Peer Revenue Equity in science

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics Physics

physics Watch Physics

Friday 3 April

Instrumentation and Detectors

Design and Performance of a Monolithic Plastic Scintillator Tracker with Embedded Scatterers

Naoki Otani, Seungho Han, Shun Ito et al. (+4 more)

We propose a new scintillator-based tracker concept based on a monolithic plastic scintillator plate with embedded scatterers and wavelength-shifting fiber readout. The embedded scatterers localize scintillation light so that channels closer to the charged-particle crossing point collect more light. The particle crossing position is reconstructed from the channel-to-channel light yield distribution with a position resolution well below the readout pitch. We performed a positron beam test with prototypes to validate the reconstruction principle and to evaluate the detection efficiency and position resolution. The beam test validated the position reconstruction principle, and demonstrated a near-100% detection efficiency and a position resolution of 1.47 mm for normal incidence and 1.85 mm for an incidence angle of 45{\deg}, with a 10-mm readout pitch. In this paper, we describe the detector concept, the reconstruction method, and the results of the beam test.
Read the full abstract

All authors Naoki Otani, Seungho Han, Shun Ito, Tatsuya Kikawa, Tsuyoshi Nakaya, Mihiro Suzuki, Atsushi Tokiyasu

Plasma Physics

Finite Ion Temperature Effects on the Merging of Current-Carrying ELM Filaments in the edge region of a tokamak

Souvik Mondal, Nirmal Bisai, Abhijit Sen et al. (+1 more)

Edge-localized-mode (ELM) filaments are crucial for cross-field transport at the tokamak edge; yet, their dynamics are often analyzed using the cold-ion approximation, despite experimental data indicating that Ti~Te . This study employs a normalized three-dimensional fluid model to investigate the influence of finite ion temperature on the dynamics of unidirectional current-carrying ELM-like filaments. We demonstrate that increasing ion temperature substantially alters filament propagation and interaction, resulting in a delay of filament merging despite an increase in total kinetic energy due to a stronger pressure-gradient drive. The examination of single-filament dynamics indicates that finite ion temperature generates asymmetric potential structures, strong poloidal flows, and persistent rotational motion, which channel kinetic energy from radial propagation into vortical dynamics. A comprehensive examination of the ion-to-electron temperature ratio reveals a distinct transition from radially dominated to rotation-dominated behavior as ion temperature increases. These results provide a unified physical explanation for reduced radial transport and delayed merging in the warm-ion domain, emphasizing the necessity of incorporating ion temperature effects in the modeling of ELM filament dynamics and edge plasma transport.
Read the full abstract

All authors Souvik Mondal, Nirmal Bisai, Abhijit Sen, Indranil Bandyopadhyay

Computational Physics · Cross-listed from math.AP

Embedding transmission problems for Maxwell's equations into elliptic theory

Yuri A. Godin and Boris Vainberg

We embed general boundary value problems for the time-harmonic Maxwell equations into the elliptic boundary value theory. This is achieved by introducing two new scalar functions to the electromagnetic field and imposing additional boundary conditions, after which the problem becomes elliptic. The results are applied to general problems for Maxwell's equations in bounded and unbounded domains, as well as to the transmission problem with inhomogeneities on the right-hand side of the equations and at all boundaries. Relations between the inhomogeneities of the elliptic problem are established that provide a one-to-one correspondence between the solutions of Maxwell's problem and the solutions of the elliptic boundary value problem. As an application, the existence of an orthogonal basis from the eigenfunctions of the general Maxwell's problem is justified.
Read the full abstract

Applied Physics

Nonlinear interface effects in multilayered structures: vibro-acoustic modeling and experimental analysis

Antoine Demiquel, Kerem Ege and Emmanuel Gourdon

This paper presents an experimental and theoretical study of the nonlinear behavior of imperfect interfaces in multilayer structures using an equivalent vibro-acoustic approach. The multilayer system is modeled through a Zig-Zag formulation, in which interfacial coupling conditions, stress continuity and displacement discontinuity, relate the kinematics of adjacent layers while preserving an independent description of each layer. This framework significantly reduces the number of kinematic unknowns without compromising the model accuracy. An equivalent Kirchhoff-Love plate formulation is then introduced to derive a frequency-dependent bending stiffness representative of the global structural response. Experimental measurements of the transverse displacement field are performed using laser vibrometry and processed via the Corrected Force Analysis Technique (CFAT).The results demonstrate that the dynamic response of a three-layer beam with imperfect interfaces depends on the excitation level. In particular, variations in the equivalent bending stiffness are observed, revealing the nonlinear nature of the interfacial behavior. The proposed methodology is applied to a glass-epoxy-glass multilayer beam under various excitation levels.
Read the full abstract

Instrumentation and Detectors

The Darkside-20k Data Acquisition System

Fabio Acerbi, Pushparaj Adhikari, Paolo Agnes et al. (+289 more)

DarkSide-20k is a WIMP search experiment using liquid argon as a target, designed to perform a background-free search for dark matter with unprecedented sensitivity, and is currently under construction at INFN Laboratori Nazionali del Gran Sasso, Italy. The detector comprises a dual-phase Time Projection Chamber complemented with external veto systems and is equipped with a total of 2720 SiPM-based readout channels. This work presents the DAQ system designed for DarkSide-20k. The system is capable of continuous, triggerless digitisation of the waveforms with high single-photoelectron detection efficiency and online processing, ensuring data reduction for long-term storage. The DarkSide-20k DAQ system employs commercial CAEN VX2745 digitisers with custom FPGA firmware implementation. Timing and synchronisation across all 48 digitisers are provided by custom Global and Crate Data Manager boards distributing a phase-aligned clock derived from a disciplined rubidium standard. Waveform segments are processed in real time by Front End Processor machines. Data are organised into collections containing whole detector information and distributed across a farm of Time Slice Processors for event reconstruction, classification, and further reduction before storage and offline analysis. A full "Quadrant" of the system, corresponding to one quarter of the final DAQ, has been assembled and validated at TRIUMF laboratory in Canada. The Quadrant has been stress-tested with simultaneous pulses and demonstrated sustained digitizer readout exceeding expected physics rates and stable long-term performance.
Read the full abstract

