Atomic Physics
Experimental observation of strong field stabilization
Anna R. Dardia, Spencer Walker, Yifei Bai et al. (+3 more)
Bound
quantum states such as atoms can be torn apart by strong oscillating fields. A natural expectation is that stronger fields lead to more certain destruction. In contradiction to this intuition, some theories predict a striking reversal: that as the field intensity is raised above some threshold, bound state wavefunctions can spatially bifurcate and become increasingly stable with increasing field intensity. This “strong field stabilization” was predicted decades ago in the context of atoms in pulsed
laser fields, but has resisted experimental observation due to extreme
laser intensity requirements and theoretical controversy. We report the experimental observation of strong-field stabilization of a ground state, using trapped neutral atoms to emulate the dynamics of atomic electrons in an extremely strong
laser field. We directly image the predicted wavepacket bifurcation, measure an ionization rate non-monotonic in field amplitude, and map out the regime of stabilization as a function of
laser pulse parameters. We observe that stabilization persists down to surprisingly low drive frequencies, near and below the scale of the lowest-energy excitations of the bound state. These results confirm and extend a long-standing prediction of extreme
quantum dynamics, and showcase a complementary tool for probing strong-field phenomena near and beyond the frontier of current
laser technology.
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All authors Anna R. Dardia, Spencer Walker, Yifei Bai, Petros Kousis, Alexandra S. Landsman, David M. Weld
Chemical Physics · Cross-listed from quant-ph
Bath-induced deviations from Gibbs statistics for strongly interacting oscillators
Felipe Recabal, Adrian E. Rubio Lopez, Johannes Schachenmayer et al. (+1 more)
The Redfield
quantum master equation is widely used to study the dynamics of interacting sub-systems that are weakly coupled to baths. Redfield dynamics under secular approximation preserves positivity of the reduced density operator and thermalizes the system into a Gibbs state at
equilibrium. Long-time effects arising from non-secular terms are often neglected, but depending on the system spectrum and relative bath couplings, non-secular contributions are shown here to drive the system into a non-Gibbs state. For two strongly interacting
quantum oscillators with independent baths at equal temperature, we analyze the microscopic origin of the deviations from Gibbs statistics. Provided that the oscillators are unequally damped by their baths, we show that steady state occupation numbers can significantly deviate from a Boltzmann distribution due to an excitation flux driven by bath-induced coherences between nearly-degenerate oscillator levels. Conditions for the recovery of thermal Gibbs statistics are discussed and experimental signatures suggested.
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All authors Felipe Recabal, Adrian E. Rubio Lopez, Johannes Schachenmayer, Felipe Herrera
Atomic Physics · Cross-listed from hep-ph
Matter-Wave Interferometers as Open-System Dark Matter Detectors
Leonardo Badurina and Kathryn M. Zurek
Matter-wave interferometers (MWIs) offer a uniquely
quantum route to dark matter (DM) detection: DM can reveal itself through phase and decoherence between spatially separated wavepackets, even when negligible energy deposition or resolvable
recoil occurs. We formulate these effects in an open effective field theory for MWIs using the Schwinger-Keldysh formalism, which highlights a structural asymmetry between the two detection channels. For elastic
spin-independent DM scattering, decoherence inherits novel Bose enhancement or Pauli blocking factors, while the phase is at most linear in the DM occupation number. By retaining the DM's coherence time, this framework spans Markovian and non-Markovian dynamics across a wide range of DM masses, and systematically organizes corrections beyond the heavy-probe limit.
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Physics and Society
Civilizational Metamaterials: Engineering Coordination Under Capability Gradients and Structural Turbulence
David Orban
We argue that governance must transition from a normative discipline to an engineering discipline, and we develop a formal framework, inspired by the physics of metamaterials, to make this transition quantitative and testable. Artificial General Intelligence affects civilization primarily by increasing decision velocity while human verification capacity remains bounded. When the cost of validating AI-generated outputs exceeds the expected utility of acting on them, rational
agents default to inaction: a stable but catastrophic Nash
equilibrium we term the Freezing
Equilibrium. Drawing on metamaterials, where emergent macro-properties arise from designed microstructure, we develop a phenomenological constitutive law for institutional coordination: $R_{\mathrm{eff}} = \beta \cdot (1-\rho) \cdot (1-\tau) \cdot (1-\gamma \rho \tau)$, where $\beta$ is the decision branching factor, $\rho$ is provenance fidelity, $\tau$ is the verification rate, and $\gamma \in [0,1]$ captures correlated-detection synergy between provenance and verification failures. The model predicts a sharp phase transition between self-healing ($R_{\mathrm{eff}} < 1$) and self-destabilizing ($R_{\mathrm{eff}} > 1$) regimes. We introduce a three-class provenance taxonomy: cryptographic, institutional, and context binding, and derive four falsifiable hypotheses with a proposed 12-week stepped-wedge cluster-randomized trial in government grant review panels. The framework bridges AI
alignment theory and institutional design.
