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Physics Physics

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Tuesday 24 February

Computational Physics

Efficient and Accurate Method for Separating Variant Components from Invariant Background and Component Model Fusion for Fast RFIC Design Space Exploration

Hongyang Liu and Dan Jiao

The design of RFIC often involves exploring a large number of design variations in an invariant background composed of the processing stack and unchanged circuit blocks. Conventional electromagnetic solvers require a full-domain simulation for every design variation. In this work, we present a fast method that effectively separates the variant components from the invariant background. It algebraically decomposes the total field solution into the contributions from the design-dependent variations and the invariant background. Hence, the field response due to the invariant background can be simulated once and reused for all design variations. Only the variant components need to be simulated at each design variation, the size of which is small. We also develop an efficient way of reusing the model of each component and fusing them accurately to obtain the model of a system composed of many components. The reduced system of variant components involves computing the field solutions in the invariant background due to all possible sources located at variant components, the number of which can be large. We develop a fast algorithm to reduce them to a few field solutions, the number of which is on the order of the layer number. The proposed method has been applied to RFIC design space exploration. Its accuracy, robustness, and efficiency have been demonstrated.
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History and Philosophy of Physics

De-Idealizing De-Idealization: Beyond Full Reversal

Yichen Luo and Eugene Y. S. Chua

There is a question of whether de-idealization is needed for justified use of – for 'checking' – idealizations. We argue that the standard philosophical account of de-idealization has become too idealized, but that this does not preclude the possibility of justificatory practices which show how models can be used to make inferences about the world. In turn, motivated by examples in physics, we provide a more expansive and practice-driven account of de-idealization by relaxing the standards for closeness to more realistic theoretical items, identifying at least three kinds of procedures for de-idealization: intra-model, inter-model, and measurement de-idealizations. These examples highlight how idealizations can be – and indeed have been – scrutinized within physics without appealing to the philosopher's idealized notion of de-idealization.
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Chemical Physics · Cross-listed from cond-mat.mtrl-sci

Automatic Identification of Compounds in Molecular Mixtures from Liquid-Phase Infrared Spectra

Yannah J.U. Melle, Thanh Nguyen, Jeffrey Lopez et al. (+1 more)

Interpreting spectroscopy data is a critical bottleneck in automating chemical research and industrial characterization. Particularly within infrared (IR) spectroscopy, identifying compounds in complex, liquid-phase chemical mixtures largely relies on expert knowledge, as variable peak assignment, broadening, and shifts hinder data-driven methods. Here, we show that an algorithmic approach can identify components in both simulated and experimental mixture spectra with high accuracy despite nonlinearities in liquid-phase IR data. The method is comprehensively benchmarked with a dataset of over 44,000 simulated liquid-phase IR spectra for mixtures and achieves up to 90% accuracy in identifying molecular components across a dataset of binary and ternary liquid mixtures. Our strategy is robust to perturbation of spectra, and its accuracy is capped by near-identical liquid-phase IR spectra that limit the resolution of chemical identification, imposing theoretical limits on achieving perfect accuracy in structure identification. Finally, we apply the method to automatically interpret IR spectra in experimental settings, correctly identifying the components of nearly all samples within a blind study. This work provides tools and data to advance automated chemical laboratories through algorithmic interpretation of liquid-phase IR spectra of mixtures.
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All authors Yannah J.U. Melle, Thanh Nguyen, Jeffrey Lopez, Daniel Schwalbe-Koda

Atomic Physics · Cross-listed from quant-ph

Optical repumping and atom number balancing in a two-color MOT

Shubha Deutschle, Lőrinc Sárkány, Milán János Negyedi et al. (+3 more)

We study a novel repumping transition for $^{88}$Sr atoms trapped in a 'blue' magneto-optical trap. We show that, while the repumping efficiency is about three orders of magnitude smaller than for traditional schemes, it is sufficient for recycling all atoms, provided the repumping laser beams are arranged to form a 'green' magneto- optical trap (MOT) helping to cool and confine the atoms and preventing their loss. Our main findings are: (i) that the green MOT configuration is able to trap 10 times more atoms in the blue MOT than using the green transition merely as a repump, and (ii) that the atom numbers in the two-color MOT can be balanced through experimental control parameters. The interest of this scheme lies in its capability of reaching low temperature and its suitability for continuous atomic beam generation.
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All authors Shubha Deutschle, Lőrinc Sárkány, Milán János Negyedi, József Fortágh, Andreas Günther, Philippe Wilhelm Courteille

Instrumentation and Detectors · Cross-listed from gr-qc

Beam tube boundary effects in stray light modeling of long Fabry-Perot arm cavities for third-generation gravitational-wave detectors

M. Andrés-Carcasona and M. Evans

Next-generation gravitational-wave detectors such as Cosmic Explorer and the Einstein Telescope will operate 10-40 km Fabry-Perot arm cavities inside vacuum beam tubes. FFT-based paraxial tools treat propagation in free space and therefore do not explicitly enforce beam tube boundary conditions. We introduce a waveguide-like mode description of the optical field that incorporates an imposed beam tube boundary condition and enables an independent benchmark of free-space FFT tools We derive the associated modal-mixing matrices for mirrors and baffles, including a closed-form series for axisymmetric circular apertures. We quantify the strain-equivalent couplings from baffle miscentering and from a localized near-wall tube defect, and show that they are suppressed as baffle density increases. In the relevant regime of densely baffled cavities and small perturbations, beam tube boundary effects are subdominant, which supports the continued use of FFT-based codes to guide the design of 3G detectors.
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Chemical Physics · Cross-listed from cond-mat.str-el