All authors Fabio Acerbi, Pushparaj Adhikari, Paolo Agnes, Iftikhar Ahmad, Sebastiano Albergo, Ivone F.M. Albuquerque, Thomas Olling Alexander, Andrew Knight Alton, Pierre-Andre Amaudruz, Gioacchino Alex Anastasi, Michele Angiolilli, Elena Aprile, David J. Auty, Maximo Ave Pernas, Oscar Azzolini, Henning Olling Back, Zoe Balmforth, Ana Isabel Barrado Olmedo, Pierre Barrillon, Giovanni Batignani, Swadheen Bharat, Pritindra Bhowmick, Sofia Blua, Valerio Bocci, Walter Bonivento, Bianca Bottino, Mark G. Boulay, Titanilla Braun, Andrzej Buchowicz, Severino Bussino, Jose Busto, Matteo Cadeddu, Mariano Cadoni, Roberta Calabrese, Vincenzo Camillo, Alessio Caminata, Nicola Canci, Andrea Capra, Mauro Caravati, Miguel Cardenas-Montes, Nicola Cargioli, Marco Carlini, Paolo Castello, Paolo Cavalcante, Susana Cebrian, Alexander Chepurnov, Sarthak Choudhary, Luisa Cifarelli, Yann Coadou, Ivan Coarasa, Valentina Cocco, Estefania Conde Vilda, Lucia Consiglio, Harrison Coombes, Andre Filipe Ventura Cortez, Barbara S. Costa, Milena Czubak, Saverio D'Auria, Manuel Dionisio Da Rocha Rolo, Alexander Dainty, Giovanni Darbo, Stefano Davini, Riccardo de Asmundis, Sandro De Cecco, Marzio De Napoli, Giulio Dellacasa, Alexander Derbin, Lea Di Noto, Philippe Di Stefano, Daniel Diaz Mairena, Carlo Dionisi, Grigory Dolganov, Francesca Dordei, Aaron Elersich, Emma Ellingwood, Tyler Erjavec, Niamh Fearon, Marta Fernandez Diaz, Luca Ferro, Andrea Ficorella, Giuliana Fiorillo, Dylon Fleming, Paolo Franchini, Davide Franco, Heriques Frandini Gatti, Federico Gabriele, Devidutta Gahan, Cristiano Galbiati, Grzegorz Galinski, Giacomo Gallina, Marco Garbini, Pablo Garcia Abia, Andrzej Gawdzik, Graham Kurt Giovanetti, Alberto Gola, Luca Grandi, Gianfrancesco Grauso, Giovanni Grilli di Cortona, Alexey Grobov, Maxim Gromov, Julian Guerrero Canovas, Marisa Gulino, Samuel Belayneh Habtemariam, Brianne Rae Hackett, Aksel Hallin, Malgorzata Haranczyk, Timothee Hessel, Celin Hidalgo, James Hollingham, Sosuke Horikawa, Jie Hu, Fabrice Hubaut, Daniel Huff, Theo Hugues, Andrea Ianni, Valerio Ippolito, Ako Jamil, Chris Jillings, Rijeesh Keloth, Nikolas Kemmerich, Ashlea Kemp, Kaori Kondo, George Korga, Lucy Kotsiopoulou, Seraphim Koulosousas, Pablo Kunze, Michael Kuss, Marcin Kuzniak, Maciej Kuzwa, Marco La Commara, Michela Lai, Emmanuel Le Guirriec, Elizabeth Leason, Alfiero Leoni, Lance Lidey, John D Lipp, Marcello Lissia, Ludovico Luzzi, Olga Lychagina, Oliver Macfadyen, Janna Machts, Igor Machulin, Szymon Manecki, Ioannis Manthos, Andrea Marasciulli, Stefano Maria Mari, Camillo Mariani, Jelena Maricic, Maria Martinez, Giuseppe Matteucci, Konstantinos Mavrokoridis, Arthur B. McDonald, Luo Meng, Stefano Merzi, Andrea Messina, Radovan Milincic, Graham Miller, Saverio Minutoli, Ankush Mitra, Jocelyn Monroe, Matteo Morrocchi, Abdulrahman Morsy, Valentina Muratova, Michael Murra, Carlo Muscas, Paolo Musico, Rosario Nania, Marzio Nessi, Grzegorz Nieradka, Konstantinos Nikolopoulos, Evangelia Nikoloudaki, Jaroslaw Nowak, Konstantin Olchanski, Andrey Oleinik, Paolo Organtini, Alfonso Ortiz de Solorzano, Anantha Padmanabhan, Marco Pallavicini, Luciano Pandola, Emilija Pantic, Eugenio Paoloni, Danial Papi, Byungju Park, Grzegorz Pastuszak, Giovanni Paternoster, Riccardo Pavarani, Alec Peck, Paolo Attilio Pegoraro, Krzysztof Pelczar, Ramon Perez, Vicente Pesudo, Stefano Piacentini, Noemi Pino, Guillaume Plante, Andrea Pietro Pocar, Stephen Pordes, Pascal Pralavorio, Elettra Preosti, Darren Price, George Prior, Manuel Pronesti, Sebastiana Puglia, Maria Cecilia Queiroga Bazetto, Fabrizio Raffaelli, Francesco Ragusa, Yorck Ramachers, Alejandro Ramirez, Sudikshan Ravinthiran, Marco Razeti, Andrew Lee Renshaw, Aras Repond, Marco Rescigno, Silvia Resconi, Fabrice Retiere, Ash Ritchie-Yates, Angelo Rivetti, Adam Roberts, Conner Roberts, Diego Rodriguez Rodas, Giovanni Rogers, Luciano Romero, Matteo Rossi, Dmitry Rudik, James Runge, Maria Adriana Sabia, Camilla Salerno, Paolo Salomone, Simone Sanfilippo, Daria Santone, Roberto Santorelli, Edivaldo M. Santos, Isobel Sargeant, Maria Luisa Sarsa, Claudio Savarese, Eugenio Scapparone, Fred Schuckman, Dmitriy Semenov, Carmen Seoane, Michela Sestu, Veronika Shalamova, Sanjay Sharma Poudel, Marino Simeone, Peter Skensved, Mikhail Skorokhvatov, Taisiia Smirnova, Ben Smith, Robert Smith, Franco Spadoni, Martin Spangenberg, Arianna Steri, Vincenzo Stornelli, Simone Stracka, Allan Sung, Clea Sunny, Yury Suvorov, Andrzej M Szelc, Oscar Taborda, Benjamin Tam, Roberto Tartaglia, Alan Taylor, Jonathan Taylor, Gemma Testera, Kevin Thieme, Angus Thompson, Sebastian Torres-Lara, Alessia Tricomi, Sara Tullio, Evgeniy Unzhakov, Marie Van Uffelen, Pedro Ventura, Guillermo Vera Diaz, Simon Viel, Alina Vishneva, Bruce Vogelaar, Joost Vossebeld, Bansari Vyas, Masayuki Wada, Marek Bohdan Walczak, Yi Wang, Shawn Westerdale, Laurie Williams, Marcin Marian Wojcik, Mariusz Wojcik, Changgen Yang, Jilong Yin, Azam Zabihi, Paul Zakhary, Andrea Zani, Haoxiang Zhan, Yongpeng Zhang, Antonino Zichichi, Grzegorz Zuzel