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Atomic Physics · Cross-listed from quant-ph
Optical Memory Optimization Across Rubidium Isotopes and Transitions
T. Danielov, I. Puljić, M. {\DJ}ujić et al. (+3 more)
We investigate optical
memory efficiency and storage time across $^{85}\mathrm{Rb}$ and $^{87}\mathrm{Rb}$ isotopes on both the D$_1$ and D$_2$ transitions. Maximum efficiency of up to $44\%$ was achieved using the D$_1$ line in both isotopes, with up to 1.5 ms storage time. %Maximum efficiencies of $44\%$ were measured for both isotopes on the D$_1$ line, in agreement within $1\sigma$, while the longest storage time reached is $1.5$ ms. These performance levels are enabled by warm vapor rubidium buffer-gas filled
cells, large optical depth, and a near-resonant EIT scheme optimized with respect to the one- and two-
photon detuning. Our results provide practical guidelines for optimizing the performance of warm rubidium vapor optical
memories in simplified experimental configurations. We expect that the optimization approach employed here, specifically operating at elevated temperatures while identifying the optimal single-
photon and two-
photon detunings, should lead to improved performance of the
quantum memory.
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All authors T. Danielov, I. Puljić, M. {\DJ}ujić, D. Aumiler, N. Šantić, T. Ban
Physics and Society · Cross-listed from q-bio.PE
Evolution of cooperation in the multiplex
Zijie Chen, Xingru Chen and Feng Fu
Across biological and social systems, cooperation often depends on phenotypic cues rather than random encounters. To account for real-world interactions unfolding across multiple, simultaneous dimensions, here we develop a general framework for the
evolution of cooperation in multiplex networks governed by multi-phenotype homophily. We derive analytical conditions for natural selection to favor cooperation across phenotypic traits that are independent or exhibit epistasis and under different modes of mutation coupling. Despite the integration of fitness across layers, the conditions for cooperation resolve into layer-specific $\sigma$-rules, depending only on the local payoff structure, the effective number of phenotypes, and the mutation rates. We show that phenotypic diversity fosters cooperation by partitioning populations into assortative niches. Furthermore, in finite populations, intensifying the prisoner's dilemma shifts the dependence of cooperation on strategy mutation from monotonically decreasing, through U-shaped, to monotonically increasing. Our work provides a unified account of how multi-phenotype homophily underpins the evolutionary dynamics of cooperation in heterogeneous populations.
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Applied Physics
Wave-based Neuromorphic Circuit Networks: Tunable 2D Transmission-Line Metamaterials
Shrey Thakkar and Anthony Grbic
Neuromorphic computing promises fast and energy-efficient information processing for emerging applications such as artificial intelligence. This paper presents neuromorphic processors based on wave-based programmable transmission-line (TLIN) metamaterials. Specifically, 2D reactive electrical networks are proposed, consisting of a grid of interconnected subwavelength TLIN-based unit
cells (
neurons) with tunable reactive elements. During inference, the input data is encoded using single-tone sources impressed onto the network, and
circuit quantities are measured to decode the output prediction. Computation is performed through wave propagation and interference across the grid, with the learned input-output relationships stored in the tunable reactive elements. A key contribution of this work is a scalable training method based on in-situ backpropagation. The adjoint variable method is used to derive a physical (electrical) realization of the backpropagation
algorithm that is typically used to compute the gradient of the objective loss function in digital neural networks. This formulation computes the gradient from voltage measurements of two steady-state excitations: the forward pass (inference) and the adjoint pass (error backpropagation). This enables efficient training since it is independent of the number of trainable parameters and avoids the simulation-reality gap. To demonstrate the effectiveness of this approach, wave-based neuromorphic
circuit networks are trained for allostery and classification tasks, and the system's robustness to damage is shown. This work paves the way for self-learning systems based on wave-based neuromorphic analog
circuit hardware.
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Applied Physics · Cross-listed from cond-mat.mtrl-sci
Advances in electrical contacts to single crystals of emerging materials for transport measurements
Huandong Chen, Abhay N. Pasupathy and Jayakanth Ravichandran
Transport measurements that probe electrical resistivity of a material under varying external stimuli, such as temperature,
magnetic field, optical illumination, and gate voltage, are among the most important experimental techniques in condensed matter physics. These measurements provide critical insights into the fundamental electronic properties of materials. In recent years, they have facilitated the discovery and exploration of intriguing physical phenomena (e.g., superconductivity and
quantum oscillations) and unique device functionalities (e.g., photoresponse and electrostatic gating effects) in various emerging materials, particularly in the form of single
crystals. However, unlike large-scale wafers or thin films, newly synthesized single
crystals often pose substantial challenges in establishing reliable electrical contacts due to their irregular geometries, limited dimensions, inherent structural characteristics, and potential susceptibility to degradation. In this review, we highlight recent technological advancements in the fabrication of high-quality, lithographically defined multi-terminal electrodes on both exfoliable and non-exfoliable single
crystals for transport measurements. Our work provides a practical guide for researchers seeking to select appropriate contact-fabrication strategies tailored to unique characteristics of emerging
crystals.
