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Physics Physics

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Thursday 18 December

Medical Physics · Cross-listed from cs.CV

ResDynUNet++: A nested U-Net with residual dynamic convolution blocks for dual-spectral CT

Ze Yuan, Wenbin Li and Shusen Zhao

We propose a hybrid reconstruction framework for dual-spectral CT (DSCT) that integrates iterative methods with deep learning models. The reconstruction process consists of two complementary components: a knowledge-driven module and a data-driven module. In the knowledge-driven phase, we employ the oblique projection modification technique (OPMT) to reconstruct an intermediate solution of the basis material images from the projection data. We select OPMT for this role because of its fast convergence, which allows it to rapidly generate an intermediate solution that successfully achieves basis material decomposition. Subsequently, in the data-driven phase, we introduce a novel neural network, ResDynUNet++, to refine this intermediate solution. The ResDynUNet++ is built upon a UNet++ backbone by replacing standard convolutions with residual dynamic convolution blocks, which combine the adaptive, input-specific feature extraction of dynamic convolution with the stable training of residual connections. This architecture is designed to address challenges like channel imbalance and near-interface large artifacts in DSCT, producing clean and accurate final solutions. Extensive experiments on both synthetic phantoms and real clinical datasets validate the efficacy and superior performance of the proposed method.
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Fluid Dynamics

Intermittent Motility of a Synthetic Active Particle in Changing Environments

Rudra Sekhri, Rahil N. Valani and Tapio Simula

We experimentally investigate the dynamics of synthetic active particles composed of gravitationally bouncing, superwalking droplets confined within an annular fluid bath. Driven by a topologically pumping dual-frequency waveform, the droplets exhibit alternating active (walking) and dormant (bouncing) phases, producing intermittent azimuthal motion. Tracking individual droplets reveals pseudolaminar chaotic dynamics in the time series of particle's angular position, characterized by laminar plateaus that are interrupted by short irregular bursts of activity. Increasing the driving amplitude induces a qualitative change in the active particle's intermittent dynamics, arising from a symmetry-breaking transition in its Faraday-wave field environment: continuous SO(2)-symmetric "channelling" waves give way to discrete "trapping" patterns. These findings demonstrate how environmental symmetry and spatiotemporal structure modulate motility and intermittency in synthetic active matter.
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Chemical Physics

Resolving electronic evolution during bond dissociation

Tian Wang, Nida Haram, Zack Dube et al. (+13 more)

Coupled electronic and nuclear motions govern chemical reactions, yet resolving how electronic structure evolves during bond dissociation remains a central challenge. Here we investigate the photodissociation of Br2 using correlated photoelectron photoion coincidence measurements. A 400 nm pulse initiates dissociation, while strong field ionization probes the evolving molecular system. Coincident measurement of three dimensional photoion and photoelectron momenta provides simultaneous access to the internuclear separation and the accompanying electronic evolution. We identify multiple distinct stages of electronic evolution during bond dissociation. The reshaping of the ionizing molecular orbital occurs first, followed by redistribution and localization of the electronic charge density, and finally by the gradual decay of residual electronic coherence between the separating atomic centers. Between the molecular and atomic limits, we observe an intermediate bond-breaking state in which localized atomic character coexists with a partially delocalized electronic response. By combining correlated observables with semiclassical modelling, we resolve the temporal ordering of these coupled electronic and nuclear processes and determine their associated dynamical timescales. These results demonstrate how correlated momentum observables can disentangle different aspects of the molecular-to-atomic transition.
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All authors Tian Wang, Nida Haram, Zack Dube, Kyle A. Hamer, Yonghao Mi, Fatemeh Karimi, Andrei Yu. Naumov, Giulio Vampa, Caterina Vozzi, Xiaojun Liu, Albert Stolow, Michael Schuurman, Nicolas Douguet, David Villeneuve, Paul B. Corkum, Andre Staudte

Optics

A dispersion-driven 3D color near-eye meta-display

Zi Wang, Dong Zhao, Li Liang et al. (+4 more)

Chromatic dispersion, an inherent wavelength-dependent phenomenon in optical systems, has traditionally been regarded as a detrimental effect to be minimized in imaging and display. Here, we present a paradigm shift by deliberately engineering and harnessing metalens dispersion as a functional mechanism for three-dimensional (3D) near-eye displays. Specifically, we exploit lateral dispersion to transform transverse offset between green and red objects into image-space angular separations that make their images intersected virtually, thereby creating color-merged 3D virtual-image perception. This meta-display architecture preserves compactness of conventional planar display while exhibiting less data requirements and lower hardware complexity than other near-eye 3D displays. Experimentally, we demonstrate a multi-color near-eye 3D system achieving an 11{\deg} field of view, 22 pixels-per-degree angular resolution, 0.9 m depth of field, and 19 distinct image planes. This work establishes a new pathway for metasurfaces toward visual displays and highlights great potential for future virtual/augmented reality.
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All authors Zi Wang, Dong Zhao, Li Liang, Hengyi Wang, Yuan Liu, Fang-Wen Sun, Kun Huang