Optics

Ho:YAG Thin-Disk Laser with 230 W Multimode and 150 W Single-Mode Output

Xiyi Wang, Xudong Yan, Weichao Yao et al. (+1 more)

We report a continuous-wave Ho:YAG thin-disk laser operating at the hundred-watt power level. In multimode operation, the laser delivers a maximum output power of 230 W, with a slope efficiency of 35.9% and an optical-to-optical conversion efficiency of 35.3%. In single-mode operation, an output power of 152.3 W is achieved, with beam quality factors M2 of 1.08 and 1.06 in the horizontal and vertical directions, respectively.
Read the full abstract

All authors Xiyi Wang, Xudong Yan, Weichao Yao, Yuxin Leng

Optics

Spatial mapping of quantum-dot dynamics across multiple timescales at low temperature using remote asynchronous optical sampling

Gen Asambo, Riku Shibata, Yushiro Takahashi et al. (+3 more)

Quantum dots (QDs) offer significant potential for applications in quantum information and optoelectronic devices; however, conventional time-resolved spectroscopy cannot generally simultaneously extract both long-lived relaxation dynamics and short-lived quantum beats from ensemble measurements. This limitation arises from the inherent trade-off between temporal resolution and total acquisition time. Here, we demonstrate that asynchronous optical sampling based on a fiber-delivered frequency comb enables simultaneous observation of QD dynamics across multiple timescales. By integrating a galvanometric scanner, we achieve spatial mapping over a $1 \times 1$-\si{\milli\meter}$^2$ area at 441 discrete points in 30.1~min, a measurement that would otherwise require more than 12~days. At each location, both quantum beats and relaxation lifetimes are resolved, giving physical insights into QD ensembles that were previously inaccessible and paving the way for rapid feedback in device fabrication.
Read the full abstract

All authors Gen Asambo, Riku Shibata, Yushiro Takahashi, Kouichi Akahane, Shinichi Watanabe, Junko Ishi-Hayase

Chemical Physics

Dataset Distillation for Machine Learning Force Field in Phase Transition Regime

Ruiyang Chen, Qingyuan Zhang and Ji Chen

Machine learning force field (MLFF) has emerged as a powerful data-driven tool for atomistic simulations, enabling large-scale and complex atomic systems to be simulated with accuracy comparable to ab initio methods. However, MLFFs often suffer from low training efficiency in the phase transition regime, where structural fluctuations are significantly elevated. To address this challenge, we propose a Central-Peripheral Distillation (CPD) algorithm for training dataset distillation. By strategically integrating representative samples with critical corner cases, the CPD algorithm ensures that the distilled dataset retains maximum structural diversity. We validated the efficacy of the CPD method on the liquid-liquid phase transition of dense hydrogen. Results show that, with the CPD approach, only 200 configurations are sufficient to train a MLFF that can fully reproduce the structural and dynamical properties of liquid hydrogen in the vicinity of its phase transition regime. This work paves the way for high-fidelity labeling of the MLFF training datasets, for instance by adopting high-level ab initio calculations beyond the standard density functional theory, thereby enhancing the predictive accuracy of MLFFs.
Read the full abstract

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

Maximizing the magnetic anisotropy of Dy complexes by fine tuning organic ligands: A systematic multireference high-throughput exploration of over 30k molecules

Lion Frangoulis, Lorenzo A. Mariano. Vu Ha Anh Nguyen, Zahra Khatibi et al. (+1 more)

The design of the coordination environment of magnetic ions is key to achieving properties such as large magnetic anisotropy and slow magnetic relaxation, but a systematic exploration of the relevant chemical space for these compounds is missing. Here, we automatically extract all entries of mononuclear Dy coordination complexes from crystallographic databases and use multireference ab initio methods to compute their magnetic anisotropy. In addition, we generate and simulate magnetic anisotropy for 25k new molecules with the general formula [Dy(H$_2$O)$_5$L$_2$]$^{n-}$ and pentagonal bipyramidal coordination geometry, a motif selected as very promising. While no molecule with record magnetic anisotropy is serendipitously identified in crystallography databases, molecules with crystal field splittings over 1600 cm$^{-1}$ are identified by systematically exploring new organic ligands. This corresponds to a ~100% increase of magnetic anisotropy over the reference compound, ~30% over any known pentagonal bipyramidal Dy complex, and approaching record values of pseudo bi-coordinated Dy ions. This study demonstrates that the fine-tuning of Dy's second coordination sphere by organic ligands design can significantly improve magnetic anisotropy and that automated computational screening is key to accelerating this chemically non-intuitive process.
Read the full abstract

