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Physics Physics

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Wednesday 17 December

Optics

Structural color palette of disordered colloids in the Rayleigh scattering regime

Kevin Vynck, Amina Bensalah-Ledoux, Chirine Saadi et al. (+5 more)

Structural coloration by Rayleigh scattering is widespread in nature and holds a prominent place in various art objects over a broad period of time. Beyond the common statement that Rayleigh scattering is the primary mechanism behind the multiple colored appearances of the sky, it appears that the relationship between material parameters and the colors appearing in different observation conditions has not been thoroughly explored so far. This study provides a comprehensive overview of Rayleigh scattering-based structural colors as functions of key material properties, and introduces a scalable, environmentally friendly method to fabricate solid composites with targeted colors in both reflection and transmission. Monte Carlo light transport simulations are performed to compute the structural color palette of disordered colloids – dielectric particles in a nonscattering matrix – in different observation modes. We provide a range of physical parameters in which the materials exhibit the same blue color in diffuse reflection and transmission. We also show that, counterintuitively, the addition of black absorbents to the matrix of a white (opaque) material can lead to the emergence of a blue coloration in diffuse reflection, thanks to the interplay between multiple scattering and absorption. Our predictions are validated by optical experiments on colloidal suspensions of Yttria-stabilized Zirconia (ZrO$_2$:Y$_2$O$_3$) nanoparticles in aqueous solutions. The potential of Rayleigh-scattering materials for visual arts and design is further supported by realizing solid-state composites based on abundant materials, namely borosilicate clays and hybrid silica-based glasses, using soft chemistry at room temperature.
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All authors Kevin Vynck, Amina Bensalah-Ledoux, Chirine Saadi, Cécile Le Luyer, Romain Thomas, Denis Chateau, Stéphane Parola, Anne Pillonnet

Computational Physics · Cross-listed from cs.LG

PIP$^2$ Net: Physics-informed Partition Penalty Deep Operator Network

Hongjin Mi, Huiqiang Lun, Changhong Mou et al. (+1 more)

Operator learning has become a powerful tool for accelerating the solution of parameterized partial differential equations (PDEs), enabling rapid prediction of full spatiotemporal fields for new initial conditions or forcing functions. Existing architectures such as DeepONet and the Fourier Neural Operator (FNO) show strong empirical performance but often require large training datasets, lack explicit physical structure, and may suffer from instability in their trunk-network features, where mode imbalance or collapse can hinder accurate operator approximation. Motivated by the stability and locality of classical partition-of-unity (PoU) methods, we investigate PoU-based regularization techniques for operator learning and develop a revised formulation of the existing POU–PI–DeepONet framework. The resulting Physics-informed Partition Penalty Deep Operator Network (PIP$^{2}$ Net) introduces a simplified and more principled partition penalty that improved the coordinated trunk outputs that leads to more expressiveness without sacrificing the flexibility of DeepONet. We evaluate PIP$^{2}$ Net on three nonlinear PDEs: the viscous Burgers equation, the Allen–Cahn equation, and a diffusion–reaction system. The results show that it consistently outperforms DeepONet, PI-DeepONet, and POU-DeepONet in prediction accuracy and robustness.
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All authors Hongjin Mi, Huiqiang Lun, Changhong Mou, Yeyu Zhang

Fluid Dynamics

AI-Accelerated Operator Learning Framework for Rarefied Microflows

Ehsan Roohi

The high computational cost of kinetic solvers such as DSMC remains a major challenge in rarefied flow simulations. This work presents a unified framework combining deep neural networks and neural operators to accelerate kinetic and hybrid solvers while preserving physical fidelity. GPU-native DNN surrogates eliminate costly moment-closure operations in Fokker Planck methods, achieving significant speedups without accuracy loss, while physics-guided and shock-aware DeepONet architectures enable accurate, data efficient modeling of multi regime micro nozzle, micro-step, and hypersonic flows. Extensions including ensemble uncertainty quantification and family-of-experts strategies further enhance robustness across wide Mach and Knudsen number ranges. Together, these results demonstrate a scalable and physics-consistent pathway toward real-time surrogate modeling in rarefied gas dynamics.
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Medical Physics

Cross-Axis Weighted Harmonic Method: A Frequency-Domain Approach for Enhanced Resolution in Magnetic Particle Imaging

Abuobaida M.khair, Wenjing Jiang, Moritz Wildgruber et al. (+2 more)

