Fluid Dynamics
Remarks on Fixed- and Variable-Order Fractional-Laplacian Closures for TurbulentDissipation
José I.H López
Two independent attempts, separated by two decades, to encode turbulent dissipation with a fractional
Laplacian both converge on the operator order as the signature of the fully developedinertial range: the additive, fixed order model, and the dynamically deforming operator of the Adaptive Fractional Navier Stokes. We show that, despite sharing this fixed point, the two constructions belongto distinct universality classes: Chen operator is a superposition of two fixed order kernels whose relative weight drifts with scale, while AFNS posits a single operator whose order itself flows continuously with the local Reynolds number. We derive a scale resolved observable, the effective spectral order, whose logarithmic anomaly term discriminates between these two mechanisms in principle, and then obtain a sharper, purely analytic verdict from the two dimensional, enstrophy conserving limit: the generative mechanism matching a stable process index to the empirical pair dispersion law has no solution once
vortex stretching is kinematically switched off. Whether this dichotomy leaves a residual signature in real quasi two dimensional flows is left as an open experimental challenge.
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General Physics
Finite-domain inverse reconstruction of a Morris–Thorne-type wormhole candidate with a derivative-consistent $f(R)$ curvature sector
Murat Metehan Türkoğlu
We present a finite-domain inverse reconstruction of a Morris–Thorne-type wormhole candidate as a methodological
benchmark for constrained numerical model building in modified
gravity. The throat condition and local
flare-out behaviour are embedded analytically in the shape-function parameterization, while the
redshift profile is kept finite by construction. Rather than fitting $f(R)$, $f_R(R)$, and $f_{RR}(R)$ as independent numerical arrays, a positive analytic generator is assigned to $f_{RR}(R)$ and integrated to obtain a derivative-consistent reconstructed
curvature sector. The frozen reconstruction is evaluated on 10,019 radial nodes over $r\in[1,10^{5}]$. The corresponding
Ricci-scalar trajectory spans $-1.1317\times10^{-9}\leq R\leq1.999999998$ and is weakly non-monotonic, so no inversion $r=r(R)$ is required. On the same finite grid, the reconstructed source variables retain positive pointwise energy-condition margins, the coordinate-radial null-energy integrals are positive both globally and in the near-throat band, and the maximum normalized
tidal-
curvature ratio is $0.8666<1$. The reconstructed source-side closure diagnostic has a maximum absolute residual of $5.3246\times10^{-5}$. The source closure is phenomenological rather than derived from a unique microphysical matter Lagrangian or a uniquely specified
curvature–matter coupling function. Accordingly, the result is not presented as a full field-equation solution of a specified nonminimally coupled $f(R)$ theory, a stability proof, an exterior-matched global spacetime, or an observer-dependent safe-traversal model. It instead provides a finite-domain computational
benchmark for auditable inverse reconstruction of Morris–Thorne-type geometries in modified
gravity.
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Instrumentation and Detectors · Cross-listed from astro-ph.IM
Engineering of titanium transition edge sensor wafers for the BA4-90/150 receiver of BICEP Array
A.Patel, P. A. R. Ade, Z. Ahmed et al. (+83 more)
BA4-90/150, the fourth receiver to be deployed in the BICEP Array (BA) series, is a dichroic 90/150 GHz instrument targeting the frequency space where sensitivity to the CMB polarization is maximized. The receiver will be deployed in the 2026-2027 austral summer, and is set to position BA to achieve exceptionally precise measurements of
cosmic microwave background (CMB) polarization and strengthen constraints on inflationary models. Recent measurements in existing BA receivers suggest that unexpectedly high loop gain in the titanium (Ti) transition edge sensors (TESs) produces excess high-frequency noise that is consequently aliased down into the science band through the time-division multiplexed readout. To reduce the loop gain, we fabricated and tested prototype Ti TES wafers containing 16 modified detector architectures designed to broaden the superconducting transition and reduce the transition steepness (alpha). We present detector performance results, which will directly inform the final integrated wafer now being designed for full receiver commissioning.