All authors Lion Frangoulis, Lorenzo A. Mariano. Vu Ha Anh Nguyen, Zahra Khatibi, Alessandro Lunghi

Chemical Physics

Regio-Connectivity and Torsional Angle Effects on Singlet Fission and SOCT-ISC in Aza-BODIPY Dimers

Sophiya Goyal and S. Rajagopala Reddy

Aza-BODIPY dimers represent promising molecular systems for efficient triplet-state generation through either intramolecular-singlet fission (iSF) or spin-orbit charge transfer intersystem crossing (SOCT-ISC). In this work, we investigate the role of molecular geometry in governing these mechanisms across four regioisomeric aza-BODIPY dimers (D[1,1], D[1,3], D[3,3], and D[2,2]) using multireference quantum-chemical calculations. Ground- and excited-state properties were analyzed at the MP2 and SA-XMCQDPT levels of theory, while diabatic couplings and spin-orbit matrix elements were evaluated to estimate iSF and SOCT-ISC rate constants, respectively. Our results reveal that triplet formation is strongly governed by the torsional angle ({\Phi}) between monomer units, with regio-connectivity exerting a secondary influence. Dimers D[1,1] and D[1,3] exhibit favorable iSF energetics and coupling magnitudes, whereas D[2,2] displays low iSF rate constant (kSF ) but enhanced SOCT-ISC activity. The D[3,3] dimer shows exothermic multiexciton formation but reduced iSF efficiency due to destructive coupling interactions. The dominant ISC channel proceeds through the S1-T3 transition with large spin-orbit coupling and a small energy gap. These findings provide critical mechanistic insights into geometry-dependent triplet generation in aza-BODIPY dimers.
Read the full abstract

Fluid Dynamics

How pore-scale disorder controls fluid stretching in two-dimensional porous media

J. Kevin Pierce, Tanguy Le Borgne, François Renard et al. (+1 more)

Fluid stretching in porous media governs the mixing of reactants, contaminants, and nutrients, yet how the solid microstructure controls the stretching statistics remains poorly understood. We investigate how porous-medium heterogeneity controls stretching using (i) particle-tracking velocimetry experiments in 3D-printed millifluidic cells, (ii) numerical simulations of solute-plume deformation in the measured flow fields, and (iii) analytical calculations of fluid stretching. The cells contain arrays of cylindrical rods with systematically-varying disorder levels, from ordered to random. Velocity and shear-rate measurements reveal that fluid deformation is strongly localized near solid boundaries for all disorder levels, suggesting that near-wall flow is the main driver of stretching. The mean stretching grows linearly in time for ordered media and quadratically for disordered media, while the stretching distributions are approximately log-normal. We analytically describe the stretching produced by flow around an isolated cylinder and embed this description in a random-walk model that reproduces the observed stretching statistics in random media. These results provide the first quantitative connection between porous-medium structure and fluid-stretching statistics, revealing the extent to which disordered media accelerate mixing relative to ordered media and enabling progress beyond the common mean-field description of stretching in two-dimensional media as a simple shear flow.
Read the full abstract

All authors J. Kevin Pierce, Tanguy Le Borgne, François Renard, Gaute Linga

Fluid Dynamics · Cross-listed from cond-mat.mes-hall

Nanomechanical detection of vortices in an electron fluid

Andrey A. Shevyrin, Askhat K. Bakarov and Arthur G. Pogosov

Electron vortices are the quintessential signature of a viscous electron fluid. For decades, their detection relied on indirect transport measurements with persistently debated interpretations. Recently, scanning magnetometry enabled direct visualization, yet these techniques demand considerable sophistication. Here we introduce a conceptually different and inherently simpler paradigm based on nanomechanics. By integrating a circular cavity into a suspended resonator, we create a vortex whose circulating current generates a magnetic moment. In an in-plane magnetic field, this moment experiences a torque, driving vibrations that directly reveal the vortex's presence and nature. We detect ballistic and hydrodynamic vortices and trace their temperature-driven crossover. Our work establishes nanomechanics as a platform for electron hydrodynamics, showing that viscosity - subtle in transport - is one of the dominant factors shaping nanoelectromechanical response.
Read the full abstract

Applied Physics · Cross-listed from cond-mat.stat-mech

Resetting dynamics in a system with quenched disorder

Riya Verma, Binayak Banerjee, Shamik Gupta et al. (+1 more)

Although resetting has widespread applicability, applying it to the dynamics in the presence of spatial quenched disorder, which is essential in many physical problems, is challenging. In this study, we consider a well-known one-dimensional model of particle hopping on a lattice with quenched disorder in the form of site-dependent hopping probabilities, drawn from a power-law distribution, and apply the resetting formalism. As a physical example, we recast the growth dynamics of microtubules with sudden catastrophic disassembly events as a resetting dynamics. We consider two distinct regimes for growth dynamics: a strongly biased case and a less biased case. Motivated by experimental results, we take a Gamma distribution for the resetting time. Our results show that occasional disassembly events are crucial for the experimentally observed distribution of reset (or catastrophe) lengths. We also analyze steady-state distributions under different resetting protocols-resetting to the initial position versus a random site. We also investigate the distribution of first-passage times to a fixed distance following reset. Finally, by considering other resetting probability distributions, we identify a regime where the mean displacement grows as slowly as $\log^2 t$. We also elucidate the role of disorder in the system properties under the resetting dynamics. Our study paves the way to treat the dynamics of complex physical systems using resetting.
Read the full abstract

All authors Riya Verma, Binayak Banerjee, Shamik Gupta, Saroj Kumar Nandi

Plasma Physics · Cross-listed from astro-ph.SR

Tearing Driven Reconnection: Energy Conversion Involving Firehose Kinetic Instabilities (2D Hybrid Möbius Simulations)

Etienne Berriot, Petr Hellinger, Olga Alexandrova et al. (+2 more)