Magnetic Particle Imaging (MPI) is a promising imaging modality that tracks magnetic nanoparticles (MNPs) to generate real time, high-resolution images. However, achieving an optimal balance between strong signal strength and sharp image clarity remains challenging. Higher drive field frequencies improve the signal-to-noise ratio (SNR), but also risk image blurring due to nanoparticle relaxation effects. To address this, we developed an end-to-end MPI simulation framework that models MNPs behavior, magnetic field dynamics, signal acquisition, and image reconstruction across a wide frequency range (20 to 85 kHz). Central to this framework is Cross-Axis Harmonic Analysis (CAHA), a novel, frequency-domain signal processing technique that adaptively extracts high-SNR harmonics from the x, y, and z directions for improved signal reconstruction. Using a simulated 3D vascular phantom, CAHA significantly enhanced image quality, achieving sub-millimeter resolution (0.8 mm FWHM at 85 kHz), strong noise suppression (nRMSE as low as 0.01), and structural fidelity (SSIM up to 0.94 at 55 kHz). The peak SNR reached 29.7 dB at 85 kHz. The signal processed with CAHA was also tested with other reconstruction methods; when combined with total variation regularization, CAHA achieved a pSNR of 37.91 dB. Evaluation on the Open MPI dataset further demonstrated up to 20% resolution improvement, confirming CAHA's robustness on real-world data. Although minor blurring was observed at the highest frequency due to relaxation, CAHA consistently maintained image clarity. By leveraging directional harmonic content rather than the full signal, CAHA sets a new benchmark for sharper, faster, and more robust MPI imaging.
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All authors Abuobaida M.khair, Wenjing Jiang, Moritz Wildgruber, Wenjun Xi, Xiaopeng Ma

Physics and Society

The Least Action-Augmented Lanchester Model

Wei Liang, Han Hu, Lijie Sun et al. (+2 more)

The principle of least action, a fundamental principle in variational mechanics with broad applicability to classical physical systems, is employed to formulate a novel attrition model for combat dynamics. This formulation extends the Lanchester's square law through second-order temporal derivatives by requiring the resultant Euler-Lagrange equation to coincide with the classical Lanchester's equation. Initial conditions at a specified temporal point enable determination of subsequent system evolution through action minimization, while terminal boundary conditions permit backward reconstruction of combat trajectories. The model's validity is examined through historical analysis of WWII engagements: the Battle of Kursk and the Battle of Iwo Jima. Comparative studies with conventional Lanchester's square models demonstrate marked improvements in predictive accuracy regarding force strength progression, particularly in capturing non-linear attrition patterns characteristic of prolonged engagements.
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All authors Wei Liang, Han Hu, Lijie Sun, Pingxing Chen, Ming Zhong

Plasma Physics

Effects of Unequal Electron-Ion Plasma Beta on Pressure-Strain Interaction in Turbulent Plasmas

M. Hasan Barbhuiya and Subash Adhikari

A common occurrence in weakly collisional space plasmas is the unequal electron-ion temperatures. The pressure-strain interaction provides a mechanism-agnostic pathway for increasing plasma internal energy through spatiotemporally local isotropic compression and volume preserving deformation, yet its behavior under thermal disequilibrium is largely unexplored. We investigate this using five fully kinetic two-dimensional particle-in-cell simulations of undriven decaying turbulence by varying the initial electron-to-ion temperature ratio. By analyzing the species' internal energy density alongside a decomposition of the pressure-strain term, with a focus on the volume-preserving deformation that contains normal and shear contributions, we quantify how the initial temperature imbalance modifies the channels through which turbulence increases each species' internal energy density. The cumulative pressure-strain interaction tracks the change in internal energy for both electrons and ions, with the total deformation channel of energy conversion dominating. We discover that local changes to electron internal energy density are governed primarily by the shear deformation power density, concentrated in electron-scale current sheets, while the ion shear and normal deformation components cancel, yielding a much smaller net deformation power density that peaks around, rather than within, those electron-scale current structures. We find that the amplitudes and localization of deformation change, but preserve these qualitative trends. Together, these results show how thermal disequilibrium could shape species-dependent turbulent "heating rate", measured via pressure-strain interaction and approximated via only its shear deformation part, and provide a framework for interpreting energy evolution and conversion in space plasmas where unequal species temperature is the norm.
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Accelerator Physics

Machine learning-based prediction of magnet errors in storage ring light sources

Jianhao Xu

Magnet errors in storage rings significantly degrade beam performance, impacting the brightness and stability of the light source. Therefore, beam-based correction is crucial for the safe operation of machines and the stability of radiated photons. Unlike traditional correction methods such as linear optics from closed orbit, this paper proposes a machine learning (ML) framework to directly predict quadrupole/sextupole gradient errors and misalignment from beam position monitor-measured optics functions and closed-orbit distortion data. Based on a four-bend achromat storage ring lattice, we generate training datasets through ELEGANT numerical simulations and compare regression performance of Linear Regression, Support Vector Machine, Radial Basis Function Neural Network and Densely Connected Convolutional Network. Results demonstrate that ML models can effectively predict magnet errors and reconstruct ideal optics. This approach offers a novel strategy for accelerating storage ring commissioning and optimization, online diagnostics, and dynamic compensation for next-generation diffraction-limited rings.
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Biological Physics

Uncovering hidden protein conformations with high bandwidth nanopore measurements

Kyril Kavetsky, Sabine Hong, Chih-Yuan Lin et al. (+2 more)

