_{\mathrm{out}}=\Lambda k_{\mathrm{in}}$) analogous to gravitational blue-shift. Thus, while the mean flow produces
entropy across the shock, the fluctuation mapping is information-preserving on the retained subspace; practical information loss arises from noise, truncation, and model mismatch, not shock physics.
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All authors Chanho Park, Gyeongho Gong, Yeachan Kwak, Seongim Choi
Applied Physics · Cross-listed from quant-ph
Unconditional full vector magnetometry using spin selectivity in Nitrogen Vacancy centers in diamond
Asier Mongelos-Martinez, Jason Tarunesh Francis, Julia Bertero-DiTella et al. (+3 more)
Quantum sensors based on nitrogen vacancy (NV) centers in diamond have been a central topic in the sensing community for more than a decade. The extraordinary properties at room temperature of the
spin system in diamond have made it one of the most prominent
quantum platforms for the development of commercial
quantum sensors. In particular, the sensitivity of the electronic
spin in NV centers has made diamond-based
magnetic sensors of special interest for their potential application in medical, industrial or
navigation solutions. However, the use of these sensors for universal vector magnetometry was constrained by the need for previous knowledge on the field being measured to fully exploit their benefits. In this work, we show a method to perform unconditional vector magnetometry without the need of external information on the
magnetic field, based only on the spatial arrangement of the diamond and the microwave
antenna combination. While previous NV-based vector magnetometry methods require partial knowledge of the
magnetic field (e.g. a calibrated bias field), we exploit the possibilities of selecting particular directions of the
spins in the diamond with elliptically polarized microwave fields. We prove that our method allows to estimate both magnitude and direction of external
magnetic fields without further assumptions or constraints.
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All authors Asier Mongelos-Martinez, Jason Tarunesh Francis, Julia Bertero-DiTella, Geza Giedke, Gabriel Molina-Terriza, Ruben Pellicer-Guridi
Instrumentation and Detectors · Cross-listed from cond-mat.soft
Solvothermal vapor annealing and environmental control setup with adjustable magnetic field module for GISAXS studies
Christian Kjeldbjerg, Bo Jakobsen, Miriam Varón et al. (+3 more)
A compact, modular environmental control and solvothermal vapor annealing chamber designed for maintaining a controlled atmosphere with regard to solvent humidity and temperature is presented. The setup allows ex situ and in situ grazing incidence small-angle X-ray scattering (GISAXS) investigations of thin film self-assembly and reorganization. Its modular slotting system enables stable reconfiguration, including the integration of an adjustable
magnetic field module. The temperature is maintained via a water-based heating and cooling loop supplemented by resistive elements, and the solvent vapor environment is regulated using a commercial controlled mixing and evaporation unit. The performance of the setup is validated through measurements of fill and quench times together with
magnetic field mapping with Gauss meter measurements and finite element simulations. Further, the versatility of the setup is demonstrated with four research examples using the chamber for solvothermal vapor annealing of block copolymer thin films together with lab-based ex situ and in situ GISAXS measurements. The portable new design offers robust environmental control and flexibility for advanced thin film investigations both in the lab and at large scale facilities. The design can be adapted for grazing incidence small-angle
neutron scattering, GISANS.