Ab Initio Random Matrix Theory of Molecular Electronic Structure

Zhen Tao and Victor Galitski

We use ab initio electronic-structure methods to investigate random-matrix theory (RMT) universality in molecular electronic structure. Using single-reference electronic structure methods, including Hartree-Fock, configuration-interaction singles (CIS), density functional theory, and linear-response time-dependent density-functional theory, we compute single-particle orbital energies and many-electron excitations of several representative molecules (benzene, alanine, 1-phenylethylamine, methyloxirane, and helicene chains). For generic low-symmetry geometries, the unfolded spectra of these ab initio Hamiltonians exhibit Wigner-Dyson level statistics of the Gaussian orthogonal ensemble (GOE). For extended helicene chains we explicitly restrict to bound valence excitations below the ionization threshold and still observe GOE statistics, indicating that the RMT universality is present for physical states of direct relevance to real molecules. We further explore the electric and magnetic field dependence of the molecular electronic spectra. The variance of electric polarizability (level curvature K) is predicted to be non-analytic in the magnetic field which serves as an infrared cutoff, <K^2> proportional to log(1/|B|). We observe a transition to the Gaussian unitary ensemble (GUE) by increasing the magnetic fields, although it occurs only at magnetic fields far beyond experimentally accessible scales. Our results indicate that random matrix universality provides a general framework for organizing ab initio predictions of interacting electron spectra in complex systems.
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Plasma Physics · Cross-listed from astro-ph.HE

Global Magnetohydrodynamic Simulations of Monster Shocks in Neutron Star Magnetospheres

Michael P. Grehan, Bart Ripperda, Andrei M. Beloborodov et al. (+2 more)

Waves launched from the neutron star surface or inner magnetosphere propagate through the magnetosphere as small perturbations, but can grow relative to the background magnetic field and steepen into “monster shocks” – ultra-relativistic magnetized shocks which can power high-energy emission. Such shocks can develop around isolated magnetars, merging binaries, and collapsing neutron stars. They occur in magnetically dominated plasma and are described by relativistic magnetohydrodynamics (MHD). We present global relativistic MHD simulations of monster shocks in unperturbed and perturbed (“wrinkled”) backgrounds with a global dipolar geometry. Our simulations confirm analytical predictions for equatorial shocks and provide new insight into the behavior of oblique shocks off the equator. Simulations where the shock is formed through Alfvén mode to fast mode conversion are also presented, demonstrating the generic nature of the monster shock mechanism. We explore how the presence of additional modes in the magnetosphere modifies the shock behavior. Modes of comparable amplitude can fragment the shock front, substantially reduce the magnetization, produce localized enhancements in the Lorentz factor relative to an unperturbed dipole background, and intermittently generate additional shocks along a line of sight.
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All authors Michael P. Grehan, Bart Ripperda, Andrei M. Beloborodov, Christopher Thompson, Elias R. Most

Plasma Physics

Kolmogorov Scaling for Total Energy and Cross Helicity in Magnetohydrodynamic Turbulence

Manthan Verma, Abhishek K. Jha and Mahendra K. Verma

The problem of scaling in isotropic magnetohydrodynamic (MHD) turbulence has remained unresolved, with competing predictions of $k^{-5/3}$ (Kolmogorov) and $k^{-3/2}$ (Iroshnikov-Kraichnan) scalings. In this paper, we address this long-standing controversy using high-resolution numerical simulations on $8192^2$ and $1536^3$ grids. We show that the total energy and cross helicity spectra are closer to $k^{-5/3}$ than $k^{-3/2}$. The fluxes and structure functions of the total energy and cross helicity also demonstrate robust support for Kolmogorov scaling. The magnetic energy shows $k^{-5/3}$ spectrum, but the kinetic energy exhibits $k^{-3/2}$ spectrum; the latter spectrum is due to the energy transfers from the magnetic field to the velocity field.
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Optics · Cross-listed from gr-qc

Lorentz-Violating Wormhole Optics

Omar Mustafa, Semra Gurtas Dogan, Abdulkerim Karabulut et al. (+1 more)

We study massless spin-1 field propagation in a static, circularly symmetric $(2+1)$-dimensional wormhole with spatial Lorentz-violating anisotropy characterized by the throat radius $a$ and deformation parameter $\eta$. The geometry is horizon-free, geodesically complete, and asymptotically flat, with negative Gaussian curvature localized near the throat. Using the fully covariant vector boson formalism and covariant Maxwell theory, we derive an exact Schrödinger-type radial equation with a curvature-induced effective potential. Recasting the dynamics in Helmholtz form yields an effective refractive-index profile, showing that the wormhole acts as an inhomogeneous optical medium with position-dependent refractive index and frequency-dependent confinement, where low-frequency modes are strongly trapped while high-frequency modes propagate almost freely. A differential-geometric correspondence with helicoidal surfaces is established via $1/[a^2(1-\eta)] \leftrightarrow w^2$, demonstrating that Lorentz-violation-induced curvature is mathematically equivalent to curvature generated by geometric twist and linking the model to twisted graphene nanoribbons as analog-gravity platforms. These results provide a geometric framework for curvature-driven localization, dispersion, and anisotropic wave propagation in topologically nontrivial $(2+1)$-dimensional backgrounds.
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All authors Omar Mustafa, Semra Gurtas Dogan, Abdulkerim Karabulut, Abdullah Guvendi

Instrumentation and Detectors · Cross-listed from hep-ex

Low-Energy Radon Backgrounds from Electrode Grids in Dual-Phase Xenon TPCs

D.S. Akerib, A.K. Al Musalhi, F. Alder et al. (+264 more)