Advanced nanopore measurements allow structural probing of molecules with high spatial and temporal resolution. We report high signal-to-noise, 1-10 MHz bandwidth, translocation measurements of the multi-state folding of heme protein cytochrome c in KCl solution through optimally designed silicon nitride pores of 2.3-3.3 nm diameter and 3.6-3.8 nm effective thickness, and an optimal concentration of a denaturant (Gdm-Cl). The pore diameter is slightly smaller than the protein size, forcing the protein to squeeze through the pore. The sufficiently large pore thickness allows enough time for protein probing at an applied field of approximately 250 kV/cm. Through Bayesian Information Criterion score analysis, current blockades reveal six distinct levels, attributed to specific protein states. We calculate the transition probabilities between the states and the conditional probabilities of the protein leaving the pore from each state. We validate the model by simulating events and comparing them to experimental data.
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All authors Kyril Kavetsky, Sabine Hong, Chih-Yuan Lin, Roger Yang, Marija Drndic

Applied Physics · Cross-listed from cond-mat.mtrl-sci

X-ray detected ferromagnetic resonance spectrometer with an out-of-vacuum photodetector

Tetsuro Ueno, Yasuo Takeichi, Masaki Mizuguchi et al. (+10 more)

X-ray detected ferromagnetic resonance (XFMR) spectroscopy is an experimental technique for element-specific spin dynamics in the GHz regime and has been utilized to study spintronic materials. The XFMR signal is usually obtained by detecting X-ray excited optical luminescence (XEOL) emitted from a sample substrate. Here, we report the development of an XFMR spectrometer that is designed to place a photodetector for XEOL detection outside an ultra-high-vacuum chamber. This configuration allows for the easy replacement of detectors, such as photodiodes, CCD cameras, and spectrometers, depending on the experimental requirements. We demonstrated the measurement of XEOL spectra from MgO using a visible light spectrometer as well as the detection of XFMR signals originating from the spin precession of a permalloy (Ni80Fe20) thin film using a photodiode detector. The XFMR spectrometer with an out-of-vacuum photodetector expands possibilities for advanced measurements such as XFMR microscopy.
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All authors Tetsuro Ueno, Yasuo Takeichi, Masaki Mizuguchi, Hideaki Iwasawa, Yoshiyuki Ohtsubo, Kanta Ono, Hiroyuki Okazaki, Songtian Li, Seiji Sakai, Tetsuya Yamaki, Tetsu Watanuki, Yoshinori Katayama, Chiharu Mitsumata

Optics · Cross-listed from cond-mat.mtrl-sci

Site-selective enhancement of Eu emission in delta-doped GaN

Amelia R. Klein, Hayley J. Austin, Fumikazu Murakami et al. (+7 more)

Europium-doped gallium nitride (GaN:Eu) is a promising platform for classical and quantum optoelectronic applications. When grown using organometallic vapor-phase epitaxy, the dominant red emission from Eu exhibits an inhomogeneous photoluminescence (PL) spectrum due to contributions from several non-equivalent incorporation sites that can be distinguished with combined excitation emission spectroscopy. Energy transfer from the GaN bandgap to the majority site is inefficient, limiting the performance of GaN:Eu LEDs and resulting in an inhomogeneous emission spectrum dominated by disproportionate contributions from minority sites. In this work, we use site-selective spectroscopy to characterize the photoluminescence properties of delta-doped structures with alternating doped and undoped layers of varying thicknesses and demonstrate that they selectively enhance emission from the majority site when compared to uniformly-doped samples. Samples with 2-nm and 10-nm doped layers show much greater PL intensity per Eu concentration as well as more efficient energy transfer to the majority site, which are both highly desirable for creating power-efficient LEDs. Meanwhile, a sample with 1-nm doped layers shows emission only from the majority site, resulting in a narrow, homogeneous emission spectrum that is desirable for quantum technologies. This utilization of delta-doping has the potential to be broadly applicable for engineering desirable defect properties in rare-earth doped semiconductors.
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All authors Amelia R. Klein, Hayley J. Austin, Fumikazu Murakami, Jamie Ford, Jun Tatebayashi, Masayoshi Tonouchi, Yasufumi Fujiwara, Volkmar Dierolf, Lee C. Bassett, Brandon Mitchell

Plasma Physics

Permanent magnet optimization of stellarators with coupling from finite permeability and demagnetization effects

Armin Ulrich, Mason Haberle and Alan A. Kaptanoglu

Permanent magnets provide an attractive path for shaping university-scale stellarator magnetic fields. Previous work has shown that greedy permanent magnet optimization (GPMO) can produce sparse, grid-aligned arrays that match target surfaces with high accuracy under an ideal rigid-remanence model. Here we extend this approach to a greedy permanent magnet optimization with macromagnetic refinement (GPMOmr) by introducing a block-level macromagnetic model that accounts for magnet-magnet and magnet-coil coupling from finite permeability and demagnetizing interactions, and apply it to the published magnet grid from the MUSE stellarator design. Finite-permeability effects produce degree-scale tilts and few-percent magnitude changes in individual magnets and modify the surface-normal field $\mathbf B\cdot\mathbf n$ only at the percent level, yet for a fixed layout they increase the standard squared-flux objective by more than a factor of two. When the same model is embedded in the greedy loop, GPMOmr achieves $f_B$ histories and final errors within a few percent of classical GPMO while producing visibly more nonuniform magnetization patterns. Our formulation provides a fast and practical tool for quantifying and incorporating finite-permeability effects in permanent-magnet stellarator designs, and offers a framework for extending permanent-magnet optimization to higher field strengths and to materials with stronger macromagnetic coupling.
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Geophysics

