Optics
Sub-shot-noise mid-infrared photothermal measurements using twin beams
Kazuki Hashimoto and Takuro Ideguchi
Mid-infrared photothermal (MIP) measurement probes refractive-index changes induced by mid-infrared (MIR) absorption using visible or near-infrared light and has recently emerged as a powerful modality for MIR spectro-imaging in the life sciences. Reducing measurement noise allows the probe power to be lowered without compromising the signal-to-noise ratio (SNR), thereby mitigating the risk of sample damage. However, even in the absence of classical noise, the SNR of conventional MIP measurements using a classical coherent probe is fundamentally limited by shot noise. Here, we demonstrate sub-shot-noise MIP measurement using twin beams generated through seeded optical parametric amplification. Balanced detection of the twin beams suppresses the noise by more than 5 dB below the shot-noise level established using a coherent beam. As a proof-of-principle demonstration, we measure the MIP signal from
liquid water using balanced twin-beam detection and achieve an SNR enhancement of more than 2 dB over the balanced coherent-beam detection.
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Optics
Thermal Holography with Nonlocal Metasurfaces
Mingze He, Lin Jing, Michele Guizzardi et al. (+7 more)
Thermal radiation and luminescence are among the most ubiquitous sources of light, yet their properties are difficult to engineer due to their incoherent nature. Recent advances in thermal emission control have endowed heat-generated light with spatial and temporal coherence, as well as control over its polarization, by judiciously patterning periodic arrays of nanostructures. However, custom wavefront engineering of incoherent light has remained an open challenge, as it requires not only sufficient spatial and temporal coherence but also arbitrary local phase control, which experimentally translates into sustaining long-range
lattice resonances in aperiodic systems while maintaining their robustness against local phase perturbations. In this work, we address this longstanding limitation and demonstrate programmable vectorial control over the thermal emission wavefront from single-layer aperiodic nonlocal metasurfaces, realized by manipulating local
geometric phases across a collective delocalized resonance. We exemplify the wavefront-shaping capabilities of our approach by demonstrating thermal beam steering,
spin-momentum-locked thermal focusing and the generation of a thermal vectorial hologram, providing custom spatial and spectral control over thermal light. Our platform addresses challenges in thermal emission engineering and provides a route for light generation and control without the need for external coherent sources or bulky setups. Future work may extend this design principle to other incoherent emission systems, such as photo- and electroluminescence.
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All authors Mingze He, Lin Jing, Michele Guizzardi, Shixiong Yin, Martina Riva, Yajun Gao, Shuwei Guo, Adam C. Overvig, Sander A. Mann, Andrea Alù
Atmospheric and Oceanic Physics
Three-dimensional Lagrangian ecosystems: carbon dynamics and potential for artificial fertilization
Stefano Campagnola, Stephanie Dutkiewicz, Michael J. Follows et al. (+1 more)
Transient supplies of nutrients to the surface ocean, both natural and artificial, stimulate blooms of phytoplankton and the formation of organic matter, driving air-sea gradients and uptake of CO$_2$. However, quantifying the associated carbon budget remains challenging, as it requires tracking the coupled biophysical
evolution of water masses while they are transported, stretched and diluted. Here, we present an idealized three-dimensional model that describes biomass production and carbon dynamics within a Lagrangian patch in the ocean. The framework reproduces observed biogeochemical patterns from an artificial fertilization experiment and provides integrated metrics for the local carbon budget. Utilizing large ensembles of simulations, we examine the sensitivity of patch-scale primary production and carbon uptake to biochemical and physical factors. Our results show that patch dilution can enhance the ecosystem response, and how carbon uptake is sensitive to initial injected area, horizontal divergence and vertical diffusivity. In the context of renewed interest in ocean fertilization strategies for
climate mitigation, our approach can thus provide quantitative tools to assess their efficacy and potential.
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All authors Stefano Campagnola, Stephanie Dutkiewicz, Michael J. Follows, Enrico Ser-Giacomi
Optics
Start-to-end simulations of non-relativistic electron acceleration along reflective grating structure by front-tilted laser pulse
I.V. Beznosenko, A.V. Vasyliev, S.M. Kovalov et al. (+2 more)
A comprehensive (start-to-end) simulation was performed regarding the formation of a front-tilted
laser pulse and the subsequent acceleration of non-relativistic electrons moving along a reflective grating structure. The
laser pulse tilt was formed using another diffraction grating – either reflective or transmissive. The pulse had a spectral range (FWHM) of 803–863 nm and an initial duration of approximately 17 fs. Acceleration under normal
laser pulse incidence was also calculated for comparison. Research results indicate that the use of a femtosecond
laser pulse with a front, tilted by means of a reflective diffraction grating, significantly enhances the efficiency of
laser acceleration of non-relativistic electrons compared to the case of a pulse at normal incidence. Furthermore, it was found that using a transmissive diffraction grating to shape the tilted pulse front also increases acceleration efficiency relative to normal incidence on the accelerating grating, although the acceleration rate is lower than when a reflective diffraction grating is used.