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All authors Christian Kjeldbjerg, Bo Jakobsen, Miriam Varón, Kim Lefmann, Cathrine Frandsen, Dorthe Posselt
Geophysics · Cross-listed from astro-ph.EP
Efficient parallel finite-element methods for planetary gravitation: DtN and multipole expansions
Ziheng Yu, Alex D.C. Myhill and David Al-Attar
The Poisson equation governing a
planet's gravitational field is posed on the unbounded domain, $\mathbb{R}^3$, whereas finite-element computations require bounded meshes. We implement and compare three strategies for handling the infinite exterior in the finite-element method: (i) naive domain truncation; (ii) Dirichlet-to-Neumann (DtN) map on a truncated boundary; (iii) multipole expansion on a truncated boundary. While all these methods are known within the geophysical literature, we discuss their parallel implementations within modern open-source finite-element codes, focusing specifically on the widely-used MFEM package. We consider both calculating the gravitational potential for a static density structure and computing the linearised perturbation to the potential caused by a displacement field - a necessary step for coupling self-gravitation into planetary dynamics. In contrast to some earlier studies, we find that the domain truncation method can provide accurate solutions at an acceptable cost, with suitable coarsening of the mesh within the exterior domain. Nevertheless, the DtN and multipole methods provide superior accuracy at a lower cost within large-scale parallel geophysical simulations despite their need for non-local communication associated with spherical harmonic expansions. The DtN method, in particular, admits an efficient parallel implementation based on an MPI-communicator limited to processors that contain part of the mesh's outer boundary. A series of further illustrative calculations are provided to show the potential of the DtN and multipole methods within realistic geophysical modelling.
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Instrumentation and Detectors
GPU-Accelerated Analytic Simulation of Sparse Ionization Signals in Pixelated Time Projection Detector
Yousen Zhang, Brett Viren, Mary Bishai et al. (+4 more)
This paper presents a GPU-accelerated simulation package, TRED, for next-generation
neutrino detectors with pixelated charge readout, leveraging community-driven software ecosystems to ensure adaptability and extensibility. We introduce two generic contributions: (i) an effective-charge representation based on Gaussian quadrature rules, in which the linear-interpolation factors for the field response inside each voxel are absorbed into the effective charge, and (ii) a sparse, block-binned tensor representation that enables efficient FFT-based computation of induced signals on readout electrodes for sparsely activated detector volumes. The former captures structure inside a voxel without dense sampling, while the latter achieves low
memory usage and scalable runtime, as demonstrated in
benchmark studies. The underlying data representation is applicable to large-scale detectors and to other computational problems involving sparse activity.
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All authors Yousen Zhang, Brett Viren, Mary Bishai, Sergey Martynenko, Xin Qian, Rado Razakamiandra, Brooke Russell
Biological Physics
A Frequency-Optimized Optogenetic Study of Network-Level Potentiation in Cortical Cultures on Microelectrode Arrays
Matteo Dominici, Ilya Auslender, Clara Zaccaria et al. (+2 more)
Objective. Long-term potentiation (LTP) is a fundamental mechanism underlying learning and
memory, yet its investigation at the network level in vitro remains challenging, particularly when optogenetic stimulation is used. The objective of this work is to develop a robust experimental and analytical framework for inducing and quantifying optogenetically driven LTP in neuronal cultures recorded with microelectrode arrays (MEAs). Approach. We first systematically investigate the effect of widefield optogenetic stimulation frequency on evoked neuronal activity, to identify a test-stimulus that reliably probes network responses without inducing activity modulation. By analyzing spike-rate dynamics during repeated stimulation, we characterize frequency-dependent response adaptation consistent with Channelrhodopsin-2 photocycle kinetics. Based on these results, an optimized low-frequency test-stimulus is selected and combined with a spatially confined tetanic optogenetic stimulation to induce LTP. Network responses are quantified using post-stimulus time histograms and a normalized efficacy metric, enabling electrode-wise and network-level analysis of plasticity. Main results. Low-frequency optical stimulation (<= 0.2 Hz) preserves stable evoked responses, whereas higher frequencies induce a pronounced sigmoid-like decay in firing rate. Following tetanic stimulation, a subset of electrodes exhibits robust and long-lasting potentiation, persisting for several hours. Significance. This work provides a systematic methodology for studying activity-dependent plasticity in optogenetically driven neuronal networks.
