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Physics Physics

physics Watch Physics

Tuesday 24 March

Instrumentation and Detectors · Cross-listed from hep-ex

KATRIN Sensitivity to keV Sterile Neutrinos with the TRISTAN Detector Upgrade

H. Acharya, M. Aker, D. Batzler et al. (+127 more)

Sterile neutrinos in the keV mass range are a well-motivated extension of the Standard Model and viable dark matter candidates. Their existence can be probed in laboratory experiments, as the admixture of a sterile state would induce a characteristic kink-like distortion in the $\beta$-decay electron energy spectrum. The KATRIN experiment is designed to measure the effective electron neutrino mass with sub-eV sensitivity by analyzing the endpoint region of the tritium $\beta$-decay spectrum. Following the completion of its neutrino mass program, KATRIN will extend its physics reach to the search for keV-scale sterile neutrinos. This effort will be enabled by the TRISTAN detector, a newly developed silicon drift detector array optimized for differential measurements at high rates and energies well below the endpoint. In this article, we present the projected sensitivity of KATRIN to keV-scale sterile neutrinos using a dedicated simulation framework. With four months of detector livetime, KATRIN has the statistical power to probe mixing amplitudes at the level of $|U_{e4}|^2 \sim 10^{-6}$ for sterile neutrino masses in the (4$-$13) keV range, significantly extending the reach of previous laboratory searches. The major experimental systematic uncertainties investigated in this work reduces the sensitivity by a factor of 10$-$50 over the same mass range.
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All authors H. Acharya, M. Aker, D. Batzler, A. Beglarian, J. Beisenkötter, M. Biassoni, B. Bieringer, Y. Biondi, B. Bornschein, L. Bornschein, M. Böttcher, M. Carminati, A. Chatrabhuti, S. Chilingaryan, B. A. Daniel, M. Descher, D. Díaz Barrero, P. J. Doe, O. Dragoun, G. Drexlin, E. Ellinger, R. Engel, K. Erhardt, L. Fallböhmer, A. Felden, C. Fengler, C. Fiorini, J. A. Formaggio, C. Forstner, F. M. Fränkle, G. Gagliardi, K. Gauda, A. S. Gavin, T. Geigle, T. Geier, S. Gentner, W. Gil, F. Glück, C. Goupy, R. Grössle, K. Habib, V. Hannen, L. Hasselmann, K. Helbing, S. Heyns, R. Hiller, D. Hillesheimer, D. Hinz, T. Höhn, A. Jansen, M. Kandler, K. Khosonthongkee, C. Köhler, J. Kohpeiß, A. Kopmann, N. Kovac, L. La Cascio, L. Laschinger, T. Lasserre, J. Lauer, T. L. Le, O. Lebeda, S. M. Lee, A. Lokhov, M. Mark, T. Marrodán Undagoitia, A. Marsteller, E. L. Martin, K. McMichael, S. Mertens, S. Mohanty, J. Mostafa, I. Müller, A. Nava, S. Niemes, I. Nutini, A. Onillon, D. S. Parno, M. Pavan, U. Pinsook, J. Plößner, J. M. L. Poyato, J. Ráliš, S. Ramachandran, C. Rodenbeck, M. Röllig, R. Sack, A. Saenz, R. Salomon, P. Schäfer, M. Schlösser, L. Schlüter, S. Schneidewind, U. Schnurr, J. Schürmann, A.K. Schütz, A. Schwemmer, A. Schwenck, J. Seeyangnok, C. Silva, F. Simon, J. Songwadhana, D. Spreng, W. Sreethawong, M. Steidl, J. Štorek, X. Stribl, M. Sturm, T. Stürwald, N. Suwonjandee, N. Tan Jerome, H. H. Telle, L. A. Thorne, T. Thümmler, K. Trost, K. Urban, K. Valerius, D. Vénos, P. Voigt, V. Wallner, C. Weinheimer, S. Welte, J. Wendel, C. Wiesinger, J. F. Wilkerson, J. Wolf, S. Wüstling, J. Wydra, W. Xu, G. Zeller

Optics

Free electrons unveil nanolaser physics at the sub-picosecond and nanometer scale

Cléo Santini, Thi Huong Ngo, Luiz H. G. Tizei et al. (+14 more)

Semiconducting nanowire lasers (NWLs) constitute nanoscale modular and tunable light sources, essential components for integrated optoelectronics. However, advancing NWL operation requires characterization of their near-field and dynamics at the nanometer scale, which is hampered by the diffraction limit of light. Here, we show a non-perturbative measurement of the absolute number of photons in a GaN/InGaN nanowire nanolaser cavity above the lasing threshold with sub-picosecond resolution and maps of the lasing mode spatial profile at the nanoscale. For this we use photon-induced near-field electron microscopy while simultaneously measuring the photons far-field, unraveling the key nanoscale and time-resolved characteristics of a NWL in operation. With this technique, we observed lasing with a pump-power-dependent time offset of 0.5-1 ps that reflects carrier thermalization and spontaneous emission, and a pulse duration of 500 to 700 fs. From the spatial maps of the lasing mode, we observe TM-polarized azimuthal whispering gallery modes along the nanowire circumference, as well as two distinct Fabry-Perot modes along the nanowire length. These spatial maps allow us to understand which of the multiple complex cavity modes available in the nanowire are responsible for lasing paving the way for their practical application into devices.
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All authors Cléo Santini, Thi Huong Ngo, Luiz H. G. Tizei, Aurélie Lloret, Tom Fraysse, Sebastien Weber, Adrien Teurtrie, Albert Polman, Virginie Brändli, Sebastien Chenot, Denis Lefebvre, Stéphane Vézian, Hugo Lourenço-Martins, Christelle Brimont, Benjamin Damilano, Thierry Guillet, Sophie Meuret