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All authors I.V. Beznosenko, A.V. Vasyliev, S.M. Kovalov, R.R. Kniaziev, G.V. Sotnikov
Instrumentation and Detectors · Cross-listed from cond-mat.mtrl-sci
Prediction of the thermal neutron response of grain-boundary impedance in Gd-doped ceria based on the radiation-ionic effect
Zhongming Zhang
The radiation-ionic effect was recently reported in 3 mol% Gd-doped CeO$_2$ (3GDC): under $^{60}$Co gamma irradiation at 35 Gy/min, the grain-boundary (GB) ionic resistance of a bulk pellet decreased 680-fold at room temperature, because electrons trapped at the GB core lower the space-charge potential. The effect has been demonstrated only with
photons. Gd has the largest thermal-
neutron capture cross section of any stable element and is also the dopant that creates the GB barrier in GDC, so the same mechanism could link GB impedance to thermal-
neutron sensing; whether it does, and under what conditions, has not been examined. Here the thermal-
neutron response of 3GDC is modelled with the gamma-calibrated Mott-Schottky/Seager framework, with unmeasured parameters carried as intervals and propagated jointly. Each capture deposits about 50 keV by conversion and Auger electrons within 1 $\mu$m, the remaining 8 MeV leaving as
prompt photons; Gd segregation to the GBs adds a factor of only 1-2 because the electron range exceeds the grain size. A thermal flux of $8\times10^{9}$ cm$^{-2}$s$^{-1}$ (6-12$\times10^{9}$) matches the GB-effective generation rate of the 35 Gy/min calibration, and the predicted room-temperature GB resistance ratio is 110 (70-170) at $10^{9}$ and 970 (600-1500) at $10^{10}$ cm$^{-2}$s$^{-1}$, falling to 2 at 61 (55-68) and 81 (73-92) $^\circ$C. The
neutron case differs from gamma irradiation in three respects: capture events are discrete, so the continuous-source approximation depends on the unmeasured trapped-charge lifetime; self-shielding (mean free path 0.27 mm) makes the response thickness dependent; and capture
photons absorbed in the pellet add a gamma term comparable to the local term for pellets of 0.3 mm or more. The intervals are conditional on the model and exclude its structural error. The conditions under which the prediction can be tested are given.
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Instrumentation and Detectors
Wavelength-Resolved Timing of Near-Infrared Scintillation in Gaseous Xenon
Robert Hammann, Steffen Form, Humaira Nazneen et al. (+3 more)
The near-infrared (NIR) scintillation signal of xenon has the potential to enhance the performance of xenon-based detectors, but a robust understanding of its properties is a prerequisite for its application. In this work, we measure the NIR time response for $\alpha$-particle interactions in gaseous xenon in 12 wavelength bands spanning approximately $(950-1620)\,$nm. The time response is decomposed into a fast (ns-scale) component and a dominant slow ($\mu$s-scale) component. The fast-component spectrum coincides with strong atomic emission lines, predominantly 6p$\,\to\,$6s, whereas the slow-component spectrum follows the broad continuum centred around $1.3\,\mu$m. The pressure dependence of the continuum can be described by a two-step kinetic model in which the emitting state is formed by a three-body process and depopulated by a two-body collisional process, with density-independent terms in both rates. Interpreting the slower of these as radiative decay yields an intrinsic lifetime of $\sim3\,\mu$s. Theoretical calculations identify a neutral-excimer transition $0_u^- \rightarrow 0_g^-$ and an ionic-dimer transition $1/2_{u} \rightarrow 1/2_g$ as plausible candidates for the continuum emission, with the ionic-dimer transition showing better overall agreement with the measurements.
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All authors Robert Hammann, Steffen Form, Humaira Nazneen, Gabriel Schöpfer, Milan Ončák, Teresa Marrodán Undagoitia
Fluid Dynamics
Extension of a mathematical analogy between vortical flows without surface tension and irrotational capillary flows
Valentin D. Kunz, Saleh Tanveer and Darren G. Crowdy
In a recent paper, a mathematical analogy was found between two physically distinct classes of two-dimensional free boundary problems in inviscid fluid mechanics. One class involves free surface flows with constant vorticity in the bulk but without boundary surface tension, the other comprises free surface flows without vorticity in the bulk but with non-zero boundary surface tension (capillarity). Several examples were given of pairs of physically-distinct free boundary problems that amount to solving the same mathematical problem, albeit with the possibility of a single constraint arising for the capillary flows. The present work shows that this analogy extends to another pair of physically-distinct problems: a hollow
vortex equilibrium in a shear flow with a third order irrotational strain and a steady bubble with surface tension in a simple straining flow. For both problems, we construct an isolated exact solution when a parameter $\gamma=0$ and provide numerical solutions for non-zero $\gamma$. An interesting feature is that non-trivial conformal mapping identities emerge from the class of problems with capillarity that apply equally for the hollow
vortex problems when the parameters are appropriately constrained.
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Data Analysis and Statistics · Cross-listed from cond-mat.other
Progress and Prospect of AI in ARPES Workflow
Sandy Adhitia Ekahana, Aalok Tiwari, Pratik Saud et al. (+4 more)
Artificial intelligence (AI) is becoming an increasingly useful tool across the experimental sciences, including angle-resolved photoemission spectroscopy (ARPES), which routinely produces large, multidimensional
datasets of electronic structure. Recent advances in AI and machine learning (ML) have opened new opportunities across the entire ARPES workflow, from automated sample preparation and real-time data acquisition to post-experiment data analysis and comparison with theoretical calculations. Despite this progress, a comprehensive review of ML applications, their capabilities, and reliability across the different stages of ARPES workflow is still lacking. In this review, we first introduce ML methods that are most relevant to experimentalists working in condensed matter physics and materials science. We then follow the ARPES workflow, reviewing existing ML applications at each step and discussing their advantages, limitations and potential for future development. We also examine the current ARPES data landscape, where several open databases are available but remain relatively small and fragmented compared with large, shared
datasets such as ImageNet. Given these limitations, we suggest that the community focus on sharing pretrained models that can be further trained, adapted to specific tasks, and redistributed, while working toward a larger and standardized open ARPES
dataset repository. Finally, we discuss our perspectives on the future of AI within the ARPES workflow using a six-level framework of laboratory automation, highlighting the opportunities and challenges in moving toward a fully autonomous, self-driving ARPES laboratory.