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All authors Matteo Dominici, Ilya Auslender, Clara Zaccaria, Yasaman Heydari, Lorenzo Pavesi
Chemical Physics · Cross-listed from cond-mat.stat-mech
Markov State Models for Tracking Reaction Dynamics on Catalytic Nanoparticles
Caitlin A. McCandler, Chatipat Lorpaiboon, Timothy C. Berkelbach et al. (+1 more)
Markov state models (MSMs) are a powerful tool to analyze and coarse-grain complex dynamical data into interpretable kinetic processes. This capability is particularly important in heterogeneous catalysis, where a medley of reactants and intermediates interact on surfaces that might simultaneously experience structural fluctuations. For these very complex systems, standard transition state theory (TST) approaches are no longer appropriate, motivating alternative approaches that can retain dynamical complexity while providing physical insight. With machine learned interatomic potentials being more and more ubiquitous, directly simulating complex catalytic systems with molecular dynamics (MD) is becoming increasingly feasible. Extending MSMs to dynamically coarse grain MD simulation data of catalytic processes, we analyze hydrogen dynamics on rhodium catalysts with slab and nanoparticle geometries over a range of hydrogen surface concentrations. Somewhat counterintuitively, nanoparticle features, such as corners and edges, effectively slow down the association/dissociation process, and the cooperative behavior of hydrogen-hydrogen interactions leads to a non-monotonic concentration dependence of the rates, which would not be predicted with standard TST.
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All authors Caitlin A. McCandler, Chatipat Lorpaiboon, Timothy C. Berkelbach, Jutta Rogal
Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Thermodynamic Stability and Hydrogen Bonds in Mixed Halide Perovskites
Liz Camayo-Gutierrez, Javiera Ubeda, Ana L. Montero-Alejo et al. (+2 more)
The stability of mixed halide perovskites against phase separation is crucial for their optoelectronic applications, yet difficult to rationalize due to the interplay of enthalpic, configurational, and dynamical effects. Here we present a simple thermodynamic framework for multicomponent halide perovskites of composition FA$_{1-x}$MA$_{x-y}$Cs$_y$Pb(I$_{1-z}$Br$_z$)$_3$, based on ab initio molecular dynamics. By decomposing the free energy of mixing into enthalpic, configurational, and rotational entropic contributions, we show that although the enthalpy of mixing is generally positive, the solid solutions are thermodynamically stable against phase separation due to the large configurational
entropy associated with random substitution on cation and halide sublattices. Mixing reduces the rotational
entropy of the organic cations, partially offsetting the configurational stabilization. However, within our model, this rotational penalty is not sufficient to overcome the configurational driving force, and a
curvature analysis within a regular-solution model does not predict a miscibility gap for any of the mixing channels considered. Analysis of hydrogen-bond dynamics shows that MA–Y (Y = I, Br) interactions are more persistent than FA–Y interactions, while the dominant FA-donated N$-$H$\cdots$I hydrogen bonds remain nearly composition-invariant. Cs-containing mixtures, in which Cs$^{+}$ forms no hydrogen bonds, can nevertheless be thermodynamically stable. These results demonstrate that hydrogen bonding does not control thermodynamic stability in mixed halide perovskites. Instead, phase stability is governed by the balance between strong configurational
entropy and a smaller, systematically destabilizing rotational-
entropy correction.
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All authors Liz Camayo-Gutierrez, Javiera Ubeda, Ana L. Montero-Alejo, Ricardo Grau-Crespo, Eduardo Menéndez-Proupin
Plasma Physics
Tuning Optical Properties of FTO via Carbonaceous Al2O3 Microdot Deposition by DC plasma sputtering
Sarah Salah, Ahmed Atlam, Nagat Elkahwagy et al. (+2 more)
Fluorine-doped tin
oxide (FTO) is a key transparent conductive
oxide for photovoltaic and optoelectronic devices, yet its high reflectance limits light-trapping efficiency. This work demonstrates a simple DC
plasma sputtering approach to deposit carbonaceous Al2O3 microdots on FTO under controlled Ar, O2, and Ar-O2 atmospheres. For
plasma discharge in the normal mode, with
plasma density 10^9 cm^-3 and temperature of 2 eV, Volmer-Weber growth produced discrete microdots whose size and distribution were tuned by gas composition: dense, uniform dots in Ar (approximately 0.89 um radius), agglomerated structures in O2, and intermediate morphologies in mixed atmospheres. Structural analysis confirmed Al2O3 formation with carbon incorporation, while SEM revealed morphology-driven optical behavior. UV-Vis measurements showed that Ar-O2 coatings achieved the lowest reflectance across the visible range, outperforming bare FTO and other conditions. These findings establish a clear link between sputtering parameters, surface morphology, and optical performance, offering a scalable route to anti-reflective, light-trapping coatings for next-generation
solar cells and optoelectronic devices.