The dual-phase xenon time projection chamber (TPC) is a powerful technology to detect rare interactions such as scatters of dark matter particles on nuclei. In particular, the built-in gain of ionization signals in a dual-phase TPC makes it sensitive to events in the few-electron regime, as expected from low-mass dark matter interactions. The pursuit of this low-energy sensitivity through ionization-only signal detection has so far been hindered by excessive electron backgrounds observed across experiments. Much of this background is attributed to the plate-out of $^{222}$Rn decay chain isotopes on the high voltage electrode grid surfaces that span the full cross section of the TPC. This work presents a first-principle model constructed for this background, the predictions of which are consistent with data from the LZ and LUX experiments. We then discuss mitigation strategies of this background in future dual-phase TPCs and the possibility of applying this grid background model to ionization-only dark matter searches.
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All authors D.S. Akerib, A.K. Al Musalhi, F. Alder, B.J. Almquist, S. Alsum, C.S. Amarasinghe, A. Ames, T.J. Anderson, N. Angelides, H.M. Araújo, J.E. Armstrong, M. Arthurs, X. Bai, A. Baker, J. Balajthy, S. Balashov, J. Bang, J.W. Bargemann, E.E. Barillier, A. Baxter, K. Beattie, T. Benson, E.P. Bernard, A. Bernstein, A. Bhatti, T.P. Biesiadzinski, H.J. Birch, E. Bishop, G.M. Blockinger, E.M. Boulton, B. Boxer, C.A.J. Brew, P. Brás, S. Burdin, D. Byram, M.C. Carmona-Benitez, M. Carter, C. Chan, A. Chawla, H. Chen, Y.T. Chin, N.I. Chott, S. Contreras, M.V. Converse, R. Coronel, A. Cottle, G. Cox, D. Curran, J.E. Cutter, C.E. Dahl, I. Darlington, S. Dave, A. David, J. Delgaudio, S. Dey, L. de Viveiros, L. Di Felice, C. Ding, J.E.Y. Dobson, E. Druszkiewicz, S. Dubey, C.L. Dunbar, S.R. Eriksen, A. Fan, N.M. Fearon, N. Fieldhouse, S. Fiorucci, H. Flaecher, E.D. Fraser, T.M.A. Fruth, P.W. Gaemers, R.J. Gaitskell, A. Geffre, J. Genovesi, C. Ghag, J. Ghamsari, A. Ghosh, S. Ghosh, R. Gibbons, M.G.D. Gilchriese, S. Gokhale, J. Green, M.G.D.van der Grinten, C. Gwilliam, J.J. Haiston, C.R. Hall, T. Hall, R.H Hampp, E. Hartigan-O'Connor, S.J. Haselschwardt, M.A. Hernandez, S.A. Hertel, D.P. Hogan, G.J. Homenides, M. Horn, D.Q. Huang, D. Hunt, C.M. Ignarra, R.G. Jacobsen, E. Jacquet, O. Jahangir, R.S. James, K. Jenkins, W. Ji, A.C. Kaboth, A.C. Kamaha, K. Kamdin, M.K. Kannichankandy, K. Kazkaz, D. Khaitan, A. Khazov, J. Kim, Y.D. Kim, J. Kingston, D. Kodroff, E.V. Korolkova, H. Kraus, S. Kravitz, L. Kreczko, V.A. Kudryavtsev, C. Lawes, E. Leason, D.S. Leonard, K.T. Lesko, C. Levy, J. Liao, J. Lin, A. Lindote, R. Linehan, W.H. Lippincott, J. Long, M.I. Lopes, W. Lorenzon, C. Lu, S. Luitz, W. Ma, V. Mahajan, P.A. Majewski, A. Manalaysay, R.L. Mannino, N. Marangou, R.J. Matheson, C. Maupin, M.E. McCarthy, G. McDowell, D.N. McKinsey, J. McLaughlin, J.B. McLaughlin, R. McMonigle, D.-M. Mei, B. Mitra, E. Mizrachi, M.E. Monzani, K. Morå, J.A. Morad, E. Morrison, B.J. Mount, M. Murdy, A.St.J. Murphy, A. Naylor, C. Nehrkorn, H.N. Nelson, F. Neves, A. Nguyen, A. Nilima, C.L. O'Brien, F.H. O'Shea, I. Olcina, K.C. Oliver-Mallory, J. Orpwood, K.Y Oyulmaz, K.J. Palladino, N.J. Pannifer, N. Parveen, S.J. Patton, B. Penning, G. Pereira, E. Perry, T. Pershing, A. Piepke, S.S. Poudel, Y. Qie, J. Reichenbacher, C.A. Rhyne, Q. Riffard, G.R.C. Rischbieter, E. Ritchey, H.S. Riyat, R. Rosero, P. Rossiter, N.J. Rowe, T. Rushton, D. Rynders, S. Saltão, D. Santone, A.B.M.R. Sazzad, R.W. Schnee, G. Sehr, B. Shafer, S. Shaw, W. Sherman, K. Shi, T. Shutt, C. Silva, G. Sinev, J. Siniscalco, A.M. Slivar, R. Smith, A.M. Softley-Brown, M. Solmaz, V.N. Solovov, P. Sorensen, J. Soria, A. Stevens, T.J. Sumner, A. Swain, N. Swanson, M. Szydagis, D.J. Taylor, R. Taylor, W.C. Taylor, B.P. Tennyson, P.A. Terman, D.R. Tiedt, M. Timalsina, W.H. To, Z. Tong, D.R. Tovey, J. Tranter, M. Trask, K. Trengove, M. Tripathi, L. Tvrznikova, U. Utku, A. Usón, A. Vacheret, A.C. Vaitkus, O. Valentino, V. Velan, A. Wang, J.J. Wang, Y. Wang, R.C. Webb, L. Weeldreyer, J.T. White, T.J. Whitis, K. Wild, M. Williams, J. Winnicki, M.S. Witherell, L. Wolf, F.L.H. Wolfs, S. Woodford, D. Woodward, C.J. Wright, Q. Xia, X. Xiang, J. Xu, Y. Xu, M. Yeh, D. Yeum, J. Young, W. Zha, C. Zhang, H. Zhang, T. Zhang, Y. Zhou