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All authors Sandy Adhitia Ekahana, Aalok Tiwari, Pratik Saud, Aaron Bostwick, Chris Jozwiak, Eli Rotenberg, Jyoti Katoch
Instrumentation and Detectors
Timing Challenges in Transmission Silicon Detectors for Light Ions
Diego Tarrio, Friedrich Karl Moraht, Lucas de Arruda et al. (+3 more)
Transmission silicon detectors are widely used in $\Delta E$–$E$
telescope configurations for particle identification and timing in nuclear physics experiments. Variations in signal rise time can introduce time-walk effects that degrade time-of-flight measurements, as recently observed in light-ion production experiments at the
Neutrons For Science (NFS) facility at GANIL using the Medley setup. This work investigates the influence of particle energy and detector non-uniformity on signal rise time.
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All authors Diego Tarrio, Friedrich Karl Moraht, Lucas de Arruda, Stephan Pomp, Xavier Ledoux, Diego Ramos
Fluid Dynamics · Cross-listed from cs.ET
Analytical Modeling of Open- and Closed-Loop Dispersive Molecular Communication Channels with Pulsatile Flow
Theofilos Symeonidis, Fardad Vakilipoor, Timo Jakumeit et al. (+3 more)
Molecular communication (MC) is a communication paradigm in which information is conveyed through the release, propagation, and reception of molecules. Many envisioned healthcare applications of MC are expected to operate inside the human body, where the cardiovascular system (CVS) may serve as the physical propagation environment and molecular transport is governed by
diffusion and blood flow. Although blood flow is inherently pulsatile, most analytical MC channel models assume steady flow. In this paper, we develop a time-variant analytical model for dispersive MC channels with pulsatile flow. We derive the straight-duct response as a Normal distribution with time-variant mean and variance, capturing the combined effects of
diffusion and pulsatile flow, and extend it to closed-loop channels through a wrapped-Normal representation. The model is validated against three-dimensional (3D) particle-based simulations (PBSs) for synthetic and physiologically motivated velocity waveforms. We further derive a closed-form first-order approximation for the first-arrival peak time and introduce the nondimensional indicator $S_{\mathrm{Rx}}$ for assessing the applicability of the reduced one-dimensional (1D) model. Our results show that pulsatility has the strongest influence when molecular transport is predominantly advective and the temporal flow variations are not averaged out, whereas stronger
diffusion and faster pulsations reduce its impact on the received signal. Moreover, a PBS-based parameter sweep supports $S_{\mathrm{Rx}} \ge 2$ as a practical criterion for the applicability of the proposed analytical model. Finally, relating the analytical assumptions to representative blood-vessel classes shows that model applicability depends not only on the transport conditions but also on physiological properties such as vessel rigidity,
geometric uniformity, and blood rheology.
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All authors Theofilos Symeonidis, Fardad Vakilipoor, Timo Jakumeit, Robert Schober, Nunzio Tuccitto, Maximilian Schäfer
Physics and Society · Cross-listed from cond-mat.dis-nn
Revealing more on complex energy landscapes by passing less local information: Cavity approach with trust region in non-convex optimization problems
Zhiqi Xu and Chi Ho Yeung
Energy landscapes of non-convex optimization problems are high-dimensional surfaces that are difficult to reveal, visualize, or analyze. Message-passing
algorithms, or equivalently cavity approaches in statistical physics, may fail to identify local minima as messages do not converge owing to the ruggedness of the energy landscapes. Here we aim to reveal the characteristics of these complex energy landscapes by limiting the amount of information passed in local messages, improving the convergence of messages for local minima. By studying a routing optimization problem with its convexity governed by a single parameter, we introduce a cavity message-passing
algorithm with a trust region, and sample ensembles of converged local minima of rugged energy landscapes across many independent realizations of the same problem instances. We observe three regimes with different characteristics of the energy landscapes: (1) a maximally rugged regime with a peak in the diversity of low-energy minima; (2) an intermediate regime with a hierarchical multi-cluster organization of low-energy solutions; and (3) a smooth regime dominated by a single minimum. Additional tests show that the converged energies are largely insensitive to the size of the trust region if the size is small or moderate, demonstrating the robustness of the proposed approach in identifying characteristics of rugged energy landscapes.
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Atomic Physics
A scanning cavity for large area coherent coupling in atom interferometry
D. O. Sabulsky, Q. Beaufils, A. Bertoldi et al. (+3 more)
Optical cavities can enhance atom-light coupling in atom interferometry, but free-fall geometries require large transverse modes. Marginally stable resonators provide such modes, yet aberrations and
alignment imperfections turn their near-degenerate response into detuning-dependent transverse ring modes, strongly limiting the usable interaction volume under static excitation. Here, we turn this limitation into a resource. By chirping the interrogation frequency across the cavity resonance while dynamically shaping the input amplitude, we map
laser detuning onto the transverse position and scan the cavity-enhanced coupling across the atomic cloud. In a cavity-enhanced Bragg diffraction experiment with $^{87}$Rb atoms, this produces a nearly uniform effective interaction region of about 15 mm and increases the transfer efficiency from about 5% to 28%. We also demonstrate phase-coherent operation of a three-pulse atom interferometer using chirped cavity-enhanced Bragg pulses. These results establish scanning-cavity interrogation as a route to large-area, cavity-enhanced atom interferometry.
