Fluid Dynamics
A consistent {\delta}-Plus-ULPH model towards higher accuracy and lower numerical dissipation with fewer neighboring particles
Shi-Xian Wu, Peng-Nan Sun, Xiao-Ting Huang et al. (+2 more)
This paper proposes a novel consistent {\delta}+- Updated Lagrangian Particle Hydrodynamics (ULPH) model. Although the Smoothed Particle Hydrodynamics (SPH) model has gained recognized achievements, it is afflicted by excessive numerical dissipation when the neighboring particles are insufficient. The present proposed consistent {\delta}+-ULPH model has advantages in overcoming this problem. To improve the accuracy, efficiency, stability, and energy conservation, several new techniques are introduced to the consistent {\delta}+-ULPH model. A novel extended support domain technique is proposed to achieve higher accuracy with fewer neighboring particles. An optimal
matrix for the velocity divergence is proposed to improve the free-surface stability. A consistent particle shifting technique for the ULPH scheme is proposed to maintain a uniform and regular particle distribution and obtain superior conservation. In addition, an acoustic damper term for the ULPH scheme is introduced to improve the pressure field stability. Five
benchmark tests were carried out to validate the consistent {\delta}+-ULPH model. The conventional ULPH and the consistent {\delta}+-SPH results are presented for comparison. Results indicate that the proposed consistent {\delta}+-ULPH model can accurately simulate both gentle waves and violent sloshing flows and shows higher accuracy and lower numerical dissipation when using fewer neighboring particles, even in long-term and long-distance wave propagation simulations. Additionally, the computational efficiency of the consistent {\delta}+-ULPH model is enhanced visibly because of fewer neighboring particles.
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All authors Shi-Xian Wu, Peng-Nan Sun, Xiao-Ting Huang, Yu-Xiang Peng, Andrea Colagrossi
Optics
Full vectorial field sensing using liquid crystal droplet arrays
Xuke Qiu, Jinge Guo, Jiahe Cui et al. (+8 more)
Determining the amplitude, phase, and polarization profile of light is essential for both fundamental scientific discovery and applications spanning optical metrology, microscopy, astronomy, and optical communication/computing technologies. However, most modern measurement approaches are unable to retrieve such parameters readily, often relying on bulky and expensive hardware, or lacking the capability for single-shot sensing. Here, we introduce a low cost, compact, full vectorial field sensor based on an inkjet-printed nematic
liquid crystal droplet array that enables simultaneous measurement of these important characteristics of light. Polarization and intensity are measured via division-of-wavefront polarimetry, exploiting the droplets' spatially varying birefringence, while the phase is reconstructed by treating each droplet as a separate microlens in a Shack-Hartmann-like wavefront sensor configuration. To demonstrate the system's performance, we characterize aberrated dual-wavelength beams carrying distinct intensity, phase, and polarization information, confirming accurate
retrieval of the optical field profiles for both spectral components.
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All authors Xuke Qiu, Jinge Guo, Jiahe Cui, Runchen Zhang, Zimo Zhao, Yifei Ma, Waqas Kamal, Steve J. Elston, Alfonso A. Castrejón-pita, Stephen M. Morris, Chao He
Atomic Physics · Cross-listed from quant-ph
Experimental Realization of Thermal Reservoirs with Tunable Temperature in a Trapped-Ion Spin-Boson Simulator
Visal So, Mingjian Zhu, Midhuna Duraisamy Suganthi et al. (+5 more)
We propose and demonstrate an experimental scheme to engineer thermal baths with independently tunable temperatures and dissipation rates for the motional modes of a trapped-ion system. This approach enables robust thermal-state preparation and
quantum simulations of open-system dynamics in bosonic and
spin-
boson models at well-controlled finite temperatures. We
benchmark our protocol by experimentally realizing out-of-
equilibrium dynamics of a charge-transfer model at different temperatures. We observe that, when the process occurs at a higher temperature, the transfer rate spectrum broadens, with reduced rates at small donor-acceptor energy gaps and enhanced rates at large gaps. We then employ our scheme to study local-temperature effects in a two-mode vibrationally assisted
exciton transfer system, where we observe thermally activated interference pathways for excitation transfer.
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All authors Visal So, Mingjian Zhu, Midhuna Duraisamy Suganthi, Abhishek Menon, George Tomaras, Roman Zhuravel, Han Pu, Guido Pagano
Fluid Dynamics
Comments on the paper `Modelling and nonclassical symmetry analysis of a complex porous media flow in a dilating channel'
Roman Cherniha
The Comments are devoted to the recently published paper 'Modelling and nonclassical
symmetry analysis of a complex porous media flow in a dilating channel' (Physica D. 481 (2025) 134834), in which a model describing an unsteady two-dimensional viscous incompressible fluid flow through a porous medium is studied. The main theoretical results of that study consists of finding Lie and nonclassical
symmetries of a fourth-order PDE, which was derived by simplification of the given model. Here it is shown that the main theoretical results derived therein are incomplete and misleading.