Geophysics

The NCS-Model: A seismic foundation model trained on the Norwegian repository of public data

Alba Ordonez, Theodor Johannes Line Forgaard, David Wade et al. (+3 more)

We present the NCS-models, a family of seismic foundation models pretrained on a large curated share of full-stack seismic cubes from the Norwegian Continental Shelf (NCS) available through the public DISKOS database. The model weights are open-sourced for the wider geoscience community. Foundation models trained with large-scale self-supervision are emerging as a promising basis for automatic seismic interpretation. However, most existing seismic models rely on limited or proprietary datasets, and it remains unclear how well natural-image foundation models transfer to seismic data. Our goals are to develop basin-scale seismic foundation models, provide practical recipes for scalable 3D training, and compare the downstream performance of practical configurations trained under similar pretraining budgets. Using masked autoencoders with Vision Transformer backbones, we pretrain models on a DISKOS-derived corpus of 3D time- and depth-migrated seismic volumes. The NCS-model variants use 2D, 2.5D multi-view, and 3D tokenization and each variant is pretrained using approximately 250 GPU-hours on the same hardware. We evaluate the models using frozen backbones together with k-nearest neighbors and linear probing on NCS interpretation benchmarks and one out-of-basin benchmark. Baselines include an ImageNet-pretrained MAE, a frontier vision foundation model, and a globally pretrained seismic foundation model. Following large-scale pretraining on the curated DISKOS corpus, NCS-2.5D achieves the highest average performance among all evaluated models. The resulting embeddings additionally support similarity search for interactive interpretation.
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All authors Alba Ordonez, Theodor Johannes Line Forgaard, David Wade, Aina Juell Bugge, Hakon Nese, Anders Ueland Waldeland

Fluid Dynamics

Steady cone-jet mode of electrospray for single-cell deposition

D. Fernández-Martínez, C. Ferrera, J. M. Montanero et al. (+2 more)

We propose using the electrospray cone-jet mode operated near its minimum-flow-rate stability limit for single-cell deposition. Because the jet is much thinner than the cells themselves, individual cells can be clearly visualized or detected during deposition. At such low flow rates, individual cells can be placed at distinct, user-defined locations, even at relatively high cell concentrations. In this sense, our approach provides a spatial resolution at the scale of a single cell. We demonstrate the method's capabilities by depositing cells onto a millimeter-scale droplet of a standard cell-culture medium. Cell viability assays indicate that many cells maintain membrane integrity after exposure to the electrosprayed liquid, suggesting that most damage is reversible.
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All authors D. Fernández-Martínez, C. Ferrera, J. M. Montanero, L. Mendoza-Cerezo, J. M. Rodríguez-Rego

Fluid Dynamics

A numerical study on the coefficient of restitution of wet collisions

Abhishek Kumar Singh, Christopher Robert Kit Windows-Yule and Prapanch Nair

Using smoothed particle hydrodynamics (SPH) simulations, we investigate the coefficient of restitution (COR) in wet collisions and identify a scaling law governing its behavior. The simulations employ an updated-Lagrangian, mesh-free framework that is validated against experimental measurements. We neglect surface tension effects since the impact conditions correspond to a moderate-to-high Weber number regime. The COR is found to depend on the Stokes number and a dimensionless film thickness defined as the ratio of the liquid film thickness to the diameter of the impacting solid bead. Two distinct regimes are observed, each characterized by different power-law exponents.
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Optics

Doppler dual-comb coherent Raman spectromicroscopy

Florian M. Schweizer, Hannah Terrasa and Manish Garg

Chemical imaging enabled by Raman processes is crucial to investigating biological and chemical samples in a label-free manner. Stimulated Raman spectroscopy (SRS) overcomes the key limitation associated with low signal levels in spontaneous Raman spectroscopy, however, at the expense of probing only narrow Raman bands. Time-domain implementation of coherent anti-Stokes Raman spectroscopy (CARS) by dual frequency combs can achieve broad Raman bandwidths; nevertheless, its execution is demanding due to strenuous temporal-synchronization of two independent ultrashort laser sources. Here, we introduce time-domain coherent Raman spectroscopy utilizing two frequency combs generated by the Doppler effect from a single ultra-broadband laser source. In contrast to CARS, in our approach, the interference of impulsively launched vibrations by two broadband frequency combs ({\tau} ~ 6 fs) periodically modulates the Kerr nonlinear response of the medium, leading to cross-phase modulation (XPM) experienced by both the combs. This phase modulation leads to spectral broadening and periodic modulation in the anti-Stokes region of the combs. Down-conversion by a factor of ~ 10-8 in the frequency of the vibrations enabled by the dual-comb approach empowered us to use photon-counting methodology in the anti-Stokes region. This makes our technique extremely versatile, background-free, sensitive and fast (millisecond acquisition times), in probing a range of samples from wide bandgap dielectrics and liquids to individual micro-particles with nondestructive pulse energies (~ 100 pJ) incident on the sample. Owing to the higher-order nonlinearity involved in the XPM process, we achieved ~ 2.5 times improvement in diffraction-limited spatial resolution (~ 280 nm) in ultra-broadband chemical imaging of a ~ 8 {\mu}m bead of poly-methyl-methacrylate.
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Atomic Physics · Cross-listed from astro-ph.IM

A High-frequency Geodetic VLBI Experiment for Optical Clock Comparison

Monia Negusini, Myoung-Sun Heo, Cecilia Clivati et al. (+40 more)