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All authors D. O. Sabulsky, Q. Beaufils, A. Bertoldi, A. Landragin, P. Bouyer, B. Canuel
Geophysics
Quantification of plastic deformation in anorthite using micropillar compression
Sarah Incel, Chunhua Tian, Anja Schreiber et al. (+2 more)
Plagioclase is the most abundant mineral group of the crust and will therefore either control or strongly influence crustal rheology. Yet, we still know little about
crystal plasticity in plagioclase as brittle deformation dominates under most laboratory conditions. To overcome past challenges in quantifying
crystal plastic deformation in plagioclase, we used micropillar compression to quantify the strength of specific slip systems as well as the stresses necessary for mechanical twinning in anorthite. Pillars with diameters of around 1 micrometre were milled from three differently oriented cuts of the same anorthite single
crystals using focused-ion beam. Uniaxial deformation of 36 pillars in total was then conducted inside a scanning-electron microscope under either 25, 300, or 800 degrees Celsius. Most pillars were deformed with a constant displacement rate that corresponds to a strain rate of around 0.001 1/s on the pillars. We find that the critical resolved shear stress (CRSS) for mechanical (pericline) twinning lies at around 300 MPa and is, as expected from previous studies on other materials, insensitive to changes in temperature or strain rate. Pillar deformation in
crystals oriented to activate slip exhibit a strong decrease in yield stress with increasing temperature. Among the deformation mechanisms active during pillar deformation, twinning is the easiest under the applied conditions, followed by slip on (011)[100] regardless of temperature. Slip on (011)[0-11] or (0-11)[011] is consistently the hardest mechanism to activate in our anorthite pillars.
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All authors Sarah Incel, Chunhua Tian, Anja Schreiber, Vladimir Roddatis, Sandra Korte-Kerzel
Space Physics · Cross-listed from astro-ph.SR
Wave-Growth-Limited Particle Confinement in a Near-Parallel Interplanetary Shock Observed by Parker Solar Probe
A. Kouloumvakos, I. C. Jebaraj, M. A. Malkov et al. (+11 more)
Collisionless shocks confine the particles they accelerate with the upstream wave field they themselves drive. Streaming particles resonantly amplify Alfvén waves, and the waves then confine the same particles by pitch-angle scattering. The rigidity a shock precursor can hold is therefore capped by how fast those waves grow, and that coupling has not previously been constrained in-situ at any interplanetary shock. Here we report Parker Solar Probe measurements of a fast, near-parallel coronal mass ejection-driven shock at 0.24~AU on 2023 March 13 that constrain this wave-particle coupling through the energetic-particle population it accelerates. We measure the spectral folding energy, the boundary between the confined and the upstream-escaping
protons, and find that it falls from $\sim$6 to $\sim$1.5~MeV as $E_\mathrm{fold}\propto\Delta t^{\,\alpha}$ with $\alpha\simeq0.34$, where $\Delta t$ is the time remaining before shock arrival. One precursor convective time before arrival this boundary is at $E_\mathrm{c}\simeq 2.46$~MeV, a characteristic confinement energy of a precursor of scale $L_\mathrm{EP}$. Read through the quasi-linear marginal-stability condition, the same
evolution implies a resonant wave-growth timescale $\tau_\mathrm{growth}(E)\propto E^{1/\alpha}\simeq E^{2.92}$ that exceeds the precursor convective time above $E_\mathrm{c}$. The post-shock pitch-angle anisotropy reverses sign across the same confinement–escape transition at 2–5~MeV. The rigidity to which a shock precursor can confine particles is therefore set, in-situ, by how quickly the streaming population builds its own confining waves.
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All authors A. Kouloumvakos, I. C. Jebaraj, M. A. Malkov, G. D. Berland, M. Gedalin, N. Wijsen, C. M. S. Cohen, O. V. Agapitov, D. J. McComas, D. G. Mitchell, E. Husidic, S. Yadav, M. E. Hill, R. McNutt
Atomic Physics
A solid-state nuclear clock based on VUV absorption spectroscopy of $^{229}$Th
Pengfei Wang, Xu-Fei Yin, Hanlin Wang et al. (+21 more)
We demonstrate sustained operation of a solid-state thorium-229 nuclear clock using continuous-wave absorption at 148.4 nm. In a $^{229}\mathrm{Th}:\mathrm{CaF}_2$
crystal, we resolve four quadrupole components of the D center and a broader O-center resonance. Feedback on the strongest narrow component is updated approximately every 10 s and remains active throughout a 30-h record. A hydrogen-maser-referenced frequency comb measures the output. Its fractional frequency instability follows approximately $1.29\times10^{-11}(\tau/\mathrm{s})^{-1/2}$ and reaches $1.24\times10^{-13}$ at $10^4$ s. A separate 6.6-h run demonstrates feedback on a second quadrupole component. These measurements connect the resolved absorption spectra with sustained nuclear-clock operation and frequency comparisons between
crystal segments.
