Applied Physics
Magnetic Particle Magnetometer Based on Langevin Response of Superparamagnetic Nanoparticles for Remote Magnetic Field Sensing
M. Jurj, C. McDonough, C. Bastajian et al. (+1 more)
We demonstrate a novel magnetometer that utilizes the Langevin nonlinear magnetization of superparamagnetic nanoparticles as the sensing medium. The
magnetic sensor exploits the even-order harmonics of the magnetization response, particularly the second harmonic, which is proportional to the local
magnetic field component. By remotely detecting the magnetization response, the magnetometer enables non-invasive, localized, and distributed
magnetic field sensing without requiring wired connections, with a small sensing volume, which can be used for in situ biomedical sensing, geomagnetic monitoring, smart diagnostics, and distributed industrial sensing. In the linear operating regime, the magnetometer provides a measurement range of $\pm$ 0.2 mT and a high sensitivity of 10 pT/$\sqrt{Hz}$, while an extended operating mode allows measurements over a range exceeding $\pm$ 0.5 mT. The sensor offers a dynamic bandwidth from dc up to a few kilohertz, determined by the excitation frequency.
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All authors M. Jurj, C. McDonough, C. Bastajian, A. Tonyushkin
Instrumentation and Detectors
Precise measurement of the thermal quenching factor of alpha particles in Li2MoO4 cryogenic calorimeters
M. Girola, R. Serino, M. Biassoni et al. (+7 more)
We present direct measurements of the thermal quenching factor (QF)for alpha-particles in Li2MoO4 scintillating
crystals, conducted at base temperatures of 13 mK and 19 mK. Using gamma-calibration peaks from a 232Th source and alpha-lines from a surface 224Ra source, the QF_alpha was determined to range from 1.07 to 1.09 which is consistent with previous studies. A slight energy-dependent trend in QF_alpha was observed.
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All authors M. Girola, R. Serino, M. Biassoni, C. Brofferio, M. Faverzani, E. Ferri, A. Gianvecchio, L. Gironi, I. Nutini, S. Pozzi
Medical Physics · Cross-listed from eess.SP
Complementary-Aperture Pulse Sequencing for Fundamental-Band Nonlinearity Parameter Imaging
Esteban Avilés, Michael Oelze, Roberto Lavarello et al. (+1 more)
The depletion method (DM) enables the estimation of the acoustic nonlinearity parameter, B/A, in pulse-echo ultrasound using fundamental-band signals from low- and high-pressure acquisitions, but requires accurate knowledge of the acoustic-pressure scaling factor. This requirement limits experimental translation because of the slightly nonlinear scaling between excitation voltage set on the ultrasound system and pressure at the probe. We propose a complementary-aperture pulse sequence (CAPS) that recovers the linearly scaled low-pressure signal by coherently summing RF acquisitions from interleaved transmit subapertures whereas a full-aperture transmission provides the high-pressure signal maintaining the same excitation voltage configured in the ultrasound system. In silico phantoms of a homogeneous sample and a reference evaluated four aperture partitions of CAPS and compared them with the DM under relative scaling-factor errors from 0.01% to 10%. Using the DM, errors of 0.1% and 1% produced absolute B/A biases of up to 27.3% and 58.3%, respectively. CAPS yielded mean B/A values of 8.9 for a prescribed value of 9, with biases of less than 1.3% across all partitions, matching an ideally calibrated DM. These results demonstrate that CAPS preserves depletion-based B/A estimation without using the pressure scaling factor as a reconstruction input, supporting experimental and in vivo implementation without pressure-ratio calibration.
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All authors Esteban Avilés, Michael Oelze, Roberto Lavarello, Andres Coila
Atmospheric and Oceanic Physics
ClimTip-GML: A global bias-corrected and downscaled dataset for assessing impacts of climate tipping events
Philipp Hess, Sebastian Bathiany, Lucas Ferreira Correa et al. (+3 more)
Assessing the impacts of future
climate scenarios including tipping events of major Earth system components such as the Amazon rainforest (ARF) or the Atlantic meridional overturning circulation (AMOC), requires accurate and high-resolution simulations. Here, we present ClimTip-GML, the first globally bias-corrected and downscaled
climate dataset for impact assessment of large-scale tipping scenarios, comprising eight key variables at 0.25{\deg} spatial resolution from three general circulation models (GCMs): CESM1-CAM5, HadGEM3-GC31-MM, and MPI-ESM1-2-HR. The
dataset includes 100-year-long
climate simulations with preindustrial and historical conditions, as well as scenarios at a +2{\deg}C warming level with and without tipping transitions of the AMOC or ARF. We apply generative machine learning (GML) techniques trained on reanalysis data to bias-correct and downscale the GCMs in a manner that is physically consistent across space, time, and all eight variables. Comprehensive validation shows substantially reduced biases, improved small-scale spatial variability, multivariate correlations, and consistent long-term
climate responses to the external forcing and tipping events. The results hence permit substantially improved impact assessments of tipping transitions of the ARF and AMOC, directly informing mitigation and adaptation policies.