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All authors A.Patel, P. A. R. Ade, Z. Ahmed, M. Amiri, D. Barkats, R. Basu Thakur, C. A. Bischoff, D. Beck, J. J. Bock, V. Buza, B. Cantrall, J. R. Cheshire IV, J. Connors, J. Cornelison, M. Crumrine, A. J. Cukierman, E. Denison, L. Duband, M. A. Echter, M. Eiben, B. D. Elwood, S. Fatigoni, J. P. Filippini, A. Fortes, M. Gao, C. Giannakopoulos, N. Goeckner-Wald, D. C. Goldfinger, S. Gratton, J. A. Grayson, A. Greathouse, P. K. Grimes, M. Halpern, S. Henderson, T. D. Hoang, J. Hubmayr, H. Hui, K. D. Irwin, M. Izquierdo Poza, J. H. Kang, K. S. Karkare, S. Kefeli, J. M. Kovac, C. Kuo, K. Lasko, K. Lau, M. Lautzenhiser, T. Liu, S. C. Mackey, N. Maher, K. G. Megerian, L. Minutolo, L. Moncelsi, Y. Nakato, H. T. Nguyen, R. O'Brient, S. N. Paine, M. A. Petroff, A. R. Polish, T. Prouve, C. Pryke, C. D. Reintsema, T. Romand, M. Salatino, A. Schillaci, B. Schmitt, B. Singari, A. Soliman, T. St. Germaine, A. Steiger, B. Steinbach, R. Sudiwala, K. L. Thompson, C. Tucker, A. D. Turner, C. Vergès, A. G. Vieregg, A. Wandui, A. C. Weber, J. Willmert, W. L. K. Wu, H. Yang, C. Yu, L. Zeng, C. Zhang, S. Zhang
Instrumentation and Detectors · Cross-listed from cs.AI
Agentic AI for operating scientific instruments for nanoscale characterization
Zahra Ayar, Marcos Penedo, Mahdi Mehdikhani et al. (+3 more)
Operating a scientific instrument such as an atomic force microscope (AFM) requires continuous expert decision-making. A trained user defines the experimental intent, translates it into instrument commands, assesses incoming data, adjusts imaging parameters, and post-processes the final image. Existing automation usually addresses only parts of this workflow through hard-coded routines, task-specific controllers, or trained machine-learning models. Here we present an agentic-AI framework that operates the executable part of the AFM workflow using a general-purpose, tool-augmented large
language model connected to instrument functions through the Model Context Protocol (MCP). The framework consists of 3 MCP-based
agents: AFM Messenger converts natural-
language instructions into checked instrument commands; AFM Pilot assesses image quality through a large
language model (LLM) and, if necessary, adapts imaging parameters; and AFM Doctor diagnoses image artifacts and applies transparent post-processing from a pre-approved tool set. Because the
language model performs image assessment rather than a fixed scalar objective or external optimizer, the same strategy can be applied across sample types and imaging modes without specific retraining. Safe hardware operation is enforced through an ambiguity check layer before execution. Benchmarking against fine-tuned and off-the-shelf tool-using models shows that this guarded execution layer, rather than model capability alone, reduces wrong-command execution to zero. In live experiments on different samples, AFM Pilot matched expert operators in image quality, iteration count, and tuning time, with no significant difference. These results demonstrate a safe route to agentic operation of scientific instruments, where experimental intent remains human-defined while command execution, image-based tuning, and post-processing are delegated to AI
agents.
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All authors Zahra Ayar, Marcos Penedo, Mahdi Mehdikhani, Nahid Hosseini, Prabhu Prasad Swain, Georg E. Fantner
Optics · Cross-listed from quant-ph
Multipair-resilient entanglement swapping with complementary linear-optical measurements
Siavash Mirzaei Ghormish and Ryan M. Camacho
Multipair emission is a principal source of false heralds in
entanglement swapping with spontaneous parametric down-conversion sources. A conventional Bell-state measurement (BSM) cannot distinguish the desired arrival of one
photon from each neighboring source from a mixed-polarization double emission by one source accompanied by
vacuum from the other. We show that a cascaded network can resolve this ambiguity by allowing its successive swapping stations to perform different measurements. A direct-basis BSM rejects same-polarization double emissions, whereas a balanced equatorial analyzer, implemented by a four-mode Green Machine (GM), uses two-
photon interference to reject mixed-polarization double emissions. At the same time, it recovers same-polarization inter-source events rejected by the BSM as resolved $\phi$-type Bell heralds. Their rejection sets jointly cover both single-source two-
photon classes while retaining contributions from both useful inter-source classes. We classify the passive four-mode, number-resolving analyzers satisfying this condition and identify the BSM and GM as canonical balanced representatives. Using a Gaussian-state analysis exact to all orders of multipair emission, we evaluate three-source BSM–GM and four-source BSM–GM–BSM Pure Bell Pair sources under coupling, detector, and channel loss. The three-source network suppresses the leading infidelity, while the four-source network heralds an exact Bell state in the lossless limit, a property that holds for every alternating BSM–GM chain with four or more sources. The fidelity advantage over source-count-matched all-BSM networks persists at every loss level studied, a single-channel rate advantage appears without multiplexing, and spectral multiplexing raises the Bell-pair delivery probability toward the asymptotically deterministic limit.