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Fluid Dynamics
Wall-Modeled Large-Eddy Simulation of Turbulent Non-Newtonian Power-Law Fluid Flows
Mohammad Taghvaei and Ehsan Amani
For high-fidelity predictions of turbulent flows in complex practical engineering problems, the Wall-Modeled (WM) Large-Eddy Simulation (LES) has aroused great interest. In the present study, we prove that the conventional Wall-Stress Models (WSMs) developed for WMLES of Newtonian fluids fail to predict the shear-thinning-induced drag reduction in power-law fluids. Therefore, we propose novel algebraic, integrated, and Ordinary-Differential-Equation (ODE) WSMs, for the first time, for WMLES of power-law Non-Newtonian (NN) fluids and assess their performance against reference Wall-Resolved (WR) LES solutions. In addition, the effects of the key model parameters, including the WSM type, sampling height, sampling
cell, and axial grid resolution are explored, and it is revealed that turbulent NN flow predictions have a much higher sensitivity to the choice of WSM, compared to their Newtonian counterparts. It is manifested that, in contrast to WRLES, accurate modeling of the mean apparent and subgrid-scale NN viscosities in the NNODE model can improve the predictions considerably. Therefore, closures with lower uncertainties on coarse WMLES grids are sought for these terms. Finally, the best performance for the present test cases is obtained via the integrated NN WSM, sampling at the lower edge of the log layer within the third off-the-wall grid
cell. Nevertheless, the new NNODE WSM can have an advantage in the presence of non-
equilibrium effects in more complex problems.
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Fluid Dynamics
Coarse-graining Algorithms for the Eulerian-Lagrangian Simulation of Particle-laden Flows
H. Eshraghi, E. Amani and M. Saffar-Avval
In the present article, novel Coarse-Graining (CG)
algorithms for the Eulerian-Lagrangian (EL) simulation of particle-laden flows are proposed. These include different variants of Reproducing Kernel Particle Methods (RKPM) and an extended
Diffusion Two-Step Method (DTSM) for highly polydisperse flows. Owing to the dynamic nature of the kernel function in RKPMs, CG
algorithms with high-order consistency properties are constructed and the extra physics of the fluid-particle interaction torque effect on the two-way coupling force distributed to the fluid is taken into consideration. To increase the robustness of RKPMs, they are hybridized with other simple CG
algorithms in such a way that each model is activated in the range of its validity. The performance of the new CG
algorithms is carefully assessed in comparison to other widely-used
algorithms by devising four
benchmarks and several grid-independence tests. Based on the analyses, the first-order RKPM demonstrates the best performance in terms of 8 attributes, including conservativity, grid-independency, smoothness, etc., among all
algorithms and is recommended when the accuracy is of
prime importance. However, due to its higher computational cost compared to the extended DTSM, the latter model would be an affordable alternative for large-scale discrete element method problems when the computational cost is critical.
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Chemical Physics
Genetically encoding stimulated Raman-scattering probes for cell imaging using infrared fluorescent proteins
David Regan, Ozan Aksakal, Athena Zitti et al. (+8 more)
Stimulated Raman scattering (SRS) microscopy offers great potential to surpass fluorescent-based approaches, owing to the sharp linewidth of Raman vibrations amenable to super-multiplex
cell imaging, but currently lacks one crucial component: genetically encodable tags equivalent to fluorescent
proteins. Here, we show that infrared fluorescent
proteins (IRFPs) can be used as genetically encoded SRS probes and benefit from the electronic pre-resonant SRS enhancement effect with near-infrared exciting pulses, comparable to synthetic dyes reported in the literature. SRS imaging of the
nucleus in mammalian
cells is demonstrated where a histone
protein is fused to an IRFP. This work opens the route towards Raman-based
cell imaging using genetically encoded probes, motivating efforts in solving the challenges of photostability and creating a vibrational palette.
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All authors David Regan, Ozan Aksakal, Athena Zitti, John McLarnon, Magdalena Lipka-Lloyd, Pierre J. Rizkallah, Anna J. Warren, Peter D. Watson, Wolfgang Langbein, D. Dafydd Jones, Paola Borri
Optics · Cross-listed from quant-ph
Beyond critical coupling: optimal design considerations for spontaneous four-wave mixing in microring resonators
Joseph M. Lukens, Karthik V. Myilswamy, Alexander Miloshevsky et al. (+1 more)
We present a self-contained analytical model for biphoton generation in microring resonators. Encompassing both all-pass and add-drop geometries, identical and distinct pump and biphoton coupling coefficients, and continuous-wave and pulsed pumping, our interaction-picture-based approach reveals time-frequency biphoton correlations while also predicting absolute generation rates. Under continuous-wave excitation, we find critical coupling of both the pump and biphoton to maximize the rate of single
photons extracted from the microring, whereas critical coupling of the pump but overcoupling of the biphoton maximize the two-
photon rate. Under pulsed pumping, overcoupling of both pump and biphoton (to different degrees) maximizes
photon extraction probabilities, albeit under a tradeoff with spectral factorability that we quantify via parameter scans over a range of coupler pairings. As a whole, our formalism should prove valuable for the practical design of integrated
photon sources, merging a flexible and intuitive biphoton-centric depiction with quantitative predictions closely tied to experimental parameters.