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All authors Philipp Hess, Sebastian Bathiany, Lucas Ferreira Correa, Laura C. Jackson, Casey R. Patrizio, Niklas Boers
Plasma Physics
Real-Time Plasma State Prediction via FPGA-Accelerated Quantized Recurrent Probabilistic Neural Networks
Daniel Gaytan-Villarreal, Aiken Xie, Tu Pham et al. (+5 more)
Real time
plasma state estimation for control of Tokamak devices are challenging due to the stringent latency requirements of the
plasma control system (PCS). We present an end-to-end workflow for deploying a recurrent probabilistic neural network (RPNN) on FPGA hardware. We combine architecture size reduction with quantization-aware training via QKeras. The model is then synthesized using hls4ml, targeting a Xilinx Alveo U50 device. We report a design that fits comfortably within all four resource budgets (DSP, LUT, FF, BRAM) at deterministic sub-10~$\mu$s single-timestep latency, meeting the requirements for real-time inference inside a model-predictive-control-style
plasma control loop.
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All authors Daniel Gaytan-Villarreal, Aiken Xie, Tu Pham, Rohit Sonker, Chiara Amendola, Matteo Cremonesi, Cong Hao, Jeff Schneider
Chemical Physics
ECENet: An Edge Cluster Expansion Line-Graph Neural Network
R. Allen LaCour and Teresa Head-Gordon
Machine-learned interatomic potentials (MLIPs) have emerged as a promising alternative to classical force fields and first-principles theory for predicting the properties of chemical and material systems. Many MLIPs are graph neural networks with O(3)-equivariant features, whose accuracy comes at substantial computational cost. Here we introduce the edge cluster expansion (ECE), an analogue of the atomic cluster expansion in which the environment is expanded around edges between atom pairs rather than single atoms, and build upon it to develop the line-graph neural network ECENet. ECENet uses O(2)-equivariant features that persist on the edges between atoms, giving it natural access to O(2) operations that are cheaper and less restrictive than their O(3) counterparts. ECENet performs at the state of the art on the MD22
benchmark and lies on the accuracy-cost Pareto frontier when trained on the SPICE-MACE-OFF
dataset. Furthermore, with long-range electrostatics implemented via latent Ewald summation, ECENet accurately predicts molecular dipole moments and the infrared spectrum of
liquid water. The frontier ECENet architecture establishes equivariant edge-centered representations as an efficient and physically expressive foundation for equivariant MLIPs.
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Instrumentation and Detectors
Single-electron detection in a high-purity Ge device
Antoine Armatol, Corinne Augier, Laurent Bergé et al. (+69 more)
High-purity germanium (HPGe) detectors are among the most powerful instruments for gamma ray spectroscopy, combining exceptional energy resolution with large active volumes. Although they operate close to the fundamental resolution limit at high energies, their performance at very low energies has long been limited by electronic noise, restricting detection thresholds to above approximately 30 electron-hole pairs ($\sim$100 eV). Here we introduce a cryogenic HPGe detector architecture that achieves single electron-hole pair sensitivity by calorimetrically measuring ionization at temperatures near 20 mK. The device integrates a NbSi transition-edge sensor into a point-contact-inspired geometry, concentrating athermal
phonon energy generated during charge drift and enabling eV-scale sensitivity ultimately set by the
semiconductor band gap. Beyond single-charge detection, the device rejects the low-energy excess background that limits existing cryogenic low-threshold technologies, establishing a pathway towards discrimination between electron- and nuclear-recoil events below 100 eV. These advances open a route towards next-generation detectors for direct dark matter searches, coherent elastic
neutrino-
nucleus scattering, and nuclear reactor monitoring for non-proliferation applications.
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All authors Antoine Armatol, Corinne Augier, Laurent Bergé, Julien Billard, Harvey Birch, Juliette Blé, Clarence Chang, Yen-Yung Chang, Luke Chaplinsky, Gordon Cline, Alec Cochard, Ion Cojocari, Jules Colas, Simon Connolly, Maryvonne De Jesus, Pierre de Marcillac, Kamil Dwinger, Romain Faure, Simon Fiorucci, Maurice Garcia-Sciveres, Jules Gascon, Ryan Gibbons, Gil Gilchriese, Cloé Girard-Carillo, Wei Guo, Leila Haegel, Scott Haselschwardt, Scott Hertel, Tyler Horoho, Keith Hunter, Leslie Juigne, Alexandre Juillard, Alex Kavner, Jacob Lamblin, Tatiana Le-Bellec, Junsong Lin, Rupak Mahapatra, Stefanos Marnieros, Claire Marrache-Kikuchi, Nicolas Martini, Will Matava, Daniel McKinsey, Connor McLaughlin, Johann Menu, Knut Moraa, Valentina Novati, Emiliano Olivieri, Björn Penning, Mark Platt, Denys Poda, Matt Pyle, Yinghe Qi, Rafsan Rabbi, Ivar Rydstrom, Bernard Sadoulet, Silvia Scorza, Bruno Serfass, Peter Sorensen, Gabrielle Soum-Sidikov, Samara Steinfeld, Henry Su, Toki Suzuki, Ronald Vaughn II, Charlie Veihmeyer, Paul Vittaz, Gensheng Wang, Yue Wang, Michael R. Williams, Joanna Wuko, Volodymyr Yefremenko, Alexandre Broniatowski, Louis Dumoulin
Fluid Dynamics
Channel confinement mollifies roll wave instabilities
Jake Langham, Cyril Gadal, Jamie P. Webb et al. (+2 more)
Under certain conditions,
gravity currents spontaneously develop large-amplitude streamwise undulations on their free surfaces ('roll waves'). The effect of channel geometry on this instability is investigated herein. Via a section-averaged stability analysis conducted independently of the rheology of the flowing material, convex open channels are found to be stabilising, relative to unconfined flows. This is shown to agree with experimental observations of laterally shallow currents of water and dry granular material in trapezoidal channels. For such flows, the influence of the geometry can be characterised by a single dimensionless parameter, which predicts stabilisation as the channel width narrows. Including the cross-stream velocity profile in the analysis further stabilises predictions and can render steady flows in triangular channels unconditionally stable - a finding borne out by our experiments. Consequently, laterally tilting a trapezoidal channel can also stabilise flows by adjusting the wetted region towards a triangular one. Implications for observations in natural channels are considered by adapting an existing model of roll waves in the Illgraben, Switzerland, to incorporate channel geometry. The resulting simulations produce suitable waves for a realistic cross-section, but are stabilised by a modest narrowing of the channel. Complementary nonlinear wave solutions are then constructed and used to show that channel confinement also diminishes amplitudes of observed waves. Finally, exceptions to the analysis are discussed, including the possibility for static material to shield waves from the effects of geometry. We demonstrate this using observations of undamped granular avalanches travelling through an arrested deposit in a triangular chute.