Fluid Dynamics

A Novel Explicit Filter for the Approximate Deconvolution in Large-Eddy Simulation on General Unstructured Grids: A posteriori tests on highly stretched grids

Mohammad Bagher Molaei, Ehsan Amani and Morteza Ghorbani

Explicit filters play a pivotal role in the scale separation and numerical stability of advanced Large Eddy Simulation (LES) closures, such as dynamic eddy-viscosity or Approximate Deconvolution (AD) methods. In the present study, it is demonstrated that the performance of commonly used explicit filters applicable to general unstructured grids highly depends on the grid configuration, specifically the cell aspect ratio, which can result in poor filter spectral properties, ultimately leading to large errors and even solution divergence. This study introduces a novel, efficient explicit filter for general unstructured grids, addressing this shortcoming through a combination of a face-averaging technique and recursive filtering. The filter parameters are then determined through a constrained multi-objective optimization, ensuring desirable spectral properties, including high-wavenumber attenuation, filter-width precision, filter stability and positivity, and minimized dispersion and commutation errors. The AD-LES of turbulent channel flow benchmarks using the new filter demonstrate a noticeable improvement in turbulent flow predictions on highly stretched boundary-layer-type grids, particularly in reducing the log-layer mean velocity profile mismatch, compared to simulations using conventional filters. The analyses show that this enhancement is mainly attributed to the sufficient level of attenuation near the Nyquist wavenumber achieved by the new filter in all spatial directions across various grid configurations, among others. The new filter was also successfully tested on unstructured prism grids for the 3D Taylor-Green vortex benchmark.
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Optics

Acoustic Guided Waves in MoS2 thin flakes

Martín Aversa, Nicolás Roqueiro, Camila Borrazás et al. (+7 more)

Guided acoustic waves in two-dimensional materials are a key channel for energy transport and dissipation, yet their generation and propagation in transition metal dichalcogenides remain poorly understood. Here, we employ in-situ and spatially decoupled ultra-fast optical pump-probe techniques to investigate guided waves in MoS2 flakes with thicknesses between 90 and 410 nm. We observe a propagating acoustic excitation with a constant velocity of (6.7 +/- 0.8) km/s, independent of thickness. Finite element simulations and symmetry analysis reveal that these vibrations deviate from the classical Lamb wave model and are better described as a superposition of decoupled longitudinal and shear modes. We show that their optical detectability is governed by the Poisson effect: longitudinal components modulate the flake thickness and generate a measurable signal, whereas shear motion remains largely optically invisible. An intrinsic attenuation length of approximately 3.3 microns indicates that dissipation is dominated by material-specific mechanisms rather than geometric spreading. Finally, we demonstrate remote excitation across a nanometric step, enabling acoustic generation in optically inaccessible regions. These results provide a foundation for nanoscale phononic circuits and engineered in-plane energy transport in 2D-based optomechanical and quantum acoustic devices.
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All authors Martín Aversa, Nicolás Roqueiro, Camila Borrazás, Juan Ignacio Sangiorgio, Hilario D. Boggiano, Juan Bonaparte, Andrés Di Donato, María Cecilia Fuertes, Andrea V. Bragas, Gustavo Grinblat

Plasma Physics

A coherent structure transport model for scrape-off layer turbulence

Zhichen Feng, James Myra, Junyi Cheng et al. (+5 more)

Understanding the locality of high-temperature plasma energy deposition on material surfaces in fusion reactors is critical for design. Here, we utilize the Gyrokinetic ElectroMagnetic turbulence including X-points (GEMX) simulation, together with SOLPS-ITER solutions for the background equilibrium electric field including drifts, to model the heat flux at the divertor plate and characterize the heat load width using realistic X-point geometry. We use a theory-based blobby transport model called the "Coherent Structure Transport" (CST) model to include the effect of plasma transport in the edge scrape-off layer. The CST model is extremely fast and can be used to quickly analyze any SOLPS-ITER solution. SOLPS-ITER provides the steady state, or equilibrium on which we superimpose blobby turbulence characterized by blob size, amplitude and frequency. We obtain the $1/B_p$ scaling of the heat load exponential decay width $\lambda_q$, in agreement with the Eich empirical scaling and with the Goldston heuristic theory. When including blobby turbulence in combination with the SOLPS-ITER electric field, we find a secondary peak in the heat flux radial profile, outwardly displaced from the strike point radius, with a relative amplitude that increases with the initial blob density. We describe the CST model in detail and provide initial investigations of the scaling of $\lambda_q$ and the secondary heat flux peak with blob size and amplitude.
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All authors Zhichen Feng, James Myra, Junyi Cheng, Calder Haubrich, Yang Chen, Xinxing Ma, Darin R. Ernst, Scott Parker

Chemical Physics

Density Functional Theory Predictions of Derivative Thermodynamic Properties of a Confined Fluid