An intercontinental metrological clock comparison between Italy and the Republic of Korea was performed by means of geodetic K-band VLBI observations. The comparison involved the hydrogen masers (H-masers) used at Medicina and Sejong radio telescopes. The same clocks were simultaneously compared by a satellite link and by high-precision optical clocks maintained at the National Metrology Institutes, KRISS in Korea and INRIM in Italy, and delivered to VLBI antennas via optical fiber. The H-masers frequency difference was estimated by extrapolating the clock rate from VLBI data using two geodetic VLBI software. This was subsequently compared with clock differences derived by satellite link and by local optical clocks. Results obtained with different approaches were in agreement at the level of $10^{-15}$ s/s. This pilot study demonstrates that standard high-frequency (K-band) geodetic VLBI campaigns could be a viable approach to conduct intercontinental clock comparisons, now only possible via satellite links. This uncertainty can be reduced thanks to the planned installation of new-generation, broadband, high-frequency receivers on the involved telescopes. K/Q/W-band geodetic observations will allow an improvement of the accuracy of the resulting group delays through broad bandwidth synthesis from 20 to 100 GHz. Furthermore, the Frequency Phase Transfer (FPT) method will also be explored together with the use of PCAL systems installed at the radio telescopes to improve phase stability and thus allow a better estimation of the station clock parameters.
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All authors Monia Negusini, Myoung-Sun Heo, Cecilia Clivati, Shuangjing Xu, Roberto Ricci, Taehyun Jung, Buseung Cho, Matteo Stagni, Claudio Bortolotti, Giuseppe Maccaferri, Federico Perini, Mauro Roma, Do-Young Byun, Do-Heung Je, Marco Pizzocaro, Davide Calonico, Elena Cantoni, Giancarlo Cerretto, Stefano Condio, Giovanni A. Costanzo, Simone Donadello, Irene Goti, Michele Gozzelino, Alberto Mura, Filippo Levi, Matias Risaro, Huidong Kim, Won-Kyu Lee, Chang Yong Park, Dai-Hyuk Yu, Young Kyu Lee, Joon Hyo Rhee, Chanjin Park, Minseong Lee, Hyo Ryoung Kim, Sung-Moon Yoo, Jungho Cho, Jongsoo Kim, Sang-Oh Yi, Ha Su Yoon, Pablo de Vicente, Javier González, Cristina García Miró

Optics

Structured Single-photon Metasource

Jun-Yong Yan, Fang-Yuan Li, Zhou Zhou et al. (+18 more)

Structured quantum light is crucial for high-dimensional quantum information processing, yet its direct generation from quantum emitters remains challenging due to their intrinsic locality and omnidirectional radiation. Metasurfaces have been adopted for quantum-light wavefront shaping, typically in cascaded or stacked configurations that suffer from low efficiency and limited resolution. Here, we demonstrate a semiconductor metasource that directly embodies single quantum dots in a nonlocal GaAs metasurface. Spontaneous emission from quantum dot is efficiently funneled into an extended quasi-bound-state-in-the-continuum mode while sustaining strong mode-emitter overlap. A lateral core-barrier heterostructure tunes mode volume and spatial distribution to balance Purcell enhancement and holographic resolution. Using spatially modulated geometric phase, our compact metasource enables deterministic generation of diverse single-photon radiation patterns, including orbital-angular-momentum beams and holographic images. Our work brings versatile single-photon wavefront control into the nanoscale cavity quantum electrodynamics regime, offering a scalable route toward integrated sources of structured quantum light.
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All authors Jun-Yong Yan, Fang-Yuan Li, Zhou Zhou, Yue-Yao Mu, Hang-Yu Ge, Severin Kruger, Jianfeng Chen, Zhe Wang, Fulong Shi, Mengqi Liu, Haoye Qin, Ying Che, Yu-Tong Wang, Yunyan Zhang, Song Han, Zongyin Yang, Chaoyuan Jin, Huiyun Liu, Arne Ludwig, Feng Liu, Cheng-Wei Qiu

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

Fine-tuning of universal machine-learning interatomic potentials for high-entropy alloys with application to 2D (Mo,Ta,Nb,W,V)S$_2$

Chun Zhou and Hannu-Pekka Komsa

High-entropy alloy (HEA) materials and their two-dimensional counterparts (2D-HEAs) have recently attracted attention due to their tunable properties and catalytic potential, yet their chemical complexity makes direct density functional theory (DFT) calculations computationally prohibitive. The complexity also makes training of machine-learning interatomic potentials (MLIPs) challenging, but this could possibly be overcome by employing universal MLIPs as starting point. In this work, we investigate the applicability of universal MLIP models for 2D transition metal dichalcogenide HEAs and develop effective fine-tuning strategies. Training structures are systematically generated and selected, and the performance of universal and fine-tuned models are benchmarked against DFT. We find that all universal MLIPs employed in this work yield unsatisfactory mixing energies without fine-tuning. Applied to the experimentally synthesized (Mo,Ta,Nb,W,V)S$_2$ system, fine-tuned models based on enumerated structures can achieve near-DFT accuracy in predicting mixing energies while enabling Monte-Carlo simulations and random structure sampling at scales inaccessible to DFT.
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Atomic Physics · Cross-listed from cond-mat.quant-gas

Transformation of the Talbot effect in response to phase disorder

Ilia Mosaki and A. V. Turlapov

Bose-Einstein condensates initially arranged in a long chain freely expand and interfere. If the initial phases of the condensates are identical, the initial density distribution is restored periodically during the expansion, giving rise to the Talbot effect. Even a slight disorder in the initial phases leads to a transformation of the interference pattern. In response to the phase disorder, the spectrum of the spatial density distribution acquires peaks that are absent in the case of identical phases. We derive an analytical expression for the spectrum of the spatial density distribution for an arbitrary phase disorder. We show that the new peaks emerging due to the phase disorder originate from pairwise interferences of the condensates. The positions of these peaks coincide with the wave vectors of the density modulations (wavelets) generated by such pairwise interferences. The absence of these peaks, when the initial phases are identical, is explained by the mutual destruction of the overlapping wavelets during their summation.
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Optics · Cross-listed from cond-mat.mes-hall