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All authors Jake Langham, Cyril Gadal, Jamie P. Webb, Chris G. Johnson, J. M. N. T. Gray
Fluid Dynamics
Equivariant Neural Prediction of the Stokes Resistance Tensors for Arbitrary Microparticle Shapes
Sanjay Pradeep, David Dandy, Candace S.J. Tsai et al. (+1 more)
The Stokes-flow hydrodynamics of an irregular microparticle is encoded by its grand resistance
matrix, a 6x6 tensor whose translational and rotational blocks (A and C) govern settling,
diffusion, and orientational transport. Empirical drag correlations compress these tensors to a single scalar, discarding drag's orientation dependence and the rotational response. We present an SO(3)-equivariant neural network that predicts the full symmetric positive-definite A and C blocks from a particle's spherical-harmonic surface representation, equivariant by construction to floating-point precision. Trained on 1.1x10^5 random shapes from near-spherical to very rough, with a sealed test set of 18,000, it achieves 1.4% and 2.7% mean relative error on the two blocks while evaluating each shape 4-5 orders of magnitude faster than the regularised-Stokeslet solver that generated its labels. A spectral-convergence study confirms the representation is faithful: truncating a shape at spherical-harmonic degree 15 changes its resistance by a median of 0.14% (translation) and 0.38% (rotation), while the training shapes, generated band-limited at degree 15, carry no truncation error. Across 1.16x10^6 orientation-sampled settling, rotation and
diffusion events, the surrogate reveals lateral drift up to 11 deg, rotational misalignment up to 46 deg, and shape-induced
diffusion spreads of 30% (translational) and 2.4x (rotational), all identically zero under any scalar or spheroid reduction. Even the orientation-averaged scalar friction the correlations target, accurate to 1.7-2.8% (median; 2.2-3.2% mean), carries no tensor orientation, whereas the surrogate reproduces that scalar to ~1% while supplying the full anisotropic tensors. A fast, equivariant tensor surrogate can replace both solver and scalar approximation in atmospheric dust transport, microplastic fate and colloidal Brownian dynamics.
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All authors Sanjay Pradeep, David Dandy, Candace S.J. Tsai, Jeff D. Eldredge
Geophysics · Cross-listed from astro-ph.EP
Super-Earth Interiors Shrink by About 10% as They Crystallise
Tim Lichtenberg, Mara Attia, Harrison Nicholls et al. (+26 more)
Super-Earth
exoplanets are among the most abundant
planets known, yet their bulk densities leave the interior state degenerate. The static structure models used to interpret them, and the interior
retrievals built on them, typically describe the cold, solidified end state of an
evolution that begins hot and molten. During this magma ocean stage the interior, the outgassed atmosphere, and the surface co-evolve and set the long-term
climate and geophysics of super-Earths. We develop and validate a fully coupled model for the structural and thermal
evolution of super-Earth
exoplanets within the PROTEUS framework, including new and upgraded models of the interior structure, mantle energetics, and volatile outgassing. In volatile-poor super-Earths of 1 to 10 Earth masses, the silicate interior contracts by about 10 % of its molten radius through cooling and crystallisation, nearly independent of
planet mass and driven by the thinning silicate shell alone. The solidified radius is set by planetary mass and core fraction, insensitive to the host
star, irradiation, and initial thermal state. In contrast, volatile-rich super-Earths at and above about 5 Earth masses may not solidify: their thick outgassed atmospheres throttle the surface heat loss until the interior settles into a deep magma ocean, keeping the
planet inflated and limiting the contraction to about half its volatile-poor value. Mantle contraction alone thus shapes the low-mass
exoplanet transit population, motivating joint interpretation of atmospheric and geophysical signatures in upcoming
exoplanet surveys.