Fluid Dynamics

Wake transitions and melting dynamics of a translating sphere in warm liquid

Zhong-Han Xue and Jie Zhang

We investigate the three-dimensional melting dynamics of an initially spherical particle translating in a warmer liquid using sharp-interface simulations that fully resolve both solid and fluid phases with the Stefan condition. A wide parameter space is explored, spanning initial Reynolds number ($Re_0$), Stefan number ($St$), and Richardson number ($Ri$). In the absence of buoyancy ($Ri= 0$), the interface evolution is governed by canonical wake bifurcations. Four regimes are identified: an axi-symmetric regime ($Re_0<212$) with a rounded front and planar rear; a steady-planar-symmetric regime ($212<Re_0<273$) with an inclined rear plane; a periodic-planar-symmetric regime ($273<Re_0<355$) where vortex shedding emerges in the wake; and a chaotic regime ($Re_0>355$) with fluctuating stagnation points and a more rounded rear. Despite these differences, all regimes exhibit a tendency toward melt-rate homogenisation over time. Besides, we introduce an aspect-ratio-based surface-area formulation that yields a predictive model, accurately capturing volume evolution across regimes. Hydrodynamic loads also reflect the coupling between shape and flow: drag follows rigid-sphere correlations only at moderate $Re_0$; planar rears enhance drag at higher $Re_0$; lift appears only in symmetry-broken regimes and reverses late in time; torque reorients the rear plane toward vertical, consistent with free-body experiments. When buoyancy is included, assisting configurations ($Ri>0$) suppress recirculation and maintain quasi-spherical shapes, whereas opposing or transverse buoyancy ($Ri<0$) destabilises wakes and promotes tilted planar rears. These results provide a unified framework for convection-driven melting across laminar, periodic, and chaotic wakes, with implications for geophysical and industrial processes.
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Computational Physics

ClusTEK: A grid clustering algorithm augmented with diffusion imputation and origin-constrained connected-component analysis: Application to polymer crystallization

Elyar Tourani, Brian J. Edwards and Bamin Khomami

Grid clustering algorithms are valued for their efficiency in large-scale data analysis but face persistent limitations: parameter sensitivity, loss of structural detail at coarse resolutions, and misclassifications of edge or bridge cells at fine resolutions. Previous studies have addressed these challenges through adaptive grids, parameter tuning, or hybrid integration with other clustering methods, each of which offers limited robustness. This paper introduces a grid clustering framework that integrates Laplacian-kernel diffusion imputation and origin-constrained connected-component analysis (OC-CCA) on a uniform grid to reconstruct the cluster topology with high accuracy and computational efficiency. During grid construction, an automated preprocessing stage provides data-driven estimates of cell size and density thresholds. The diffusion step then mitigates sparsity and reconstructs missing edge cells without over-smoothing physical gradients, while OC-CCA constrains component growth to physically consistent origins, reducing false merges across narrow gaps. Operating on a fixed-resolution grid with spatial indexing ensures the scaling of O(nlog n). Experiments on synthetic benchmarks and polymer simulation datasets demonstrate that the method correctly manages edges, preserves cluster topology, and avoids spurious connections. Benchmarking on polymer systems across scales (9k, 180k, and 989k atoms) shows that optimal preprocessing, combined with diffusion-based clustering, reproduces atomic-level accuracy and captures physically meaningful morphologies while delivering accelerated computation.
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Physics Education

Share, Rotate, Split: The Effects of Group Work Role Distributions on Student Outcomes

Jacob Feinleib, Matthew Dew and N.G. Holmes

Education literature recommends many different strategies for structuring student group work in labs. Many of these strategies, however, have not been sufficiently evaluated for their effects on student outcomes. One prior study suggested that sharing roles, rather than splitting roles, in lab groups can boost students' physics interest and self-efficacy. Here, we expand upon this literature by evaluating the effects of a broader range of role distributions across several student outcomes from a large sample at two different institutions. We developed a survey item to probe the ways students distribute their roles in lab groups. The item asks for the percent of time in lab they spent working together on lab roles (sharing), working alone on roles but rotating each session (rotating), and working alone in the same role throughout the semester (splitting). We employed hierarchical linear modeling to measure the effects of these role distributions on student critical thinking, self-efficacy, perceived agency, belonging, and sense of recognition based on survey items specific to physics lab contexts. We found that role distributions did not differentially impact student critical thinking. We also found that sharing roles tended to have a positive impact on student attitudes; splitting had a negative effect on attitudes; and rotating fell in between. Statistical significance varied across these attitudinal outcomes. Our findings invite further research and controlled studies to better understand the apparent benefits of sharing, rotating, and splitting roles in introductory physics labs.
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Data Analysis and Statistics · Cross-listed from cond-mat.stat-mech

Complete Decomposition of Anomalous Diffusion in Variable Speed Generalized Lévy Walks