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All authors Joseph M. Lukens, Karthik V. Myilswamy, Alexander Miloshevsky, Hsuan-Hao Lu
Applied Physics · Cross-listed from cond-mat.mtrl-sci
Low-Field Ferroelectricity in 10 nm AlBScN Thin Films
Xiaolei Tong, Pedram Yousefian, Ziyi Wang et al. (+5 more)
Ferroelectric aluminum scandium nitride (Al1-xScxN, AlScN) offers CMOS-compatible integration but suffers from high coercive fields and leakage currents that hinder thickness scaling. Further reduction in thickness is essential for low-voltage embedded nonvolatile
memory applications. Boron incorporation into AlScN (AlBScN) suppresses leakage current in films down to 40 nm, yet its ferroelectric characteristics in ultrathin films remains unexplored. This letter demonstrates robust ferroelectric switching in 10 nm sputtered AlBScN capacitors with a low coercive field and approximately two orders of magnitude lower leakage than AlScN. Notably, ferroelectric switching was observed at 2.2 MV/cm in capacitance-voltage measurements, and symmetric polarization reversal occurred near 4.6 MV/cm in positive-up-negative-down (PUND) measurements using 2 {\mu}s pulses. Moreover, Weibull analysis revealed a breakdown-to-coercive-field ratio (EBD/Ec) of ~2.2. These findings demonstrated AlBScN as a promising candidate for CMOS back-end-of-line (BEOL) compatible ferroelectric applications with improved energy consumption and reduced leakage current.
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All authors Xiaolei Tong, Pedram Yousefian, Ziyi Wang, Meenakshi A. Saravanan, Rajeev Kumar Rai, Giovanni Esteves, Eric A. Stach, Roy H. Olsson III
Biological Physics · Cross-listed from q-bio.NC
Cognition as least action: the Physarum Lagrangian
Ricard Solé and Jordi Pla-Mauri
The slime mould Physarum polycephalum displays adaptive transport dynamics and network formation that have inspired its use as a model of biological computation. We develop a Lagrangian formulation of Physarum's adaptive dynamics on predefined graphs, showing that steady states arise as extrema of a least-action functional balancing metabolic dissipation and transport efficiency. The organism's apparent ability to find optimal paths between nutrient sources and sinks emerges from minimizing global energy dissipation under predefined boundary conditions that specify the problem to be solved. Applied to ring, tree, and
lattice geometries, the framework accurately reproduces the optimal conductance and flux configurations observed experimentally. These results show that Physarum's problem-solving on constrained
topologies follows a physics-based variational principle, revealing least-action dynamics as the foundation of its adaptive organization.
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Chemical Physics
Nuclear spin relaxation in zero- to ultralow-field magnetic resonance spectroscopy
Florin Teleanu, Anne M. Fabricant, Chengtong Zhang et al. (+4 more)
Nuclear-
magnetic-resonance experiments can interrogate a broad spectrum of molecular-tumbling regimes and can accurately measure interatomic distances in solution with sub-nanometer resolution. In the zero- to ultralow-field (ZULF) regime, population and coherence decay reveal nontrivial behavior due to strong coupling between
nuclear spins. We note, in particular, the surprising effects that different resonances show different relaxation rates, depending on (i) the (pre)polarizing magnet field and the shuttling trajectory to the detection region at nano- and microtesla fields, (ii) the strength of the measurement field, (iii) the detection method (single-channel or quadrature), and even (iv) the nutation angle induced by the excitation pulse. We describe herein experimental data of relaxation rates measured for a 13C-labeled formic acid sample, with an atomic-magnetometer-based ZULF setup, and develop a theoretical framework to explain the detected effects and extract molecular properties. The observed effects could be used for spectral assignment, for the establishment of specific motional regimes, for image contrast, and for the characterization of relaxation processes at nano- to microtesla
magnetic fields.