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Fluid Dynamics · Cross-listed from cs.GR
Hamiltonian Two-Way Coupling of Nonlinear Waves and 3D Flows
Sinan Wang, Ruicheng Wang, Taiyuan Zhang et al. (+5 more)
Simulating large-scale free-surface water by coupling a localized 3D fluid solver to a cheaper 2D surface model has long faced a mismatch in wave dynamics: efficient 2D wave models used in graphics are typically either linear or non-dispersive. These models are fast, simple, and accurate for calm, small-amplitude seas, but coupling them with strongly nonlinear 3D solvers produces visible reflections and artifacts at the 2D–3D interface. We address this problem by introducing a nonlinear and dispersive 2D wave model based on the canonical Zakharov formulation. Its
Hamiltonian structure, in which the surface elevation and surface potential form a canonical pair ($\eta$, $\psi$) governed by the wave energy, enables a canonically consistent two-way coupling scheme, allowing information to pass smoothly across the 2D–3D interface. Our 2D solver reduces mean wave-height error by 1.7–5$\times$ over SWE, BEM, and Airy baselines while running more than $10^3\times$ faster than BEM; it achieves greater nonlinear accuracy and coupling fidelity than SWE and Airy, with minor losses in speed and stability. Coupling it with a 3D Navier–Stokes solver yields a full system that suppresses visible seam artifacts across a range of experiments, including dispersion-matching and Kelvin-wake tests, and runs over 4$\times$ faster than a pure GPU NB-FLIP simulation on the same domain.
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All authors Sinan Wang, Ruicheng Wang, Taiyuan Zhang, Fan Feng, Jinjin He, Yuchen Sun, Zhiqi Li, Bo Zhu
Applied Physics
Oscillator-Based Processing Unit for Formant Recognition
Tamás Rudner-Halász, Wolfgang Porod and Gyorgy Csaba
Oscillatory neural networks have been successfully applied to a number of computing problems, such as associative
memories and computationally hard optimization tasks. In this paper, we show how to use oscillators to process time-dependent waveforms with minimal or no preprocessing. Since preprocessing and first-layer processing are often the most power-hungry steps in neural networks, our findings may open new doors to simple and power-efficient edge-AI devices.
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Fluid Dynamics
First-principles perturbative theory of anomalous scaling in a stochastic shell model of turbulence
Alexei A. Mailybaev
Deriving anomalous scaling exponents from the equations of motion remains a central problem in the statistical theory of
turbulence. Here we obtain a first-principles perturbative solution for a nonlinear
stochastic dyadic shell model. The model preserves the conservative cascade structure and exact scaling
symmetry of the deterministic dynamics, while
stochastic transfer fluctuations provide a perturbative setting in which the leading-order rescaled dynamics is Gaussian. Using the statistically restored hidden scaling
symmetry of the inertial-range equations, we determine the stationary statistics of the rescaled variables. We then formulate anomalous scaling as a Perron–Frobenius
eigenvalue problem for the multiplier statistics. The resulting perturbative expansion yields explicit analytical expressions for the scaling exponents of structure functions of arbitrary order in the weak-noise regime. Direct numerical simulations provide an independent verification of the theoretical predictions. The results demonstrate that the hidden-
symmetry perturbation framework extends from linear random models to a genuinely nonlinear cascade system.
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Geophysics · Cross-listed from math.NA
ROMNet: a hybrid reduced order modeling and machine learning approach to waveform inversion
Liliana Borcea, Alexander Mamonov, Kui Ren et al. (+2 more)
Waveform inversion seeks to estimate the wave speed of a heterogeneous, inaccessible medium, from time-resolved measurements of the waves at user controlled sensors. We consider this inverse problem for acoustic waves and an active array of source/receiver sensors that emit probing signals and measure the generated pressure waves. The forward map, from the wave speed to the measurements, is nonlinear and oscillatory. The oscillations cause cycle skipping, the main impediment to using the standard, nonlinear least-squares data fitting formulation, known as full waveform inversion (FWI). A recently introduced alternative waveform inversion approach computes from the measurements an algebraic surrogate of the wave operator, a reduced order model (ROM)
matrix, which is then used to estimate the wave speed. The mapping from the measurements to the ROM is nonlinear, but well understood. It is computed efficiently, in a non-iterative manner. The nonlinear mapping from the ROM to the wave speed is less understood, and its approximation involves time-consuming optimization. Our goal in this paper is to use a neural network to map the ROM
matrix to a nearby one, that has a simpler and explicit dependence on the wave speed. This simplifies and reduces the computational cost of the ROM-based waveform inversion. We introduce the methodology, called ROMNet, and test it with numerical simulations, using two training data sets: The first set consists of random media with variations of the wave speed modeled by a superposition of Gaussians with random amplitudes and standard deviations. The second is the publicly available GeoFWI
dataset introduced for benchmarking FWI using deep learning. We compare the performance of ROMNet with the direct ROM-based inversion and with two representative deep learning approaches to FWI: “
Fourier-DeepONet" and “InversionNet".