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All authors Sarah Salah, Ahmed Atlam, Nagat Elkahwagy, Abdelhamid Elshaer, Mohammed Shihab
Accelerator Physics
Intrabeam Scattering
Andrzej Wolski
Intrabeam scattering refers to the effects of the Coulomb interaction acting between pairs of charged particles within a bunch in an accelerator. One of the main consequences of intrabeam scattering is a change in the emittances of a bunch: in some circumstances (in particular, in
hadron storage rings operating above transition), the transverse and longitudinal emittances may grow over time without limit. This may restrict the performance of machines for which maintaining low beam emittance is an important requirement. In this note, we describe some of the models used to analyse the effects of intrabeam scattering, and present in particular the Piwinski formulae for the emittance growth rates. We compare the predicted changes in emittance with measurements in a number of machines operating in different parameter regimes.
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Optics
Topology-Enabled Switchable Unidirectional Radiative Band in a Bilayer Photonic Crystal
Zhiyi Yuan, Vytautas Valuckas, Yuhao Wang et al. (+6 more)
Controlling how an open photonic system exchanges energy with its environment-and in particular how it radiates into the far field-is a cornerstone of non-Hermitian wave physics and a key enabler for directional photonic functionalities. Here, we propose a new route to robust unidirectional emission based on the non-Hermitian hybridization of resonances localized in spatially separated layers of a hetero-
bilayer photonic
crystal. By tailoring the interlayer coupling, we engineer hybrid photonc bands that exhibit strong unidirectional radiation across a broad spectral and momentum range while maintaining theoretically high quality factors. This asymmetric emission is organized by a topological
vortex in a pseudo-polarization field defined from the front/back intensity imbalance, which endows the directionality with robustness against perturbations. We further show that, by tuning the surrounding refractive index, this singularity can be displaced in parameter space, enabling reversible switching of the emission direction and a reconfigurable far-field response. This framework opens perspectives for topological photonic sensing and for directional and switchable light sources, including unidirectional lasing supported by high-quality-factor modes.
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All authors Zhiyi Yuan, Vytautas Valuckas, Yuhao Wang, Thi Thu Ha Do, Ningyuan Nie, Yu-Cheng Chen, Hai Son Nguyen, Cuong Dang, Son Tung Ha
Plasma Physics · Cross-listed from astro-ph.SR
Signatures of Damping Nonlinear Oscillations by KHI-induced Turbulence in Synthetic Observations
Sihui Zhong, Andrew Hillier and Iñigo Arregui
Large-amplitude decaying kink oscillations of coronal loops are strongly influenced by nonlinear processes, such as Kelvin-Helmholtz instability (KHI) and
turbulence, though comprehensive theory and observational confirmation remain limited. Building on the recently developed theory on nonlinear damping by KHI-induced
turbulence in impulsively driven transverse loop oscillations, we investigate its observational signatures using 3D magnetohydrodynamic simulations and forward-modelled EUV images. The simulated oscillations exhibit time-varying frequency shifts and damping rates, which are broadly consistent with nonlinear
turbulence-damping theory. Additionally, they exhibit excitation of higher-order modes, slightly increased periods relative to the linear kink period, and reduced displacement amplitudes. These features are generally preserved in synthetic observations, though resolving higher-order modes requires higher spatial resolution than currently available. For loops embedded in a hotter background, hotter channels (e.g., 193 Angstroms) are more sensitive to boundary dynamics, thus their oscillations decay faster with smaller displacements and larger phase shifts than those in cooler channels (e.g., 171 Angstroms). Comparisons of simulated and synthetic oscillations show close agreement at the early stage. At later times, synthetic oscillations exhibit smaller displacements and larger phase shifts, due to
turbulence-induced asymmetry in the loop cross-section.