Exploring Spectral Singularities in Dirac Semimetals: The Role of Non-Hermitian Physics and Dichroism

Mustafa Sarisaman, Murat Taş and Enes Talha K{\i}rca

In this study, motivated by recent advancements in non-Hermitian physics, we explore new characteristics of Dirac semimetals (DSMs) using the spectral singularities by means of scattering techniques, with the goal of uncovering additional unique properties. To achieve this, we investigate how the axion texture of a DSM affects its topological properties by analyzing its interaction with electromagnetic waves. We examine the transverse electric (TE) mode configuration, where the magneto-electric effect induces a dichroic property in these materials. This behavior is particularly interesting and commonly seen in potential DSM candidates. Consequently, we report for the first time that a dichroic DSM generates 12 unique topological laser types. We discover that surface currents are generated by topological terms on the surface of the DSM slab. Furthermore, we examine how the {\theta} term associated with axions in topological materials contributes to these topological properties. Our study reveals distinct topological role of the {\theta} term more clearly than ever before. Our results confirm that the topological properties of DSMs with a single Dirac cone remain stable under external influences and that a topologically robust DSM laser can be developed accordingly
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Plasma Physics

Anisotropic truncation for turbulent transport and zonal flows in the Hasegawa-Wakatani system

Pierre L. Guillon, Robin Angles, Yanick Sarazin et al. (+1 more)

Reduced models based on an anisotropic truncation of the Fourier space, retaining only a few poloidal wave-numbers while keeping the full radial resolution, are developed and first applied to the Hasegawa-Wakatani system. The impact of the truncation is studied first by considering the fixed-gradient formulation, and by comparing to direct numerical simulations (DNS). The turbulent particle flux, and the transition from quasi-two dimensional turbulence to the zonal flow (ZF) dominated state, are used as the main criteria for validation. It is found that at least 4 poloidal modes, distributed around the most unstable mode, are needed to observe a sharp transition, and that about 10 modes are needed to reproduce each transport regime. Then, similar reduced models are developed in a flux-driven formulation and compared to the DNS, focusing on two cases far from the nonlinear threshold of the transition from turbulence to zonal dominated states of the fixed gradient formulation. In that case, using 10 modes allows to match the probability distribution function of the particle flux of the DNS approximately. Considering the role played by different poloidal scales in the turbulent cascade, it is observed that in the turbulent state, an inverse energy cascade in radial wave-numbers takes place at large poloidal scales, while a forward enstrophy cascade in radial wave-numbers is observed to occur at smaller poloidal scales. Moreover, when they form, ZFs feed on poloidal scales that are around and slightly smaller than the injection scale, while giving their energy to the larger poloidal scales. In that case, there is an anisotropic inverse energy transfer, akin to inverse cascade, from the energy injection to the large poloidal scales through ZFs, while the forward enstrophy cascade seems to stay isotropic.
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All authors Pierre L. Guillon, Robin Angles, Yanick Sarazin, Özgür D. Gürcan

Atomic Physics

In-orbit Test of the Weak Equivalence Principle with Atom Interferometry

Dan-Fang Zhang, Jing-Ting Li, Wen-Zhang Wang et al. (+22 more)

The Weak Equivalence Principle (WEP) is a central pillar of general relativity. Its precise test with quantum systems in space offers a unique window onto new physics. Here we report the first in-orbit quantum test of the WEP. A dual-species (85Rb/87Rb) atom interferometer is realized aboard the China Space Station. Methods of platform motion suppression, fluorescence detection switching, and two-photon detuning switching are developed to eliminate phase noise and improve measurement accuracy. A test uncertainty of 2.8*10-8 is obtained from 280 days of WEP test data, and a test result of (-3.1+/-4.6)*10-7 is achieved after error estimation. This improves prior atom-interferometric WEP tests in microgravity by three orders of magnitude. This work paves the way for space-borne quantum inertial sensors and their application to future fundamental physics in space.
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All authors Dan-Fang Zhang, Jing-Ting Li, Wen-Zhang Wang, Wei-Hao Xu, Jia-Yi Wei, Xiao Li, Yi-Bo Wang, Dong-Feng Gao, Jia-Qi Zhong, Biao Tang, Lin Zhou, Run-Bing Li, Huan-Yao Sun, Qun-Feng Chen, Lei Qin, Mei-zhen An, Zong-Feng Li, Shu-Quan Wang, Xiao-Xiao Guo, Yao Tian, Xi-He Yu, Hong-En Zhong, Xi Chen, Jin Wang, Ming-Sheng Zhan

Physics and Society

Cooperation in Public Goods Games over Uniform Random Hypergraphs with Game Transitions

Nankun Wei, Xiaojin Xiong, Qin Li et al. (+2 more)

The evolution of cooperation is a central enigma in evolutionary game theory. Traditionally, the combination of pairwise networks and repeated Public Goods Games with a single state fails to adequately describe realistic group interaction scenarios. On the one hand, pairwise networks lack clear group definitions. On the other hand, a participant's decision affects not only competitors' fitness but also the state of the surrounding environment. To address this problem, we propose a Public Goods Game with game transition mechanisms based on Uniform Random Hypergraphs. In our model, game groups formed by hyperedges transition between two types of games, one with abundant public resources and the other with scarce public resources. The transition probability is closely related to the strategies of players within the hyperedges. By developing a Monte Carlo simulation framework that incorporates payoff accumulation, strategy imitation, and game state transitions, we aim to reveal the coevolutionary patterns of strategies and game states in group interactions. Our study highlights a nonlinear relationship between defection sensitivity and cooperation frequency under game transitions, as well as the asymmetric effects of the two sensitivities in state-dependent transitions. These observations open new directions for how to approach social dilemmas.
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All authors Nankun Wei, Xiaojin Xiong, Qin Li, Minyu Feng, Attila Szolnoki