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All authors Florin Teleanu, Anne M. Fabricant, Chengtong Zhang, Gary P. Centers, Dmitry Budker, Danila A. Barskiy, Alexej Jerschow
Space Physics
Monitoring the Solar Wind Before It Reaches L1
Erika Palmerio
Space weather predictions of the
solar wind impacting Earth are usually first based on remote-sensing observations of the
solar disc and corona, and eventually validated and/or refined with in-situ measurements taken at the Sun$-$Earth Lagrange L1 point, where real-time monitoring probes are located. However, this pipeline provides, on average, only a few tens of minutes of lead time, which decreases to $\sim$30 minutes or less for large
solar wind speeds of $\sim$800 km/s and above. The G5 geomagnetic storm of 2024 May provided an opportunity to test predictions generated employing real-time data from the STEREO-A spacecraft, placed 13{\deg} west of Earth and 0.04 au closer to the Sun than L1 at the time of the event, as shown recently by Weiler et al. (2025). In this Commentary, we contextualise these results to reflect upon the advantages of measuring the
solar wind in situ upstream of L1, leading to improvements in both fundamental research of interplanetary physics and space weather predictions of the near-Earth environment.
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Computational Physics · Cross-listed from cond-mat.soft
Multiscale Dynamics of Roughness-Driven Flow in Soft Interfaces
Qian Wang, Suhaib Ardah, Tom Reddyhoff et al. (+1 more)
Soft lubricated contacts exhibit complex interfacial behaviours governed by the coupled effects of multiscale surface roughness and non-linear fluid-solid interactions. Accurately capturing this interplay across thin-film flows is challenging due to the strong synergy between contact mechanics and hydrodynamic flow, spanning over various spatiotemporal scales. Here, we develop a rigorous computational framework to simulate the frictional behaviour of soft lubricated interfaces; its modularity and the use of optimal solvers provides solutions for realistic configurations in lubrication regimes ranging from direct solid contact to complete fluid separation. Surface roughness is described via Persson's statistical theory as well as a deterministic Conjugate Gradient with Fast
Fourier Transform (CG-FFT) approach, while limitations associated with classical half-space models are addressed by developing the Reduced Stiffness Method (RSM) to rigorously model pressure-induced surface responses. The integrated framework captures the full
evolution of frictional behaviour, validated against experiments on rough elastomer-glass interfaces, revealing how surface roughness and material compliance together drive the transition from solid contact to fluid-mediated sliding. The developed approach establishes a robust and versatile simulation tool for analysing a plethora of soft interfacial systems shaped by fluid-solid interactions, with potential applications including but not limited to biomechanics, soft robotics and microfluidic systems.
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All authors Qian Wang, Suhaib Ardah, Tom Reddyhoff, Daniele Dini
Instrumentation and Detectors
Design and Performance Studies of a Granular Thin HCAL-MuID Detector for the EIC Optimized for AI-Based Reconstruction
Rowan Kelleher, Anselm Vossen, William W. Jacobs et al. (+4 more)
We describe the design concept and estimated performance of an iron-scintillator sampling calorimeter for the future Electron Ion
Collider. The novel aspect of this detector is a multi-dimensional readout coupled with foreseen excellent timing resolution, enabling time-of-flight capabilities as well as a more compact overall assembly. Machine learning has been integrated into the detector design process from the ground up. Detector design objectives are defined using Machine Learning based reconstruction and Machine Learning is used to optimize the detector design. The highly segmented readout is implemented with Machine Learning
algorithms in mind to reach performance levels usually reserved for much more expensive detector systems. The primary physics objective is to serve as a
muon detector/ID system and a neutral
hadron calorimeter. In EIC kinematics, charged particles are best measured through tracking rather than calorimetry, but the hKLM can identify and measure the momentum of neutral
hadrons. The latter are mainly $K_L$'s and
neutrons: for lower energies, excellent relative momentum measurements of a few 10% are achieved using time of flight, while for higher particle momenta, the energy can be measured calorimetrically with a resolution significantly better than that demonstrated for similar calorimeters read out with less granularity.
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All authors Rowan Kelleher, Anselm Vossen, William W. Jacobs, Gerard Visser, Simon Schneider, Yordanka Ilieva, Pawel Nadel-Turonski
Physics and Society
A High-Scale Assessment of Social Media and Mainstream Media in Scientific Communication
Yang Yang, Tanya Tian, Brian Uzzi et al. (+1 more)
Communication of scientific knowledge beyond the walls of science is key to science's societal impact. Media channels play sizable roles in disseminating new scientific ideas about human health, economic welfare, and government policy as well as responses to emergent challenges such as
climate change. Indeed, effectively communicating science to the public helps inform society's decisions on scientific and technological policies, the value of science, and investment in research. At the same time, the rise of social media has greatly changed communication systems, which may substantially affect the public's interface with science. Examining 20.9 million scientific publications, we compare research coverage in social media and mainstream media in a broad corpus of scientific work. We find substantial shifts in the scale, impact, and heterogeneity of scientific coverage. First, social media significantly alters what science is, and is not, covered. Whereas mainstream media accentuates eminence in the coverage of science and focuses on specific fields, social media more evenly sample research according to field, institutional rank, journal, and demography, increasing the scale of scientific ideas covered relative to mainstream outlets more than eightfold. Second, despite concerns about the quality of science represented in social media, we find that social media typically covers scientific works that are impactful and novel within science. Third, scientists on social media, as experts in their domains, tend to surface high-impact research in their own fields while sampling widely across research institutions. Contrary to prevalent observations about social media, these findings reveal that social media expands and diversifies science reporting by highlighting high-impact research and bringing a broader array of scholars, institutions and scientific concepts into public view.