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All authors Pengfei Wang, Xu-Fei Yin, Hanlin Wang, Jinming Liu, Qichen Qin, Zhouzhi Tan, Chengrun Leng, Mingxuan Zhang, Zixuan Li, Wenxin Bu, Xuan Fan, Yihang Liu, Kjeld Beeks, Benedikt Gerstenecker, Sebastian Lahs, Meng Wang, Tung-Hsun Chung, Yong-Heng Huo, Yin Hang, Hanning Dai, Thorsten Schumm, Zhiqiang Zhang, Jian-Wei Pan, Yu-Ao Chen
Applied Physics · Cross-listed from cs.LG
Matching of signal, noise and hardware timescales for filtering and forecasting of correlated noise signals
Joshua Donald, Alex Gabbitas, Arthur G. T. Coveney et al. (+2 more)
Physical reservoir computing exploits the nonlinear dynamics of physical systems to process time-dependent data with greater energy efficiency than conventional machine learning approaches. However, physical reservoirs have fixed intrinsic response timescales, whereas real-world signals combine deterministic and
stochastic components across multiple timescales. Here we show, using a nanoporous niobium oxide reservoir, synthetic noisy signals and cryptocurrency-price
volatility, that the relationship among noise correlation time, reservoir
memory and forecast horizon determines whether correlated noise is filtered or predicted. Noise varying faster than the relevant reservoir
memory and forecast horizon is averaged by the reservoir, whereas the temporal structure of slower-varying noise is sufficient for algorithmic forecasting. We introduce the reservoir
memory horizon and forecasting regime index to distinguish these operating regimes. These contributions demonstrate that timescale matching can guide the encoding of input time series and development of physical reservoir architectures that filter, analyse and predict
stochastic signal components across distinct temporal scales.
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All authors Joshua Donald, Alex Gabbitas, Arthur G. T. Coveney, Sergey Savel'ev, Pavel Borisov
Chemical Physics
Cotunneling-Assisted Redistribution of Nonpassivity in a Photosynthetic Junction
Manjet Rajak, Trishna Kalita, Debasish Sharma et al. (+1 more)
We investigate how cotunneling affects passive-state ordering in a Photosystem II reaction center modelled as a nonequilibrium molecular junction. We use a full pigment excitation
manifold, with excitonic and charge-transfer rates computed within a Nakajima-Zwanzig formalism using realistic spectral densities. Cotunneling is introduced through a microscopically constructed doubly reduced acceptor state obtained from relevant quinone-side two-electron configurations, while photoexcitation is allowed into the full excitonic
manifold. Passive-state permutations are quantified through ergotropy and energetic capacitance. We find that thermodynamic smoothness in ergotropy and energetic capacitance can conceal microscopic state rearrangements. Cotunneling redistributes the extractable nonequilibrium energy among the quinone acceptor, the donor-pheophytin radical pair, and excitonic states with strong contributions from pigments on the inactive branch. At high Coulomb interaction, cotunneling produces no passive-state reordering. Piecewise-linear relations among ergotropy, energetic capacitance, and mean energy further reveal the population reorderings generated by cotunneling.
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All authors Manjet Rajak, Trishna Kalita, Debasish Sharma, Himangshu Prabal Goswami
General Physics
Is MOND an effect of cosmic frame-dragging à la Mach?
Manuel Uruena Palomo
The physical origin of Modified Newtonian Dynamics (MOND), which predicts
galaxy rotation curves via a single empirical acceleration constant $a_0$ without the need for dark matter, remains unknown. I propose a modified-inertia origin for both MOND's interpolating function and $a_0$ within a framework closely related to Gravitoelectromagnetism, the linearized limit of General Relativity. Following Sciama's model unifying
gravity and inertia, which implements Mach's principle and the relativity of acceleration through gravitoelectric induction, I consider an idealized homogeneous universe undergoing constant Hubble expansion. I identify $a_0 \sim H_0^2R_u \sim c^2/R_u$ with the relative recession acceleration of
cosmic matter near the horizon, which dominates the cosmological contribution. I show that this scale enters local inertial dynamics only when the relative acceleration of the universe becomes anisotropic and the Rindler horizon is comparable to or larger than the
cosmic Hubble horizon, at accelerations of order $a_0$ and below. By the simplest Ansatz for the observer's acceleration-dependent causal volume, accounting for the interplay between the
cosmic and Rindler horizons, I derive MOND's simple interpolating function as a modified inertia law without the need to insert it by hand or make any further ad hoc adjustments. Physically, the region brought into causal connection ahead of the accelerating observer by the deformation of the
cosmic horizon contributes less inertial drag than is lost from the region removed behind him by the Rindler horizon. This proof of concept motivates the possibility that MOND arises from large-scale linear inertial frame-dragging induced by the expanding universe within General Relativity.
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Plasma Physics
On the particle and electromagnetic boundary conditions in a mesothermal plasma flow
J. Gonzalez
The fully kinetic modeling of mesothermal
plasma flows presents significant challenges in the description of boundary conditions for the electrons and the electromagnetic field. Due to their higher mobility compared to ions, electrons extend downstream of the ions, which hinders the implementation of the outflow boundary conditions during transient states. Although the electron drift velocity, $u_e$, is usually neglected as $u_e \simeq u_i < v_{th,e}$, where $u_i$ is the bulk velocity of the ions and $v_{th,e}$ is the thermal velocity of the electrons, we will show how accounting for it, both at the injection of particles and at the outflow boundary condition, is of great importance to achieve quasi-neutrality of charge and current densities. A new partial reflection model for electrons is presented to represent quasi-steady and transitory states. Additionally, we will show how we can employ Ampere-Maxwell's law to better represent the transitory electric field at the outflow boundary compared to the classical `zero-field' Neumann boundary without requiring any numerical parameters. With these new boundary conditions, we improve the quasi-steady and transitory descriptions of expanding mesothermal
plasmas.