Contemporary Shrinking of Colombia's Highest Mountains: Pico Simon Bolivar and Pico Cristobal Colon

Eric Gilbertson, Kathryn E. Stanchak and Scott Hotaling

Pico Cristobal Colon and Pico Simon Bolivar are the highest peaks in Colombia and were last accurately surveyed in 1939. This historical survey measured Cristobal Colon, Colombia's recognized highpoint, at 5775m and Simon Bolivar at 5773m. Both peaks have permanent icecaps at their summits. For this study, multiple differential GPS units and an Abney level were used to re-survey each peak with sub-meter vertical accuracy. As of December 2024, the elevation of Simon Bolivar was 5720.42m +/- 0.08m and Cristobal Colon was 5712.79m +/- 0.87m. These measurements indicate that the ice caps of both peaks have shrunk dramatically since 1939: Simon Bolivar by 53m and of Cristobal Colon by 62m. Contrary to official recognition, Pico Simon Bolivar is now the highest mountain in Colombia. Increasing local temperatures suggest that the icecap melting of both peaks is due to climate change.
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Instrumentation and Detectors

High voltage and electrode system for a cryogenic experiment to search for the neutron electric dipole moment

M. A. Blatnik, S. M. Clayton, S. A. Currie et al. (+16 more)

The cryogenic approach to the search for the neutron electric dipole moment–performing the experiment in superfluid liquid helium–holds promise for a substantial increase in sensitivity, potentially enabling a sensitivity level of $10^{-28}$ e-cm. A crucial component in realizing such an experiment is the high voltage and electrode system capable of providing an electric field of 75 kV/cm. This, in turn, requires an electric potential of 635 kV to be applied to the high voltage electrode, while simultaneously satisfying other experimental constraints, such as those on heat load and magnetic noise requirements. This paper describes the outcome of a comprehensive development program addressing these challenges. It outlines the system requirements, discusses new insights into relevant physical phenomena, and details selected technical solutions with their corresponding experimental demonstrations and expected performance. The results collectively demonstrate the successful development of the necessary technology for the high-voltage and electrode system for this approach.
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All authors M. A. Blatnik, S. M. Clayton, S. A. Currie, B. W. Filippone, M. Makela, C. M. O'Shaughnessy, N. S. Phan, J. C. Ramsey, G. V. Riley, A. Roberts, T. Sandborn, T. J Schaub, G. M. Seidel, E. Smith, I. L. Smythe, J. Surbrook, W. Wei, W. Yao, T. M. Ito

Optics

Observation of non-Hermitian point gap in photonic crystals

Yuto Moritake, Nozomi Ogawa, Issei Takeda et al. (+7 more)

Non-Hermitian point gap (NHPG) is a unique phenomenon in non-Hermitian systems and induces non-Hermitian skin effect (NHSE). In photonic crystals, NHPG and the NHSE have previously been explored mainly through material loss, where the typically low $Q$ factors make direct observation of complex frequencies challenging. Here, we demonstrate the direct experimental observation of an NHPG by using a radiation-loss-based non-Hermitian photonic crystal. Radiation loss can be engineered through structural design, enabling control of the imaginary part of the complex frequency and allowing relatively high $Q$ factors. This approach is compatible with widely used absorption-free silicon-slab photonic crystals. We developed a measurement system that can measure photonic bands along arbitrary lines in $k$-space. Our measurements demonstrated direct observation of the NHPG in photonic crystals, and the reversal of non-Hermitian topology through the flip of loop rotation in a complex plane. Our platform, which requires neither gain media nor synthetic dimensions, establishes radiation-loss engineering as a simple and versatile route for photonic functionality using an NHSE in nanophotonic systems.
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All authors Yuto Moritake, Nozomi Ogawa, Issei Takeda, Yusuke Ohinata, Takahiro Uemura, Taiki Yoda, Kenta Takata, Eiichi Kuramochi, Hisashi Sumikura, Masaya Notomi

Tuesday 16 December

Optics

Self-referenced nonlinear interferometry for chromatic dispersion sensing across multiple length scales

Romain Dalidet, Sébastien Tanzilli, Gregory Sauder et al. (+2 more)