Bayesian fitting shows that the initial oscillation amplitude and kink period are robustly constrained, whereas parameters controlling the damping profile are degenerate, indicating that additional observables would aid reliable seismological inference. These results provide a quantitative basis for identifying nonlinear damping and detecting KHI-driven
turbulence in transverse loop oscillations.
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Medical Physics · Cross-listed from eess.IV
Time-resolved aortic 3D shape reconstruction from a limited number of cine 2D MRI slices
Gloria Wolkerstorfer, Stefano Buoso, Rabea Schlenker et al. (+3 more)
Background and Objective: To assess the feasibility and accuracy of reconstructing time-resolved, three-dimensional, subject-specific aortic geometries from a limited number of standard cine 2D
magnetic resonance imaging (MRI) acquisitions. This is achieved by coupling a statistical shape model with a differentiable volumetric mesh optimization
algorithm. Methods: Cine 2D MRI slices were manually segmented and used to reconstruct subject-specific aortic geometries via a differentiable mesh optimization
algorithm, constrained by a statistical shape model. Optimal slice positioning was first evaluated on synthetic data, followed by in-vivo acquisition in 30 subjects (19 volunteers and 11 aortic stenosis patients). Time-resolved aortic geometries were reconstructed, from which
geometric descriptors and radial strain were derived. In a subset of 10 subjects, 4D flow MRI data was acquired to provide volumetric reference for peak-systolic shape comparison. Results: Accurate reconstruction was achieved using as few as six cine 2D MRI slices. Agreement with 4D flow MRI reference data yielded a Dice score of (89.9 +/- 1.6) %, Intersection over Union of (81.7 +/- 2.7) %, Hausdorff distance of (7.3 +/- 3.3) mm, and Chamfer distance of (3.7 +/- 0.6) mm. The mean absolute radius error along the aortic arch was (0.8 +/- 0.6) mm. Secondary analysis demonstrated significant differences in
geometric features and radial strain across age groups, with strain decreasing progressively with age at values of (11.00 +/- 3.11) x 10-2 vs. (3.74 +/- 1.25) x 10-2 vs. (2.89 +/- 0.87) x 10-2 for the young, mid-age, and elderly groups, respectively. Conclusion: The proposed framework enables reconstruction of time-resolved, subject-specific aortic geometries from a limited number of standard cine 2D MRI acquisitions, providing a practical basis for downstream computational analysis.
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All authors Gloria Wolkerstorfer, Stefano Buoso, Rabea Schlenker, Jochen von Spiczak, Robert Manka, Sebastian Kozerke
Optics
Resonant optical tunnelling in planar three-layer photonic microstructures
Yago Arosa, Alejandro Doval and Raúl de la Fuente
We present a unified analytical framework for resonant optical tunnelling in three-layer photonic systems embedded in a transparent dielectric medium. Compact expressions for the transmission coefficient are derived using a generalized Fresnel-coefficient formalism, enabling us to distinguish between two fundamentally different tunnelling regimes determined by the nature of the waves supported in the core layer. When harmonic waves propagate within the core, resonances satisfy the conventional Fabry-Perot phase condition. In contrast, when evanescent or damped waves are supported, resonant tunnelling arises from an amplitude-matching condition governed by the magnitude of the composite reflection coefficient. This distinction leads to qualitatively different transmission characteristics and markedly different tunnelling behaviors. For clarity, transparent materials are treated first (including ideal metals), and the role of absorption is subsequently analyzed, revealing the transition from
unitary resonant tunnelling to attenuated optical tunnelling. Angular-spectral maps illustrate the general features of each configuration and demonstrate that resonant tunnelling may occur in structures whose thickness exceeds several wavelengths. The results provide a consistent physical interpretation of resonant tunnelling phenomena in both dielectric and metal-dielectric multilayer systems.