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Fluid Dynamics · Cross-listed from astro-ph.SR
The existence of null points of flow and magnetic fields as prerequisites for the presence of astropauses and their co-location
Dieter H. Nickeler, Kuljeet S. Saddal, Rodrigo Meneses Pacheco et al. (+1 more)
Astropauses can be defined via
magnetic or fluid separatrices. For the boundary layer between the stellar wind and the local interstellar medium, two separatrices can occur, the magnetopause and the hydropause. The question is whether they are identical. To address this, we investigate under which conditions the null points of the
magnetic and velocity field, which define the corresponding separatrices, coincide spatially. We analysed the case of a non-monotonous pressure distribution driving stationary counterstreaming ideal HD flows and demonstrate that the existence of an extremum of the pressure in the 3D case together with a non-degeneracy condition on the velocity field implies that this point is also a stagnation point. Turning to ideal MHD and considering the regularity of all fields, we formulated the momentum equations, revealing their quasi-linearity. This allowed us to prove the occurrence of null points by examining the rank of the Jacobians of the vector fields. We found that for a given null point of either the velocity or the
magnetic field at the pressure extremum, the pendant vector field has a co-located null if the Jacobian of this field is non-singular. We extended the analysis to resistive MHD and further to MHD with general non-ideal terms and proved that if at least one of the first-order momentum equations is ideal, the stagnation point and the
magnetic null point are co-located. Even for general fluid theory, the two null points co-locate as long as the curl of the generalised non-ideal terms is zero at one of them or can be represented by a linear operator in the
magnetic and velocity field. In general, it is not excluded that the velocity and
magnetic nulls are dislocated. However, this would require specific properties of the curl of the non-ideal term, which would reduce the probability of a relaxed quasi-stationary configuration.
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All authors Dieter H. Nickeler, Kuljeet S. Saddal, Rodrigo Meneses Pacheco, Michaela Kraus
Chemical Physics
Nonuniform Screening Reshapes Collective Excitons in Molecular Aggregates from Stochastic Bethe-Salpeter Theory
Barry Y. Li, Chern Chuang, Tim Duong et al. (+3 more)
We build and apply an $\textit{ab initio}$
stochastic Bethe-Salpeter Equation (sBSE) approach to planar cyanine dye aggregate clusters containing up to 2,856 valence electrons. Using a transferable, parameterized screened exchange kernel, we resolve dielectric response,
exciton delocalization, and optical spectra within a unified many-body framework. Remarkably, the sBSE transition densities validate the Frenkel
exciton picture in real space and provide a practical first-principles route to its screened couplings. The calculations reproduce $\textit{H}$-, $\textit{I}$-, and $\textit{J}$-like spectral
evolution and reveal that spatially dependent screening does not merely shift excitonic bands, but reshapes their dispersion, leading to changes in the relative energies of bright and dark
exciton states. These results establish sBSE as a predictive framework for large molecular aggregates.
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All authors Barry Y. Li, Chern Chuang, Tim Duong, Tucker Allen, Justin R. Caram, Daniel Neuhauser
Optics · Cross-listed from quant-ph
Beyond Spectroscopic Strong Coupling: Operational Benchmarks for Cavity-to-Magnon Quantum Transfer
Huang Xinyi, Zhang Xiang and Zhao Dongxing
Normal-mode splitting reveals coherent cavity–
magnon hybridization but does not certify finite-time
quantum-state transfer. We describe
quantum transfer in a passive, linear cavity–
magnon system coupled to thermal reservoirs as a thermal-loss channel specified by its coherent transmissivity $\eta$ and output-referred thermal population $\nu$. For single-rail
qubits, we calculate the phase-corrected average fidelity and compare it with the deterministic measure-and-prepare
benchmark of $2/3$. A Bell pair shared by the cavity and an isolated reference retains reference–
magnon entanglement if and only if $\eta>\nu$. An input squeezed
vacuum of strength $r$ yields sub-
vacuum magnon fluctuations if and only if $\nu<\eta(1-e^{-2r})/2$. When the initial
magnon and both reservoirs have the same occupation, an analytically determined peak-transmissivity time optimizes all three tasks. These task-dependent
benchmarks show that a conventional linewidth-based strong-coupling criterion does not guarantee
quantum-transfer performance. Conversely,
entanglement or squeezing can survive below that spectroscopic reference when the added noise is sufficiently low. These
benchmarks provide quantitative targets for transfer timing and thermal-noise control in intracavity-to-
magnon quantum interfaces.