Abhijit Bera and Kevin E. Bassler

Variable Speed Generalized Lévy Walks (VGLWs) are a class of spatio-temporally coupled stochastic processes that unify a broad range of previously studied models within a single parametrized framework. Their dynamics consist of discrete random steps, or flights, during which the walker's speed varies deterministically with both the elapsed time and the total duration of the flight. We investigate the anomalous diffusive behavior of VGLWs and analyze it through decomposition into the three fundamental constitutive effects that capture violations of the Central Limit Theorem (CLT): the Joseph effect, reflecting long-range increment correlations, the Noah effect, arising from heavy-tailed step-size distributions with infinite variance, and the Moses effect, associated with statistical aging and non-stationarity. Our results show that anomalous diffusion in VGLWs is typically generated by a nontrivial combination of all three effects, rather than being attributable to a single mechanism. Strikingly, we find that within the VGLW framework the Noah exponent $L$, which quantifies the strength of the Noah effect, is unbounded from above, revealing a richer and more extreme landscape of anomalous diffusion than in previously studied Lévy-walk-type models.
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Accelerator Physics · Cross-listed from nlin.SI

Frequency Extraction from Invariant Flows

Derong Xu, Yongjun Li, Yue Hao et al. (+1 more)

In non-degenerate integrable Hamiltonian systems, invariant tori can be parameterized equivalently by action variables or by their fundamental frequencies. We introduce an invariant-flow formulation for extracting fundamental frequencies of integrable Hamiltonian systems. By treating invariants as generators of commuting Hamiltonian flows, the frequencies are obtained from time-of-flight parameters along these flows, providing a direct alternative to action-angle constructions and spectral methods based on long time series. The approach yields an explicit numerical procedure that extends naturally to systems with multiple degrees of freedom. Its effectiveness is demonstrated using the McMillan map, where machine-precision accuracy is achieved.
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All authors Derong Xu, Yongjun Li, Yue Hao, Sergei Nagaitsev

Wednesday 17 December

Chemical Physics

NMIRacle: Multi-modal Generative Molecular Elucidation from IR and NMR Spectra

Federico Ottomano, Yingzhen Li and Alex M. Ganose

Molecular structure elucidation from spectroscopic data is a long-standing challenge in Chemistry, traditionally requiring expert interpretation. We introduce NMIRacle, a two-stage generative framework that builds upon recent paradigms in AI-driven spectroscopy with minimal assumptions. In the first stage, NMIRacle learns to reconstruct molecular structures from count-aware fragment representations, capturing both fragment identities and their occurrences. In the second stage, a spectral encoder maps input spectra (IR, 1H-NMR, 13C-NMR) into a latent embedding used to condition the pre-trained generator, which is fine-tuned for direct spectra-to-molecule generation. This formulation bridges fragment-level chemical modeling with spectral evidence, yielding accurate molecular predictions. Empirical results demonstrate that NMIRacle outperforms existing baselines on molecular elucidation, while maintaining robust performance across increasing levels of molecular complexity.
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Plasma Physics · Cross-listed from hep-ph

Characteristic features of the resonant trident process in the field of a strong monochromatic electromagnetic wave

S.P. Roshchupkin and M.V. Shakhov

The characteristic features of the resonant trident process (Oleinik resonances) have been theoretically studied in a wide range of frequencies and intensities of a circularly polarized strong electromagnetic wave. The resonant trident process is defined by two characteristic quantum energies: the characteristic energy of the nonlinear Compton effect and the characteristic energy of the nonlinear Breit-Wheeler process. These characteristic energies depend significantly on the frequency and intensity of the wave, as well as on the angle between the momenta of the initial electrons and the electromagnetic wave. The resonant trident process is effective when the energy of the initial electrons is greater than or on the order of magnitude of the corresponding characteristic energies. It is shown that quantum entanglement of final particles takes place in this resonant process. An important aspect of the resonant trident process is the equality of the energies of the electron and positron pairs. Analytical expressions for the differential rates of the resonant trident process on the energy of final particles are obtained. The corresponding analytical expressions for full rates have also been obtained. It is shown that the rate data of the resonant trident process in the field of optical and X-ray wave frequencies significantly exceed the corresponding rate of the non-resonant trident process. Results obtained can be used in experiments at leading laser centers, as well as to explain QED processes in strong X-ray fields near neutron stars and magnetars.
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Physics and Society

Identifying and understanding obstacles to heating sobriety and thermal comfort in collective housing: Insights from a survey in France

Enzo Cabezas-Rivière, Maxime Robillart, Aline Barlet et al. (+3 more)