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All authors Yang Yang, Tanya Tian, Brian Uzzi, Benjamin Jones
Optics
Direct experimental access to the bulk band inversion in a topological metamaterial
Simon Widmann, Johannes Düreth, Siddhartha Dam et al. (+9 more)
Topological phases in
exciton-polaritons and other metamaterial platforms have attracted significant
attention due to their flexibility as
Hamiltonian simulators. In previous works, signatures of
topology have mainly been investigated from the perspective of edge states - strongly localised modes with exponentially decaying intensity into the bulk. While these edge states have become the hallmark of topological systems as they can facilitate non-reciprocal transport in potential applications, the
topology is fundamentally encoded in the bulk band structure. In particular, the momentum-dependence of the eigenstates, i.e., the wave functions, determines the
topology, usually reflected in a bulk band inversion. We present a band inversion in the paradigmatic Su-Schrieffer-Heeger (SSH) model, characterised by a reversal of the sublattice
symmetry, quantified by the expectation value $\langle \sigma_\mathrm{x} \rangle$, when going from the centre of the Brillouin zone to the zone boundary. Here, we show direct experimental access to this bulk band inversion in SSH
exciton-polariton chains, using two-dimensional momentum-space ($k$-space) mapping - without the need for real-space imaging. This technique enables the direct observation of the momentum-dependent inversion of the sublattice
symmetry in the bulk bands, providing a unique perspective on topological phases beyond conventional edge state measurements. Our approach establishes effective momentum-resolved sublattice phase measurements as a powerful tool for accessing the wave function and bulk
topology in photonic and polaritonic systems and beyond.
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All authors Simon Widmann, Johannes Düreth, Siddhartha Dam, Christian G. Mayer, David Laibacher, Monika Emmerling, Martin Kamp, Friedrich Reinert, Maximilian Ünzelmann, Simon Betzold, Sven Höfling, Sebastian Klembt
Accelerator Physics
High Power RF Pulse Shaping Tests with NG-LLRF and Cool Copper Collider Prototype Structure
Chao Liu, Ankur Dhar, Ronald Agustsson et al. (+4 more)
RF pulse modulation techniques are widely applied to shape RF pulses for various types of RF stations of particle accelerators. The amplitude and phase modulations are typically implemented with additional RF components that require drive or control electronics. For the RF system-on-chip (RFSoC) based next generation LLRF (NG-LLRF) platform, which we have developed in the last several years, RF modulation and demodulation are fully implemented in the digital domain. Therefore, arbitrary RF pulse shaping can be realized without any additional analogue components. We performed a range of high-power experiments with the NG-LLRF and a prototype Cool Copper
Collider (C3) structure. In this paper, the RF field measured at different stages with different pulse shapes and peak power levels up to 5.4 MW and pulse width about 1 microsecond will be demonstrated and analyzed. The high precision pulse shaping schemes of the NG-LLRF can be applied to realize the phase modulation for a linear accelerator injector, the phase reversal for a pulse compressor, or the modulation required to compensate for the beam loading effect.
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All authors Chao Liu, Ankur Dhar, Ronald Agustsson, Diego Amirari, Dennis Palmer, Martin Breidenbach, Emilio Nanni
Optics
Reply to "Comment on Brilliant source of 19.2 attosecond soft X-ray pulses below the atomic unit of time" by Han (arXiv:2510.17949)
Fernando Ardana-Lamas, Seth L. Cousin, Juliette Lignieres et al. (+1 more)
We recently reported a refine analysis of a previously conducted soft X-ray (SXR) attosecond streaking measurement [1], employing the Variational Phase Gradient Temporal Analysis (VPGTA) retreival
algorithm [2]. This re-evaluation, prompted by new metrological insights, revealed a 19.2 attosecond pulse - consistent with the expectations and estimates of our earlier work [3]. Shortly thereafter, a comment by M. Han [4] challenged our findings, citing "physical and technical issues concerning the original experiment and the new characterisation" inclusing purported contributions from Auger electrons, unfiltered low-energy harmonics, and uncompensated intrinsic chirp. These concerns, however, stem from misinterpretation of the experimental regime, selective citation of context, and disregard for well-established results in the peer-reviewed literature. In this reply, we address and clarify these points, demonstrating that the issues raised are not relevant under our experimental conditions. Given the highly specialized nature of attosecond genertaion and metrology in the soft X-ray water-window regime, we consider it essential to clarify these aspects of different regimes and reaffirm teh validity of our conclusions.