Plasma Physics

CMA-Unfold A Covariance Matrix Adaptation unfolding algorithm for stacked calorimeter detectors

G. Fauvel, A. Arefiev, M. Manuel et al. (+3 more)

Stacking calorimeters also refered as bremsstrahlung cannons widely used in inertial confinement fusion and ultra-intense laser plasma experiments have become essential diagnostics for characterizing short bursts of high-energy photons and charged particles. Extracting the underlying energy spectrum from these detectors requires solving an ill-posed inverse problem, often complicated by noise, secondary particle contamination, and uncertainties in the detector response. In this work, we introduce an open-source unfolding framework available under the username ggfauvel under CMA-unfold based on the Covariance Matrix Adaptation Evolution Strategy (CMA-ES), designed to reconstruct photon spectra directly from depth-dose profiles without imposing restrictive parametric assumptions. The algorithm demonstrates high robustness, accurately recovering complex spectral shapes while tolerating percent-level deviations in individual detector layers. This approach provides a flexible and noise-resilient tool for the analysis of stacking calorimeter data, with particular relevance for bremsstrahlung diagnostics in inertial confinement fusion and high-intensity laser applications.
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All authors G. Fauvel, A. Arefiev, M. Manuel, K. Tangtartharakul, S. Weber, F.P. Condamine

Fluid Dynamics

Direct Numerical Simulation of MILD Combustion: Mixing and Autoignition from Non-Premixed Streams

Lorenzo Frascino, Gandolfo Scialabba, Hongchao Chu et al. (+1 more)

Moderate or intense low-oxygen dilution (MILD) combustion is achieved by strongly diluting and preheating the reactants through mixing with hot combustion products before ignition. To better understand how fuel/air/product mixing and interaction govern MILD combustion dynamics, a novel direct numerical simulation (DNS) dataset of a temporally evolving three-stream mixing layer consisting of fuel, air, and hot combustion products has been performed. In this configuration, both fuel-air and air-hot products mixing processes are considered with varying time scales, through four carefully designed DNS cases, to assess how their combined interaction controls ignition under MILD conditions. It is observed that the cases with higher dilution levels fall within the MILD combustion regime, whereas those with lower dilution correspond to non-MILD conditions. The results show that, as long as MILD conditions are observed, ignition is mainly driven by mixing with hot products. Flame index (FI) combined with chemical explosive mode analysis (CEMA) further identifies the local combustion mode: in MILD cases, ignition occurs predominantly through a premixed-autoignition mode, while in non-MILD scenarios, the premixed-deflagrative contribution to the heat release rate is more substantial. Conditional analysis of scalar dissipation rates shows that the combustion modes in MILD conditions are sensitive to mixing by both the fuel and hot products, whereas the combustion modes in non-MILD conditions are mainly influenced by the mixing of the fuel with the surrounding gases.
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All authors Lorenzo Frascino, Gandolfo Scialabba, Hongchao Chu, Heinz Pitsch

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

Cooperative effect of local active stresses on the macroscopic contractility of elastic fiber networks

Abhinav Kumar, David A. Quint and Kinjal Dasbiswas

The collective action of actively contractile units embedded in elastic biopolymer networks plays a crucial role in regulating the network's macroscopic mechanical response. Here, we investigate how the macroscopic boundary stress in model elastic fiber networks depends on the number and nature of embedded contractile units, each exerting an isotropic force dipole, as well as on the bending stiffness of fibers. We find that the macroscopic stress increases nonlinearly with the number of dipoles due to mutual stiffening of initially soft, bending-dominated networks. Using effective medium theory, we relate this enhanced contractility to an increase in the effective average network coordination number due to constraints imposed by the force dipoles. By comparing three distinct force dipole models that differ in their local structures, we demonstrate that the specific manner in which an active unit constrains the network strongly influences the onset and nature of the stiffening transition. Our results highlight that not only the quantity but also the local geometry of force-generating units critically determines the macroscopic mechanical behavior. This framework provides a physical basis for understanding how biological systems-such as molecular motors in the cytoskeleton, or adherent cells in the extracellular matrix-can modulate network-scale nonlinear elastic properties through local tuning of active force-generating units.
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Optics

GHz control of THz QCL band structure and gain by standing acoustic strain

Alexander S. Kuznetsov, Valentino Pistore, Lutz Schrottke et al. (+2 more)

Active frequency comb generation and waveform control are central challenges in the terahertz (THz) domain. In THz quantum cascade lasers (QCLs), these functions have typically been achieved through active bias modulation, which alters the operating point of the device and imposes severe limitations on its flexibility. To address these challenges, we propose an approach based on the direct modulation of the QCL bandstructure using GHz-frequency standing bulk acoustic waves (BAWs), promising direct and localized control of the optical gain and chromatic dispersion. To this end, we fabricated a bulk acoustic transducer on top of a THz QCL in order to excite GHz standing BAWs within its active region. We demonstrate that radio-frequency driving of the transducer leads to the tunable generation of standing BAWs in 5-12 GHz frequency range with wavelengths commensurate to the QCL period length. The effect of the BAW on the QCL bandstructure is revealed by measuring photoluminescence (PL) of the active region, where the BAW strain leads to a considerable modulation of the PL energy up to a few meV around its non-modulated value. We also develop a model and perform bandstructure simulations to predict the effect of the BAW on the QCL subband structure and gain. These results mark the first demonstration of dynamic bandstructure modulation in a THz QCL using GHz acoustic strain, introducing a fundamentally new paradigm that establishes a powerful synergy between QCLs and BAWs towards coherent control and frequency comb engineering in the THz domain.
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All authors Alexander S. Kuznetsov, Valentino Pistore, Lutz Schrottke, Klaus Biermann, Xiang Lü