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Optics
Enhanced Magneto-Optical Kerr Effect in Nano-Magnetic Metamaterials with Near-Perfect Coherent Absorption
Xiaofei Xiao, Tingjun Zheng, Alex Vanstone et al. (+6 more)
The ability to control
magnetic systems without external
magnetic fields has attracted
attention recently, with all-optical
magnetic switching showing increasing promise. Gaining fine control over light-matter interactions in
magnetic nanostructures is essential for advancing opto-
magnetic technologies, but remains challenging because strong optical coupling must be achieved within ultrathin
magnetic structures at the target wavelength. Here, we show that coherent optical interference can increase this interaction in patterned
magnetic metasurfaces. Arrays of permalloy nanomagnets are placed on a thin dielectric spacer above a reflective back-plane, forming a
magnetic metasurface whose reflected wavefront is defined by the nanomagnet geometry, fill factor, and spacer thickness. Destructive interference between the metasurface and back-plane reflections yields near-perfect absorption, exceeding 95% for circular nanomagnet arrays in both simulation and experiment. The absorbed power is dissipated almost entirely within the nanomagnets, with only a few percent lost in the metallic back-plane. Enhanced absorption is also accompanied by a stronger magneto-optical Kerr effect, driven by both increased light-nanomagnet interaction and reduced reflected background. These results provide a general approach for achieving high optical absorption and strong magneto-optical response in nanoscale
magnetic systems, supporting advances in optically addressable spintronics,
magnetic sensing, and all-optical
magnetic control.
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All authors Xiaofei Xiao, Tingjun Zheng, Alex Vanstone, Daniel S. Bromley, Holly Holder, Kilian D. Stenning, Jack C. Gartside, Will R. Branford, Rupert F. Oulton
Atmospheric and Oceanic Physics · Cross-listed from stat.AP
Learning joint probabilistic weather forecasts from station observations alone
Chaeyeon Yi and Yun Am Seo
Assessing compound weather risks requires forecasts representing dependence between variables. CLARA (Calibrated Advection-Routing
Attention) learns joint Gaussian predictive distributions of five surface variables from station observations alone, without numerical weather prediction or reanalysis; the approximately 28,000-parameter model supports CPU training and prediction. Across six multi-year folds on 96 stations, its lead-mean energy score is 4.9% lower than that of a learned comparator with matched temporal inputs (4.7% with a similar parameter count) and 11-65% lower than those of statistical baselines. Holding marginal variances fixed, removing learned correlations worsens joint negative log-likelihood by 1.0-2.8 nats per station. A covariance-scale
estimator, proved consistent under stated assumptions, improves short-lead calibration but over-corrects at long leads. Synthetic interventions show an
attention-bias coefficient alone does not measure forecast influence. Retrained in ten regions on six continents, CLARA outperforms persistence in all 60 multi-year region-lead comparisons and a similarly sized learned model in 57 of 60.
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Fluid Dynamics · Cross-listed from cs.CE
A dynamic pore-network model with discrete microbubble transport
Kristoffer Skjelanger, Anna Mareike Kostelecky, Maziar Veyskarami et al. (+1 more)
We develop a hybrid pore-network model (PNM) for discrete microbubble transport coupled to connected two-phase flow in porous media. We apply the model to simulate flow in the porous transport layer of a rotating
proton exchange membrane (PEM) electrolyser. At sufficiently large apparent gravitational forces, bubbles growing at the catalyst layer can detach at sizes smaller than the characteristic pore size and move through
liquid-filled pores via buoyancy and advection. The model couples a dynamic two-phase PNM to a Lagrangian bubble tracker. Pore-scale Stokes simulations in square throats provide closures for the bubble buoyancy velocity, the hydraulic resistance of bubble-occupied throats, and the reciprocal coupling between
liquid flow and bubble motion. Verification tests assess conservation, pressure-flow coupling, bubble growth, advection, merging, trapping, and transfer to the connected gas phase. The network simulations show that increasing apparent gravitational forces shifts a larger fraction of the produced gas toward discrete-bubble transport. The increase mostly comes from a reduced detachment radius, which decreases bubble size and lets them move more freely through the network.
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All authors Kristoffer Skjelanger, Anna Mareike Kostelecky, Maziar Veyskarami, Timo Koch
Medical Physics
How Can Technology Improve Acetabular and Pelvic Fractures Management in the Operating Room? A Systematic Review
Marie Le Baron, Martine Pithioux, Stéphane Candoni et al. (+1 more)
In recent years, there has been a proliferation of literature describing new technologies increasingly integrated into the surgical management of pelvic fractures. However, the available data are heterogeneous, scattered, and sometimes limited to small series or single-center studies. This review aims to present new technologies in the field of pelvic and acetabular fractures and explore their potential benefits for surgeons and patients. The goal is to describe current concepts, advantages, and limitations and to open a discussion about future use and development. The search was conducted through Medline, Central and Embase databases from inception to January 2025 following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) protocol. A total of 841 records were reviewed and 115 studies were included according to the inclusion and exclusion criteria. Technologies such as robotics, navigation, patient-specific management, and 3D printing are being developed for the management of pelvic injuries. These technologies demonstrate greater surgical accuracy without increasing complications. In pelvic and acetabular fractures surgery, new technologies are very attractive and are a promising help for management of these complex injuries and need to be improved before being included in routine care.