Chromatic dispersion critically impacts the performance of numerous applications ranging from telecommunication links to ultrafast optics and nonlinear devices, yet fast and precise measurements are challenging, especially for short length-dispersion products. We present a fully fiber-integrated nonlinear Sagnac interferometer that exploits cascaded second-order processes to generate frequency-anticorrelated idler light and achieve odd-order dispersion cancellation without active stabilization. The measurement is intrinsically self-referenced, as the dispersion-induced phase is extracted from the interference between counter-propagating nonlinear processes within the same Sagnac loop, eliminating the need for an external reference arm or prior calibration. Operating entirely at telecom wavelengths and read out on a standard optical spectrum analyzer, the device produces instantaneous, high-visibility fringes and calibration-free spectra using dual-port normalization. We demonstrate chromatic dispersion measurements on fiber samples ranging from 25 cm to 4 km, spanning short fiber segments to long-haul links. This architecture combines self-stability, broadband compatibility, and rapid acquisition, offering a practical metrology tool for both research and industry.
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All authors Romain Dalidet, Sébastien Tanzilli, Gregory Sauder, Laurent Labonté, Anthony Martin

Computational Physics

Non-Negativity, Non-Singularity and Energy Conservation of the Zonal Method with Non-Reciprocal Exchange Factors

Nikolaj Maack Bielefeld

This paper proves that the zonal balances of Hottel's method, written in power variables for a first-interaction exchange factor matrix $\mathbf{F}$, have a unique and non-negative solution for any combination of prescribed temperatures and prescribed source terms in which at least one element with prescribed temperature absorbs radiation, and that they conserve energy as an algebraic identity. The results hold for media ranging from transparent to absorbing, emitting and scattering, and for boundaries ranging from absorbing to reflecting. They require only that $\mathbf{F}$ be non-negative, row stochastic and irreducible: reciprocity is not needed, so the guarantees hold for Monte Carlo exchange factors as traced, without smoothing, which the symmetric notation of the zonal method does not make apparent. Both the non-singularity and the non-negativity follow from a single discrete minimum principle, and both have been machine-checked in Lean 4. To this end the balances are written as one linear system in the total radiant powers, $\mathbf{M}\mathbf{j} = \mathbf{h}$, assembled row by row from the prescribed temperatures and source terms, with a system matrix that inherits the sparsity of $\mathbf{F}$; the total exchange areas of Noble's matrix formulation are in general dense, and the two agree symbolically and numerically to machine precision. Validation is provided symbolically against the textbook closed-form solutions for infinite parallel plates and concentric cylinders, numerically against the results of Crosbie and Schrenker for pure and partial scattering, against an exact symmetry identity in a three-dimensional enclosure, and against the diffusion approximation in an optically thick problem with about $10^6$ elements, solved in about one minute.
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Fluid Dynamics

Entropy-Time Geodesics as a Universal Framework for Transport and Transition Phenomena

Sami Lakka

We develop a geometric framework for irreversible transport phenomena in which macroscopic evolution equations arise from the combined structure of a thermodynamic state metric and an Onsager-based dissipation metric. The construction begins by defining a pseudo-Riemannian manifold from the Hessian of an appropriate thermodynamic potential. When the enthalpy is used and written in variables (S,P), the resulting metric possesses a Lorentzian-type signature: entropy acts as a time-like coordinate, while pressure forms a spatial-like coordinate associated with mechanical response. Local irreversible dynamics are incorporated through the inverse Onsager matrix, which defines a positive-definite dissipation metric on the space of fluxes and gradients. A thermodynamic action integrating these two geometric layers yields geodesic evolution equations. For a Newtonian fluid with constant viscosity, the resulting Euler–Lagrange equations reproduce the incompressible Navier–Stokes equations without requiring an externally imposed constitutive closure. Within this framework, turbulence scaling emerges from competition between inertial curvature and dissipation metric stiffness. The Kolmogorov length scale appears as a minimum geometric resolution length where these contributions balance, providing a geometric interpretation of energy cascade termination and dissipation onset. Finite-time singularities in the classical PDE formulation correspond to curvature divergences in the transport geometry; however, the thermodynamic proper time diverges in such limits, suggesting that blow-up is dynamically suppressed in single-phase continua. Although derived explicitly for fluid flow, the framework is general: by choosing different thermodynamic potentials and Onsager matrices, the same geometric formulation applies to heat conduction, diffusion and other irreversible processes.
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Physics and Society

Physicists Are Still Joking

Igor Halperin

This volume, Physicists Are Still Joking, serves as a definitive almanac of scientific humor spanning sixty years. It traces the evolution of professional folklore across geopolitical divides and technological eras. Part I restores the classic 1966 anthology Physicists Joke, which originally served as a window for Soviet scientists into the best traditions of Western scientific humor; it consists primarily of articles translated from English, here meticulously restored to their original wording. Part II presents the 1992 sequel, Physicists Keep Joking, which captures the shift toward an original, introspective Russian scientific folklore born during the end of the Cold War and the collapse of the Soviet Union. Part III: Still Joking explores the modern digital age, compiling contemporary science humor from physics, astronomy, biology, computer science and AI research. While the tools of science have evolved from slide rules to neural networks, the tradition of skeptical, self-referential wit remains a constant. Spanning from the "Golden Age" of vacuum tubes to the era of AI and Large Language Models, this collection documents the enduring ability of scientists to laugh at the universe and themselves.
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Physics and Society

Women in Theoretical Quantum Physics in Brazil:demographics, career profiles, recognition, and leadership