Gennady Y. Gor, Geordy Jomon and Andrei L. Kolesnikov

Fluids in nanopores are of importance for many engineering applications, including energy storage in supercapacitors, hydrocarbons recovery from unconventional sources, or water desalination. Thermodynamic properties of fluids confined in nanopores differ from the properties of the same fluids in bulk. Density functional theory (DFT) has been widely used for modeling thermodynamics of confined fluids. However, it is rarely used for calculations of derivative thermodynamic properties. Here we use a rather simple DFT model for argon based on the Percus-Yevick equation, and showed that with standard parametrization it fails to predict derivative properties. However, slight adjustment in parameters leads to quantitative predictions of isothermal compressibility and thermal expansion coefficient at a selected temperature. Using the adjusted parameterization we performed the calculations of compressibility of argon confined in carbon slit pores of various sizes, and demonstrated that the compressibility of argon in confinement is lower than that in bulk and is pore size dependent. We confirmed the DFT predictions using the Monte Carlo molecular simulations. In addition to isothermal compressibility, we calculated the thermal expansion coefficient of confined argon. Our calculations showed that it behaves similar to compressibility – it is always lower than the bulk value and gradually increases for smaller pore sizes. For several selected pore sizes we verified the DFT calculations by Monte Carlo simulations. Overall, our results suggest that the classical DFT can be utilized for calculations of derivative thermodynamic properties of confined fluids, which are computationally challenging to predict using molecular simulations.
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Optics

Accessibility of doping ranges of semiconductors by terahertz spectroscopy

Joshua Hennig, Jens Klier, Stefan Duran et al. (+4 more)

While established semiconductor measurement techniques such as four-point probe or capacitance-voltage measurements require a physical contact to the material, terahertz spectroscopy is completely contact-free. Its capability to measure the doping of semiconductors is well known, yet the exact doping ranges that are accessible to terahertz spectroscopy are not obvious. Therefore, we introduce a sensitivity metric to clarify whether a semiconductor sample can be characterized in principle by reflection terahertz time-domain spectroscopy. This quantity takes into account the semiconductor material with a certain layer thickness, doping type, and doping level and is based on numerical simulations. In this work, we calculate this sensitivity value for relevant semiconductor materials (SiC, Si, GaN) in realistic layer stacks with up to three layers. It is used to create meaningful heat maps depending on the thicknesses and charge carrier densities of the sample structures of interest. The plausibility of the sensitivity is validated by mapping a variety of measurements with terahertz techniques from us and from other groups onto these heat maps. Based on these, the accessible range of charge carrier densities for terahertz spectroscopy spans roughly from 10$^{15}$ cm$^{-3}$ to 10$^{20}$ cm$^{-3}$, but with dependencies on material, doping type, and sample thickness. Furthermore, the sensitivity value allows for a substantiated assessment of the possible benefits future improvements of photoconductive antennas and terahertz systems could have, which is demonstrated by simulations based on varied bandwidths.
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All authors Joshua Hennig, Jens Klier, Stefan Duran, Mirco Kutas, Joachim Jonuscheit, Georg von Freymann, Daniel Molter

Fluid Dynamics

Pressure beneath a periodic travelling water-wave in constant-vorticity flow over a flat bed

Adrian Constantin, Nicolas Gindrier and Otmar Scherzer

We investigate within the framework of linear theory the behaviour of the total (hydrodynamic) pressure and of the dynamic pressure in a regular wave train which propagates at the surface of water with a flat bed in a flow with constant vorticity. We show that nonzero vorticity, the hallmark of a non-uniform underlying current, may strongly alter the behaviour with respect to the case of irrotational flows, for which the maximum and minimum of the dynamic pressure always occur at the wave crest and at the wave trough, respectively (the extrema of the dynamic pressure may occur along the flat bed or along the critical level, depending on the vorticity strength). While vorticity does not modify the increase of the hydrodynamic pressure with depth, it can significantly alter the location of the extrema of the hydrodynamic pressure at a fixed depth level.
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Space Physics · Cross-listed from astro-ph.HE

The no-hair theorems at work in the tidal disruption event AT2020afhd

Lorenzo Iorio

Recently, the coprecession of both the accretion disk and the jet formed following the tidal disruption event associated with the optical transient AT2020afhd, driven by a supermassive black hole of almost ten million solar masses, were independently measured in both the X and radio bands, respectively, showing a periodicity of nearly 20 days over about 300 days. An analytical model of the general relativistic gravitomagnetic Lense-Thirring precession of the effective orbit of a fictitious test particle revolving about a spinning primary can explain the observed precessional features. It yields allowed regions in the system's parameter space which, as far as the hole's dimensionless spin parameter is concerned, are essentially in agreement with those obtained in the literature with general relativistic magnetohydrodynamic simulations. The present analytical approach can be extended to include the precession due to the hole's quadrupole mass moment as well. It breaks the degeneracy in the allowed regions occurring for negative and positive values of the spin parameter when only the Lense-Thirring effect is considered. The best estimate for the hole's mass yields the range $0.185-0.215$ for the dimensionless spin parameter. Using the same strategy with the gravitomagnetic frequency for an extended disk of finite size with a parameterized power-law mass density yields to distinct, generally non-overlapping allowed regions for each value of the power-law index adopted.
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Physics and Society · Cross-listed from stat.AP

On the non-uniformity of the 2026 FIFA World Cup draw

László Csató, Martin Becker, Karel Devriesere et al. (+1 more)

The group stage of a sports tournament is often made more appealing by introducing additional constraints in the group draw that promote an attractive and balanced group composition. For example, the number of intra-regional group matches is minimised in several world championships. Under such constraints, the traditional draw procedure may become non-uniform, meaning that the feasible allocations of the teams into groups are not equally likely to occur. Our paper quantifies this non-uniformity of the 2026 FIFA World Cup draw for the official draw procedure, as well as for 47 reasonable alternatives implied by all permutations of the four pots and two group labelling policies. We show why simulating with a recursive backtracking algorithm is intractable, and propose a workable implementation using integer programming. The official draw mechanism is found to be optimal based on two of five non-uniformity measures, including the average distortion of the 771 non-zero assignment probabilities. Nonetheless, non-uniformity can be more than halved if the organiser aims to treat the best teams drawn from the first pot equally.
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All authors László Csató, Martin Becker, Karel Devriesere, Dries Goossens