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Data Analysis and Statistics · Cross-listed from nlin.AO
Decomposition of Anomalous Diffusion in two-state random walks
Abhijit Bera and Kevin. E. Bassler
Two-state
stochastic models, where motion alternates between distinct dynamical modes, are widely observed in complex systems. Here we study the Two-State Random Walk (TSRW), which switches between a continuous-time random walk (CTRW) rest state and a standard L'evy walk (LW) motion state, each with power-law distributed sojourn times. Using anomalous
diffusion decomposition, we show that TSRWs exhibit a generic coexistence of Joseph (correlation), Noah (heavy-tailed increments), and Moses (aging) effects. Strikingly, although classical L'evy walks alone possess only the Joseph effect, both Noah and Moses effects emerge in TSRWs solely due to
stochastic switching with the CTRW phase. Our results demonstrate that coupling between dynamical states can fundamentally reshape the mechanisms driving anomalous
diffusion, offering a minimal yet powerful framework for transport in heterogeneous and intermittently switching environments.
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Classical Physics
Relativistic deceleration vs acceleration, Unruh effect observation, and the Schott energy
Yefim S. Levin
This article examines finite-time relativistic deceleration and its energy balance within the Lorentz-Abraham-Dirac equation, with special
attention to boundary Schott-energy terms. From experimental and kinematical viewpoints, deceleration differs from acceleration. Proper accelerations or decelerations relevant to Unruh-effect observations may be more naturally realized in deceleration than in comparable acceleration scenarios. Deceleration from finite initial energy to rest can occur only over a finite time interval, unlike idealized acceleration, which can continue indefinitely. Thus, finite acceleration or deceleration must include boundary transitions in the radiation-energy balance. We first obtain expressions for the time and distance required for a relativistic particle with nonzero initial velocity to stop under constant deceleration. Applied to the Lynch-Cohen-Hadad-Kaminer (LCHK) estimate, they show that the quoted extremely large deceleration cannot represent sustained classical uniform proper deceleration over a macroscopic
crystal length. The stopping time and distance would be too small, and the upper bound on sustained deceleration is far below that estimate. We next consider a charged particle entering and leaving a uniform acceleration or deceleration interval without a velocity jump. This motion can be described within the LAD equation if the external force includes impulses during the short transitions between inertial and uniformly accelerated or decelerated motion. External work is not locally converted directly into radiation during the uniform segment. The Schott energy acts instead as an intermediate reservoir: it changes during the transitions and supplies the radiated energy during the subsequent uniform interval. This idealized LAD radiation mechanism is absent from the Lorentz-equation description and from LAD descriptions that neglect boundary conditions.
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Chemical Physics
Richardson-Gaudin states of non-zero seniority III: The Perfect-Pairing limit
Paul A. Johnson
Strongly correlated electrons can be treated with a configuration interaction of Slater determinants grouped by number of unpaired electrons with exponential cost. The first two papers in this series demonstrated that single reference methods built from Richardson-Gaudin states gave results of similar quality at
polynomial cost. In this contribution, the states are simplified substantially yielding the perfect-pairing state as a reference along with its low-lying excitations. The states are much simpler, the computational cost is substantially reduced, and there is no sacrifice in numerical accuracy. Second-order Epstein-Nesbet perturbative corrections for the valence electrons are similar in quality to the complete active space self-consistent field.
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Chemical Physics
All-Electron Relativistic Fully Self-Consistent $GW$ Study of Heteronuclear Actinide-Containing Diatomics
Jacob Adamski, Vibin Abraham and Dominika Zgid
The fully self-consistent $GW$ (sc$GW$) approximation provides a Green's-function approach that is starting-point independent and offers a favorable cost-to-accuracy balance compared to high-level wavefunction methods. Here, we present an all-electron sc$GW$ study of uranium-containing diatomics (UC, UN, UO, and UF), incorporating relativistic effects through the exact two-component (X2C) formalism. We evaluate adiabatic ionization energies as well as electron-attachment and detachment energetics (AEA and VDE), together with
equilibrium structures and harmonic vibrational frequencies, and we assess their sensitivity to basis-set choice and relativistic treatment. We find that sc$GW$ yields ionization energies and vibrational properties in very good agreement with experiment and high-accuracy theoretical estimates. For AEA and VDE, diffuse basis sets are essential for convergence. UF is a particularly challenging case for scalar relativistic methods because its electron-attachment and vertical detachment energies are strongly affected by
spin–orbit coupling, highlighting the need for a variational two-component treatment. These results establish all-electron X2C-sc$GW$ as a practical route for accurate actinide-molecule energetics and spectroscopy and motivate future applications to larger uranium-containing systems.
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Applied Physics · Cross-listed from cs.CE
Can dents and gouges compromise the structural integrity of hydrogen transport pipelines?