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All authors Tim Lichtenberg, Mara Attia, Harrison Nicholls, Mariana Sastre, Dan J. Bower, Karen Stuitje, Flavia C. Pascal, Laurent Soucasse, Daniel Apai, Patrick Bos, Robb Calder, Lorenzo Cesario, Lisa Dang, Emeline Decocq, Marijn van Dijk, Mohammad Farhat, Kaustubh Hakim, Tadahiro Kimura, Imre Kisvárdai, Sebastiaan Krijt, Yamila Miguel, Ioannis Panagiotou, Emma Postolec, Martin Schlecker, Sara Seager, Anat Shahar, Oliver Shorttle, Paolo A. Sossi, Wim van Westrenen
Fluid Dynamics · Cross-listed from cond-mat.soft
Apparent Breakdown of the Stress-Optic Rule in Rigid-Rod Suspensions: A Stress-Partitioning Interpretation
William Kai Alexander Worby, Yuto Yokoyama, Misa Kawaguchi et al. (+1 more)
A fundamental problem in the field of anisotropic macromolecular materials concerns how the flow-induced orientational order connects microscopic structure to macroscopic rheological stress and optical anisotropy. This study considered cellulose nanocrystal suspensions as rigid-rod model systems for the purpose of isolating orientational effects from chain stretching. Simultaneous rheo-optical measurements of birefringence, orientation angle, and shear stress were combined with a Fokker-Planck orientation model and stress decomposition. Our results show that, at low values of the Peclet number, birefringence and total stress exhibit proportionality similar to the stress-optic rule. However, the concentration dependence indicates that this proportionality reflects stress partitioning rather than a unique material coefficient. With increasing flow strength, orientational saturation is accompanied by a reduced relative Brownian stress contribution and a corresponding change in the total stress-based relation. Referencing the optical response to an estimated Brownian stress contribution yields a substantially more unified response across concentrations and flow conditions, supporting a stress-partitioning interpretation of apparent stress-optic rule breakdown.
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All authors William Kai Alexander Worby, Yuto Yokoyama, Misa Kawaguchi, Yoshiyuki Tagawa
Fluid Dynamics
Exact explicit wave-angle solutions for equilibrium oblique detonations
Jing Li and Changtong Luo
The
equilibrium oblique-detonation polar is a fundamental gasdynamic relation. This relation links the deflection angle, the wave angle, the flow state and the heat release. However, the wave angle is usually determined by numerical iteration. There is no explicit formula to determine the wave angle from a prescribed deflection angle, referred to as the inverse problem, even for the classical oblique-detonation model: a calorically perfect gas with a constant specific-heat ratio and a fixed heat release. This is inconvenient in practical applications. In this work, we solve this inverse problem for the classical model and derive explicit formulae for the wave angle. Inspired by the derivation of the oblique-shock inverse relation, the oblique-detonation inverse relation also reduces to a cubic equation. Heat release only changes the cubic coefficients, so the equation can still be solved explicitly. We also derive the complete analytical branch structure. We further find that the detachment point and the downstream total-sonic point can be determined explicitly by solving a cubic and a quadratic equation, respectively. We extend the explicit formulae to the two-$\gamma$ model and apply them to oblique-detonation calculations with
equilibrium chemistry. These explicit formulae for the wave angle and critical points promote the theoretical understanding of oblique detonations and support their practical calculation.
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Physics and Society
What a collective can hold in common: a gauge framework for private representations
Mohammad Salahshour
Many models of collective behavior write headings, beliefs, and meanings in one experimenter-defined frame. Organisms do not live there: each represents the world in a private space, and comparison requires translation. Consensus becomes an existence problem before it becomes a dynamical one. Reciprocal pairwise translations need not compose consistently around a loop. This return transformation (the holonomy) can expose a mismatch no isolated reciprocal pair can carry. We develop a gauge-covariant theory in which physical predictions are invariant under private relabeling. For reciprocal
unitary translations, the kernel of the connection
Laplacian is isomorphic to the joint fixed space of loop holonomies: a collective can hold in common exactly what all its loops leave unchanged. A blind-subgroup criterion identifies invisible defects. Common-frame comparison, such as in traditional models of collective behaviour, occupies the flat sector. For independent uniform translations from a finite group $G$, a connected graph with $E$ relations among $N$ individuals is flat with probability $|G|^{-(E-N+1)}$. Exact cycle spectra determine persistence under linear relaxation. The consequence is operational as well as structural. For unrecorded routes under a specified model with isotropic Gaussian source and readout noise, we derive the smallest mean-squared error achievable by any decoder. At fixed signal-to-noise ratio, the jointly preserved feature fraction fixes its long-route limit. Networks with identical loop angles can differ in recoverable content when their preserved axes differ. The relational geometry of a collective sets both the states it can share and the content it can recover.