Tatiana Pauletti, Paula Homem de Mello, Thereza Paiva et al. (+1 more)

Gender imbalance in Physics remains a persistent global challenge, and Brazil is no exception. While women account for only 24% of Physics faculty in the country, their representation in Quantum Physics is even smaller. In this work, we provide the first comprehensive overview of women working in Theoretical Quantum Physics in Brazil, here referred to as the SheQ (She + Quantum) community. Using data from the CNPq Lattes platform, we identify 93 researchers and analyze their geographic distribution, academic trajectories, scientific productivity, international experience, recognition through awards and fellowships, and engagement with initiatives promoting gender equity. Our results reveal both progress and persistent disparities: SheQ researchers have a strong scientific output, leadership roles, and international training; yet, their recognition through productivity fellowships remains modest, and their involvement in gender-related initiatives, although increasing among younger generations, remains limited. By combining quantitative indicators with institutional perspectives, we highlight structural barriers as well as opportunities for fostering a more inclusive environment in Quantum Physics. his study thus contributes to a broader reflection on how diversity not only promotes fairness but also strengthens creativity, innovation, and scientific progress.
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All authors Tatiana Pauletti, Paula Homem de Mello, Thereza Paiva, Vivian V.França

General Physics

From the thermodynamics of irreversible processes to dissipative structures and active matter

Pierre Gaspard

A historical perspective is presented on thermodynamics from the pioneering contributions by Carnot and Clausius to recent advances on active matter. Non-equilibrium thermodynamics develops from the identification of the irreversible processes contributing to entropy production in various types of materials and systems. These processes include friction, viscosity, heat and electric conductions, diffusion, reactions, and more. In 1954, Glansdorff and Prigogine formulated a general evolution criterion, which led to the theory of dissipative structures like chemical clocks, reaction-diffusion patterns, and convection patterns. Non-equilibrium statistical mechanics provides the microscopic foundations for the thermodynamics of irreversible processes.
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Physics and Society

Forsaking your own: unveiling the delayed recognition of Garfield's work on the "delayed recognition" phenomenon

Tariq Ahmad Mir and Marcel Ausloos

Delayed recognition (DR) implies that the full scholarly potential of certain scientific papers is recognized belatedly many years after their publication. Such papers are initially barely cited (sleep), and then suddenly, sometime in the future, their citation numbers burst (are awakened). After van Raan (2004a) called them "Sleeping Beauties" the DR phenomenon has drawn considerable attention. However, long before van Raan (2004a) Garfield studied the phenomenon in a series of articles from 1970 up to year 2004. In the present study we ask the pertinent question; Has the phenomenon of DR itself suffered the delayed recognition? In search of an answer we study the citation history of the Garfield (1980a) paper in which Garfield addressed DR directly for the first time. We find that the paper hardly received the attention befitting the Garfield's stature as an information scientist. Specifically, the paper received a meager of 10 citations up to the publication year of van Raan (2004a) and was then, in 2007, feebly awakened from its deep sleep of twenty-eight years receiving 20 citations in next four years; up to 2010. Being the undisputed giant of information science that even Garfield's paper on DR can suffer DR is hardly anticipated.
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General Physics

Constructing de Sitter space and Dark Matter with Dynamical Tension Strings

Eduardo Guendelman

The string tensions can be dynamical in the modified measure formalism and appear as an additional dynamical degrees of freedom . These tensions may not be universal, instead, each string generates its own tension. We then consider a new bulk field that can couple to the strings, the tension scalar which changes locally the tension along the world sheet. In the case with two string tensions there is a braneworld solution which gives rise to an induced de Sitter space in the brane, avoiding swampland constraints of the standard string theory. Strings with different tension to ours can appear also as Dark Matter and since they share the same space and compactifications as visible matter, they should lead to Dark copies of the standard model,
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Instrumentation and Detectors · Cross-listed from cond-mat.mtrl-sci

A High-Flux and High-Efficiency Setup for Magneto-Infrared Spectroscopy

Zeping Shi, Wenbin Wu, Zhiwei Zhang et al. (+14 more)

We report the design and implementation of a high-flux, high-efficiency magneto-infrared spectroscopy system optimized for broadband measurements in high magnetic fields. The setup integrates a Fourier transform infrared spectrometer, a 12 T cryogen-free superconducting magnet, precision-polished and gold-plated light tubes, custom-designed reflective focusing modules for Faraday and Voigt geometries, and an external multi-detector chamber with motorized selection. Optical throughput is maximized by reducing light tube loss from 65.5%/m to 22.0%/m via abrasive flow and mechanical polishing followed by gold electroplating, and by adopting a single-on-axis parabolic-mirror Faraday module that increases the effective numerical aperture from 0.14 to 0.36, enhancing collection efficiency by nearly an order of magnitude. An eight-position motorized sample stage and fully automated control over magnetic field, temperature, optical path, and detector choice enable high-throughput measurements without repeated warm-ups. The optimized configuration achieves a root-mean-square noise level of 0.0061% in a 2-minute integration for a 40% reflectivity sample, corresponding to a signal-to-noise ratio exceeding 16000. System capabilities are demonstrated by resolving weak replica bands in EuCd2As2 and faint Landau level transitions in LaAlSi.
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All authors Zeping Shi, Wenbin Wu, Zhiwei Zhang, Yuhan Du, Chenyao Xu, Guangyi Wang, Mingsen Zhou, Congming Hao, Xianghao Meng, Xiangyu Jiang, Chunhui Pan, Wei Lu, Hao Shen, Haifeng Pan, Zhenrong Sun, Junhao Chu, Xiang Yuan