R. Das, B. Bezensek and E. Martínez-Pañeda
Repurposing natural gas pipelines for hydrogen transport requires understanding how external defects, like dents and gouges, affect structural integrity under H$_2$ exposure. To address this, we combine experiments with a new hydrogen embrittlement model aimed at large plastic straining scenarios, which integrates: (i) multi-trap hydrogen transport, (ii) finite-strain plasticity, and (iii) a hydrogen- and triaxiality-dependent damage law. Each constituent of the model is validated with experiments on X65 pipeline steel: (i) hydrogen permeation, (ii) full-scale pipe-indentation, and (iii) mechanical testing at different hydrogen and triaxiality levels. The validated model is used to study passive (indent before H$_2$ exposure) and active (indent with H$_2$) dents and gouges. Results reveal that hydrogen does not significantly increase the damage severity of those defects, unless hydrogen egress is completely precluded at the outer surface of a pipeline that is being pressurised internally and contains a pre-existing passive dent with a gouge.
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Space Physics · Cross-listed from math.DS
Orbital Networks in the Three-Body Problem
Abdullah Braik and Shane D. Ross
Orbital transfers in multi-body systems are often studied as isolated trajectory design problems, making it difficult to identify the larger transport structure connecting families of periodic orbits, including which families act as hubs, gateways, relays, or persistently difficult-to-access regions. This work introduces a reachable-set-based framework for constructing orbital networks in the circular restricted three-body problem. Finite-$\Delta V$ and finite-time-of-flight reachable-set overlaps are used to infer accessibility relationships between representative periodic orbit families on a common Jacobi energy
manifold and to assemble these relationships into a weighted orbital network. Applied to the Earth-Moon system, the resulting network reveals distinct accessibility regimes in which direct reachability, graph connectedness, and feasible multileg closure emerge separately. The analysis identifies multi-orbiter cycler orbits as the dominant hub, gateway, and relay families, with the (3,2)-cycler dominating across much of the sampled budget plane and the short-period (1,1)-cycler dominating in the low-time-of-flight regime, while the stable 2:1 resonant orbit remains persistently difficult to access. Although the maximum-budget network is nearly complete in a binary sense, its weighted accessibility remains strongly non-uniform. Selected proxy-supported connections are refined into concrete trajectories through differential correction, with corrected transfer costs remaining below the proxy estimates in all tested cases. Together, the results demonstrate how reachable-set overlap geometry can expose large-scale transport structure in nonlinear gravitational systems without requiring exhaustive pairwise trajectory optimization.
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Fluid Dynamics · Cross-listed from cond-mat.soft
Recovering the Shape of a Contact Line
Ashbell Abraham, Audrey Profeta, Jeanette Smit et al. (+7 more)
We study the conditions for a three-phase contact line to return to a previous position. We drive a water-air-glass contact line between two horizontal plates, by slowly adding and removing water with a constant volume amplitude. For the first several cycles, the contact line ends each cycle with a different shape, in contrast with previously published work. Eventually the shapes begin to repeat, and the system has
memory: a cycle with a smaller amplitude ends in a different shape, but even one cycle at the original amplitude recovers the steady-state shape. After a cycle at a larger amplitude, the steady-state shape is erased. We find that our tight control of the enclosed volume creates a global interaction, wherein only the least stable part of the contact line can move. Using theory and minimal models, we show that this interaction gives rise to the transient behaviors. Our study sheds light on the origins of reversibility and
memory in a system where neither is guaranteed, and shows that the physics of contact line motion changes in a confined environment.
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All authors Ashbell Abraham, Audrey Profeta, Jeanette Smit, Esmeralda Orozco, Charity Lizardo, Dani Medina, Aidan McGuckin, Bri Kroger, Shae Cole, Nathan C.Keim
Data Analysis and Statistics · Cross-listed from math.ST
Closed-form linear moments of the two-dimensional angular central Gaussian distribution
Siméon Vareilles
The polar-angle marginal of a centred bivariate Gaussian distribution, obtained after integrating out the radial coordinate, gives the two-dimensional angular central Gaussian (ACG) distribution of Tyler. While its trigonometric and vector-valued moments have been studied in detail, to our knowledge there are no explicit closed-form expressions for the linear moments $\mathbf{E}[\theta]$ and $\mathbf{E}[\theta^{2}]$ on the natural domain $\theta\in\left]-\pi/2,\pi/2\right[$. Here linear refers to the ordinary moments $\int\theta^{k}f(\theta)\,d\theta$ of the angle regarded as a real-valued variable, in contrast to the circular (trigonometric) moments $\mathbf{E}[e^{ik\theta}]$ customary in directional statistics. We provide such expressions: the mean is a simple arctangent of the parameters, while the second moment is given by the real part of a dilogarithm. The derivation, based on a contour integration around the branch cut of $\arctan z$, is elementary. These quantities naturally arise in physics, where $\theta$ is interpreted as a real-valued phase rather than a circular variable.