History and Philosophy of Physics

Mars excitement in Australian newspapers, 1877-1899: Humour and the public negotiation of astronomical knowledge

Richard de Grijs

Speculation about Martian canals was a recurring feature of late nineteenth-century popular astronomy. This paper examines how colonial newspapers used humour to negotiate the epistemic uncertainty and interpretive excess associated with canal theory. Drawing on over one thousand metropolitan and regional Australian newspapers published between 1877 and 1899, we identify five overlapping modes of humour: imported metropolitan wit; satire of modern engineering culture; humour grounded in observational uncertainty; scale-based exaggeration and colonial self-comparison; and overt sceptical parody. These modes tracked shifting relationships between observation, interpretation and authority, allowing newspapers to entertain speculative ideas while marking the limits of scientific credibility. At the same time, humorous treatments positioned Australian readers within a global culture of science and modernity. Comparisons with projects such as the Suez and Panama Canals, and with European and American astronomers, aligned colonial audiences with metropolitan discourse, even as local experience with land, water and scale shaped the tone of satire. We demonstrate that Australian newspapers did not passively transmit overseas ideas but actively reworked them through humour, balancing fascination with restraint. More generally, this case suggests that humour could function as a cultural strategy through which historical newspaper audiences engaged with speculative scientific claims without abandoning trust in scientific authority.
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History and Philosophy of Physics

Mars in the Australian Press, 1875-1899. 2. Circulation and Attribution

Richard de Grijs

Between 1875 and 1899, Mars occupied a prominent and recurring position in newspaper reporting across Europe, North America and beyond. Although the scientific and cultural dimensions of this "Mars excitement" have been well studied in metropolitan contexts, far less attention has been paid to how planetary astronomy circulated through colonial press systems. This paper examines the Australian press as a case study in the global mediation of nineteenth-century astronomical knowledge. Drawing on a structured compilation of 1040 digitised newspaper articles accessed via the National Library of Australia, the study analyses patterns of first appearance, reprinting, attribution and temporal persistence in Australian Mars reporting. Mars-related news entered Australia primarily through international telegraphic networks and overseas syndication before circulating widely through metropolitan, regional and provincial newspapers. Distinguishing between novel reports and subsequent reprints reveals that apparent abundance often masked a small number of originating items that achieved extensive colonial reach. Attribution practices evolved over time, shifting from anonymous or institutional authority towards increasing reliance on named overseas figures such as Asaph Hall, William H. Pickering and, most notably, Percival Lowell. This shift reshaped both the form and longevity of Mars reporting, allowing interpretive and personality-driven material to persist independently of specific observational events. By emphasising circulation, attribution and temporal rhythm, this study situates Australian newspapers within international systems of scientific communication. Colonial journalism actively mediated astronomical knowledge rather than merely transmitting it, shaping how Mars became a durable object of public scientific attention in the late nineteenth century.
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Fluid Dynamics

A diffuse-interface model for N-phase flows with liquid-solid phase change

Jiangxu Huang, Chengjie Zhan, Zhenhua Chai et al. (+2 more)

In this work, we first propose a diffuse interface model for simulating N phase flows with solid liquid phase change. In this model, a phase field approach is adopted to capture multiphase fluid interfaces, and an enthalpy based formulation is used to describe the phase change. The volume changes resulting from density differences during phase change are incorporated by introducing a source term into the continuity equation. The method also satisfies the reduction consistent property, allowing it to rigorously degenerate to both the conservative phase field method for N phase flows and the classical enthalpy method for solid liquid phase change. Then a coupled lattice Boltzmann (LB) method is developed to solve this diffuse interface model. Some numerical tests, including film freezing, single droplet freezing, and compound droplet freezing are performed, and the results are in good agreement with the analytical solutions and data reported in the previous works. Furthermore, the proposed method is applied to study freezing dynamics of complex systems with insoluble impurities, capturing the interaction between the advancing freezing front and embedded impurities. It is found that the proposed diffuse interface method is accurate and efficient for studying N phase systems with phase change.
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All authors Jiangxu Huang, Chengjie Zhan, Zhenhua Chai, Changsheng Huang, Xi Liu

Atomic Physics

Finite-nuclear-size effect for hydrogenlike ions under high external pressure

Dengshan Liu, Huihui Xie, Pengxiang Du et al. (+4 more)

The influence of pressure on finite-nuclear-size corrections to atomic energy levels and electron-capture decay rate is investigated in confined hydrogenlike ions. The ions are modeled inside an impenetrable spherical cavity, with a Gaussian distribution used to represent the nuclear charge distribution. For each confinement radius used to simulate external pressure, the energies and wave functions of the lowest-lying bound states are determined by numerically solving the Dirac equation via the kinetically balanced generalized pseudospectral method. In contrast to unconfined ions, both the FNS corrections and electron-capture decay rates increase markedly under pressure and exhibit parallel trends with increasing confinement. Pressure also removes level degeneracies and alters the relative magnitudes of FNS corrections across different bound states. Moreover, the nuclear charge radius is found to significantly affect the pressure-enhanced electron-capture decay rate.
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All authors Dengshan Liu, Huihui Xie, Pengxiang Du, Tianshuai Shang, Jian Li, Jiguang Li, Tomoya Naito

Applied Physics · Cross-listed from cond-mat.mes-hall

Solitary waves in a phononic integrated circuit

Timothy M.F. Hirsch, Xiaoya Jin, Nicolas P. Mauranyapin et al. (+6 more)