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All authors Liliana Borcea, Alexander Mamonov, Kui Ren, Haizhao Yang, Chugang Yi
Chemical Physics
An embedding method with constant potential boundary conditions
Lisa Hetzel, Martin Head-Gordon and Christopher J. Stein
We present a self-consistent field framework for finite embedded
quantum-chemical clusters with constant potential boundary conditions. The coupling is realized through an energy-independent self-energy commonly employed in
quantum-transport calculations within the wide-band approximation. Starting from the corresponding non-
equilibrium Green's function formalism, we derive an analytic expression for the one-particle density
matrix update that can be incorporated into conventional Hartree–Fock and density functional theory. The resulting non-Hermitian self-consistent field equations are solved using adapted Pulay-type mixing schemes. Applications to a quasi-periodic hydrogen ring demonstrate that a finite fragment coupled through an optimized self-energy accurately reproduces the polarization response of the extended system, while calculations on a lithium cluster capture metallic charge transfer and fractional occupations under open-boundary conditions. The proposed framework establishes practical grand-canonical boundary conditions for finite
quantum-chemical clusters and lays the methodological foundation for
quantum embedding methods for electrochemical systems.
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Fluid Dynamics
Wing-Rotor Aerodynamic Interactions in Small UAVs During Hover and Cruise
Dev Pradeepkumar Nayak, Seungmin Choi and Muhammad Saif Ullah Khalid
A compact vertical take-off and landing aircraft requires the same tilt-rotor configuration to perform two fundamentally different aerodynamic tasks: sustain hover and deliver efficient cruise. This work investigates the underlying wing-rotor interactions in both operating regimes using a validated unsteady Reynolds-averaged Navier-Stokes equations-based computational framework. For cruise, the advance ratio governs the balance between thrust production, propulsive efficiency, and wake coherence. Lower advance ratios produce a tightly wound slipstream that undergoes strong
vortex interactions, leapfrogging, and early wake bifurcation. At higher advance ratios, the slipstream retains a narrower and more coherent jet-like structure, improving propulsive efficiency while reducing both thrust of the propellor and lift of the wing. The flow impingement at the wing is characterized through the approaching, interaction, and convection phases, revealing the combined influence of
vortex stretching, wake bifurcation, blockage, image-induced velocity, and streamwise momentum convection on the downstream wake. In hover, the propeller's rotational speed governs the overall aerodynamic performance more strongly than the wing's placement. Although the position of the wing with respect to the propellor modifies the local wake interactions and flow impingement on its leading edge, its influence on the integrated thrust coefficient and figure of merit remains limited. We also explain the
vortex and wake dynamics around the propellor and the wing responsible for governing these aerodynamic performance.
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Accelerator Physics
Enhancing 10 TeV $\gamma\gamma$-collider luminosity through scattering-laser wavelength selection in the presence of prolific electron-positron pair production
S. S. Bulanov, T. Barklow, C. Benedetti et al. (+8 more)
A $\gamma\gamma$-
collider capable of reaching the 10 TeV parton-center-of-momentum (pCM) frontier of particle physics may enable the study of phenomena beyond the Standard Model. Based on compact linear wakefield accelerator technology, such a
collider could be realized by Compton scattering multi-TeV
lepton beams off moderate-intensity
laser pulses close to the
collider interaction point, producing the required $\gamma$-
photons. It is shown that, for a wide range of scattering-
laser wavelengths, $\gamma\gamma$-collisions at the interaction point can meet the luminosity requirements for novel particle physics studies, even in the presence of the prolific electron-positron pair production that accompanies the interaction of the scattering
laser with the multi-TeV
lepton beam. Notably, this pair production imposes a natural limit on the maximum achievable
photon luminosity. Accounting for this limit and for the angular divergence of the Compton
photons yields an enhanced $\gamma\gamma$-
collider luminosity for 250 nm and 1.25 nm scattering
lasers. Moreover, the secondary pairs can themselves be exploited in physics studies, since their luminosity is high enough to produce heavy particles at rates needed for discoveries well beyond the reach of existing
colliders.