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All authors Fernando Ardana-Lamas, Seth L. Cousin, Juliette Lignieres, Jens Biegert
Optics
The effect of discrete-time evolution on thermalisation in a lattice
Thomas Moorcroft, Alberto Amo, François Copie et al. (+3 more)
Particles subject to weak contact interactions in a finite-size
lattice tend to thermalise. The
Hamiltonian evolution ensures energy conservation and the final temperature is fully determined by the initial conditions. In this work we show that equilibration processes are radically different in
lattices subject to discrete-step
unitary evolution, which have been implemented in photonic
circuits, coin polarisation walkers and time-multiplexed pulses in fibres. Using numerical simulations, we show that weak nonlinearities lead to an
equilibrium state of equal modal occupation across all the bands, i.e, a thermal state with infinite temperature and chemical potential. This state is reached no matter the initial distribution of modes and independent of the bands dispersions and gaps. We show that by engineering the temporal periodicity inherent to these systems, equilibration can be accelerated through resonant Floquet channels. Our results demonstrate that discrete time plays a crucial role in wave dynamics, fundamentally altering thermalisation processes within weak wave
turbulence theory.
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All authors Thomas Moorcroft, Alberto Amo, François Copie, Stéphane Randoux, Pierre Suret, Davide Proment
Applied Physics
Reservoir computing in a lithium-based magneto-ionic device
Sreeveni Das, Rhodri Mansell, Aarne Piha et al. (+4 more)
In-materio computing exploits the intrinsic physical dynamics of materials to perform complex computations, enabling low-power, real-time data processing by
embedding computation directly within physical layers. Here, we demonstrate a voltage-controlled magneto-ionic device that functions as a reservoir computer capable of
forecasting chaotic time series. The device consists of a crossbar structure with a Ta/CoFeB/Ta/MgO/Ta bottom electrode and a LiPON/Pt top electrode. A chaotic Mackey-Glass time series is encoded into a voltage signal applied to the device, while 2D
Fourier transforms of voltage-dependent
magnetic domain patterns form the output. Performance is influenced by the input rate, smoothing of the output, the number of elements in the reservoir state vector, and the training duration. We identify two distinct computational regimes: short-term prediction is optimized using smoothed, low-dimensional states with minimal training, whereas prediction around the Mackey-Glass delay time benefits from unsmoothed, high-dimensional states and extended training. Reservoir computing metrics reveal that slower input rates are more tolerant to output smoothing, while faster input rates degrade both
memory capacity and nonlinear processing. These findings demonstrate the potential of magneto-ionic systems for neuromorphic computing and offer design principles for tuning performance in response to input signal characteristics.
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All authors Sreeveni Das, Rhodri Mansell, Aarne Piha, Lukáš Flajšman, Maria-Andromachi Syskaki, Jürgen Langer, Sebastiaan van Dijken
Fluid Dynamics
Effect of Turbulence-Closure Consistency on Airfoil Identification
Zhen Zhang and George Em Karniadakis
We consider an inverse flow problem in which the airfoil shape is identified from its wake signature, namely the velocity field in the wake of a target airfoil. This is an ill-posed problem and highly sensitive to the accuracy and consistency of the employed
turbulence closure. We first demonstrate that shape identification based on a single flow condition is ill-posed, whereas incorporating multiple wake signatures obtained at different angles of attack substantially mitigates this ill-posedness. We then compare the inferred geometries obtained using different
turbulence closures and find that inconsistencies among the models lead to markedly divergent shapes. Consequently, we directly compare the
geometric sensitivities obtained from different models at fixed shapes, and find up to a 250 percent difference among these sensitivities. These findings underscore that
turbulence-closure consistency is essential for reliable shape identification and further suggest that effective
turbulence models must ensure not only accurate predictions but also physically consistent sensitivities-a principle that should guide the development of both classical and data-driven closure models.
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Optics
Supercontinuum Generation in the Low-Peak-Power Regime Using a Single-Stage Multipass Cell
Zeyang Hu, Kilian Fritsch and Oleg Pronin
We demonstrate a single-stage multipass
cell (MPC) compressor driven directly by a 500 nJ, 5 W, 120 fs, 10 MHz oscillator that delivers efficient spectral broadening from 800 to 1200 nm with >75% transmission. The compressed pulses approach the
Fourier limit (FTL) of 8.1 fs, representing, to the best of our knowledge, the first realization of supercontinuum (SC) generation and compression in a single-stage MPC at such low, MW-level, input peak power. This compact, high-repetition-rate source holds strong potential for multiphoton microscopy and coherent Raman imaging.