Computational Physics · Cross-listed from cs.SE

A Modular Multi-Document Framework for Scientific Visualization and Simulation in Java

David Heddle

This paper presents the design and implementation of a modular multi-document interface (MDI) framework for scientific visualization and simulation in the Java Virtual Machine (JVM) ecosystem. The framework emphasizes architectural separation between visualization layers, simulation engines, and optional hardware-accelerated 3D rendering. 3D functionality is isolated into a separate module to prevent unnecessary dependency coupling in 2D-only applications. We describe the core abstractions, threading model, simulation integration strategy, and dependency isolation approach. A case study involving a real-time 3D gas expansion simulation integrated with synchronized 2D entropy plotting demonstrates architectural cohesion. The framework is publicly available via Maven Central and targets long-lived scientific and engineering desktop applications.
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Computational Physics · Cross-listed from astro-ph.GA

HINORA II: Testing the Existence of the Council of Giants in {\Lambda}CDM simulations

Edward Olex, Alexander Knebe, Noam I. Libeskind et al. (+2 more)

The discovery of the galaxy ring known as the Council of Giants (CoG) highlights the need to explain such structures in the Local Universe. In the first paper of this series we presented HINORA - a code to locate (ring-like) structures in 3D point sets - and used it to identify the CoG in the most complete observations of the Local Volume. Here, in Part II, we apply the same method to cosmological simulations to quantify the possible existence of such objects in the LCDM model of structure formation. We analyze DM-only simulations with random and constrained initial conditions, selecting regions that reproduce the properties of the Local Group and Volume, respectively. In order to use the same selection criteria as previsouly done for observations, we relate K-band luminosities to halo masses through semi-empirical relations. After confirming that the selected regions from the simulations match the observed mass function and density of the Local Universe, we use HINORA to search for ring-like structures in them. We find that the existence of CoGs in LCDM simulations is a rather unusual phenomenon. The observed CoG represents an anomaly of more than 2.7 sigma from what is expected in the distribution of massive galaxies in LCDM. These results hint that the CoG could either be a rare chance configuration or the imprint of physical processes at intermediate scales that standard DM-only simulations fail to capture.
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All authors Edward Olex, Alexander Knebe, Noam I. Libeskind, Stefan Gottlöber, Dmitry I. Makarov

Biological Physics · Cross-listed from cond-mat.soft

Lost in Projection? Gaussian Filtering Recovers Hidden Conformational States

Sofia Sartore, Daniel Nagel, Georg Diez et al. (+1 more)

To interpret molecular dynamics (MD) simulations, it is common practice to reduce the dimensionality of the molecular coordinates to a low-dimensional collective variable $x$. Projecting the high-dimensional MD data onto $x$ yields a free energy landscape $\Delta G(x)$, which highlights low-energy regions corresponding to conformational states. The accurate definition of these states, however, is often impeded by projection artifacts, resulting in artificially shortened state lifetimes or even the complete disappearance of states from the analysis. As demonstrated for a two-dimensional toy model, Gaussian low-pass filtering of the high-dimensional MD coordinates can restore the underlying free energy landscape, allowing to recover previously hidden states. When applied to an all-atom folding trajectory of HP35, the number of microstates increases by an order of magnitude, which leads to metastable states that are long-lived and much better defined structurally, even compared to dynamically cored state trajectories.
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All authors Sofia Sartore, Daniel Nagel, Georg Diez, Gerhard Stock

Geophysics

The UK and Ireland Geophysical Array – Concept and Design

Andrew Curtis, Karen Lythgoe, Stephen P. Hicks et al. (+63 more)

Scientific exploration of the UK and Ireland's subsurface has made important contributions to scholarship and prosperity for people and the planet, including economic growth, sustainable use of natural resources, storage of greenhouse gases, and inspiring curiosity about the Earth beneath our feet. This article outlines a vision for an array of seismological instruments spanning the UK and Ireland, UKI Array, augmented by other types of geophysical sensors, to maximise the value offered by existing equipment pools. The mission is to research natural phenomena and structure in the deep and shallow Earth, to solve problems concerning hazards and resources, to connect scientists to schools and the broader public, and thus to inspire a new generation to learn about geophysics. The vision was created through a community driven process of engagement and participation. This paper describes the concept and design of the UKI-Array; a companion paper discusses related opportunities and potential applications.
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All authors Andrew Curtis, Karen Lythgoe, Stephen P. Hicks, Lidong Bie, Dominik Strutz, Emma Chambers, Brian Baptie, Dave Cornwell, Juliane Huebert, Jessica Irving, Glenn Jones, Sergei Lebedev, Walid Ben Mansour, Aideliz Montiel Álvarez, Stuart Nippress, Koen Van Noten, Tim Pharaoh, Romesh Palamakumbura, Nick Rawlinson, Pablo Rodriguez Salgado, James Verdon, Chuanbin Zhu, Wen Zhou, Jelle Assink, Ian Bastow, Dino Bindi, Tom Blenkinsop, Raffaele Bonadio, Michael Braim, Tim Craig, Elizabeth Day, Giovanni Diaferia, Stuart Dunning, Ben Edwards, Ake Fagereng, Stewart Fishwick, Amy Gilligan, David Green, David Healy, Anna Horleston, Mark Ireland, Jenny Jenkins, Jessica Johnson, Mike Kendall, Tom Kettlety, Duygu Kiyan, Paula Koelemeijer, Rita Kounoudis, Victoria Lane, Chuanchuan Lu, Alan MacDonald, Fabrizio Magrini, Auggie Marignier, Carl Martin, Martin Möllhoff, Iain Neill, Andy Nowacki, Bob Paap, Simone Pilia, Sjoerd de Ridder, Elmer Ruigrok, Peidong Shi, Anna Stork, Alice Turner, Jim Whiteley, Anton Ziolkowski