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Space Physics · Cross-listed from astro-ph.HE
Monitoring the upper atmospheric temperature and interplanetary magnetic field with the GRAPES-3 muon telescope
S. Paul, K.P. Arunbabu, M. Chakraborty et al. (+17 more)
We study the influence of variations in the upper atmospheric temperature and interplanetary
magnetic field on the
cosmic ray induced atmospheric
muon flux measured by the GRAPES-3 experiment over 22 years (2001–2022) of data; spanning three
solar cycles: the declining phase of
Solar Cycle 23, the full Cycle 24, and the rising and maximum phases of Cycle 25. Located in Ooty- India, the GRAPES-3 large area (560\,$m^2$)
muon telescope detects $\sim$4 billion
muons daily above 1\,GeV, with an angular resolution of $\sim$4$^\circ$, enabling a statistical precision $<$0.01% on the hourly
muon rate. After accounting for the effect of atmospheric pressure variations, we compare this data with the upper atmospheric temperature inferred from NASA's MERRA-2
dataset as well as
magnetic field data from the ACE and WIND spacecraft at Lagrange point L1. A simultaneous iterative fitting method employing Fast
Fourier Transforms and a narrow band-pass filter reveals the temperature and
magnetic field coefficients to be $\alpha_T=-\,0.2241\,\pm\,0.04\, (stat.)\,\pm\,0.0220\, (syst.)\,\%\,K^{-1}$ and $\gamma_{M}=-\,0.574\,\pm\,0.027\, (stat.)\,\pm\,0.011\, (syst.)\,\%\,\text{nT}^{-1}$, respectively, for an assumed hadronic attenuation length $\lambda$=120 g cm$^{-2}$, underscoring the potential of the GRAPES-3
muon telescope to serve as a real time monitor of the upper atmospheric temperature or interplanetary
magnetic field.
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All authors S. Paul, K.P. Arunbabu, M. Chakraborty, S.K. Gupta, B. Hariharan, Y. Hayashi, P. Jagadeesan, A. Jain, M. Karthik, H. Kojima, S. Kawakami, P.K. Mohanty, Y. Muraki, P.K. Nayak, T. Nonaka, A. Oshima, M. Rameez, K. Ramesh, S. Shibata, K. Tanaka
Atmospheric and Oceanic Physics · Cross-listed from cs.LG
CAAL: Confidence-Aware Active Learning for Heteroscedastic Atmospheric Regression
Fei Jiang, Jiyang Xia, Junjie Yu et al. (+6 more)
Quantifying the impacts of air pollution on health and
climate relies on key atmospheric particle properties such as toxicity and hygroscopicity. However, these properties typically require complex observational techniques or expensive particle-resolved numerical simulations, limiting the availability of labeled data. We therefore estimate these hard-to-measure particle properties from routinely available observations (e.g., air pollutant concentrations and meteorological conditions). Because routine observations only indirectly reflect particle composition and structure, the mapping from routine observations to particle properties is noisy and input-dependent, yielding a heteroscedastic regression setting. With a limited and costly labeling budget, the central challenge is to select which samples to measure or simulate. While active learning is a natural approach, most acquisition strategies rely on predictive uncertainty. Under heteroscedastic noise, this signal conflates reducible epistemic uncertainty with irreducible aleatoric uncertainty, causing limited budgets to be wasted in noise-dominated regions. To address this challenge, we propose a confidence-aware active learning framework (CAAL) for efficient and robust sample selection in heteroscedastic settings. CAAL consists of two components: a decoupled uncertainty-aware training objective that separately optimises the predictive mean and noise level to stabilise uncertainty estimation, and a confidence-aware acquisition function that dynamically weights epistemic uncertainty using predicted aleatoric uncertainty as a reliability signal. Experiments on particle-resolved numerical simulations and real atmospheric observations show that CAAL consistently outperforms standard AL baselines. The proposed framework provides a practical and general solution for the efficient expansion of high-cost atmospheric particle property databases.