This study focuses on energy conversion related to tearing-driven magnetic reconnection in the context of weakly collisional astrophysical plasmas. We present results from a two-dimensional hybrid particle-in-cell simulation employing novel periodic conditions with a topology akin to the Möbius strip, which double the computation efficiency as compared to regular periodic conditions. Evaluation of the ion electric work rate ($\mathbf{j}_i \cdot \mathbf{E}$) and pressure strain interaction ($\mathbf{P}_i : \mathbf{\nabla u}_i)$ shows that most of the energy conversion occurs during the nonlinear phase of the instability, where magnetic energy is transferred towards ion kinetic energy (bulk outflows) and internal energy (heating). These energy conversion rates are of the same order but inhomogeneous. Heating predominantly occurs within the magnetic islands, while near the X-points, nearly the same amount of magnetic energy is transferred to bulk plasma flow and heating. The reconnected plasma moreover exhibits an ion temperature higher parallel than perpendicular to the local magnetic field $\mathbf{B}$. This temperature anisotropy is sustained by the islands' contraction, but eventually gets regulated by kinetic firehose instabilities (parallel and oblique), and/or firehose-like processes, whose main effect is to redistribute the internal energy from the parallel to the perpendicular direction.
Read the full abstract

All authors Etienne Berriot, Petr Hellinger, Olga Alexandrova, Alexandra Alexandrova, Pascal Démoulin

Atomic Physics

Optimization and vectorization of a Mz-type optically-pumped Rubidium magnetometer

Zhengyu Su, Yang Li, Yongbiao Yang et al. (+3 more)

Optically pumped magnetometers (OPMs) have demonstrated significant potential in weak magnetic field detection due to their high sensitivity. In this study, we developed an Mz-type optically pumped rubidium magnetometer using a paraffin-coated anti-relaxation vapor cell. The system optimization and performance characterization were conducted inside a magnetic shield. Specifically, the pump light intensity and radio-frequency (RF) magnetic field were jointly optimized by using the linewidth-amplitude ratio as the core metric. Based on the frequency-domain noise spectrum, the sensitivity in open-loop mode was measured to be approximately 30.8 pT/Hz^{1/2}. Furthermore, a closed-loop feedback locking technique was applied, reducing the measured noise floor under the tested conditions and improving the sensitivity to 22.9 pT/Hz^{1/2}, with a measured -3 dB bandwidth of 123 Hz. The dynamic characteristics were evaluated via magnetic-field step response, showing that the system could track magnetic-field changes stably under closed-loop operation. Finally, by using tri-axial modulation and frequency-domain demodulation, we overcame the scalar measurement limitation of traditional Mz magnetometers. This work realizes vector magnetic field detection and provides a technical basis for applications such as geomagnetic navigation and magnetic anomaly detection.
Read the full abstract

All authors Zhengyu Su, Yang Li, Yongbiao Yang, Yanhua Wang, Jun He, Junmin Wang

Atomic Physics

The Bell-Bloom-type optically-pumped FID Rubidium atomic magnetometer with a multi-passing probe beam and two counter-propagating pump beams

Yongbiao Yang, Zhengyu Su, Yang Li et al. (+4 more)

The Bell-Bloom-type optically pumped atomic magnetometers are well suited for weak geomagnetic field detection. However, conventional single-beam pumping introduces an atomic spin polarization gradient, which limits the measurement accuracy and sensitivity. To address this issue, this paper proposes and experimentally demonstrates a Bell-Bloom-type rubidium FID magnetometer scheme integrating orthogonally polarized counter-propagating pumping and multi-pass probe detection. This design homogenizes the atomic spin polarization distribution and suppresses light shifts and power broadening effects induced by the pump beam. Meanwhile, the five-pass probe configuration significantly enhances the signal amplitude. Experimental results reveal that, compared with the traditional single-beam pumping and single-pass detection scheme, the proposed magnetometer achieves a remarkable improvement in magnetic field measurement accuracy, and the magnetic field sensitivity is improved from 18.9 pT/\sqrt{Hz} to 3.1 pT/\sqrt{Hz}. This work provides an effective technical approach and reference for optimizing the performance of atomic magnetometers and extending their applications in integrated arrays.
Read the full abstract

All authors Yongbiao Yang, Zhengyu Su, Yang Li, Yanhua Wang, Jun He, Xiaojun Jia, Junmin Wang

Atmospheric and Oceanic Physics

High-resolution probabilistic estimation of three-dimensional regional ocean dynamics from sparse surface observations

Niloofar Asefi, Tianning Wu, Ruoying He et al. (+1 more)

The ocean interior regulates Earth's climate but remains sparsely observed due to limited in situ measurements, while satellite observations are restricted to the surface. We present a depth-aware generative framework for reconstructing high-resolution three-dimensional ocean states from extremely sparse surface data. Our approach employs a conditional denoising diffusion probabilistic model (DDPM) trained on sea surface height and temperature observations with up to 99.9 percent sparsity, without reliance on a background dynamical model. By incorporating continuous depth embeddings, the model learns a unified vertical representation of the ocean states and generalizes to previously unseen depths. Applied to the Gulf of Mexico, the framework accurately reconstructs subsurface temperature, salinity, and velocity fields across multiple depths. Evaluations using statistical metrics, spectral analysis, and heat transport diagnostics demonstrate recovery of both large-scale circulation and multiscale variability. These results establish generative diffusion models as a scalable approach for probabilistic ocean reconstruction in data-limited regimes, with implications for climate monitoring and forecasting.
Read the full abstract

All authors Niloofar Asefi, Tianning Wu, Ruoying He, Ashesh Chattopadhyay

Instrumentation and Detectors

Analytical model for the photomultiplier single photoelectron response including the electron back-scattering contribution

Emanuele Angelino, Veronica Beligotti, Lorenzo Bellagamba et al. (+12 more)

Many models exist to describe the single photoelectron response of photomultipliers. Generally to describe the spectral region between the fully amplified primary photoelectron peak and the electronics pedestal an ad hoc function is used (often an exponentially modified gaussian) without a clear physical justification. In this paper, following the physical description of back-scattered primary photoelectrons at the first dynode described in the "The Photomultiplier Handbook" by A.~G. Wright published by Oxford University Press, we derive an analytical function describing these partially amplified primary photoelectrons. This function depends only on intrinsic parameters of the photomultiplier such as the gain at the first dynode and the intrinsic resolution of the dynode chain following the first. Furthermore, analytical descriptions of the fully amplified peak and very low charge signals are derived. The model has been successfully validated with data from two different photomultipliers acquired with a low-noise amplifier.
Read the full abstract