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Chemical Physics · Cross-listed from cond-mat.soft
Cooperative Conformational Transitions in Macromolecules under Mechanical Stretching. An Exactly Solved Model for Single Molecule Experiments
Javier Orradre, Pablo M. Blanco, Sergio Madurga et al. (+3 more)
The stretching behavior of linear macromolecules undergoing conformational transitions is investigated. An exact solution is provided for a two-state system within the elastic freely jointed chain model. This minimal framework contains the smallest set of parameters required to describe such transitions: two Kuhn lengths, two elastic force constants, a free energy difference between both states and a nearest-neighbor interaction energy accounting for cooperativity. Explicit analytical expressions are derived for the chain extension and the probabilities of each state as functions of the applied force.The approach accurately reproduces the experimental force-extension curves of poly(ethylene-glycol) (PEG) and hyaluronic acid (HA), revealing no cooperativity for PEG and negative cooperativity for HA. It also describes the B-DNA to S-DNA conformational transition, a process that exhibits positive cooperativity.We analyze the mathematical conditions required for a transition and identify two fundamental driving mechanisms: differences in Kuhn lengths and differences in force constants.Extensions of the model to systems with more than two conformational states per Kuhn segment are also discussed. The results presented here apply equally to transitions that are intrinsic to the macromolecular structure or induced by ligand-receptor interactions, unifying both cases within a single thermodynamically consistent framework.
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All authors Javier Orradre, Pablo M. Blanco, Sergio Madurga, Marina I. Giannotti, Francesc Mas, Josep L. Garcés
Optics
Toroidal pulse enhanced XUV generation
Lu Wang, Clément Lacoste, Paul Corkum et al. (+2 more)
Extreme ultraviolet (XUV) radiation plays a central role in a wide range of applications. Despite being a cornerstone of attosecond science, efficient XUV generation remains highly challenging. Here, we investigate XUV generation via nonlinear Thomson scattering driven by a toroidal pulse. Unlike conventional
laser pulses, toroidal pulses possess intrinsically non-separable spatiotemporal field distributions. This unique field structure produces strongly asymmetric electron acceleration, resulting in substantially enhanced XUV emission that is 2-4 orders of magnitude stronger than that generated by a Gaussian pulse. Our results identify toroidal pulses as a promising route toward compact ultrafast XUV sources and advanced strong-field light-matter interaction studies.
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All authors Lu Wang, Clément Lacoste, Paul Corkum, Thomas Brabec, Zenghu Chang
Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Crystallisation kinetics of supercooled liquid palladium
Zuzanna Kostera, Przemyslaw Dziegielewski, Christian Bressler et al. (+13 more)
In this study, we employ classical molecular dynamics (MD) simulations to investigate the crystallisation kinetics of supercooled
liquid palladium and relate the results to time-resolved X-ray diffraction measurements on rapidly quenched Pd thin films.
Crystal nucleation and growth rates are determined over the temperature range $700$–$1150~\mathrm{K}$ ($0.38$–$0.65 T_{\mathrm{m}}$) by analysing the
evolution of the microstructure during the
liquid-to-
crystal transition. The self-
diffusion coefficient of Pd, obtained from the atomic mean-squared displacement, follows Arrhenius behaviour over the investigated temperature range, with an activation energy of $467(6)~\mathrm{meV/atom}$, consistent with available data for supercooled
liquid metals. The steady-state homogeneous nucleation rate exhibits a maximum of approximately $4 \times 10^{35}~\mathrm{m^{-3} s^{-1}}$ near $0.5 T_{\mathrm{m}}$.
Crystal growth occurs at velocities of the order of metres per second, with a temperature dependence consistent with
diffusion-limited Wilson-Frenkel kinetics rather than the collision-limited regime. Based on multiple statistically independent simulations, a time-temperature-transformation (TTT) diagram for crystallisation onset is constructed. The TTT curve exhibits a nose near $0.5 T_{\mathrm{m}}$ and $100~\mathrm{ps}$, corresponding to a critical cooling rate for vitrification on the order of $10^{13}~\mathrm{K s^{-1}}.$ The simulations reproduce the crystallisation onset time and temperature observed in time-resolved X-ray diffraction experiments on optically molten Pd thin films quenched at $5 \times 10^{11}~\mathrm{K s^{-1}}.$ These results indicate that homogeneous, rather than heterogeneous, nucleation governs the achievable supercooling in the experimentally studied films.
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All authors Zuzanna Kostera, Przemyslaw Dziegielewski, Christian Bressler, Wojciech Gawelda, Konstantinos Georgarakis, Dmitry Khakhulin, Oleksii I. Liubchenko, Adam Olczak, Angel Rodriguez-Fernandez, Ryszard Sobierajski, Klaus Sokolowski-Tinten, Peihao Sun, Robert W.E. van de Kruijs, Hazem Yousef, Peter Zalden, Jerzy Antonowicz
Instrumentation and Detectors
Deep-learning-based low-energy trigger algorithms for the Hyper-Kamiokande experiment
Katharina Lachner, Saúl Alonso-Monsalve, Benjamin Richards et al. (+1 more)
Modern machine learning techniques have become increasingly important in particle physics because of their powerful pattern-recognition capabilities, including in real-time data acquisition where stringent runtime constraints apply. This paper details the performance of deep-learning-based trigger
algorithms for a large water Cherenkov detector such as Hyper-Kamiokande, aimed at low-energy
neutrino events (below 7 MeV). The performance of custom neural-network supervised classifiers is shown alongside two anomaly-detection approaches trained solely on detector noise: a pure autoencoder and a model based on
Manifold Projection-
Diffusion Recovery. The supervised model shows signal identification efficiencies of 76.7% for single electrons of 3 MeV kinetic energy, significantly exceeding signal efficiencies obtained from a traditional hit-count-based trigger of 26.4%, while the
Manifold Projection-
Diffusion Recovery approach reaches 35.4% at the same operating point. Runtime evaluations on GPU yield per-window inference latencies well below the millisecond scale.