Optics

Optical Response in Spintronic Poisson Bolometers

Ziyi Yang, Sakshi Gupta, Jehan Shalabi et al. (+5 more)

Analog bolometers based on temperature-dependent phase-transition materials such as vanadium oxide (VOx) and barium titanate (BTO) represent the state of the art in uncooled infrared detectors. Recently, the first room-temperature spintronic Poisson bolometer based on magnetic tunnel junctions (MTJs) was proposed and demonstrated as a promising infrared detector. Unlike conventional bolometers, the spintronic Poisson bolometer operates in a probabilistic regime dominated by Poissonian noise, where the response is governed by resistance fluctuations arising from thermally activated magnetization transitions. Spontaneous transitions between two metastable magnetic states occur even in the absence of incident light, and the transition probability increases under illumination. In this work, we experimentally study the statistical properties of the optical response of the spintronic Poisson bolometer under illumination. We demonstrate that transitions in spintronic Poisson bolometers, both in the absence and presence of light, exhibit Poissonian behavior, with transition rates and interarrival times modulated by incident radiation. Under illumination, we observe a 153% increase in the count rate accompanied by a 70% reduction in interarrival time. These results establish spintronic Poisson bolometers as a promising platform for probabilistic, high-speed, and high-sensitivity infrared detection at room temperature.
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All authors Ziyi Yang, Sakshi Gupta, Jehan Shalabi, Leif Bauer, Daien He, Mohamed A. Mousa, Angshuman Deka, Zubin Jacob

Computational Physics

Design of a specimen to train path-dependent deep learning material models from a single uniaxial test: eliciting strain diversity via automatically differentiable elastoplastic topology optimization

Shunyu Yin, Bernardo P. Ferreira, Gawel Kus et al. (+1 more)

Artificial neural networks accurately learn nonlinear, path-dependent material behavior. However, training them typically requires large, diverse datasets, often created via synthetic unit cell simulations. This hinders practical adoption because physical experiments on standardized specimens with simple geometries fail to generate sufficiently diverse stress-strain trajectories. Consequently, an unreasonably large number of experiments or complex multi-axial tests would be needed. This work shows that such networks can be trained from a single specimen subjected to simple uniaxial loading, by designing the specimen using a novel automatically differentiable elastoplastic topology optimization method. Our strategy diversifies the stress-strain states observed in a single test involving plastic deformation. We then employ the automatically differentiable model updating (ADiMU) method to train the neural network surrogates. This work demonstrates that topology-optimized specimens under simple loading can train large neural networks, thereby substantially reducing the experimental burden associated with data-driven material modeling.
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All authors Shunyu Yin, Bernardo P. Ferreira, Gawel Kus, Miguel A. Bessa

Instrumentation and Detectors

Adding Radio Frequency Capabilities to a millikelvin Scanning Tunneling Microscope

Jonathan Marbey, Michael Dreyer and R.E. Butera

We present a simple home made solution enabling in-situ RF reflectometry measurements with a millikelvin scanning tunneling microscope (mk-STM). The additions described below were made using RF best practices following similar detection schemes commonly employed in the quantum information science (QIS) community. Using a Niobium STM tip to form a superconductor-insulator-normal metal (SIN) tunnel junction, the evolution of coherence peaks at the SC-gap edge are carefully measured to characterize the RF losses and electron temperature. We further identify impedance matching as a crucial factor to achieve high sensitivity in the reflectometry by tuning the tip-sample capacitance as a function of approach distance. As a demonstration of this capability, we measure a 50x50 nm$^2$ area of island features that have been condensed onto the surface of a gold single crystal. Position dependent reflectometry losses allow us to image island sizes down to a total surface area of 5 nm$^2$ given our current sensitivity.
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Instrumentation and Detectors

The PANDA Barrel DIRC: From design to assembly

G. Schepers, A. Belias, R. Dzhygadlo et al. (+16 more)

The Barrel DIRC counter will serve as the primary particle identification detector in the PANDA experiment, enabling high-precision hadron physics studies through antiproton-proton annihilations across a momentum range of 1.5 GeV/c to 15 GeV/c. It is designed to distinguish charged pions from kaons with a separation of at least 3 standard deviations up to 3.5 GeV/c within polar angles of 22 degrees to 140 degrees. A lens focusing is used the first time in a DIRC detector. After a successful evaluation in particle beams, the key components, i.e. radiator bars and photon sensors, were purchased and tested.
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All authors G. Schepers, A. Belias, R. Dzhygadlo, A. Gerhardt, D. Lehmann, K. Peters, C. Schwarz, J. Schwiening, M. Traxler, Y. Wolf, L. Schmitt, M. Böhm, K. Gumbert, S. Krauss, A. Lehmann, D. Miehling, M. Schmidt, C. Sfienti, A. Ali