All authors Emanuele Angelino, Veronica Beligotti, Lorenzo Bellagamba, Elena Bonali, Graziano Bruni, Pietro Di Gangi, Gian Marco Lucchetti, Andrea Mancuso, Virginia Mazza, Gabriella Sartorelli, Marco Selvi, Franco Semeria, Alessandro Razeto, Stefania Vecchi, Guido Zavattini

Atmospheric and Oceanic Physics

MAG-Net: Radar-Satellite Fusion for Severe Convective Nowcasting with Matched Evaluation of Satellite Contributions

Dandan Chen, Yaqiang Wang, Anyuan Xiong et al. (+1 more)

Radar-based nowcasting remains challenging for intense convective echoes because extrapolation cannot represent storm growth and decay, while regression-trained deep networks tend to smooth small-scale high-reflectivity structures. We present MAG-Net, a radar-satellite nowcasting framework that combines composite radar reflectivity with three Fengyun-4A (FY-4A) Advanced Geostationary Radiation Imager (AGRI) infrared fields through separate encoders and a Dual-Head decoder with Gradient-Preserving Fusion (GPF). We evaluate 73,928 spatial forecast windows, each covering a 90-minute forecast, from hourly initialization times across 122 severe-convective outbreaks over southeastern China in 2023. Matched variants separate the effects of output design and satellite input. For radar-only input, the critical success index (CSI) at 40 dBZ increases from 0.092 with regression output to 0.252 with Dual-Head/GPF. Adding AGRI fields under the same output design raises CSI at 40 dBZ to 0.273. The paired gain is 0.021, with a 95% confidence interval of 0.018-0.024 based on outbreak-level resampling. Object-based lifecycle evaluation shows satellite gains across growth, mature, and decay stages. At the 90-minute lead, the largest relative gain occurs before the birth of a new radar core, when radar-only skill is lowest. These findings show that the output formulation and the satellite observations contribute jointly, with the larger share of the severe-echo improvement coming from the output formulation, and identify when the satellite contribution is most pronounced.
Read the full abstract

All authors Dandan Chen, Yaqiang Wang, Anyuan Xiong, Enda Zhu

Applied Physics · Cross-listed from eess.SP

Mutual-Coupling-Aware Optimization of a Time-Floquet RIS for Harmonic Backscatter Communications

Aleksandr D. Kuznetsov, Ville Viikari and Philipp del Hougne

This Letter studies the optimization of a wireless communications system empowered by a periodically time-modulated reconfigurable intelligent surface, coined time-Floquet RIS (TF-RIS), in the presence of mutual coupling (MC) among the RIS elements. In contrast to a conventional RIS whose elements may be reconfigured between signaling intervals, a TF-RIS periodically modulates its elements within a signaling interval, thereby inducing frequency conversion. Periodic time modulation is particularly attractive for harmonic backscatter communications to avoid self-jamming. Based on time-Floquet multiport network theory, we formulate an MC-aware optimization problem for binary-amplitude-shift-keying (BASK) harmonic backscatter communications with practical 1-bit-programmable TF-RIS elements. We propose a general discrete-optimization algorithm and evaluate its performance based on realistic model parameters. We systematically examine the performance dependence on the time resolution of the periodic modulation and the number of retained harmonics. Benchmarking against an MC-unaware approach reveals the importance of MC awareness for the more challenging optimization problem of simultaneous desired-harmonic-channel-gain maximization and undesired-harmonic-channel-gain minimization.
Read the full abstract

Fluid Dynamics

Wave-appropriate reconstruction of compressible flows: physics-constrained acoustic dissipation and rank-1 entropy wave correction

Amareshwara Sainadh Chamarthi

The wave-appropriate reconstruction approach decomposes the reconstruction procedure into characteristic wave families, centralizing non-acoustic waves to minimize dissipation while retaining an upwind bias for acoustic waves. In previous implementations, the acoustic upwind parameter $\eta_a$ was fixed at its maximum value of $1.0$; however, this choice is conservative and motivated a systematic search for the minimum value that is robust across flow regimes. To this end, the CFD solver is treated as a black box within a bounded scalar minimization, which minimizes an accuracy objective for the subsonic inviscid TGV subject to a stability constraint enforced by the supersonic viscous TGV. Because the wave-appropriate framework leaves $\eta_a$ as the sole degree of freedom, the optimization converges in approximately 25 evaluations. The resulting optimal values generalize without retuning across a wide range from subsonic turbulence to hypersonic flows with shocks and contact discontinuities. The second contribution focuses on eliminating the need for an explicit contact-discontinuity detector, which is commonly required in flows involving both shock waves and contact discontinuities. In such cases, the reconstruction deficiency appears solely within the entropy characteristic wave and can be corrected by a rank-1 update along the entropy right eigenvector. The proposed algorithm relies only on the Ducros sensor and is limiter-agnostic, facilitating direct use in other schemes, such as WENO. This approach reduces wall time by $29$–$41\%$ compared to full characteristic decomposition. To further demonstrate the method's generality, introducing a controlled acoustic bias exclusively to the normal momentum in a KEP scheme eliminates spurious vortices in periodic shear layers, confirming that the acoustic stability mechanism operates independently of the discretization framework.
Read the full abstract

Plasma Physics

Collimation of diamagnetic laser-driven plasma outflows by an ambient magnetic-pressure gradient

Yigeng Tian, Chung Hei Leung, Arijit Bose et al. (+3 more)