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Computational Physics · Cross-listed from quant-ph
Quantum annealing for lattice models with competing long-range interactions
Jan Alexander Koziol and Kai Phillip Schmidt
We use superconducting
qubit quantum annealing devices to determine the ground state of Ising models with algebraically decaying competing long-range interactions in the thermodynamic limit. This is enabled by a unit-
cell-based optimization scheme, in which the finite optimizations on each unit
cell are performed using commercial
quantum annealing hardware. To demonstrate the capabilities of the approach, we choose three exemplary problems relevant for other
quantum simulation platforms and material science: (i) the calculation of devil's staircases of magnetization plateaux of the long-range Ising model in a longitudinal field on the triangular
lattice, motivated by atomic and molecular
quantum simulators; (ii) the evaluation of the ground state of the same model on the Kagome
lattice in the absence of a field, motivated by artificial
spin ice metamaterials; (iii) the study of models with additional few-nearest-neighbor interactions relevant for frustrated Ising compounds with potential long-range interactions. The approach discussed in this work provides a useful and realistic application of existing
quantum annealing technology, applicable across many research areas in which
lattice problems with resummable long-range interactions are relevant.
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Computational Physics
An Improved High-order Adaptive Mesh Refinement Framework for Shock-turbulence Interaction Problems based on cell-centered finite difference schemes
Yuqi Wang, Yadong Zeng, Ralf Deiterding et al. (+2 more)
This work presents a high-order finite-difference adaptive mesh refinement (AMR) framework for robust simulation of shock-
turbulence interaction problems. A staggered-grid arrangement, in which solution points are stored at
cell centers instead of at the vertices, is presented to address the boundary conservation issues encountered in previous studies. The key ingredient in the AMR framework, i.e., the high-order nonlinear interpolation method applied in the prolongation step together with the determination of fine-grid boundary conditions, are re-derived for staggered grids following the procedures in prior work [1] and are thus used here. Meanwhile, a high-order restriction method is developed in the present study as the coarse and fine grid solutions are non-collocated in this configuration. To avoid non-conservative interpolation at discontinuous
cells that could incur instabilities, a hybrid interpolation strategy is proposed in this work for the first time, where the non-conservative WENO interpolation is applied in smooth regions whereas the second-order conservative interpolation is applied at shocks. This significantly mitigates the numerical instabilities introduced by non-conservative interpolation and pointwise replacement. The two interpolation approaches are seamlessly coupled through a troubled-
cell detector achieved by a scale-irrelevant Riemann solver in a robust way. The present work is developed on a publicly available block-structured adaptive mesh refinement framework AMReX [2]. The canonical tests demonstrate that the proposed method is capable of accurately resolving a wide range of complex shock-
turbulence interaction problems that have been proven intricate for existing approaches
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All authors Yuqi Wang, Yadong Zeng, Ralf Deiterding, Jinhui Yang, Jianhan Liang
Computational Physics · Cross-listed from cond-mat.mtrl-sci
Machine-learning interatomic potential for AlN for epitaxial simulation
Nicholas Taormina, Emir Bilgili, Jason Gibson et al. (+3 more)
A machine learned interatomic potential for AlN was developed using the ultra-fast force field (UF3) methodology. A strong agreement with density functional theory calculations in predicting key structural and mechanical properties, including
lattice constants, elastic constants, cohesive energy, and surface energies has been demonstrated. The potential was also shown to accurately reproduce the experimentally observed atomic core structure of edge dislocations. Most significantly, it reproduced the experimentally observed wurtzite
crystal structure in the overlayer during homoepitaxial growth of AlN on wurtzite AlN, something that prior potentials failed to achieve. Additionally, the potential reproduced the experimentally observed layer-by-layer growth mode in the epilayer. The combination of accuracy, transferability, and computational speed afforded by the UF3 framework thus makes large-scale, atomistic simulations of epitaxial growth of AlN feasible.
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All authors Nicholas Taormina, Emir Bilgili, Jason Gibson, Richard Hennig, Simon Phillpot, Youping Chen
Atomic Physics
Cryogenic source of atomic tritium for neutrino-mass measurements and precision spectroscopy
Aleksei Semakin, Janne Ahokas, Tom Kiilerich et al. (+9 more)
We propose a concept for a cryogenic source of atomic tritium at sub-Kelvin temperatures and energies suitable for
magnetic trapping. The source is based on the dissociation of solid molecular T2 films below 1 K by electrons from a pulsed RF discharge, a technique recently demonstrated for atomic hydrogen, combined with buffer-gas cooling and
magnetic confinement. We analyze the key processes limiting the source performance, adsorption,
spin exchange and recombination, and show that atomic tritium fluxes exceeding 1e15 1/s at kinetic energies of 100 mK can be achieved at the entrance to the
magnetic trap. Such a source would enable Doppler-free two-
photon 1S-2S spectroscopy in atomic tritium for high-precision measurements of the triton charge radius, providing a crucial
benchmark for bound-state QED and improving the comparison between electronic, muonic, and scattering determinations of
nuclear sizes in light systems. Beyond spectroscopy, an atomic tritium source avoids molecular final state broadening in the beta decay and is therefore necessary for next generation
neutrino mass measurements; combined with detector technologies such as sub-eV resolution
quantum sensors or cyclotron radiation emission spectroscopy, it enables an order of magnitude improvement compared to the current best experimental limit. Additionally, the source can be used to generate a beam of low field seeking deuterium atoms for loading
magnetic traps, an important
benchmark before trapping tritium atoms, which is useful for precision spectroscopy.