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All authors Katharina Lachner, Saúl Alonso-Monsalve, Benjamin Richards, Davide Sgalaberna
Fluid Dynamics
Algebraic models of plane Couette equilibria
Pratik P. Aghor and John F. Gibson
Recent computations of weakly unstable
equilibria, traveling waves, and periodic orbits in transitional shear flows suggest a spatiotemporal, dynamical-systems approach to low-Reynolds
turbulence. Many invariant solutions have been computed precisely using high-dimensional direct numerical simulations, but little is known about how many solutions exist, how they are organized, or which sets of solutions best characterize the flow. In this paper we present a framework for addressing these questions in a low-dimensional context. Using classical approximation methods and exploiting
symmetries and kinematic constraints, we derive ordinary differential equation models of plane Couette flow whose
equilibria are governed by systems of quadratic algebraic equations. Solutions of these algebraic systems approximate known
equilibria of plane Couette flow in as few as 17 dimensions and converge toward the known solutions as dimension increases. Searches over the systems produce sixteen distinct
equilibrium solution branches in seven different
symmetry groups. These results suggest that the
equilibrium and traveling-wave solutions of closed shear flows are organized by the algebraic structure of systems of quadratic equations. Additionally, the differential equations and divergence-free basis provide explicit, closed-form, and convergent dynamical-systems representations of plane Couette flow.
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Instrumentation and Detectors
Development of a Multi-Purpose Optical TPC for Neutron-Induced Reaction Studies at SARAF
R. Felkai, M. Borysova, L. Moleri et al. (+6 more)
Neutron-induced reactions play a central role in
stellar and Big Bang nucleosynthesis models. Yet many of the cross sections remain poorly constrained at astrophysically relevant energies. To address these needs, we are developing a multi-purpose Optical Time Projection Chamber (OTPC) optimized for precision
neutron-reaction studies at the Soreq Applied Research Accelerator Facility (SARAF) upcoming high-intensity, time-of-flight
neutron beam. The detector combines a drift chamber filled with CF4-based scintillating gas mixtures, fast photodetectors for
prompt scintillation detection, and high-speed optical readout of avalanche-induced secondary scintillation to enable full 3D reconstruction of charged-particle tracks. A prototype system has been assembled and tested. This has enabled systematic characterization of electron drift velocity, charge and light amplification, and 2D optical imaging of alpha-particle tracks in an Ar/CF4 gas mixture. These studies guide the design of a larger, fully integrated OTPC system intended for operation at SARAF. In parallel, we are exploring advanced image sensors to further enhance tracking resolution. We report on recent progress with the prototype and outline the next steps toward commissioning the full system.
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All authors R. Felkai, M. Borysova, L. Moleri, J. Pienaar, D. Vartsky, A. Breskin, I. Mor, L. Weissman, S. Bressler
Fluid Dynamics
Subcritical transition to turbulence in buoyancy-driven flows with multiple hysteresis loops under quasi-one-dimensional confinement
Lu Zhang and Ke-Qing Xia
We present both static and quasi-static direct numerical simulations of Rayleigh-Bénard convection in a quasi-one-dimensional domain, revealing for the first time a clear subcritical transition to
turbulence in a buoyancy-driven flow. Within a narrow range of Rayleigh number (Ra), three coexisting flow states are identified: steady convection, oscillatory chaos, and intermittent
turbulence. The transitions between these states are accompanied by abrupt jumps in both the Nusselt number (Nu) and Reynolds number (Re), the key global transport quantities in buoyancy-driven flows. Additionally, they exhibit pronounced hysteresis, forming three distinct hysteresis loops in the Nu-Ra plane: normal, reverse, and anomalous loops. More importantly, we show that the steady convection state is linearly stable against infinitesimal perturbations but can transition to intermittent
turbulence when subjected to finite-amplitude disturbances, which is a defining hallmark of subcriticality. Thus, contrary to the prevailing view that the transition from convection to
turbulence is supercritical, our results demonstrate that buoyancy-driven
turbulence can emerge via a subcritical route, paving the way for a unified framework that describes instability mechanisms in both buoyancy-driven and shear-driven flows.