Solitons are universal nonlinear excitations that appear in settings as varied as optics, water waves, and quantum gases [1-5]. While reduced models of soliton dynamics are well established, their validity and dynamical behaviour in strongly nonlinear regimes with frequent interactions remain largely unexplored experimentally. Progress has been constrained by the difficulty of simultaneously achieving precise control of dispersion and nonlinearity, together with the temporal and spatial resolution required for dynamical observations. Here we overcome these difficulties by producing acoustic solitons in integrated phononic waveguides. We exploit the interplay between waveguide dispersion and mechanical Kerr nonlinearity to generate 'dark' solitons that persist over metre-scale propagation distances. The slow phonon velocity allows direct imaging of hundreds of dark soliton collisions – two orders of magnitude more than have previously been accessible [6, 7] – as well as soliton fission and the melting of a soliton Wigner crystal. Furthermore, the unprecedented dynamical resolution allows us to verify two long-predicted aspects of dark soliton behaviour: the existence of a collisional phase shift and two depth-dependent collision regimes [8, 9]. These results not only illuminate fundamental nonlinear energy transport processes, but also show a path towards acoustic versions of soliton-enabled technologies such as frequency combs and mode-locked lasers [1, 2, 10].
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All authors Timothy M.F. Hirsch, Xiaoya Jin, Nicolas P. Mauranyapin, Nishta Arora, Erick Romero, Matthew Reeves, Glen I. Harris, Warwick P. Bowen, Christopher G. Baker

Atomic Physics · Cross-listed from cond-mat.mes-hall

Electron scattering by a magnetic monopole in solid-state experiments

P. S. Sidorov, N. A. Vlasov, I. S. Terekhov et al. (+1 more)

The scheme of experiment for studying electron scattering in the field of a magnetic monopole in two dimensional electron gas is proposed. The differential scattering cross section is obtained in the eikonal approximation. For unpolarized initial electron, the differential cross section coincides with that in the field of an infinitely long solenoid, up to redefinition of a magnetic flux. It is shown that the scattered electron becomes polarized even for unpolarized initial electron. Besides, in an experimental setup similar to the Hall experiment, the spin polarization arises in the direction perpendicular to the electron current.
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All authors P. S. Sidorov, N. A. Vlasov, I. S. Terekhov, A. I. Milstein

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

Ultrafast optical route to coupled ferroelectric and altermagnetic switching

Yuhao Gu, Yu-Hui Song, Peng-Jie Guo et al. (+5 more)

Exploring novel magnetoelectric coupling mechanisms to achieve control of ferroelectric polarization and magnetism is highly significant for both fundamental science and electronic device applications. Although extensive studies have been conducted on electrical switching of magnetism in multiferroic materials, simultaneous ultrafast laser switching of ferroelectric polarization and altermagnetism remains unexplored. In this letter, we propose that the ultrafast laser can be used to switch ferroelectric polarization and altermagnetism concurrently in charge-order-induced altermagnetic ferroelectrics. Building on this idea, we further demonstrate that such dual switching can be realized in charge-order-induced altermagnetic ferroelectric LiV$_2$F$_6$ by symmetry analysis and time-dependent density functional theory (TDDFT) calculation. Given that LiV$_2$F$_6$ has already been experimentally synthesized, our work not only provides an ideal material platform for experimentally realizing simultaneous switching of ferroelectric polarization and altermagnetism but also holds potential application value in future ultrafast spintronic devices.
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All authors Yuhao Gu, Yu-Hui Song, Peng-Jie Guo, Yihao Wang, Zhe Li, Ze-Feng Gao, Huan-Cheng Yang, Zhong-Yi Lu

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

Profound impacts of interlayer interactions in bilayer altermagnetic V2S2O

Siqi Xu, Qilong Cui, Shaowen Xu et al. (+6 more)

Two-dimensional altermagnets exhibit exceptional potential for low-power spintronics via nonrelativistic spin splitting and zero net magnetization. Here, we systematically investigate the influence of interlayer interactions on the electronic, magnetic and quantum transport properties of bilayer vanadium oxysulfide (V2S2O), a prototypical layered altermagnet, using DFT and NEGF calculations. Our results reveal that interlayer interactions predominantly modulate the p-orbital derived top valence bands, inducing a profound competitive valence band maximum position between Gamma-point pz and X/Y-point pxy orbitals, with an energy difference as small as 9 meV. Furthermore, interlayer interactions suppress the piezomagnetic effect and impose additional requirements on the type of strain for the bilayer system, compared to its monolayer counterpart. Out-of-plane external electric fields effectively weaken interlayer coupling by enlarging the energy difference of Gamma/X-Y top valence bands to 170 meV. Quantum transport simulations on a bilayer Au/V2S2O/Au two-probe device demonstrate the presence of pronounced spin current. Interlayer interactions reduce the transmission spin polarization from nearly 100% (monolayer) to 60% (bilayer) for energies above the Fermi level. Notably, gate-voltage modulation exhibits significant asymmetry in controlling charge-to-spin current conversion efficiency, originating from the out-of-plane symmetry breaking induced by the electrode geometry. Specifically, a positive gate voltage markedly enhances the contribution of the bottom layer to the overall spin polarization, while a negative gate voltage induces a marginal reduction of transmission spin polarization, attributed to the inherently weak polarization contribution of the bottom layer. These findings provide essential insights for the design and optimization of multilayer altermagnetic spintronics.
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All authors Siqi Xu, Qilong Cui, Shaowen Xu, Xianbo Chenwei, Jiahao Zhang, Ruixue Li, Yuan Li, Gaofeng Xu, Fanhao Jia

Computational Physics

Wafer-to-Wafer Bonding: Part: I – The Coupled Physics Problem and the 2D Finite Element Implementation