We present magnetohydrodynamic simulations of laser driven plasma outflows propagating along an externally applied poloidal magnetic field, designed to mimic coronal open-field plasma jets. Using the FLASH code with non-ideal terms (resistivity, Biermann battery, and Nernst advection) included, we model a CH target driven by a 3$\omega$ (351 nm) beam delivering 5 kJ over 10 ns and a uniform background field $\text{B}_0$ = 0 to 50 T. Under these conditions, the expanding plume develops a central low-density diamagnetic cavity bounded by a high-magnetic-pressure shell. Magnetic flux is advected from the plume center to its edge, and azimuthal diamagnetic currents form that decrease fields inside the cavity and amplify fields outside, producing a radial magnetic-pressure gradient that exerts an inward $\text{J}\times \text{B}$ force and radially confines the flow. We show that the collimation strengthens with increasing applied magnetic field, as stronger fields reduce the plasma $\beta$ and correspondingly enhance the confining $\text{J}\times \text{B}$ force.
Read the full abstract

All authors Yigeng Tian, Chung Hei Leung, Arijit Bose, Riddhi Bandyopadhyay, Michael A. Shay, William H. Matthaeus

Applied Physics

Nanodiamond sensing in dynamic environments with fast-tracking through four-point positioning

Guoli Zhu, Ming-Zhong Ai, Zhiyu Zhao et al. (+8 more)

Nitrogen-vacancy (NV) centers in nanodiamonds are excellent nanoscale sensors for measuring parameters such as temperature, magnetic field, and viscosity in complex fluidic environments, including living cells. However, the rapid motion of nanodiamonds in such dynamic systems imposes a significant challenge for continuous, real-time tracking and sensing measurements. Here, we present a fast single particle tracking (SPT) method featuring a tetrahedral detection geometry for time-efficient parallel fluorescence collection using four avalanche photodiodes (4-APDs), which eliminates the temporal latency of traditional sequential scanning. We demonstrate an improvement of about an order of magnitude in the temporal resolution and the upper limit of measurable diffusion coefficient compared to previously reported nanodiamond tracking methods based on single APD. The SPT is integrated with multi-parameter quantum sensing based on optically detected magnetic resonance (ODMR) of NV centers. The sensitivities of ODMR-based temperature and 3D rotation sensing are evaluated at different diffusion coefficients, which shows no significant degradation within our measurement range. We apply the system for thermorheology measurements in glycerol/water mixtures under thermal ramps. Additionally, we perform simultaneous translation and rotation tracking in live cells, revealing correlated translational and rotational dynamics. This approach advances multi-parameter nanoscale sensing for soft matter and biological applications, paving the way for real-time nanoscale sensing in highly dynamic fluidic environments.
Read the full abstract

All authors Guoli Zhu, Ming-Zhong Ai, Zhiyu Zhao, Weng-Hang Leong, Shining Chen, Xi Liu, Jingwei Fan, Xi Feng, Ren-Bao Liu, Yue Cui, Quan Li

Optics

Wavelength-multiplexed massively parallel diffractive optical information storage and image projection

Che-Yung Shen, Yuhang Li, Cagatay Isil et al. (+7 more)

We introduce a wavelength-multiplexed massively parallel diffractive information storage platform composed of dielectric surfaces that are structurally optimized at the wavelength scale using deep learning to store and project thousands of distinct image patterns, each assigned to a unique wavelength. Through numerical simulations in the visible spectrum, we demonstrated that our wavelength-multiplexed diffractive system can store and project over 4,000 independent desired images/patterns within its output field-of-view, with high image quality and minimal crosstalk between spectral channels. Furthermore, in a proof-of-concept experiment, we demonstrated a two-layer diffractive design that stored six distinct patterns and projected them onto the same output field of view at six different wavelengths (500, 548, 596, 644, 692, and 740 nm). This diffractive architecture is scalable and can operate at various parts of the electromagnetic spectrum without the need for material dispersion engineering or redesigning its optimized diffractive layers. The demonstrated storage capacity, reconstruction image fidelity, and wavelength-encoded massively parallel read-out of our diffractive platform offer a compact and fast-access solution for large-scale optical information storage, image projection applications.
Read the full abstract

All authors Che-Yung Shen, Yuhang Li, Cagatay Isil, Jingxi Li, Leon Lenk, Tianyi Gan, Guangdong Ma, Fazil Onuralp Ardic, Mona Jarrahi, Aydogan Ozcan

Optics

Dispersion Engineered Metastructures Enabling Broadband Angular Selectivity

Phillippe Pearson, Zhaowei Dai, Yiran Gu et al. (+2 more)

Angle-selective optical devices are of importance to several applications such as photovoltaics, high-sensitivity photodetectors and displays. There are several approaches to realizing angular selectivity, but it remains challenging to obtain isotropic responses over large spectral bandwidths in optically thin structures. We introduce a dispersion engineering approach coupled with topology optimization to design 2D metastructures, leveraging guided-mode resonances (GMRs), that exhibit isotropic angular selectivity over relative bandwidths of approximately 20%. We experimentally demonstrate metastructures with complementary angular selectivities, either scattering light strongly near normal incidence and transmitting efficiently at higher incident angles, or vice versa. A key finding is that these designs enable operation over spectral bandwidths greater than the GMR linewidths would suggest, a result of carefully tailored interactions between the Fabry-Perot background and resonantly scattered light. This work marks a significant step forward for the realization of broadband, angle-selective scattering in readily fabricated structures of subwavelength thickness, and enables new possibilities in sensing, analog information processing, high-efficiency photovoltaics, and displays.
Read the full abstract

All authors Phillippe Pearson, Zhaowei Dai, Yiran Gu, Owen D. Miller, Andrei Faraon

Plasma Physics

Self-subsidizing Mercury Remediation with Fusion Reactors

J. F. Parisi and J. Azad

Fusion reactors can permanently remediate mercury by using it as a neutron multiplier: each (n,2n) reaction reduces the neutron number towards ${}^{197}$Hg which quickly decays into stable gold, irreversibly removing it from the environment while generating substantial economic value. Fusion energy is therefore not merely environmentally benign, but anti-polluting through the continuous consumption of an environmental pollutant. The history of nuclear fission demonstrates that environmental concerns can be decisive obstacles to low-carbon power deployment, suggesting that integrated pollution remediation fundamentally improves the policy calculus for fusion energy. We show that at high neutron flux (achievable in muon-catalyzed and inertial confinement fusion), nuclear reactions make all mercury isotopes eligible for gold transmutation, incentivizing mercury recovery and valuing the world mercury extractable stock at ${\sim}\$200$ trillion, exceeding all in-ground gold reserves. Co-producing gold alongside electricity can triple a fusion plant's revenue, aligning economic incentives with complete, permanent mercury remediation.
Read the full abstract