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Applied Physics
Sharp periodic Ge concentration modulations beyond the conduction band valley wavevector $k_0$ in nuclear spin-free Si quantum wells
Ivo Rahlff, Carsten Richter, Martin Schmidbauer et al. (+13 more)
Periodic Ge modulations within strained Si
quantum wells in SiGe
heterostructures offer a route to deterministically enhance conduction-band valley splitting in Si, a key requirement for scalable
spin-
qubit quantum computing. Efficient enhancement requires modulations in the order of the Si valley wavevector $k_0$ (9.7 nm$^{-1}$), corresponding to a period of 0.64 nm and near-monolayer growth control. Using
nuclear-
spin-free molecular beam epitaxy with $^{28}$Si and $^{72}$Ge, we demonstrate Ge-modulated Si
quantum wells with periods from 2.00 to 0.49 nm, including modulations at $k_0$ and $2k_0/3$. Synchrotron X-ray techniques and scanning transmission electron microscopy reveal laterally homogeneous Ge modulations over micrometer scales, with amplitudes up to 10 at-% and gradients reaching 20 at-%/nm. Two-bands $\mathbf{k}\cdot\mathbf{p}$ simulations suggest deterministic enhancement of valley splittings in steep trapezoidal $2k_0/3$
heterostructures, while the effect in $k_0$-type
quantum wells is much weaker.
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All authors Ivo Rahlff, Carsten Richter, Martin Schmidbauer, Maximilian Oezkent, Thilo Remmele, Michael Hanke, Lars R. Schreiber, Denny Dütz, Sammy Umezawa, Martin Albrecht, Yann-Michel Niquet, Tancredi Salamone, Biel Martinez Diaz, Thomas Schroeder, Jens Martin, Kevin-P. Gradwohl
Biological Physics · Cross-listed from cond-mat.soft
Spontaneous flows and interfacial instabilities in oxygen-sensitive living active matter
Azam Gholami, Sangram Gore, Sai V. R. Ambadipudi et al. (+2 more)
Active fluids generate motion and stress internally, but in living systems their activity is often regulated by environmental fields that organisms consume or produce. How such fields localise active stresses and create flow-generating interfaces remains unclear. Here we show that oxygen organises suspensions of the flagellated microswimmer Euglena gracilis into an annular living interface. In circular chambers with an air-exposed periphery, a labyrinthine bioconvective pattern and an annular cellular accumulation emerge nearly simultaneously, whereas sealing the periphery suppresses the annulus. The accumulation then sharpens, develops finite-wavelength protrusions and forms a long-lived, collectively rotating corona. An oxygen-coupled polar active-fluid model qualitatively recapitulates this progression: oxygen transport, cellular consumption and oxygen-regulated swimming and reorientation assemble and position the annulus, whereas dipolar active stresses destabilise it and generate collective flow. These results show how a metabolically shaped chemical field can create and activate a living interface, linking taxis, bioconvection and active interfacial hydrodynamics.
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All authors Azam Gholami, Sangram Gore, Sai V. R. Ambadipudi, Iraj Gholami, Albert J. Bae
Optics
Optimisation and Precision Tuning of Localised Surface Plasmon Resonance in AuFON Systems
Luis Alfonso Guerra Hernández, Osmar Gil Salas, Jorge Enrique Rueda Parada et al. (+2 more)
Metal film on nanosphere (MFON) plasmonic systems have emerged as nanostructures with useful properties for molecular detection. This work presents the optimisation and discussion of the characterisation results of Au-film on nanosphere (AuFON) systems. Through experiments and numerical simulations, the resonance energies of localised surface plasmon modes and the spatial distribution of light on the nanostructured surface were identified. The results highlight the dependence of these modes on changes in nanostructure dimensions and the optical conditions of the incident radiation, thereby optimising the amplification of optical signals for applications in molecular detection.
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All authors Luis Alfonso Guerra Hernández, Osmar Gil Salas, Jorge Enrique Rueda Parada, Alejandro Fainstein, Andrés Alejandro Reynoso
Instrumentation and Detectors
Optimization of the light detection system of the ICARUS detector
C. Saia, C. Petta, G. L. Raselli et al. (+1 more)
The ICARUS detector, a key component of the Short Baseline
Neutrino (SBN) Program at
Fermi National Acelerator Laboratory (FNAL), is a 600-ton
Liquid Argon Time Projection Chamber (LArTPC) equipped with a Light Detection System (LDS) that uses 360 Hamamatsu R5912-MOD 8-inch photomultiplier tubes (PMTs), specifically designed to operate under cryogenic conditions ($\sim 87 \ K$). These PMTs feed the trigger signal to the readout, improve the spatial and timing resolution of the events, and contribute to
cosmic rays mitigation. During operation at FNAL, a progressive degradation in the PMT gain was observed. We developed an experimental setup to investigate the temperature dependence of PMT performance. Gain measurements were carried out from room temperature to $-70 ^\circ C$ using an environmental chamber. The results show that, while the PMTs exhibit stable performance at room temperature, a significant and irreversible reduction in gain emerges at lower temperatures. Al though $-70 ^\circ C$ remains above the
liquid argon temperatures, the trend clearly reveals a gain-sensitive degradation mechanism. A simplified physical model was developed to reproduce and interpret the observed behavior. Based on these findings, a series of mitigation strategies were implemented in the ICARUS detector to preserve PMT performance and ensure reliable operation under cryogenic conditions.