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History and Philosophy of Physics · Cross-listed from quant-ph
The Requirement of (at least) Complex Structure for Quantum Mechanics
M.P. Vaughan
It is argued that many real-valued constructions of
quantum mechanics are only nominally real in that the operators and states are restricted to impose a complex structure on the
Hilbert space. That is, complex
algebra between pairs of elements representing complex numbers is preserved in these formulations. It is therefore mistaken to think of these constructions as being `real' as they are actually a representation of complex linear
algebra. It is then shown that under the assumptions of state normalisation and strict energy conservation, this complex structure (at the very least) is required to allow for time
evolution in
quantum mechanics. This is only a minimum requirement, as our arguments do not preclude the formulation of
quantum mechanics in terms of hyper-complex entities, such as quaternions.
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Medical Physics · Cross-listed from eess.IV
Signal recovery in the polychromatic computed tomography model: Injectivity and complexity
Xuanzhou Chen and Ashwin Pananjady
We consider a nonlinear model motivated by polychromatic computed
tomography (CT). Here, $W$ distinct $d$-dimensional signals $x^*_1, \ldots, x^*_W \in \mathbb{R}^d$ must be recovered from $n$ measurements $(a_i, y_i)_{i = 1}^n$ that obey the nonlinear model $\mathbb{E}[y_i|a_i] = h(\langle a_i, x^*_1 \rangle, \ldots, \langle a_i, x^*_W \rangle)$, where $h: \mathbb{R}^W \to \mathbb{R}$ is a known nonlinearity that models a certain type of exponential attenuation law. Even when there is no noise in the measurements, the sample size $n$ (for any measurement ensemble $\{a_i\}_{i = 1}^n$) must exceed the number of unknowns $Wd$ to guarantee that the underlying signals are identifiable. We construct a measurement ensemble that ensures perfect signal recovery almost surely provided $n \geq Wd + W - 1$, thereby isolating the injectivity threshold up to an additive factor $W - 1$. We also study computational complexity of signal recovery in this model with a general measurement ensemble $\{a_i\}$. We show that if $W \geq 2$, then there is a measurement ensemble for which deciding whether there exist signals consistent with the measurements is NP-hard. In particular, this implies that polychromatic, multimaterial CT reconstruction is NP-hard in general. This finding stands in sharp contrast to the single-material setting, for which a
polynomial-time
algorithm can provably perform signal recovery for any measurement ensemble.
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Physics and Society
Towards Supporting Quantum Grassroots Organizations in ASEAN
Amalina Lai and Bethel Loke Hui Ting
This paper investigates the role of
quantum grassroots organizations in The Association of South-east Asian Nations (ASEAN), the challenges they face, and how these organizations can be better supported by other players in the ecosystem of
quantum technologies. We look into the goals and strategies of ASEAN grassroots organizations and their potential impacts and investigate the obstacles and challenges currently faced by these groups. We propose providing mentors with specialized knowledge to assist in the refinement of technical content and organizational management, building connections between grassroots and key stakeholders in the
quantum space, and creating opportunities to obtain stable funding. These can help to mitigate the aforementioned challenges and ensure its longevity, sustainability, and impact on the wider
quantum community.
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Optics · Cross-listed from quant-ph
Secure Quantum Metasurfaces for Direct Quantum Key Distribution Measurements
Yan He and Adetunmise C. Dada
Quantum key distribution (QKD) can deliver information-theoretic security, but its receivers are still typically assembled from cascaded bulk optics. Metasurfaces offer a radical reduction in this complexity. Here, we make the metasurface function as the QKD measurement device itself. We design wavelength-specific dielectric apertures at 780, 1550, 2000, and 10 600 nm that interweave the linear H/V and circular R/L phase libraries at a 0.44–0.49{\lambda}
cell pitch, i.e., below half the operating wavelength, and map the complete passive-BB84 measurement directly onto four detector channels. This subwavelength basis co-location prevents an ordinary propagating-wave aperture mask from isolating one basis without simultaneously attenuating or perturbing the other. Simulated full-wave focal-plane intensities are converted directly into conditional Born probabilities using fitted, calibration-fixed detector regions. The selected designs achieve probability fidelities of 97.96–99.08%, four-port collected efficiencies of 17.43–40.94%, and mean intrinsic
quantum bit error rates of 1.42–3.96%. At 1550 nm, the selected design gives an asymptotic device-level yield of 0.151 secret bits per incident
photon under an ideal single-
photon model. Six-state detector
tomography gives positive both-basis security bounds for all six reconstructed receiver models, including their polarization-dependent loss, basis imbalance and crosstalk. These results establish protocol-matched meta-optics as a route to compact, passive QKD receivers.
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Physics and Society
Slow Context, Fast Symptoms: Multiscale Temporal Dynamics and Context-Induced Coupling in Psychological Systems
Kyuri Park, Denny Borsboom, Mike H. Lees et al. (+3 more)
Psychological dynamics unfold across multiple timescales: symptoms and other psychological states can change rapidly, whereas social, environmental, biological, and developmental conditions often evolve more slowly. We formulate this structure as a
stochastic slow-fast system in which binary symptom states form a fast interacting network embedded within a slow contextual field. Pairwise symptom coupling governs interactions within the fast layer, while the contextual field shifts symptom-specific activation tendencies and can itself receive feedback from sustained symptom activation. Simulations show that changes in the slow field can shift the macroscopic activation state of the symptom system even when the underlying interaction
matrix remains fixed. Perturbations to the field generate transient increases in symptom activation followed by recovery, while feedback between the fast and slow layers delays recovery and, when sufficiently strong, produces dependence on initial conditions. We further show that when between-person variation in the contextual field is omitted from network estimation, the inferred system exhibits stronger total coupling and nonzero couplings between symptom pairs that are uncoupled in the data-generating model. Thus, slowly varying context can alter both the dynamics and the apparent interaction structure of a fast psychological system. The framework connects psychological network models with slow-fast dynamical systems and provides a formal basis for distinguishing changes in activation from changes in coupling.