Fluid Dynamics

Quasi-geostrophic Rayleigh-Bénard convection on the tilted $f$-plane

Benjamin Miquel, Abram Ellison, Michael A. Calkins et al. (+2 more)

Rapidly rotating Rayleigh-Bénard convection on a $f$-plane at colatitude $\vartheta_f$ is investigated numerically using an asymptotically reduced equation set valid in the limit of very rapid rotation. The equations provide a non-hydrostatic but quasi-geostrophic description in a non-orthogonal coordinate system. The tilt changes the structure of the large-scale barotropic condensate from large-scale vortices to zonal flows as the colatitude of the $f$-plane increases, with bistable states present for certain parameter ranges, extending prior work to a geophysically significant parameter regime. This behaviour is understood through the impact of broken rotation symmetry on the barotropic source terms resulting from baroclinic vortical stresses and baroclinic torque. As the tilt angle $\vartheta_f$ increases, global heat and momentum transport is reduced relative to upright-polar convection, a result that is explained through linear theory and nonlinear power maps both of which demonstrate increased attenuation of the domain of dynamically active spatial scales as the convective modes depart from a North-South alignment in the horizontal plane. A key finding is that the predominance of lateral thermal mixing allows for the maintenance of a persistent unstable mean temperature gradient that saturates at increasing forcing levels and remains insensitive to the colatitude.
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All authors Benjamin Miquel, Abram Ellison, Michael A. Calkins, Keith Julien, Edgar Knobloch

Optics

Spatiotemporal Terahertz Emission Nanoscopy of Spintronic Photocurrents

F. Paries, R. Rouzegar, J. Cai et al. (+9 more)

Capturing ultrafast spin and charge photocurrents on nanoscopic scales is essential for fundamental research in physics and engineering, as well as for future applications, such as novel spinorbitronic devices. Accessing the fundamental dynamics driven by changes in electronic energy, linear momentum, and angular momentum requires probing at its native spatiotemporal scales: femtoseconds and nanometers. However, experimental approaches achieving this simultaneous resolution remain scarce and instrumentally demanding. Near-field probing offers promising platforms to combine ultrafast and nanometer resolution typically with high sensitivity to out-of-plane electric fields. However, applying this technique to in-plane ultrafast coupled spin and charge currents is largely unexplored, although being highly application-relevant - from ultrafast spin transport in 2D materials to spin-to-charge conversion in spintronic terahertz emitters (STEs). Here, we fill this gap by performing spatiotemporal terahertz (THz) emission nanoscopy (TEN) of a photoexcited fiber-coupled STE using a scanning-probe microscope. We uncover a counterintuitive, dipolar spatial evolution of the near-field THz signal, which we show originates from the out-of-plane electric fields emerging from the in-plane spin-driven charge currents. Our findings explain why TEN is sensitive to ultrafast spin-driven in-plane charge currents, paving the way for TEN to become a fully vectorial probe for the spatiotemporal mapping of coupled nanoscale THz charge and spin dynamics.
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All authors F. Paries, R. Rouzegar, J. Cai, M. Dai, F. Selz, J. Koelbel, G. Lezier, D. Molter, D. M. Mittleman, G. von Freymann, X. Wu, T.S. Seifert

Physics and Society

Empathy Modeling in Active Inference Agents for Perspective-Taking and Alignment

Mahault Albarracin, Hongju Pae, Philip Wilson et al. (+4 more)

Artificial agents that model other agents must predict their behavior and determine whether their outcomes matter within action selection. We introduce an active inference framework that separates these components by combining a history-conditioned Theory of Mind model with an explicit other-regarding valuation parameter, $\lambda$. We instantiate the framework in the Iterated Prisoner's Dilemma. The joint empathy configuration $(\lambda_i,\lambda_j)$ reorganizes the long-run cooperation landscape: sufficiently strong and symmetric other-regarding valuation supports sustained mutual cooperation, whereas strong asymmetry exposes the more empathic agent to systematic exploitation. Along the symmetric diagonal, cooperation exhibits a sharp but continuous finite-precision crossover. Fixed-partner sweeps reveal that the apparent cooperation boundary is path-dependent and that temporal variability is elevated where those paths cross it. Online Bayesian inference over opponent parameters modestly facilitates cooperation near the behavioral boundary but does not substitute for other-regarding valuation. Direct model comparison likewise shows that opponent-sensitive prediction at $\lambda=0$ does not generate cooperation. Planning depth has a partner-dependent effect: it slightly reduces cooperation when modeled reciprocity is weak but strongly increases cooperation against a reciprocating partner such as tit-for-tat. These results distinguish prediction, planning, and prosocial valuation as separable but interacting components of social agency. They also reveal a central limitation of unconditional empathic concern: the same valuation that stabilizes mutual cooperation creates predictable vulnerability when concern is not reciprocated.
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All authors Mahault Albarracin, Hongju Pae, Philip Wilson, Anna Mikeda, Alejandro Jimenez-Rodriguez, Sanjeev V. Namjoshi, Harshil Shah

Optics · Cross-listed from quant-ph

Experimental Asynchronous Measurement-Device-Independent Quantum Cryptographic Conferencing

Yifeng Du, Yang Hu, Yufeng Liu et al. (+4 more)