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All authors C. Saia, C. Petta, G. L. Raselli, M. Rossella
Optics
Size, Shape, and Material matter: All-optical Mie void sensor for complex nanoplastic mixtures
Dominik Ludescher, Julian Schwab, Serkan Arslan et al. (+5 more)
The fragmentation of plastic debris and the direct release of nanoplastics have emerged as a pressing ecological concern. Once dispersed, these enduring particles infiltrate food webs, accumulate within organisms, and bind toxic co-contaminants, posing long-term risks to ecosystems and human health. Despite growing awareness, the detection and characterization of nanoplastics remain highly challenging due to their minute size. Moreover, obtaining additional critical information, such as the particle shape or material composition, further exacerbates these detection hurdles. Conventional analytical techniques capable of providing more detailed information often demand substantial experimental and lab-bound effort, costly instrumentation, and lengthy measurement times. Here, we introduce a novel photonic sensing platform based on nanoscale voids that enables the simultaneous material- and morphology-sensitive detection of particles below 500 nm. Arrays of voids embedded in a high-refractive-index material act in parallel as both sorting elements and direct color reporters. Spherical and elongated particles are selectively trapped in circular and elliptical voids, while
polymer types such as PS, PMMA, and PET are distinguished via the specific color signatures arising from their refractive index contrasts. This approach offers a cheap and scalable route toward rapid optical identification of nanoplastics in complex environmental and biological settings. Its compatibility with quick, high-throughput analysis positions it as a promising tool for real-time monitoring and comparative studies of heterogeneous nanoplastic populations.
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All authors Dominik Ludescher, Julian Schwab, Serkan Arslan, Evelyn Kubacki, Monika Ubl, Markus Retsch, Harald Giessen, Mario Hentschel
Plasma Physics
Gyrokinetic global simulation of Alfvenic ion temperature gradient mode in reversed magnetic shear
Gengxian Li, Zhixin Lu, Philipp Lauber et al. (+3 more)
In this work, a systematic study of electromagnetic instabilities driven by the temperature gradient in magnetically confined fusion
plasmas with reversed
magnetic shear is conducted using gyrokinetic particle-in-
cell simulations. An electromagnetic instability arising in the low-beta regime is investigated, where beta=8*pi*nT/B^2 denotes the ratio of
plasma pressure to
magnetic pressure. Within a reversed shear safety factor (q) profile, when a mode rational surface coincides with the position of zero shear, an instability dominated by only one poloidal harmonic emerges, rather than the conventional ion-temperature-gradient (ITG) mode. Simulation results demonstrate that the instability exhibits pronounced electromagnetic polarization even in the low-beta regime, with a real frequency significantly higher than that of ITG modes, and show that it is destabilized by the temperature gradient and not by the density gradient. This instability can be observed even for a monotonic q profile with weak
magnetic shear. Based on a systematic comparison with other typical electrostatic and electromagnetic instabilities, this instability is identified as a weak shear Alfvenic-ion-temperature-gradient (WSAITG) mode, which may provide an explanation for the low-frequency Alfven modes (LFAM) observed in experiments. Wave-particle resonance analysis in phase space reveals that, in contrast to the ITG mode, well-passing particles provide an additional resonant population that drives the WSAITG mode.
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All authors Gengxian Li, Zhixin Lu, Philipp Lauber, Matthias Hoelzl, Guo Meng, Yong Xiao
Applied Physics · Cross-listed from cond-mat.mes-hall
Feasibility study of continuous electronic Pomeranchuk cooling with a flavor-degenerate Wigner crystal
Robin J. Dolleman, Ammon Fischer, Lennart Klebl et al. (+5 more)
Achieving sub-millikelvin electron temperatures in nanoelectronic devices could unveil new transport phenomena, extend
quantum coherence times, and enhance the precision of
quantum metrology. However, maintaining such low temperatures continuously remains a long-standing challenge. Here, we propose and simulate an on-chip cooling cycle that harnesses the
entropy difference between an electron
liquid (EL) and a Wigner
crystal (WC) in
flavor-degenerate flat-band materials. Cooling is driven by a current through a device with a locally gated region. Within this region, the charge carrier density is tuned such that a WC forms beneath the gate. As carriers transition from an EL to WC phase, their
entropy increases, extracting heat and the sliding WC advects this heat along the device. The heat is then released when carriers transition back to the EL phase, which establishes distinct hot and cold regions and a steady temperature gradient over the device. Simulations show net cooling for sufficiently low current densities, typically below $1~\mathrm{nA}/\mu\mathrm{m}$, whereas Joule heating dominates at higher currents. Within the gated region, we estimate cooling powers of up to $8.4~\mathrm{aW}/\mu\mathrm{m}$ at a bath temperature of $4~\mathrm{mK}$. Our approach can achieve electron temperatures well below $1~\mathrm{mK}$ under suitable conditions, promising a route towards continuous on-chip cooling in this temperature regime. Our approach applies to any flat-band material with low-energy
flavor degeneracy (valley and/or orbital) and low disorder, including gapped Bernal-stacked
bilayer graphene, rhombohedral-stacked multilayer
graphene, and magic-angle twisted
bilayer graphene.
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All authors Robin J. Dolleman, Ammon Fischer, Lennart Klebl, Alexander Rothstein, Dante M. Kennes, Bernd Beschoten, Florian Libisch, Christoph Stampfer