Kamalendu Ghosh, Bhavesh Shrimali and Subin Jeong

Wafer-to-wafer (WxW) bonding is a key enabler for three-dimensional integration, including hybrid bonding for fine-pitch Cu–Cu interconnects. During bonding, wafer deformation and the air entrapped between the wafers interact through a strongly coupled, time-dependent fluid–structure interaction (FSI) that can produce non-intuitive bonding dynamics and process sensitivities. This paper develops a mathematically consistent reduced-order model for WxW bonding by deriving a Kirchhoff–Love plate equation for wafer bending from three-dimensional linear elasticity and coupling it to a Reynolds lubrication equation for the inter-wafer air film. The resulting nonlinear plate–Reynolds system is discretized and solved monolithically in the high-performance FEniCSx framework using a $C^0$ interior-penalty formulation for the fourth-order plate operator, standard continuous Galerkin discretization for the pressure field, implicit time integration, and a Newton solver with automatic differentiation. Simulations reproduce experimentally reported wafer displacement histories for multiple initial gaps and verify force equilibrium at the bond front, where the Reynolds pressure acts as an effective contact reaction. Parametric studies reveal nonlinear, and in some cases non-monotonic, sensitivities of bonding-front kinetics to the initial gap, air viscosity, and interfacial energy, providing actionable trends for process optimization.
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Optics

Toward scalable and bias-stable optical phased arrays on lithium tantalate

Gongcheng Yue, Xuqiang Wang, Yihan Miao et al. (+9 more)

Ferroelectric materials are an ideal platform for high-speed reconfigurable photonic integrated circuits (PICs) for classical and quantum photonic computations, communications, and sensing. Most reconfigurable PIC devices achieve their functionalities via interference and are therefore highly sensitive to phase errors. Under static bias, carrier drift in ferroelectric waveguides induces continuous phase drift, creating a severe bottleneck for both PIC functionality and scalability. Here we propose achieving bias-stable and scalable ferroelectric PICs by exploiting the intrinsically low carrier drift of lithium tantalate (LT). Taking one of the PIC devices that is most sensitive to phase drift, the optical phased array (OPA), as an example, we designed and fabricated an integrated LT OPA that can keep the far-field main lobe 8 dB higher than side lobes for over 4 hours, representing at least a two-order-of-magnitude improvement over the state of the art. We demonstrated our device's capability in generating arbitrary spatiotemporal waveforms with a modulation frequency as low as 0.1 Hz, leading to practical applications in optical tweezers, trapped-ion quantum computers, adaptive optics for astronomy, AR, 3D printers, LiDAR, and free-space optical communications. Beyond OPA, our work establishes LT as a bias-stable, scalable, and high-speed PIC platform for large-scale classical and quantum photonic systems.
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All authors Gongcheng Yue, Xuqiang Wang, Yihan Miao, Bowen Chen, Yangming Zhan, Weiran Zhou, Phatham loahavilai, Jiachen Cai, Siyuan Yu, Chengli Wang, Xin Ou, Yang Li

Computational Physics

A Residual-Attention Physics-Informed Neural Network for Irregular Interfaces and Multi-Peak Transport Fields

Baitong Zhou, Ze Tao, Fujun Liu et al. (+1 more)

In complex engineering systems such as electro-thermal-fluid coupling, rapid and accurate prediction of multi-physics fields is essential for advanced applications like digital twins and real-time condition monitoring. Traditional numerical methods often suffer from high computational latency, whereas standard Physics-Informed Neural Networks (PINNs) frequently fail to capture critical local features, such as irregular interfaces, localized high-gradient regions, and multi-peak transport structures. To address these limitations and provide high-fidelity intelligent predictions for engineering decision-making, this paper proposes a Residual-Attention Physics-Informed Neural Network (RA-PINN) as a powerful surrogate modeling engine. The proposed method incorporates residual learning and attention enhancement into the network backbone to improve the representation of oblique transition structures, narrow charge layers, and distributed hotspots while strictly preserving global field consistency. To evaluate its effectiveness as an intelligent prediction framework, three representative benchmark cases are constructed, including an oblique asymmetric interface, a bipolar high-gradient charge layer, and a multi-peak Gaussian charge migration field. Under unified training settings, the proposed RA-PINN is systematically compared with a standard pure PINN and an LSTM-PINN in terms of average error, local maximum error, structural similarity, and convergence behavior. The results show that RA-PINN consistently achieves the best overall performance across all benchmark cases, demonstrating its tremendous potential as a highly reliable core inference engine for the condition monitoring and digital twin modeling of complex multi-physics engineering systems.
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All authors Baitong Zhou, Ze Tao, Fujun Liu, Xuan Fang

Atomic and Molecular Clusters

Interatomic Coulombic decay initiated by electron removal and excitation processes in helium ion and argon dimer collisions

Darij Starko and Tom Kirchner

The electron removal and excitation channels in argon dimer target and helium ion projectile collision systems that facilitate interatomic Coulombic decay (ICD) are investigated. We implement an independent-atom and independent-electron model of the collision system with the dimer target fixed at its equilibrium bond length and the He$^{2+}$ and He$^+$ ion projectiles travelling parallel to the dimer axis at impact energies ranging from 10 keV/amu to 150 keV/amu. The coupled-channel two-center basis generator method for orbital propagation is used within both a frozen atomic target approximation and a dynamic response framework. Given that ICD is facilitated through electron excitation pathways in argon dimers, a statistical technique called determinantal analysis is employed to investigate these channels. The analysis is further subdivided into models that exclude and include projectile charge changes during the collision. Electron configurations of the form Ar$^{+}$($3p^{-2}nl$) offer a pathway to ICD and are investigated, along with other one- and two-electron removal channels that lead to Ar$^{+}$-Ar$^{+}$ fragmentation. We find that the $3d$ excited state is an overall dominant channel for ICD with other excited states ranging from $4s$-$4f$ also being significant contributors. Our study notes differences between static and dynamical potential models across the projectile impact energy range, though of decreasing significance as the impact energy approaches 150 keV/amu. We also find that a He$^{+}$ projectile offers a strong pathway for ICD as the projectile impact energy decreases.
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