In many countries, central heating systems are widely used in multifamily housing allowing maintenance and costs to be shared. However, these systems often limit residents' control over their own consumption, complicating efforts to reduce energy use and maintain comfort. Despite the growing importance of household energy savings in national and European climate targets, little research has examined user experiences with these systems. This study addresses that gap through an exploratory survey conducted in France. Grounded in scientific literature, technical analyses, and current policy frameworks, the survey was distributed through various channels-including public institutions, online platforms, and field outreach-and collected 403 responses. It examined user difficulties in managing heating, including challenges with controls, bill comprehension, and communication with landlords. It also explored behaviours with high energy-savings impact: reducing heating at night or during absences, window opening, and shutter use. Findings show that many residents face barriers to energy-efficient heating, often due to difficult-to-use controls, limited feedback on consumption, and poor support from landlords or property managers. Those who do not reduce heating at night or when away frequently report these challenges. Participants expressed strong interest in solutions such as personalized advice, real-time feedback, and connected radiator valves to improve comfort, control, and energy management. This work highlights the need to better integrate user experience into multifamily housing energy policies. It provides actionable insights for policymakers and housing providers seeking to enhance comfort and energy savings while supporting France and Europe's broader energy transition goals.
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All authors Enzo Cabezas-Rivière, Maxime Robillart, Aline Barlet, Thomas Recht, Laurent Mora, Patrick Sebastian

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

Pulse-Mode Operation and Reliability of BEOL-Compatible Ferroelectric Non-Volatile Capacitive Memories with Amorphous Oxide Semiconductor Channels

Junmo Lee, Chengyang Zhang, Tae-Hyeon Kim et al. (+2 more)

Non-volatile capacitive memories (nvCAPs) exhibiting AC small-signal capacitance on/off ratio (Con/Coff) with non-destructive read have emerged as a promising device for next-generation memory paradigms. Recently, BEOL-compatible ferroelectric nvCAPs with an amorphous oxide semiconductor channel have been reported, suggesting the possibility of monolithic 3D integration of nvCAPs on top of CMOS. So far, the characterization studies on oxide-channel ferroelectric nvCAPs have been done using dual DC sweep C-V measurements which are typically performed over a time scale of a few seconds. However, non-volatile memory arrays typically require nvCAPs to operate under pulse-mode. It is thus crucial to advance understanding of the behavior of oxide-channel ferroelectric nvCAPs under pulse-mode operation, governed by the unique interplay between ferroelectric layer and oxide channel physics. In this study, we provide a systematic study of the pulse-mode operation of ferroelectric nvCAPs with an amorphous oxide semiconductor channel, including its pulse-based write characteristics and reliability characteristics. We examine overlap area, wake-up and pulse-width dependent Con and Coff writing characteristics under pulse-mode. Further, we suggest the importance of optimizing ferroelectric depolarization for Con retention, while reducing read-after-delay for Coff retention under pulse-mode. Lastly, non-destructive read operation for >10^9 read stress cycles at |Vread|=1V is demonstrated.
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All authors Junmo Lee, Chengyang Zhang, Tae-Hyeon Kim, Suman Datta, Shimeng Yu

Fluid Dynamics · Cross-listed from astro-ph.SR

Direct calculation of steady-state hydrodynamic solar wind solutions with newtonian viscosity

Roger B. Scott, Stephen J. Bradshaw, Mark G. Linton et al. (+2 more)

Steady-state solutions to the Navier-Stokes equations are known to admit solutions that are singular at the sonic point. Consequently, inviscid solar wind models require special treatment of the solution near the sonic points, and this has proven to be a significant impediment to efficient modeling of the solar wind. In this paper we revisit the governing hydrodynamic equations for the expanding solar wind, with the inclusion of the classical (Newtonian) viscous stress , and we show how this inclusion eliminates the singularities that emerge from the inviscid equations. This result has been previously reported and used to generate solar wind profiles from initial conditions in the asymptotic limit; however, those studies did not include realistic treatments of the inner corona, and generally rejected the prospect of extrapolating solutions outward from the Sun into the heliosphere. Here, we expand this method to include external heating and optically thin radiative losses and show that solutions can be computed from initial conditions near the solar surface, thereby capturing the entire range of scales from below the transition region to the outer heliosphere in a single solution. Our approach is to cast the steady-state Navier-Stokes equations as a system of five coupled, ordinary differential equations (ODEs), which we solve using conventional methods, without any special treatment of the governing equations in the vicinity of the sonic point. The representative solutions that we present here demonstrate the utility and efficiency of this extrapolation method, which is considerably more realistic than commonly used analytical or empirical models. This method provides a direct approach to generating accurate solar wind profiles subject to observationally motivated initial conditions near the solar surface, at a fraction of the computational cost of comparable relaxation-based models.
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All authors Roger B. Scott, Stephen J. Bradshaw, Mark G. Linton, Chris Lowder, Leonard Strachan

Atomic Physics

Precision continuous-wave laser measurement of the $\text{1}^\text{3}\text{S}_\text{1} \to \text{2}^\text{3}\text{S}_\text{1}$ interval in positronium

Lucas de Sousa Borges, Edward Thorpe-Woods, Evans Javary et al. (+1 more)