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All authors Fei Jiang, Jiyang Xia, Junjie Yu, Mingfei Sun, Hugh Coe, David Topping, Dantong Liu, Zhenhui Jessie Li, Zhonghua Zheng
Biological Physics · Cross-listed from cond-mat.stat-mech
Early stages of collective cell invasion: Biomechanics
R. González-Albaladejo, M. Carretero and L. L. Bonilla
The early stages of the collective invasion may occur by single mesenchymal
cells or hybrid epithelial-mesenchymal
cell groups that detach from cancerous tissue. Tumors may also emit invading protrusions of epithelial
cells, which could be led (or not) by a basal
cell. Here we devise a novel fractional step cellular Potts model comprising passive and active
cells able to describe these different types of collective invasion before
cells start proliferating.
Cells moving toward stiffness gradients (durotaxis) and active forces pulling them away from the tumor have different
symmetry properties under cellular extension and retraction that sometimes hamper collective invasion when put together. Thus, these forces are included in different half steps of the fractional step method. Compared with a single step method, fractional step produces more realistic collective invasion scenarios with little extra computational effort. Biochemical mechanisms that determine how
cells acquire their different phenotypes and cellular proliferation will be incorporated to the model in future publications.
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Geophysics
pycopm: An open-source tool to tailor OPM Flow geological models
David Landa-Marbán
Reservoir simulations help the energy industry make better decisions by predicting how fluids like oil, gas, water, hydrogen, and carbon dioxide will flow underground. To keep these predictions accurate, engineers often need to update geological models quickly as new information becomes available. pycopm is a tool designed to make this process faster and easier. It allows users to adjust geological models in several ways, such as simplifying complex grids, focusing on specific parts of a reservoir, or changing the shape and position of the model. These capabilities help engineers test different scenarios efficiently. Although pycopm was first used on two well-known public
datasets, it has since become useful in many other situations because of its easy-to-use features and recent extensions. Today, it supports studies involving model refinement, comparing coarse and detailed models, analyzing interactions between nearby sites, and speeding up troubleshooting in large simulations.
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Plasma Physics · Cross-listed from cond-mat.mes-hall
Phase-Space Topology and Spectral Flow in Screened Magnetized Plasmas
Xianhao Rao, Adil Yolbarsop, Hong Li et al. (+1 more)
Topological wave phenomena in continuous media are fundamentally challenged by unbounded spectra and the absence of a compact Brillouin zone, which obstruct conventional bulk–interface formulations. We develop a unified phase-space framework for screened magnetized
plasma based on a pseudo-Hermitian formulation with a positive-definite metric, enabling a generalized Schrödinger description and a Weyl-symbol analysis of the bulk generator. We show that the bulk symbol hosts isolated band degeneracies acting as Berry–Chern monopoles, including a higher-order
spin-1 degeneracy with topological charge $+2$ that generically splits into two
spin-$\tfrac{1}{2}$ Weyl points under
symmetry breaking. To characterize
topology in this noncompact setting, we introduce a strip-gap Chern number associated with finite real-frequency strips of the bulk spectrum, extending band Chern
topology to continuum systems. This invariant governs the spectral flow of interface modes induced by spatial variations of the
magnetic field and establishes a bulk–interface correspondence at the level of phase-space symbols. By solving the interface
eigenvalue problem, we demonstrate that the net spectral flow across the strip gap is determined by the enclosed monopole charge. We further show that this correspondence persists under collisional damping, provided that a finite strip gap remains and no exceptional points enter it. Our results provide a systematic phase-space framework for topological wave transport in continuous media beyond compact-band and idealized Hermitian settings.