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All authors S. S. Bulanov, T. Barklow, C. Benedetti, A. Formenti, S. Gessner, R. Lehe, A. Rastogi, S. Pagan Griso, C. B. Schroeder, A. Schwartzman, J. Osterhoff
Space Physics · Cross-listed from astro-ph.IM
Capra: Scalable HEALPix-Native Intensity Reconstruction for High-Resolution IMAP Analyses
Nikola Bukowiecka, Daniel B. Reisenfeld and Maciej Bzowski
We present Capra, a HEALPix-native pipeline for reconstructing all-sky energetic neutral atom (ENA) intensity maps from the NASA Interstellar Boundary Explorer (IBEX) and Interstellar Mapping and Acceleration (IMAP) missions' event-counting data. Capra produces two products: (1) a baseline boresight-assigned map, and (2) an optional smoothed map on the HEALPix grid. This produces smooth, physically interpretable maps with consistent resolution changes and reference-frame transformations. The smoothed Capra maps recover the large-scale ENA morphology while reducing sampling-driven mottling and strip-like artifacts. Relative comparison with the Theseus reconstruction shows broadly consistent large-scale structure, with the discrepancies reflecting differences in reconstruction methods, rather than major morphological discrepancies. We verify invariance (preservation) of count numbers, rates, and intensities across tessellations under coordinate transformations, and demonstrate numerical convergence up to HEALPix resolution Nside = 64 for a representative
dataset. We show that thread-based parallelism performance exhibits approximately linear strong scaling, with bounded
memory usage, enabling efficient high-resolution reconstruction and making Capra well-suited for high-resolution IMAP reconstruction.
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Medical Physics
Evaluation of the Exradin A30 Parallel Plate Ion Chamber as a Reference Dosimeter in Ultra-High Dose Rate (UHDR) Electron Beams
Mervat Alharbi, Kevin Liu, Brian Hooten et al. (+8 more)
Reliable reference dosimetry for ultra-high dose-rate (UHDR) beams (>40 Gy/s) is challenging because conventional ionization chambers (ICs) exhibit saturation from ion recombination. The Exradin A30 IC uses an ultra-thin 0.3-mm electrode spacing to improve charge-collection efficiency (CCE). This study evaluated the commercial A30 as a reference dosimeter for UHDR electron beams by characterizing leakage current, CCE, polarity correction (Ppol), and beam-quality correction factors (kQ). Measurements were performed with a 9-MeV IntraOp Mobetron from the accelerator head, achieving up to 9 Gy per pulse (DPP) and an instantaneous dose rate of 2.25 MGy/s. Data were acquired in grounded water-equivalent plastic, distilled water, and saline water. DPP was varied by changing SSD at a fixed 4-{\mu}s pulse width, while pulse repetition frequency (PRF) ranged from 5 to 90 Hz. CCE was determined using EBT-XD film under matched UHDR and conventional dose and energy conditions. CCE and Ppol were also evaluated as functions of DPP and PRF in distilled and saline water. Values of kQ were calculated using Monte Carlo simulations and measured in TrueBeam electron beams. Leakage current was <2 fA. Both CCE and Ppol decreased with increasing DPP; however, CCE remained 90-99% across all three phantoms, while Ppol decreased from 0.990 to 0.981 in
liquid and solid water. Neither CCE nor Ppol depended on PRF over 5-90 Hz. Measured and calculated kQ values agreed within 0.8% at all energies except 9 MeV, where they differed by 2%. The A30 exhibited 5% recombination at DPP up to 5 Gy in distilled and saline water. Its response in solid phantoms was affected by charge buildup, which was mitigated by grounding. With appropriate CCE corrections and grounded solid phantoms, the commercial A30 is suitable for reference dosimetry in UHDR electron beams.
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All authors Mervat Alharbi, Kevin Liu, Brian Hooten, Shannon Holmes, Stefanno Alarcon-Nunez, Jeffrey Radtke, Larry DeWerd, Sam Beddar, Wesley Culberson, Emil Schueler, Ahtesham Khan
Medical Physics
Clustering of anterior corneal surface shapes in normal adults
Hala Bouazizi, Isabelle Brunette and Jean Meunier
In the present study, we investigated a large
dataset of normal adult corneal topographies in an exploratory attempt to identify the natural groupings of their 3D shapes, with the practical clinical aim of categorizing the shape of a future generation of biosynthetic corneal implants. Because of the wide range of shapes among normal corneas, we needed to identify a limited number of normal corneal shape categories to guide the conception of different implants to match the patient's own corneal shape category. At this stage of our research, we focused on the anterior surface, which exhibits greater variation in a normal population and is responsible for most of the refractive power of the eye. The corneal surface 3D data used were the anterior elevation maps taken from corneal topographies. Clustering corneal topography elevation maps was performed to reveal the normal corneal shape categories. To facilitate groupings, corneal data had their dimensionality reduced by Zernike
polynomial modeling. The resulting clusters were evaluated using different clustering scores, representations and statistical cluster comparisons. While several hard and soft linear and nonlinear clustering methods were tested in this way, k-means proved to be sufficient for this task. The best number of clusters was three and they were primarily differentiated according to corneal
curvature (Zernike defocus coefficient). These clusters were related to established clinical parameters, confirming that the
algorithm extracted relevant information based solely on the normal 3D shape of corneas.