We report a 4.9\,ppb measurement of the positronium $\text{1}^\text{3}\text{S}_\text{1} \to \text{2}^\text{3}\text{S}_\text{1}$ interval using continuous-wave two-photon laser spectroscopy. The transition is detected via photoionization by the same excitation laser. The resulting positrons are guided to a microchannel plate detector, surrounded by scintillators to detect the annihilation photons in coincidence, thereby reducing the background. A Monte Carlo lineshape simulation, accounting for effects such as the second-order Doppler shift and the AC Stark shift, is used to extract a transition frequency of $1233607224.1(6.0)\,\text{MHz}$, consistent with the previous 2.6\,ppb determination of this transition and with the most recent QED calculations at order $\mathcal{O}(\alpha^7\ln^2(1/\alpha))$, which predict $1233607222.12(58)\,\text{MHz}$. Combining the two measurements gives $1233607218.1(2.8)\,\text{MHz}$, reducing the tension with QED to about $1.4\,\sigma$. We also present a semi-analytical lineshape model of $\text{1}^\text{3}\text{S}_\text{1} \to \text{2}^\text{3}\text{S}_\text{1}$ of positronium, which shows excellent agreement with detailed simulations and is validated by the experimental data. This expands on previous work with stable atoms by incorporating effects such as limited lifetime of the atoms, photoionization and AC Stark shift. The lineshape modelling is also applicable to other unstable systems, such as muonium. This provides a powerful tool for optimizing the experimental parameters and gaining deeper insights without the need for computationally intensive simulations.
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All authors Lucas de Sousa Borges, Edward Thorpe-Woods, Evans Javary, Paolo Crivelli

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

Magneto-optical Kerr effect in pump-probe setups

Amir Eskandari-asl and Adolfo Avella

We develop a general theoretical framework for computing the time-resolved magneto-optical Kerr effect in ultrafast pump-probe setups, formulated within the Dynamical Projective Operatorial Approach (DPOA) and its application to the generalized linear-response theory for pumped systems. Furthermore, we exploit this formalism to express the post-pump optical conductivity and consequently the Kerr rotation in terms of the time-evolved single-particle density matrix (SPDM), providing a transparent and computationally efficient description of photo-excited multi-band systems. This extension, in addition to its lower computational cost, has the advantage of allowing the inclusion of phenomenological damping. We illustrate the formalism using both (i) a two-band tight-binding model, which captures the essential physics of ultrafast spin-charge dynamics and the Kerr rotation, and (ii) weakly spin-polarized germanium, as a realistic playground with a complex band structure. The results demonstrate that, by exploiting DPOA and/or its SPDM extension, one can reliably reproduce both the short-time features under the pump-pulse envelope and the long-time dynamics after excitation, offering a versatile framework for analyzing time-resolved magneto-optical Kerr effect experiments in complex materials. Moreover, this analysis clearly shows that the Kerr rotation can be used to deduce experimentally the relevant n-photon resonances for a given specific material.
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Computational Physics

Sparse Operator-Adapted Wavelet Decomposition Using Polygonal Elements for Multiscale FEM Problems

Furkan Ş{\i}k, F.L.Teixeira and B.Shanker

We develop a sparse multiscale operator-adapted wavelet decomposition-based finite element method (FEM) on unstructured polygonal mesh hierarchies obtained via a coarsening procedure. Our approach decouples different resolution levels, allowing each scale to be solved independently and added to the entire solution without the need to recompute coarser levels. At the finest level, the meshes consist of triangular elements which are geometrically coarsened at each step to form convex polygonal elements. Smooth field regions of the domain are solved with fewer, larger, polygonal elements, whereas high-gradient regions are represented by smaller elements, thereby improving memory efficiency through adaptivity. The proposed algorithm computes solutions via sequences of hierarchical sparse linear-algebra operations with nearly linear computational complexity.
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Fluid Dynamics

Analytical Solutions for Turbulent Channel Flow Using Alexeev and Navier-Stokes Hydrodynamic Equations: Comparison with Experiments

Alex Fedoseyev

Understanding turbulent boundary layer flows is important for many application areas. Enhanced theoretical models may provide deeper insights into the fundamental mechanisms of turbulence that elude current models; therefore, the search for improved kinetic equations and their respective hydrodynamic equations continues. In this work, we consider the Generalized Boltzmann Equation (GBE), proposed by Alexeev (1994). The GBE accounts for finite particle size and the variation of the distribution function over timescales of the order of the collision time. The Alexeev hydrodynamic equations are derived from the GBE. In this work, the Alexeev hydrodynamic equations (AHE) and Navier-Stokes (NS) equations are solved analytically for turbulent channel flow under the assumption that stationary solutions yield the mean flow velocity. The analytical solutions of the AHE are validated by numerical solutions and compared with the NS solutions and experimental data for turbulent channel flow from multiple sources, spanning Reynolds numbers from 3,000 to 35,000,000. Solutions of the AHE demonstrate significantly better agreement with experimental data than those obtained from the NS equations. The analytical solution revealed a new similarity parameter: the boundary layer thickness scale, which coincides with the Kolmogorov microscale observed in experiments. The mechanisms for turbulence generation and control are discussed.
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Applied Physics

Vertical NAND in a Ferroelectric-driven Paradigm Shift

Giuk Kim, Hyojun Choi, Prasanna Venkat Ravindran et al. (+12 more)