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All authors Kyuri Park, Denny Borsboom, Mike H. Lees, Lourens J. Waldorp, Johan Bollen, Vítor V. Vasconcelos
Atmospheric and Oceanic Physics
Blinded Evaluation of Oceanic Sound Source Locations via Sequential Bound Estimation
John L. Spiesberger and Julien Bonnel
A non-linear, non-
Bayesian method called sequential bound estimation (SBE) derived 100% confidence intervals of location (CIL) for 219 explosions in the ocean from measurements of their time differences of arrivals among five widely-spaced time-unsynchronized receivers on the ocean bottom. The explosion's locations were measured with the global positioning system. A blind evaluation revealed all 219 explosions were within their CIL. The probability this could happen by chance is $4 \times 10^{-116}$. The explosions were detonated in shallow water on the eastern continental shelf of the U.S. over the so-called New England Mud Patch.
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Plasma Physics
Interaction renormalization and the plasma staircase
Alexander V. Milovanov, Alexander Iomin and Jens Juul Rasmussen
We resolve an existing question concerning dynamical and structural stability of the E {\times} B staircases in magnetically confined fusion
plasma. The problem has stirred considerable interest in the literature due to a unique combination of its scientific and practical aspects. Here, we report a new approach to the problem by combining the paradigmatic Hasegawa-Wakatani model of electrostatic drift-wave
turbulence with an idea of interaction renormalization, imported from
quantum field theory. It is shown based on the Schrödinger-Newton equation with renormalized interaction constant that the
plasma staircase is robust and stable as soon as the nonadiabaticity parameter, {\delta}, goes above a certain critical value, and is unstable otherwise. This critical value is an exact result of the interaction model and is found to be {\delta}c = {\pi}. For {\delta} < {\delta}c , the unstable system expands in the radial direction, resulting in a radial second moment that grows with time t as t^(2/3). The results obtained bear important implications with regard to the implementation of arrays of semipermeable transport barriers in tokamaks, suggesting a threshold condition for their generation.
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Atomic Physics
Loss induced dynamics of optical pulses in saturable nonlinear media
Golam Ali Sekh
We consider pulse propagation in a saturable nonlinear coupler whose other arm is dissipative and other is transparent. A flow of energy from transparent to dissipative arm takes place for weak value of dissipation and the coupler losses its energy. The energy loss of the coupler reduces for strong dissipation. This energy loss depends on the saturable nonlinearity. We find that the flow of relative energy at the output of a finite-sized coupler has a peak at a particular value of nonlinear strength. The peak value decreases with the increase of dissipation and it vanishes for stronger dissipation due to Zeno effect.
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Physics and Society
Below the Surface: Creep, Corrosion, and Tipping Points in the Social Resilience of Science
Pawel Sobkowicz
By its most visible quantitative metrics: numbers of researchers, papers, journals, and institutions, science has never looked healthier. Yet a set of subsurface indicators points the other way: the disruptiveness of the average paper and patent is falling, progress slows in the largest fields, replication is rare and often unsuccessful. Incentive systems can select for poor methods even when no one is actually cheating. Lay society shows a curious mixture of admiration and lack of trust for scientists and their work. We argue that a healthy-looking surface can coexist with, and mask, an accumulation of below-the-surface damage due to slow-acting, internally and externally driven pressures, weakening the social position of science. This process is best understood not as an acute shock but as a creeping crisis. And while the damage grows slowly, it may result in a sudden collapse of the research as social institution. To make this diagnosis tractable rather than merely alarming, we import the conceptual and mathematical apparatus of two mature research fields that already study such slow degradation and sudden collapse processes: the continuum damage mechanics of creep, fatigue, and corrosion, and the ecology of resilience, regime shifts, and critical transitions. We do not claim to resolve whether science is merely robust under strain or is approaching a tipping point; the available data are too fragmentary. This remains a question of importance and we propose what would answer it: finding measurable early-warning indicators, use of
agent-based models of the coupled trust-incentive-funding feedback system, understanding
adversarial attacks, and the design of resilience building and recovery interventions. The result is a research agenda, and an argument for why the health of science cannot be read off its own success reports.