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Optics
First-Principles Prediction of Nonlinear Optical Response in TiO$_2$ for High-Power Dielectric Mirror Applications
Koya Shimaoka, Yusuke Kondo, Kazunori Shibata et al. (+1 more)
Dielectric multilayer mirrors are essential components in optical experiments using high-power
lasers, where titanium dioxide (TiO$_2$) is widely employed as a high-refractive-index dielectric material. In this study, we investigate the nonlinear optical response of TiO$_2$ under intense ultrashort
laser pulses using real-time first-principles electron-dynamics simulations based on time-dependent density functional theory (TDDFT). We reveal intensity-dependent absorption driven by multiphoton excitation and optically excited free carriers, and simulate the resulting electron-light coupled dynamics in TiO$_2$ nanofilms using a multiscale Maxwell-TDDFT framework. Direct evaluation of the reflected and transmitted fields shows reduced reflectance at high intensities ($I \sim 10^{13}$ W/cm$^2$), demonstrating a pronounced nonlinear optical response. Furthermore, the optical response properties are compared among various stable and metastable crystalline phases of TiO$_2$-rutile, anatase, brookite, TiO$_2$-II, and TiO$_2$-B-as well as an amorphous supercell model. These results provide microscopic insight into intensity-dependent optical degradation in TiO$_2$-based dielectric optical components exposed to intense femtosecond
laser fields.
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All authors Koya Shimaoka, Yusuke Kondo, Kazunori Shibata, Mitsuharu Uemoto
Biological Physics · Cross-listed from cond-mat.soft
Micromechanical statistical model links induced nematic order to mechanical response in fiber networks
Ehud Haimov, Yoni Koren, Ayelet Lesman et al. (+2 more)
Contractile
cells and external loads reorganize the fibrous extracellular
matrix, aligning and compacting fibers over distances far exceeding a
cell's size, strongly affecting bioprocesses such as wound healing, angiogenesis and tumor invasion. We develop a continuum micromechanical theory that links, at every material point, the load-induced orientational order to the mechanical response that the reoriented network then exhibits. The network is described statistically, by the probability density of fiber orientations, and deforms affinely, so that a single-fiber stress-strain law is carried into the network stress, with the deformation set self-consistently by mechanical
equilibrium. Critical to realistic biological relevant conditions, this theory allows both geometrical and material nonlinearities. Applied to a two-dimensional network under uniaxial stretch, the theory collapses onto a single anisotropy parameter that governs the orientation distribution, the nematic order, the Poisson ratio, and the densification of fibers. Our theory reveals that induced order and densification are highly positively correlated, and in the case of uniaxial stretch they collapse onto a nearly universal curve, independent of the single-fiber stiffness behavior. For a contracting
cell, we find that buckling controls how far nematic orientational order and densification propagate. We find an algebraic decay of deformations with distance and solve for the dependence of the power-law exponent on the buckled-reduced stiffness of a single fiber. We validate our theory by comparison with non-affine discrete fiber-network simulations.
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All authors Ehud Haimov, Yoni Koren, Ayelet Lesman, Jonathan Selinger, Yair Shokef
Optics · Cross-listed from cond-mat.mes-hall
Carrier-Resolved Attosecond Valley Polarimetry of Monolayer MoS$_2$
Navdeep Rana, Lun Yue and Mette B. Gaarde
In recent years, all-optical writing and switching of valley polarization in two-dimensional
semiconductors has been demonstrated on femtosecond timescales. Reading this polarization out on the same timescale, carrier by carrier, has so far remained out of reach. Employing
semiconductor Bloch equation simulations of monolayer MoS$_2$, we show that attosecond transient absorption closes this gap by turning the Mo $4p$ semicore edge into a quantitative valley polarimeter. We find that pump-enabled core-to-valence absorption probes the holes while core-to-conduction bleaching probes the electrons, so that a single spectrum identifies each carrier by its photoabsorption energy. The hole channel, Pauli-blocked in
equilibrium, emerges background-free. Its circular dichroism reverses sign with the pump helicity, and its normalized magnitude is proportional to the valley polarization. Finally, we show that scanning the probe delay clocks the few-femtosecond write in real time. Thus, attosecond core-level dichroism is a carrier-sensitive, quantitative probe of the creation and
evolution of valley polarization.