Over the past decades, the relentless scaling and mass production of flash memory have underpinned the data-centric era. Yet charge-trap-based 3D NAND flash is now constrained by intrinsic physical and architectural limits, including reliability degradation at the device level, high operating power at the array level, and vertical scaling saturation at the system level. These bottlenecks hinder further advances in storage density and energy efficiency required by memory-centric computing. This Perspective outlines how coupling ferroelectric polarization with charge trapping can reconfigure the foundations of flash memory. In these hybrid architectures, polarization offers an energy-efficient pathway for charge modulation through enhanced Fowler-Nordheim tunneling, while trapped charges reinforce polarization-driven states to ensure stability. Such synergistic dynamics enable low-voltage operation and integration beyond one thousand layers without compromising process compatibility. We discuss the material, device, and architectural transitions required to realize this hybrid technology and chart future research directions to overcome the remaining scaling bottlenecks. Hybrid ferroelectric NAND extends conventional flash toward a scalable and energy-efficient platform, marking a paradigm shift for next-generation non-volatile memory.
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All authors Giuk Kim, Hyojun Choi, Prasanna Venkat Ravindran, Moonyoung Jung, Sanghyun Park, Kijoon Kim, Suhwan Lim, Kwangyou Seo, Kwangsoo Kim, Wanki Kim, Daewon Ha, Sukjoong Shin, Asif Khan, Sanghun Jeon, Kai Ni

Chemical Physics

Exploring Overlapping Mechanisms of Dynamic Nuclear Polarization in Type 1b HPHT Diamond

Brendan C. Sheehan, Margaret Hubble, Daphna Shimon et al. (+1 more)

The inhomogeneous distribution of P1 centers in type 1b HPHT diamond samples allows multiple DNP mechanisms to occur within the same crystal, resulting in complex DNP spectra. At some crystal orientations, different DNP mechanisms can compete to drive hyperpolarization with different signs at the same applied microwave frequency. We perform microwave-irradiated DNP using both monochromatic and frequency-modulated microwave excitation to explore the competition between these DNP mechanisms in diamond at room temperature. We demonstrate that frequency-modulated DNP is a tool for suppressing certain DNP mechanisms while enhancing others in a single-crystal diamond sample. Frequency modulation also enables higher enhancement of the NMR signal beyond traditional monochromatic DNP under some conditions. In a powder sample, competing enhancement mechanisms can also arise from different crystallite orientations in the powder. We observe that at certain microwave frequencies the DNP signal changes sign during the polarization build-up, even with monochromatic microwave irradiation. We do not observe this phenomenon in any single-crystal spectrum. We discuss both methods of investigating competing mechanisms of DNP as a means of selectively enhancing different DNP mechanisms driving $^{13}$C NMR signal enhancement.
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All authors Brendan C. Sheehan, Margaret Hubble, Daphna Shimon, Chandrasekhar Ramanathan

Optics

Optical coprocessor based on spontaneous Brillouin scattering

I. V. Vovchenko, A. A. Zyablovsky, A. A. Pukhov et al. (+1 more)

Analog coprocessors for neural networks are an intensively developing field. They provide approximate results of computations for relatively low energy cost and at high speed. We show that a set of ring resonators with Brillouin interaction between photons and phonons, being coupled to a waveguide, can be used to implement matrix-vector multiplication. The input vector is formed by occupancies of the anti-Stokes optical modes pumped via spontaneous Brillouin scattering, i.e, scattering on thermal phonons. Brillouin scattering rates and coupling constants between ring resonators and the waveguide form the matrix. The system allows for parallel computations in frequency band.
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All authors I. V. Vovchenko, A. A. Zyablovsky, A. A. Pukhov, E. S. Andrianov

Instrumentation and Detectors

Measurement of Light Yield Response of Gd-compatible Water-based Liquid Scintillator with the Brookhaven 1-ton testbed

S. Gwon, M. Askins, D.M. Asner et al. (+19 more)

The Water-based Liquid Scintillator (WbLS) enables hybrid detection by combining scintillation and Cherenkov signals, providing superior event reconstruction capabilities compared to conventional neutrino detectors. We measured the light yield of Gd-compatible WbLS at varying concentrations from 0.35% to 1% by mass, using cosmic-ray muons in a 1-ton scale detector at BNL. The light yield is measured as (69.16 $\pm$ 6.92) ph / MeV at 0.35% concentration, which increased to (87.32 $\pm$ 8.73) ph / MeV at 1%. These results establish a quantitative basis for optimizing future WbLS-based detectors in neutrino physics.
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All authors S. Gwon, M. Askins, D.M. Asner, A. Baldoni, D.F. Cowen, R. Diaz Prerez, M.V. Diwan, S. Gokhale, S. Hans, P. Kumar, G. Lawley, S. Linden, G.D. Orebi Gann, J. Park, C. Reyes, R. Rosero, K. Siyeon, M. Smiley, J.J. Wang, M. Wilking, G. Yang, M. Yeh