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All authors Marie Le Baron, Martine Pithioux, Stéphane Candoni, Xavier Flecher
Physics and Society
Adjusting for Social Groups in Spatial Point Process Models for Waiting Pedestrian Configurations
Lars Sickert Karam, Rui M. Castro, Maarten Schoukens et al. (+1 more)
The spatial distribution of waiting pedestrians has two primary drivers: environmental preference and interaction with other pedestrians. Spatial point processes naturally capture both spatial heterogeneity and repulsive interaction. In previous work (Sickert Karam et al., arXiv:2606.14532, 2026), we proposed a Gibbs model with inhomogeneous intensity and a modified Diggle-Gates-Stibbard interaction function, which reproduces many phenomena in replicated patterns of pedestrians waiting at a train station. Its single interaction function acts as an effective interaction, averaging over behavioral regimes such as interactions within social groups and among strangers. In this article, we show how groups affect distance-based summary statistics and take first steps towards accounting for them. We detect groups from pairwise distances and contact durations, replace each group by a “macro-pedestrian” at its average position, and refit the model. This yields a larger interaction range and better agreement in nearest-neighbor statistics than the original model, although the two fits concern different
datasets and centroid-based distances likely overstate repulsion. This first attempt thus resolves some discrepancies but falls short of a fully adequate solution, opening avenues for further research.
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All authors Lars Sickert Karam, Rui M. Castro, Maarten Schoukens, Alessandro Corbetta
Geophysics
An AI-assisted conditioning and geological interpretation workflow for usage in implicit geological modeling
Stefan Carpentier, Jan Diederik van Wees, Eva de Boever et al. (+5 more)
Implicit modeling and Relative Geologic Time are geological modeling techniques that enable more efficient, faster, less biased and more reproducible modeling results. For optimal operation, these techniques require many well-constrained input data. In the framework of the Horizon Europe GO-Forward and MOOI WarmingUP GOO projects and to accelerate Implicit modeling, Machine Learning (ML) methods have been tested and implemented in a toolkit for the interpretation of (onshore) seismic data from the shallow to deep range (+- 300 - 3500 m). The goal is to rapidly characterise this depth domain by efficient interpretation of horizons and faults in seismic data. The first step is to improve the signal by applying AI techniques like self-supervised and semi-supervised contrastive learning CNN's for noise reduction and interpolation. Next, horizons and faults are interpreted with minimal use of human-generated training data by using (semi-) self-supervised methods. The resulting developed toolkit supports the application of the implemented
algorithms in an efficient workflow. As a first demonstration, the top of the Dutch Maassluis Formation has been interpreted in the Leeuwarden and Waalwijk 3D seismic cubes. Overall, this study demonstrates that AI-assisted interpretation workflows have reached a level of maturity that allows their integration into applied geological modeling and decision-making.
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All authors Stefan Carpentier, Jan Diederik van Wees, Eva de Boever, Jan Niederau, Camille Chapeland, Suzanne Atkins, Boris Boullenger, Jens Wollenweber
Atomic and Molecular Clusters · Cross-listed from hep-ph
Tensor-structure sum rules for spin-1 targets at all $Q^2$
Vladimir Pascalutsa and Marc Vanderhaeghen
We derive a family of sum rules for the tensor structure functions of targets with
spin one or higher, rooted in exact Siegert relations. The mixed rank-two $TT$–$LT$ degeneracy combines amplitudes of opposite crossing parity and, under the superconvergence assumption, gives $\int_0^1\! d x\,[b_2(x,Q^2)-3b_4(x,Q^2)]=0$ in the Hoodbhoy–Jaffe–Manohar (HJM) basis. At large $Q^2$, the protected moment agrees with Detmold's target-mass-complete twist-two OPE; in the strict Bjorken projection, and if $b_4$ is neglected, it reduces to the Efremov–Teryaev (ET)-type condition $\int_0^1\! d x\,x\,b_1(x)=0$, whose measured-range footprint is consistent with the HERMES data. Two further rank-two combinations connect crossing-even amplitudes and determine the corresponding subtraction functions through weighted HJM moments. The protected combination can be isolated through separated tensor $LT$ and $TT$ responses, providing a direct experimental strategy for JLab and, ultimately, a future EIC.
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Atmospheric and Oceanic Physics
Generative and deterministic deep learning models comparison for fine-scale precipitation retrievals from infrared brightness temperature
Matthieu Meignin, Cécile Mallet and Nicolas Viltard
Accurate precipitation estimation at fine spatial scales is critical for hydrology, agriculture, and
climate studies. Infrared brightness temperatures from geostationary satellites offer excellent temporal coverage over continental-scale domains. However, because these measurements primarily characterize cloud-top properties rather than precipitation processes near the surface, their correlation with rainfall intensity remains limited, making quantitative precipitation estimation challenging. In this study, we conduct a systematic inter-comparison of state-of-the-art deep learning models for high-resolution precipitation
retrieval from Meteosat Second Generation infrared brightness temperatures over metropolitan France. These models include deterministic U-Nets,
transformer-based architectures, conditional GANs, and
diffusion models. We construct a curated
dataset spanning 2008–2023, combining Météo-France radar mosaics as reference with multi-channel infrared observations, and design preprocessing and sampling strategies to address the heavy-tailed, intermittent nature of rainfall. Our results show that deterministic models provide robust mean estimates and excel in pixel-wise accuracy, but systematically underestimate extreme precipitation. In contrast, generative models better capture the full precipitation distribution, including rare and heavy rainfall events, producing more realistic spatial structures at the cost of reduced pixel-wise fidelity. These results highlight a trade-off between pixel-wise accuracy and precipitation variability, showing that generative approaches are advantageous for extreme-event detection and probabilistic applications. This work establishes a reproducible framework for evaluating infrared- based precipitation
retrieval methods and provides guidance for designing models that balance precision, variability, and extreme-event representation.
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