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Chemical Physics
Exploring electron transport in carbon wire systems using a wave function-based multiconfigurational non-equilibrium Green's function approach
Pranesh Raghavendran, Gabriela E. Campbell, Erik P. Hoy et al. (+1 more)
One-dimensional carbon wire materials are an interesting class of materials which have potentially useful applications in sub-nanoscale junction technology due to their unique
quantum transport properties. In this work, we apply a non-
equilibrium Green's function approach based on multiconfiguration pair-density functional theory (NEGF-MCPDFT). NEGF-MCPDFT is a wave-function-based non-periodic framework to study electron transport in systems exhibiting strong correlation. The advantage of this approach is multiconfigurational wave functions are used which offer enhanced abilities to describe strong electron correlation beyond single-determinant approaches. MC-PDFT necessitates the use of an active space, and a key step in such calculations is the determination of which orbitals to include. In application of this theory to carbon wire junctions of various lengths, we find that NEGF-MCPDFT is capable of reproducing trends from recent experimental results, and we use our findings to further the development of best practices in active space design for transport calculations of this type.
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All authors Pranesh Raghavendran, Gabriela E. Campbell, Erik P. Hoy, Andrew M. Sand
Atomic Physics
High-density Optical Quantum Sensors with Pulsed Probe Read-out for Correlated Spin-Noise Reduction
Igor Savukov and Young Jin Kim
Optical
quantum sensors based on alkali-metal atoms enable highly sensitive
magnetic-field measurements at room temperature. Their ultimate performance is limited by intrinsic
spin noise once technical noise sources are sufficiently suppressed. Reducing and characterizing this noise is therefore essential for improving sensor sensitivity and for investigating
quantum-enhanced sensing protocols. Here we investigate correlated
spin fluctuations in a
radio-frequency optical
quantum sensor based on a high-density potassium vapor
cell using a pulsed probe readout scheme. The system employs orthogonal pump and probe
laser beams, while a static
magnetic field defines the sensing frequency and synchronizes the probe pulses with the
spin precession. To detect weak
spin correlations, we implement a measurement protocol that combines periodic probing, phase cycling, and window-shifted acquisition. Phase cycling suppresses reproducible probe-induced coherent transients, while subtraction of temporally correlated signals acquired within the
spin-relaxation time reduces the measured
spin-noise level. The observed noise reduction is consistent with temporal
spin correlations, including those expected in
spin-squeezing protocols, although the present measurements do not uniquely distinguish this interpretation from other correlated-noise mechanisms. The demonstrated measurement protocol provides a practical route toward operating warm-vapor optical
quantum sensors closer to their fundamental
spin-noise limit and may benefit
radio-frequency magnetometry and sensing of weak coherent signals, including emerging dark-matter detection schemes.
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Space Physics · Cross-listed from astro-ph.IM
A Singular Value Decomposition Framework for Jovian Radio Emissions from Parker Solar Probe
Evan Wille, Zack Li, Marc Pulupa et al. (+3 more)
Jovian decametric and hectometric
radio emissions provide critical insights into Jupiter's magnetospheric dynamics and its electrodynamic coupling with Io. Across 21 perihelion encounters since its first light in 2018, the Parker
Solar Probe mission has repeatedly recorded high-resolution
radio and
plasma wave data near closest approach, as a result serving as a long-term distant observer of the Jovian system. However, extracting these relatively faint planetary signals from the continuous
solar wind background presents a significant analytical challenge, as the data is routinely saturated by quasi-thermal
plasma noise, spacecraft instrumental interference, and
solar bursts. To overcome these observational barriers, we present a generalized empirical pipeline that utilizes Singular Value Decomposition coupled with a deterministic, dual-stage noise filtering process. By converting dynamic spectra into a periodic, phase-folded reference frame, this model isolates structured Jovian emissions from the
stochastic heliospheric background, demonstrating empirical Signal-to-Noise Ratio improvements of $1.54 \pm 0.11$ dB, reaching up to $3.32$ dB. Additionally, a secondary “Eigenfaces”
matrix factorization is applied to identify long-term global morphological trends and serve as a detection method for future Jovian emissions. This automated mathematical framework extracts transient planetary signals without relying on localized spatial constraints, establishing the viability of PSP as a Jovian
radio observatory.