Optics

Full-field-of-view aberration correction for large arrays of focused beams

Yohann Machu, Gautier Creutzer, Clément Sayrin et al. (+1 more)

We propose and implement an aberration correction method for the creation of extended arrays of spots well beyond the isoplanatic region of any optical system. The method relies on an extensive calibration of aberrations in terms of Zernike polynomials over the full accessible field of an optical system. We introduce a modified Gerchberg-Saxton algorithm for generating holographic phase masks creating fully corrected arbitrary arrays of spots. By applying the method to an aspherical lens, and using a liquid-crystal spatial light modulator (SLM), we increase the aberration-free field of view from 50 to 500 $\mu$m, only limited by the largest diffraction angles accessible to the SLM. This opens new perspectives for the generation of large arrays of optical tweezers, especially for neutral atom based quantum processors and simulators.
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All authors Yohann Machu, Gautier Creutzer, Clément Sayrin, Michel Brune

Optics

Off resonant Fano enhanced single molecule resolution imaging with a CW source

Rasim Volga Ovali, Taner Tarik Aytas, Ramazan Sahin et al. (+1 more)

Apertureless scanning near-field optical microscopy (a-SNOM) is typically limited to ~10 nm resolution by the tip apex size. We demonstrate that ~1-nm resolution can be achieved under continuous-wave (CW) illumination by exploiting Fano path interference. A defect center that naturally forms at the apex of a metal-coated AFM tip acts as a quantum object and induces Fano interference, forcing a stronger but normally off-resonant plasmonic mode (597 nm) to operate effectively on resonance at the driving wavelength (520 nm). Because this interference occurs only beneath the defect, a ~1-nm-wide, strongly enhanced near-field hotspot is created. Using this off-resonant Fano-enhanced field, we achieve single-molecule-resolution imaging based on exact three-dimensional Maxwell simulations.
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All authors Rasim Volga Ovali, Taner Tarik Aytas, Ramazan Sahin, Mehmet Emre Tasgin

Plasma Physics

Tensor network approaches for plasma dynamics

Ryan J.J. Connor, Preetma Soin, Callum W. Duncan et al. (+1 more)

The dynamics of plasmas are governed by a set of non-linear differential equations which remain challenging to solve directly for large 2D and 3D problems. Here we investigate how tensor networks could be applied to plasmas described by the Vlasov-Maxwell system of equations and investigate parameter regimes which show promise for efficient simulations. We show for low-dimensional problems that the simplest form of tensor networks known as a Matrix Product State performs sufficiently well, however in regimes with a strong permanent magnetic field or high-dimensional problems one may need to consider alternative tensor network geometries. We conclude the study of the Vlasov-Maxwell system with the application of tensor networks to an industrially relevant test case and validate our results against state of the art plasma solvers based on Particle-In-Cell codes. We also extend the application of tensor networks to the alternative plasma description of Magnetohydrodynamics and outline how this can be encoded using Matrix Product States.
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All authors Ryan J.J. Connor, Preetma Soin, Callum W. Duncan, Andrew J. Daley

Computational Physics · Cross-listed from cs.LG

Introduction to Symbolic Regression in the Physical Sciences

Deaglan J. Bartlett, Harry Desmond, Pedro G. Ferreira et al. (+1 more)

Symbolic regression (SR) has emerged as a powerful method for uncovering interpretable mathematical relationships from data, offering a novel route to both scientific discovery and efficient empirical modelling. This article introduces the Special Issue on Symbolic Regression for the Physical Sciences, motivated by the Royal Society discussion meeting held in April 2025. The contributions collected here span applications from automated equation discovery and emergent-phenomena modelling to the construction of compact emulators for computationally expensive simulations. The introductory review outlines the conceptual foundations of SR, contrasts it with conventional regression approaches, and surveys its main use cases in the physical sciences, including the derivation of effective theories, empirical functional forms and surrogate models. We summarise methodological considerations such as search-space design, operator selection, complexity control, feature selection, and integration with modern AI approaches. We also highlight ongoing challenges, including scalability, robustness to noise, overfitting and computational complexity. Finally we emphasise emerging directions, particularly the incorporation of symmetry constraints, asymptotic behaviour and other theoretical information. Taken together, the papers in this Special Issue illustrate the accelerating progress of SR and its growing relevance across the physical sciences.
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All authors Deaglan J. Bartlett, Harry Desmond, Pedro G. Ferreira, Gabriel Kronberger

Physics Education

Macroscopic Brownian Motion on a Chaotic Fluid Interface

Jack-William Barotta, Caroline M. Barotta, Eli Silver et al. (+1 more)

Brownian motion is the erratic motion of an object due to collisions with the fluid in which it is immersed. In this work, we detail a tabletop laboratory demonstration of underdamped Brownian motion wherein a macroscopic particle resting on a driven fluid interface exhibits ballistic motion at short times and diffusive motion at long times. We observe the trajectory of a millimetric disk driven by a field of chaotic Faraday waves excited by a shaker. The crossover from ballistic to diffusive motion occurs at time and length scales experimentally accessible through particle tracking of a video recorded with a standard phone camera. Along with representative data, we provide a complete assembly guide, and operating procedure for students so that the experiment can be readily applied in the classroom. The tabletop setup can also be adapted for other student projects and active research topics relating to particle motion on a vibrating fluid interface.
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All authors Jack-William Barotta, Caroline M. Barotta, Eli Silver, Daniel M. Harris