Thursday 2 April

Geophysics

Toward buoyancy-driven flow at Campi Flegrei: coupled phase change and asymmetric geometry

Arturo Tozzi

Bradyseism at Campi Flegrei is usually interpreted in terms of hydrothermal pressurization and magmatic degassing. Fluid flow, often treated as a passive response to pressure accumulation, is commonly modeled using simplified geometries and homogeneous permeability fields. We introduce a model in which phase transition, structural heterogeneity and geometric asymmetry jointly influence fluid flow and pressure distribution within a heterogeneous subsurface environment. We hypothesize that coupling among phase change, density gradients and flows may follow a mechanism similar to the self-propulsion observed in asymmetric floating bodies like melting ice blocks, where phase change generates buoyancy-driven currents along their inclined surfaces and net motion in the opposite direction. We simulate pressure evolution in a shallow gas-rich reservoir subject to time-dependent forcing and hydraulic relaxation, coupled to buoyancy-enhanced Darcy flow along prescribed preferential pathways. Our numerical simulations, grounded in reported deformation rates and seismicity depths at Campi Flegrei, reproduce temporal variations in uplift and the persistence of spatially localized flow. Within this framework, asymmetric geometry may promote channelized upward transport, while phase change may enhance buoyancy and contribute to pressure redistribution. Our model predicts nonlinear uplift acceleration, shallow localized seismicity and velocity scaling with pressure and buoyancy. Integration with existing multiphase models would enable the examination of how buoyancy-driven flows influence pressure evolution and deformation during volcanic unrest.
Read the full abstract

Physics Education

The Physics of Gudeg: Learning the Mechanics and Thermal Properties Using Collaborative Project based Activities for the High School Physics

Bayu Setiaji, Pramudya Wahyu Pradana, Febrina Siska Widyaningtyas et al. (+3 more)

In this paper, we describe a presentation on the physics of Gudeg, a traditional food from Indonesia specifically originated in the Special District of Yogyakarta. This learning context is designed for the high school physics curricula. The physics presentation focuses on the making processes of Gudeg. Qualitative interviews with Gudeg makers were carried out by the researchers to thematize the process of making Gudeg and highlight its educational connections for the physics learning. Five extracted learning themes are how the density concept behind peeling the jackfruit skin (main Gudeg ingredient), how the relation between the Youngs modulus concept and the jackfruit sections, how the texture-torque experiment of the sweet and tasty gudeg, how the effect of boiling mechanism on the texture of the jackfruit, and how the conduction and convection of the preserved Gudeg. Using our learning strategy which is so-called Collaborative Project based Teaching, we provide simple experimentations and demonstrations of the physical concepts behind these Gudeg processes that are promising for conceptual physics learning by managing triple educational roles between teachers, students, and Gudeg practitioners. This approach can be generally adopted beyond physics to promote the excitement of traditional knowledge which can enhance pedagogical approach in educational setting.
Read the full abstract

All authors Bayu Setiaji, Pramudya Wahyu Pradana, Febrina Siska Widyaningtyas, Purwoko Haryadi Santoso, Yusman Wiyatmo, Heru Kuswanto

Medical Physics · Cross-listed from cs.LG

General Explicit Network (GEN): A novel deep learning architecture for solving partial differential equations

Genwei Ma, Ting Luo, Ping Yang et al. (+1 more)

Machine learning, especially physics-informed neural networks (PINNs) and their neural network variants, has been widely used to solve problems involving partial differential equations (PDEs). The successful deployment of such methods beyond academic research remains limited. For example, PINN methods primarily consider discrete point-to-point fitting and fail to account for the potential properties of real solutions. The adoption of continuous activation functions in these approaches leads to local characteristics that align with the equation solutions while resulting in poor extensibility and robustness. A general explicit network (GEN) that implements point-to-function PDE solving is proposed in this paper. The "function" component can be constructed based on our prior knowledge of the original PDEs through corresponding basis functions for fitting. The experimental results demonstrate that this approach enables solutions with high robustness and strong extensibility to be obtained.
Read the full abstract

All authors Genwei Ma, Ting Luo, Ping Yang, Xing Zhao

Computational Physics

Meta-optimization of maximally-localized Wannier functions

Sabyasachi Tiwari, Bruno Cucco, Viet-Anh Ha et al. (+1 more)

Maximally-localized Wannier functions are quantum wavefunctions resembling atomic orbitals that are used to describe electrons in condensed matter. Since their introduction in 1997, these functions have become ubiquitous in ab initio materials simulations, including applications in linear-scaling methods, strongly-correlated electron systems, quantum transport, electron-phonon interactions, and topological materials. Despite their widespread adoption in a vast software ecosystem, Wannier functions have not yet attained their fullest potential in the presence of entangled bands, as their optimization remains challenging and labor-intensive. Here, we introduce a universal meta-optimization method that leverages workflow abstraction and machine learning techniques like differential evolution and Bayesian optimization to generate globally optimized Wannier functions without human intervention. We demonstrate this approach through three applications: (i) autonomous interpolation of entangled band structures with millielectronvolt accuracy starting from coarse Brillouin zone grids, (ii) thousand-fold acceleration of fully ab initio Boltzmann transport calculations via the use of minimal coarse Brillouin zone grids, and (iii) ultra-fast high-throughput calculations of high-precision Wannier functions for large materials libraries. This work brings calculations that previously required supercomputers within the reach of personal computers.
Read the full abstract

All authors Sabyasachi Tiwari, Bruno Cucco, Viet-Anh Ha, Feliciano Giustino