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Optics
High-Q Magneto-Optical Microdisk Resonators Based on Monocrystalline Bismuth-substituted Yttrium Iron Garnets
Takeru Yambe, Kota Taniguchi, Tatsuya Kitai et al. (+7 more)
Microresonators based on diverse material platforms have driven the progress of integrated photonics by enhancing light-matter interactions in compact volumes. Extending this strategy to magneto-optical (MO) media is highly attractive for nonreciprocal photonics, magnonics, and
quantum transduction, yet compact high-Q resonators based on single-crystalline yttrium iron garnet (YIG) have remained elusive because of the difficulty of its nanofabrication. Here we demonstrate high-Q, small-mode-volume MO microdisk resonators based on monocrystalline Bi-substituted YIG (Bi:YIG). Low-loss Bi:YIG thin films prepared by bonding and thinning, combined with optimized Ar-
plasma etching, enable submicron-thick, air-suspended microdisks that support telecom-band whispering-gallery modes with $Q = 1.52\times 10^5$, a mode volume $V \approx 200$ cubic wavelengths, and $Q/V \approx 760$, representing an orders-of-magnitude improvement for integrated high-Q YIG MO cavities. The device exhibits clear
magnetic-field-dependent spectral responses, including reciprocal resonance shifts and nonreciprocal frequency splitting of counter-propagating modes. A perturbative analytical model quantitatively reproduces these responses and indicates an effective MO coefficient about twice the bulk value, suggesting a possible miniaturization-induced enhancement. These results establish monocrystalline YIG microdisks as a compact high-Q MO platform for integrated isolators, optomechanics, microcombs, and
photon-
magnon quantum interfaces.
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All authors Takeru Yambe, Kota Taniguchi, Tatsuya Kitai, Daisuke Sato, Syuan Gao, Hajime Kumazaki, Shun Fujii, Takasumi Tanabe, Satoshi Iwamoto, Yasutomo Ota
Computational Physics
Exact ballistic energy transport and emergent XXZ dynamics in an integrable three-state chain
Hanbing Liang and Fujun Liu
We investigate the coupling dependence of ballistic energy transport and the emergent
spin dynamics in an integrable Hermitian three-state chain that connects a clock interaction to a highly degenerate flag limit. By constructing a regular $R$-
matrix to establish a globally conserved energy current, we analytically evaluate its full variance to obtain the exact, strictly positive leading high-temperature coefficient of the thermal Drude weight and the ballistic growth rate of the energy-correlation second moment. In the strong-coupling limit, the degeneracy is lifted by virtual transitions of a delocalized third-color spectator state, which generates an effective
spin-$1/2$ XXZ
Hamiltonian with anisotropy $\Delta = -1/2$ and fundamentally selects the all-active two-color sector as the true ground state. For periodic boundaries, this virtual spectator motion introduces a positive length-changing XXZ supercharge squared that, for $L\ge4$, strictly annihilates all states within a finite, length-independent energy interval above the ground state. Consequently, we rigorously prove that the full periodic effective theory perfectly replicates the exact low-energy XXZ spectrum, including all state multiplicities, as well as its macroscopic bulk free-energy density.
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Optics
Non-Polynomial Wave Computation through Recurrent Resonant Scattering
Junyu Zhu, Enzong Wu, Xiaomeng Li et al. (+2 more)
Structural nonlinearity enables nonlinear input–output mappings to emerge from otherwise linear wave dynamics. Repeated interactions with an input-encoded structure can enhance such mappings, but finite-depth implementations restrict the accessible functional order. Here we show that recurrent scattering in a resonant cavity provides a distinct regime for structural nonlinearity. Repeated interactions are coherently accumulated into a non-
polynomial response to structural perturbations. The resulting mapping naturally takes a Kolmogorov–Arnold form: perturbation-induced resonance shifts realize the inner univariate mappings, while the resonant spectral response provides the outer mapping. We identify two complementary physical controls of representation capacity: the resonance linewidth governs the functional richness within each branch, whereas combining multiple branches expands the accessible function space. Microwave-cavity measurements validate the two-stage mapping and demonstrate a two-branch nonlinear computation through XOR classification. Our results connect recurrent resonant scattering with controllable non-
polynomial computation in linear wave systems.
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All authors Junyu Zhu, Enzong Wu, Xiaomeng Li, Hongsheng Chen, Zuojia Wang
Chemical Physics
Can Chemically Inspired Parameter Initialization Mitigate Barren Plateaus in Variational Quantum Eigensolvers?
Zhangyu Yang, Jinzhao Sun, Jianpeng Chen et al. (+2 more)
Recent advances in the variational
quantum eigensolver (VQE) have strengthened its promise for molecular electronic-structure calculations on near-term noisy intermediate-scale
quantum (NISQ) devices. However, barren plateaus (BPs) remain a major obstacle to scaling VQE, as vanishing gradients can severely obstruct optimization at large scale. While most BP studies focus on randomly initialized
circuits and global gradient behavior, practical
quantum chemistry VQE typically uses chemically motivated initializations and local optimization around HF- or MP2-derived states. Although chemically informed initializations are widely expected to improve VQE trainability, how they mitigate local barren plateaus remains unclear. We therefore study the occurrence of local barren plateaus in molecular UCCSD-VQE, considering both chemically motivated initialization points and iterates along the corresponding optimization trajectories. In the
benchmarks considered here, chemically initialized starting points and variational trajectories show
polynomial decay of local gradient variance with system size instead of the exponential BP-like decay observed for random controls, indicating that chemical initialization mitigates barren plateaus in the local optimization regions and highlights the trainability advantage of chemically motivated VQE strategies.