Chemical Physics

Tree Tensor Networks Methods for Efficient Calculation of Molecular Vibrational Spectra

Shuo Sun, Richard M. Milbradt, Stefan Knecht et al. (+2 more)

We develop and employ general Tree Tensor Networks (TTNs) to compute the vibrational spectra for two model systems: a set of 64-dimensional coupled oscillators and acetonitrile. We explore various tree architectures, ranging from the simple linear structure of Matrix Product States (MPS), to trees where only the leaf nodes carry a physical leg – as commonly seen in the underlying ansatz of the Multilayer Multiconfiguration Time-Dependent Hartree (ML-MCTDH) method – and further to more general trees in which all nodes are allowed to possess a physical leg. In addition, we implement Locally Optimal Block Preconditioned Conjugate Gradient (LOBPCG) methods and Inverse Iteration methods as eigensolvers. Benchmarking runtime and accuracy shows that all tested topologies can reach high accuracy. For acetonitrile, inverse-iteration refinement brings all 84 computed states below 1~cm$^{-1}$ error, while the fork-4 tree, a comb-like tree with four backbone nodes, provides the best overall balance between accuracy and cost. MPS remains computationally attractive, whereas more connected trees generally improve accuracy at fixed bond dimension. All numerical simulations were performed using PyTreeNet, a Python package designed for flexible tensor network computations.
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All authors Shuo Sun, Richard M. Milbradt, Stefan Knecht, Chandan Kumar, Christian B. Mendl

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

Self-confinement of relativistic pair beams in magnetized interstellar plasmas: the case of pulsar X-ray filaments

Luca Orusa and Lorenzo Sironi

The observation of filamentary X-ray structures near bow-shock pulsar wind nebulae (PWNe) – such as the Guitar, Lighthouse, and PSR J2030$+$4415 nebulae – and of slow-diffusion regions around pulsars like Geminga, Monogem, and PSR J0622$+$3749, challenges the standard picture of cosmic-ray transport in the interstellar medium, implying a diffusion coefficient two orders of magnitude smaller than the Galactic average. The suppressed diffusion can be attributed to self-generated magnetic turbulence, driven – via the non-resonant streaming instability – by electron-positron pairs escaping the PWNe. This instability requires a net current, yet the beam of escaping pairs is expected to be charge-neutral. We show that a charge-neutral pair beam propagating through an electron-proton plasma can spontaneously generate a net current. Using fully kinetic two-dimensional particle-in-cell simulations with realistic mass ratio, we find that beam electrons get focused into self-generated magnetic filaments produced by the nonlinear evolution of the Weibel instability, while beam positrons remain unconfined. We show that in three-dimensional simulations the resulting net (positron) current drives the non-resonant streaming instability, further amplifying the magnetic field. This mechanism provides a pathway for the onset of charge asymmetries in initially charge-neutral pair beams and for the growth of magnetic fluctuations that efficiently scatter the beam particles, with implications for the formation of X-ray filaments and, potentially, for particle self-confinement in TeV halos around PWNe.
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Optics · Cross-listed from gr-qc

An introduction to nonlinear fiber optics and optical analogues to gravitational phenomena

Dimitrios Kranas, Andleeb Zahra and Friedrich König

The optical fiber is a revolutionary technology of the past century. It enables us to manipulate single modes in nonlinear interactions with precision at the quantum level without involved setups. This setting is useful in the field of analogue gravity (AG), where gravitational phenomena are investigated in accessible analogue lab setups. These lecture notes provide an account of this AG framework and applications. Although light in nonlinear dielectrics is discussed in textbooks, the involved modelling often includes many assumptions that are directed at optical communications, some of which are rarely detailed. Here, we provide a self-contained and sufficiently detailed description of the propagation of light in fibers, with a minimal set of assumptions, which is relevant in the context of AG. Starting with the structure of a step-index fiber, we derive linear-optics propagating modes and show that the transverse electric field of the fundamental mode is well approximated as linearly polarized and of a Gaussian profile. We then incorporate a cubic nonlinearity and derive a general wave envelope propagation equation. With further simplifying assumptions, we arrive at the famous nonlinear Schrödinger equation, which governs fundamental effects in nonlinear fibers, such as solitons. As a first application in AG, we show how intense light in the medium creates an effective background spacetime for probe light akin to the propagation of a scalar field in a black hole spacetime. We introduce optical horizons and particle production in this effective spacetime, giving rise to the optical Hawking effect. Furthermore, we discuss two related light emission mechanisms. Finally, we present a second optical analogue model for the oscillations of black holes, the quasinormal modes, which are important in the program of black hole spectroscopy.
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