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All authors Aleksei Semakin, Janne Ahokas, Tom Kiilerich, Sergey Vasiliev, Francois Nez, Pauline Yzombard, Valery Nesvizhevsky, Eberhard Widmann, Paolo Crivelli, Caroline Rodenbeck, Marco Röllig, Magnus Schlösser
Atomic Physics
Excited $\Sigma$ states of the hydrogen-antihydrogen molecule
L. Brumm, J. Schürmann and A. Saenz
Adopting explicitly correlated Kolos-Wolniewicz-type basis functions, the Born-Oppenheimer potential curves of a number of excited $\Sigma$ states of the hydrogen-antihydrogen system ($\bar{\rm H}$) were calculated for both, even and odd, Q
symmetries, including also free positronium states. It is demonstrated that the excited leptonic states support ro-vibrational states with energies close to the ground-state dissociation threshold. As a consequence, the excited leptonic states need to be considered in theoretical treatments of ground-state H-$\bar{\mathrm{H}}$ collisions.
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Physics and Society
Metros reduce car use in European cities but trams do not
Rafael Prieto-Curiel
Despite the evident drawbacks, car ownership and usage continue to rise globally, leading to increased pollution and urban sprawl. As alternatives, Active Mobility and Public Transport are promoted for their health, economic, and environmental benefits. However, the efficiency of Public Transport varies widely. Metro systems, in particular, offer a high-capacity, long-distance solution, but they are expensive and only found in a limited number of cities. Trams, on the other hand, may serve as a substitute. This study compares the modal share in European cities, analysing the differences between those that have a metro, a tram, or neither. The analysis draws on a comprehensive
dataset from CitiesMoving.com, which compiles and harmonises mobility surveys from around the world according to the ABC framework (A for Active mobility, B for Bus and other forms of Public Transport, and C for Cars). Findings reveal that cities with a metro have a significantly lower share of car journeys than those with only a tram or no rail system.
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Instrumentation and Detectors
RSstitcher – Merging 2D diffraction frames for Wide Range Reciprocal Space Maps with absorption correction and integration functions
Xiaodong Wang, Michael W. M. Jones and Adam Smith
Wide Range Reciprocal Space Mapping (WRRSM) is a technique that allows visualisation of the
geometric relationships among multiple hkl spots in a whole reciprocal space map. However, commercial softwares for WRRSMs generation are associated with several issues or limitations, which are overcome by the currently reporting open-source python program RSstitcher (Reciprocal Space Stitcher). RSstitcher merges 2D scan frames formats supported by FabIO and enables WRRSM function on most laboratory X-ray diffractometers equipped with a goniometer cradle and a 2D detector of any sensor size. It is so far the only WRRSMs generation tool that applies diffraction intensity correction due to sample self-absorption, which enables quantitative analyses for WRRSMs including texture measurement and 1D data integration. The conversion equations used in the python program is explained geometrically, including novel WRRSM measurements in {\omega}-{\phi} compensated Side Inclination Grazing Incident Diffraction mode for thin film samples. The applications of RSstitcher for bulk and thin film samples are demonstrated using two common 2D X-ray diffraction systems.
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Fluid Dynamics
Stochastic Backscatter for Grey-Area Mitigation in Hybrid RANS-LES Simulations
Angelo Passariello, Pietro Catalano, Carmine De Lucia et al. (+1 more)
A scale-resolving simulation methodology that includes
stochastic energy backscatter is incorporated into a proprietary block-structured compressible flow solver. Particular
attention is devoted to the discretisation of the convective terms in the averaged/filtered governing equations. The objective is to achieve satisfactory dissipation and dispersion properties, while minimising the number of modifications to be made to the existing RANS solver, which employs, by default, a second-order accurate central scheme with Jameson-Schmidt-Turkel scalar artificial dissipation. A novel blending strategy, combining non-dissipative and strongly dissipative numerical discretisations, is proposed to enhance the overall numerical stability. First of all, the model is calibrated using the classic decay of isotropic homogeneous
turbulence. Then, its effectiveness in mitigating the grey area is shown through the simulation of the mixing co-flow between the wake originating downstream of an airfoil at zero angle of attack and the zero-pressure-gradient turbulent boundary layer developing over a flat plate.
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All authors Angelo Passariello, Pietro Catalano, Carmine De Lucia, Renato Tognaccini