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All authors Zhangyu Yang, Jinzhao Sun, Jianpeng Chen, Weitang Li, Zhigang Shuai
Applied Physics
Understanding Ideality Factor in Wide-Band Gap Semiconductor Devices with Strong Recombination Planes
Iris Celupica-Liu, Tanay Tak, Yuh-Renn Wu et al. (+1 more)
Ideality factor of a diode will depend on the location of the plane of maximum recombination within the diode's depletion region. It will have a minimum of one, but can range up to infinity depending on placement of the plane. Case studies analyzed in this work demonstrate better agreement with experimental data from GaN-based p-i-n diodes.
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All authors Iris Celupica-Liu, Tanay Tak, Yuh-Renn Wu, James S. Speck
Applied Physics · Cross-listed from cond-mat.mtrl-sci
Three-dimensional atom-by-atom measurement of interface diffusion dynamics
Doojin Park, Hyesung Jo, Yongmin Kwon et al. (+7 more)
Diffusion at interfaces governs how materials and devices form, evolve and function. It is usually measured through smooth concentration profiles and bulk transport coefficients, which average over the discrete atomic rearrangements. At nanoscale interfaces only a few atomic layers wide, however, such coarse-graining obscures the local three-dimensional (3D) atomic transport, and scalar
diffusion coefficients cannot fully describe species-, layer- and facet-resolved redistribution. The essential observable is the discrete 3D redistribution of atoms themselves, beyond an averaged profile. Here we combine micro-electro-mechanical systems (MEMS) pulse-quench heating with atomic electron
tomography (AET) to reconstruct five 3D atomic configurations of the same coherent Pd@Pt core-shell nanoparticle, each corresponding to a well-defined thermal state. Species-conserving one-to-one assignment links neighbouring configurations, and labelled reference simulations correct the displacement bias caused by indistinguishable same-species atoms. The corrected Pd diffusivities follow Arrhenius behaviour, giving an apparent activation energy of 1.10 eV, consistent with migration-limited vacancy-mediated transport. Atomic-layer transition statistics further show that increasing 3D mobility can coexist with declining net chemical transfer and reveal facet-dependent pathways hidden by the scalar diffusivity. Together, these measurements establish a 3D atom-by-atom framework that connects identity-corrected mobility to species-, layer- and facet-resolved transport at buried nanointerfaces.
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All authors Doojin Park, Hyesung Jo, Yongmin Kwon, Seokjo Hong, Jaewhan Oh, Youngjoo Whang, Eunjik Lee, Gu-Gon Park, Sang Woo Han, Yongsoo Yang
Fluid Dynamics
Underwater bubble transport on superhydrophobic cylindrical rod
Rajalingam A, Sunghwan Jung and Pallab Sinha Mahapatra
The transport of bubbles along a curved superhydrophobic surface is not governed by buoyancy alone, but also by the interaction between the
geometric confinement, the capillary and contact-line resistance, and the hydrodynamic resistance. We systematically investigated the capillary number ($Ca$) and Bond number ($Bo$) of the transported bubble, as well as the size of the rod relative to the bubble. An analytical force-balance model was developed to predict transport velocity, accounting for buoyancy, hydrodynamic drag, and capillary resistance. The transition from transport to detachment was identified. The experiments were carried out sequentially and supplemented by axisymmetric numerical simulations to investigate wake-induced interactions between bubbles. Bubble transport is strongly influenced by rod inclination and the bubble-to-rod size ratio, demonstrating that
curvature-induced confinement alters the balance between driving and resistive forces. The analytical model captured the experimental trends with deviations of less than 10% in most cases. The bubble detaches from the inclined rod at a critical Bond number that depends on rod diameter, facilitating the development of a transport regime map. The study also found that the motion of successive bubbles is strongly coupled. When a following bubble enters the wake of a preceding bubble, it speeds up and attains a higher capillary number than the leading bubble. Both experiments and numerical simulations consistently reproduce this wake-mediated acceleration, which shows that bubble transport is governed by both the force balance on individual bubbles and the hydrodynamic interactions between adjacent bubbles. These findings form the basis for controlling bubble transport, detachment, and collective motion on superhydrophobic interfaces.
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Accelerator Physics
Experimental Verification of Circumferential Bunch Length Variation and Head-Tail Exchange Affecting Microwave Instability in a Storage Ring
Jihong Bian, Xiujie Deng, Arne Hoehl et al. (+5 more)
Classical analyses of microwave instability are built upon the longitudinal adiabatic approximation, which assumes that the bunch length remains constant around the storage ring. However, in a storage ring with small global phase slippage, the bunch length can vary around the ring and some particles can experience head-tail exchange due to the partial phase slippage and transverse-longitudinal coupling. Our theoretical study reveals that these effects can be beneficial for suppressing microwave instability. A new microwave instability threshold evaluation method has been correspondingly proposed to account for these effects. Here we present the first experimental evidence supporting our theoretical analysis. The measurements confirm that the microwave instability threshold can be increased by a factor of up to six compared to the classical prediction in our cases. Our results can also provide practical guidance for the design of extremely short bunch storage rings.
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All authors Jihong Bian, Xiujie Deng, Arne Hoehl, Wenhui Huang, Arnold Kruschinski, Carsten Mai, Markus Ries, Chuanxiang Tang