The quantum cryptographic conferencing (QCC) protocol, which distributes identical secure keys to user groups, is a crucial component of the quantum network. Previous experimental works have implemented the measurement-device-independent (MDI) QCC, of which the key rate in an N-user network scales as $R\sim O(\eta^N)$. Building on the MDI QCC protocol, the asynchronous MDI QCC protocol theoretically integrates the mode-pairing scheme into QCC, significantly boosting the key rate to $R\sim O(\eta)$ in the ideal case, which is independent of the number of users, thus demonstrating greater application potential. Experimentally, in this Letter, we implement the three-user asynchronous MDI QCC network without phase locking by adopting the fast Fourier transform-based frequency difference estimation and the phase drift compensation technique. Finally, we achieve a key rate of about $4.470\times 10^{-9}$ bits per pulse under a maximum overall loss of about 59.6 dB. This Letter provides a scalable solution for the development of large-scale quantum communication networks in the future.
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All authors Yifeng Du, Yang Hu, Yufeng Liu, Wenhan Yan, Jinghao Zhang, Shining Zhu, Xiao-Song Ma

Fluid Dynamics

Advection-modulated gaseous diffusion through an orifice

Mario Sánchez Sanz and Antonio L. Sánchez

We examine flow and transport through an orifice in a flat wall separating semi-infinite atmospheres of two dissimilar gases. The analysis assumes steady conditions and order-unity values of the Schmidt number Sc and Péclet number Pe, such that advection and diffusion contribute comparably to mass and momentum transport. Mixing between the two gases induces order-unity variations in viscosity and density, resulting in coupled concentration and velocity fields. The solution yields the mass transfer rates of both gases, expressed in terms of an appropriately defined Sherwood number, as well as the overpressure required to sustain the flow, all as functions of Sc and Pe. An explicit analytical solution is obtained in the limit of small Pe, while numerical integration is used to describe flows with Pe = O(1). The mixing of hydrogen and air is used as an illustrative example that serves to highlight the influence of large gas-molecular-weight differences on the flow structure and associated mixing rate, with additional selected results given for the case of hydrogen and water vapor.
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Optics

Novel High-Scalability Architecture for Photonic Deep Learning

Yuxin Sun, Chun Gao, Jin Xie et al. (+5 more)

Photonic computing promises ultrafast and energy-efficient artificial intelligence. However, existing photonic neural networks (PNNs) remain functionally shallow and difficult to scale. Here we establish a theory-guided framework showing that power stability and complex-field correlation are the fundamental prerequisites for scalable, coherent PNNs. Building on these macroscopic principles, we introduce the Coherent, Compensated and Cross-connected (C3) unit - an architecture that integrates coherent nonlinearity, active loss compensation and native optical residual connectivity. Implemented on a silicon-on-insulator platform, the C3 unit provides reconfigurable activation functions and dynamic energy stabilization without external amplification. We validate this framework using a width-constrained spiral benchmark, in which the C3 unit substantially improves parameter utilization and power robustness relative to incoherent nonlinearities. In a high-complexity 1,623-class recognition task, our C3-enabled coherent residual network (CoP-ResNet) achieves a top-1 accuracy of 77.92%, whereas non-residual architectures fail to converge. Together, these results offer a physically grounded, theory-guided pathway toward greater optical processing depth, laying the foundation for next-generation, large-scale photonic computing architectures.
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All authors Yuxin Sun, Chun Gao, Jin Xie, Pan Wang, Zejie Yu, Yiwei Xie, Huan Li, Daoxin Dai

Applied Physics

LED-based multibeam photoacoustics combined with electrical circuit-based modeling for the analysis of multispecies mass transport through thin membranes

Pawel Rochowski

This work develops photoacoustic-based experimental methods for comprehensive characterization of multispecies mass transport from donor compartments to thin-membrane acceptor systems in perfect contact, supported by a dedicated mass transfer modeling framework. Multibeam configurations are implemented in photoacoustic setups operating in front-side detection and diffuse-reflection geometries. The setups are calibrated and adjusted prior to measurements by means of transmission-mode photoacoustic experiments conducted under steady-state conditions. Finally, the methodologies were applied to a model system undergoing photoinduced decay, enabling characterization of bulk transport kinetics as well as interfacial equilibration monitored through time-dependent changes in interfacial reflectivity. For the analysis of bulk transport data, a lumped electrical-circuit (EC) model is introduced. The model is formulated in tableau form, linking species population dynamics to an interaction matrix representing mass-transport couplings consistent with the underlying diffusion-reaction framework. A simplified approximation of the model is further proposed and validated against experimental results. The combined experimental-modeling framework provides an effective approach for quantitative analysis of coupled diffusion, reaction, and interfacial processes in thin-membrane systems.
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Chemical Physics

Electron Attachment Induced Shape Resonances in AT Base Pairs

Sneha Arora, Jishnu Narayanan SJ and Achintya Kumar Dutta

In this work, we investigated the influence of base pairing and {\pi}-{\pi} stacking interactions on electron attachment induced shape resonances in the adenine-thymine (AT) base pair. Resonance positions and widths are computed using a DLPNO based equation of motion coupled-cluster approach in conjunction with the Padé analytical continuation method. Seven {\pi}* shape resonances are identified for both linear and stacked AT geometries, consistent with the total number of resonances in isolated adenine and thymine. Natural orbital analysis reveals that low-energy resonances exhibit significant electron density delocalization over both nucleobases. This delocalization is enhanced in the stacked geometry, leading to appreciable stabilization and increased lifetimes of the resonance states. These results highlight the important role of intermolecular interactions in modulating electron attachment processes in DNA.
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