Fluid Dynamics

A Dynamic Subgrid-Scale Model Based on Liutex Theory for Wall-Bounded Turbulent Flows

Jiawei Chen, Yifei Yu and Chaoqun Liu

Accurate subgrid-scale (SGS) modeling remains a major challenge in large eddy simulation (LES), particularly for wall-bounded turbulent flows with strong near-wall anisotropy. This study proposes a novel SGS model based on Liutex theory, featuring a dynamically adaptive model coefficient and a physics-based length-scale formulation. The magnitude of the Liutex vector is employed as the characteristic velocity scale, enabling a direct and objective quantification of local vortical intensity. The length scale is determined from local flow properties and reflects the physical nature of turbulent diffusion, which occurs predominantly in directions perpendicular to the rotation axis. The dynamic model coefficient adapts locally to variations in vortical structures and naturally vanishes at the wall. Importantly, this coefficient is free of empirical tuning, as it is derived rigorously from the triple decomposition. The model is validated through LES of turbulent channel flow at the friction Reynolds number of 544. Results show improved predictions of both normal and shear Reynolds stresses, particularly in near-wall regions, compared with other SGS models. The proposed model demonstrates competitive computational efficiency, with only a 4.21% overhead.
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Applied Physics · Cross-listed from nlin.CD

Scaling law for the slow flow of an unstable mechanical system coupled to a nonlinear energy sink

Baptiste Bergeot

In this paper one first shows that the slow flow of a mechanical system with one unstable mode coupled to a Nonlinear Energy Sink (NES) can be reduced, in the neighborhood of a fold point of its critical manifold, to a normal form of the dynamic saddle-node bifurcation. This allows us to then obtain a scaling law for the slow flow dynamics and to improve the accuracy of the theoretical prediction of the mitigation limit of the NES previously obtained as part of a zeroth-order approximation. For that purpose, the governing equations of the coupled system are first simplified using a reduced-order model for the primary structure by keeping only its unstable modal coordinates. The slow flow is then derived by means of the complexification-averaging method and, by the presence of a small perturbation parameter related to the mass ratio between the NES and the primary structure, it appears as a fast-slow system. The center manifold theorem is finally used to obtain the reduced form of the slow flow which is solved analytically leading to the scaling law. The latter reveals a nontrivial dependence with respect to the small perturbation parameter of the slow flow dynamics near the fold point, involving the fractional exponents 1/3 and 2/3. Finally, a new theoretical prediction of the mitigation limit is deduced from the scaling law. In the end, the proposed methodology is exemplified and validated numerically using an aeroelastic aircraft wing model coupled to one NES.
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Chemical Physics

Sample-based quantum diagonalization as parallel fragment solver for the localized active space self-consistent field method

Qiaohong Wang, Mario Motta, Ruhee D'Cunha et al. (+7 more)

Accurately and efficiently describing strongly correlated electronic systems is a central challenge in quantum computational chemistry, with classical and quantum computers. The localized active space self-consistent field method (LASSCF) uses a product of fragment active spaces as a variational space, with the Schrödinger equation solved exactly in each fragment and the fragment active-space orbitals defined in a self-consistent manner. LASSCF is accurate for systems with strong intra-fragment and weak inter-fragment correlation, and its computational cost is combinatorial with respect to the size of the individual fragment active spaces, rather than their product. However, exactly solving the Schrödinger equation in each fragment remains a substantial bottleneck. Here, we address the possibility of solving the fragment active space Schrödinger equation with approximate methods, particularly sample-based quantum diagonalization (SQD). SQD is a technique that uses a quantum computer to sample configurations from a chemically motivated quantum circuit and a classical computer to mitigate errors and solve the Schrödinger equation in a subspace of the configuration space. We apply the proposed method, LASSQD, to the [Fe(H$_2$O)$_4$]$_2$bpym$^{4+}$ compound and the [Fe$^{\mathrm{III}}$Fe$^{\mathrm{III}}$Fe$^{\mathrm{II}}$($\mu$$_3$-O)-(HCOO)$_6$] complex for calculating the intermediate-spin ground state energies. We observe that LASSQD can tackle fragment sizes intractable by LASSCF, achieves within 1kcal/mol agreement to LASSCF, and delivers results that are competitive with alternative classical methods to solve the Schrödinger equation, and thus can be used as a starting point for a perturbative treatment (LASSQD-PDFT) to recover correlation external to the active space.
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All authors Qiaohong Wang, Mario Motta, Ruhee D'Cunha, Kevin J. Sung, Matthew R. Hermes, Tanvi Gujarati, Yukio Kawashima, Yu-ya Ohnishi, Gavin O. Jones, Laura Gagliardi