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All authors Xianhao Rao, Adil Yolbarsop, Hong Li, Wandong Liu
Optics
Broadband Tunable Photon-Pair Generation and Spectrum Measurement Based on Noncritical Lithium Niobate Crystals
Zhao-Qi-Zhi Han, Bo-Wen Liu, He Zhang et al. (+8 more)
Photon pairs play a vital role in modern science, driving extensive research into their generation. Yet, the narrow phase-matching bandwidth of conventional
crystals has largely confined studies to specific wavelengths, leaving research on broadband tunable sources underexplored. Here, we employ a non-critical phase-matched lithium niobate (LN)
crystal to generate widely tunable
photon pairs. The generated near-infrared (NIR)
photon pairs exhibit a high coincidence-to-accidental ratio (CAR > 20 dB) and are tunable across the 800-1600 nm range. We further showcase the utility of NIR
photon pairs in spectroscopy by detecting carbon monoxide (CO) gas absorption. This approach will facilitate the design of advanced LN-based photonic experiments.
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All authors Zhao-Qi-Zhi Han, Bo-Wen Liu, He Zhang, Zhi-You Li, Xiao-Hua Wang, Jin-Peng Li, Zheng-He Zhou, Qi-Yu Chen, Yin-Hai Li, Zhi-Yuan Zhou, Bao-Sen Shi
Applied Physics
Experimental setup for the combined study of spin ensembles and superconducting quantum circuits
Lukas Vogl, Gerhard B. P. Huber, Ana Strinić et al. (+5 more)
A hybrid
quantum computing architecture combining
quantum processors and
quantum memory units allows for exploiting each component's unique properties to enhance the overall performance of the total system. However, superconducting
qubits are highly sensitive to
magnetic fields, while
spin ensembles require finite fields for control, creating a major integration challenge. In this work, we demonstrate the first experimental setup that satisfies these constraints and provides verified
qubit stability. Our cryogenic setup comprises two spatially and magnetically decoupled sample volumes inside a single dilution refrigerator: one hosting flux-tunable superconducting
qubits and the other a
spin ensemble equipped with a superconducting solenoid generating fields up to 50 mT. We show that several layers of Cryophy shielding and an additional superconducting aluminum shield suppress
magnetic crosstalk by more than eight orders of magnitude, ensuring stability of the
qubit's performance. Moreover, the operation of the solenoid adds minimal thermal load on the relevant stages of the dilution refrigerator. Our results enable scalable hybrid
quantum architectures with low-loss integration, marking a key step toward scalable hybrid
quantum computing platforms.
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All authors Lukas Vogl, Gerhard B. P. Huber, Ana Strinić, Achim Marx, Stefan Filipp, Kirill G. Fedorov, Rudolf Gross, Nadezhda P. Kukharchyk
Computational Physics
Ultra-Fast 3D Porous Media Generation: a GPU- Accelerated List-Indexed Explicit Time-Stepping QSGS Algorithm
Ruofan Wang and Mohammed Al-Kobaisi
Efficient generation of high-resolution synthetic microstructures is essential in digital rock physics, yet classical Quartet Structure Generation Set (QSGS)
algorithms become prohibitively expensive on large three-dimensional grids. We develop a list-indexed explicit time-stepping (LIETS) formulation of QSGS that restricts
stochastic growth operations to an explicit active front instead of the entire voxel grid. The method is implemented in Python using NumPy on CPUs and CuPy on GPUs, and incorporates seed-spacing control via diamond dilation together with a volume-fraction-dependent directional growth probability. For a 400^3 domain, LIETS reduces generation time from tens of minutes for a serial CPU implementation and several minutes for vectorized CPU and GPU QSGS to about 24 s on a consumer-grade RTX 4060, achieving peak throughputs up to 2.7x10^7 nodes/s. A Fontainebleau sandstone
benchmark at 500^3 resolution shows that LIETS reproduces the dependence of pore and grain size distributions on seed spacing (optimal s=30 voxels) and yields permeability-porosity trends within the experimental envelope and consistent with previously published Fast-QSGS results.
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