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All authors Evan Wille, Zack Li, Marc Pulupa, Leon V.E. Koopmans, Philippe Zarka, Stuart Bale
Physics and Society
The complex relationship between anti-immigrant sentiment and exposure in the Netherlands
Benedikt Meylahn, Tommaso Giommoni, Mike Lees et al. (+1 more)
We study the relationship between exposure to immigrants and right-wing votes used as a proxy for anti-immigrant sentiment in the Netherlands. Exposure to immigrants is measured using a novel indicator, adapted from the residential segregation literature, applied to grid data available for the entire country at the aggregate level. Using the proxy of election results, we are able to study the entire voting population instead of a limited subset of panel respondents. In our cross-sectional study of the 2023 national election, we find that municipalities and neighbourhoods with greater exposure have less anti-immigrant sentiment. However, looking at the increase in right-wing vote share from the 2021 to the 2023 national elections, we find evidence of an “overexposure effect”, as this relationship reverses, and the areas that saw significant increases in migrants subsequently experienced an increase in right-wing votes. Furthermore, we see that at high levels of exposure, wealth (and inequality) plays an important role in the voting dynamics, indicating that relative deprivation theory may play a role.
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All authors Benedikt Meylahn, Tommaso Giommoni, Mike Lees, Alessandro Nai
Optics
Single-Mode Control of High-Speed and Low-Threshold III-V/Si Quantum Dot Microring Lasers via Azimuthal Gratings
Xucheng Yang, Yingtao Hu, Eunso Shin et al. (+9 more)
Hybrid III-V/silicon
quantum-dot microring
lasers are compact, energy-efficient O-band sources, but their whispering-gallery cavities are inherently multimode and bidirectional, producing unstable mode hopping that is incompatible with dense wavelength-division multiplexing. We show that an azimuthal grating patterned into the silicon ring - a single lithographic degree of freedom - converts this multimode cavity into a wavelength-addressed, single-mode source. A coupled-mode analysis derives the angular-momentum selection rule from first principles and shows that the inner-wall corrugation replaces the degenerate counter-propagating pair with symmetric and anti-symmetric standing-wave supermodes of unequal radiative loss. At the second-order Bragg condition the anti-symmetric mode is
symmetry-protected, yielding a high-quality-factor state at exactly one azimuthal order; finite-element simulations confirm this and identify grating depth as the primary loss-engineering handle. Devices fabricated in-house on a 100 mm silicon-on-
insulator platform hold a single longitudinal order with a side-mode suppression ratio of 37.9 dB and continuous, hop-free tuning, while the emission wavelength stays fixed across a factor-of-two change in cavity loading, set lithographically rather than by the gain peak. Because the grating decouples the lasing wavelength from the
quantum-dot gain, the detuning becomes a mask-level design variable that sets the temperature of minimum threshold current, reaching 1.95 mA near 50 {\deg}C. Combined with side-mode suppression beyond 37 dB and multi-gigahertz direct modulation, these
lasers are practical building blocks for cascaded, wavelength-addressed transmitter arrays in data communication and co-packaged optics.
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All authors Xucheng Yang, Yingtao Hu, Eunso Shin, Antoine Descos, Yatiraj Ramanujam, Bassem Tossoun, Yuan Yuan, Geza Kurczveil, Jonathan Wierer, Ray Beausoleil, Di Liang, Stanley Cheung
Fluid Dynamics
The Hidden Second Law of Thermodynamics behind the Boltzmann-Grad Limit
Zhaohua Wu
We show that the Boltzmann-Grad (BG) limit, $N\varepsilon^{d-1}=\alpha=\text{const}$, is not a neutral scaling condition but already encodes the Second Law of Thermodynamics, resolving Loschmidt's paradox. Newton's First Law is the bridge: applying the BG condition locally to two adjacent
cells at different temperatures, we decompose their
evolution into a free-streaming period $\delta t_f$, governed by inertia alone, during which molecules cross the interface ballistically and still carry their
cell of origin's velocity distribution; and a collisional adjustment period $\delta t_a$, governed by Newton's Second Law, during which the locally mixed, non-Gaussian population relaxes toward a new Gaussian
equilibrium. Using the one-dimensional Gaussian velocity distribution, we show that isotropy alone produces non-zero net molecular and momentum flux across the interface, directed from the warmer to the cooler
cell – the microscopic origin of the pressure gradient driving the system toward uniformity. Treating relaxation as a sum of random collisional increments, the Central Limit
Theorem fixes the collision count $n^*$ required for convergence, giving $\delta t_a \sim n^*\,\ell/\bar v$. This decomposition resolves Loschmidt's paradox: his reversal acts on a fixed, identifiable set of molecules, while the temperature field Boltzmann's equation tracks is carried by an ever-changing local population; the step relating the two – convergence under the Central Limit
Theorem – is itself a coarse-graining that discards microscopic information by construction, recoverable only at an unavoidable thermodynamic cost, by Landauer's principle. Temporal irreversibility is present from the moment the BG framework, and the coarse-graining it requires, are adopted – not generated during derivation.
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Chemical Physics
Visualizing and Quantifying Atomic Contributions to Raman Intensities governed by Spatially-Resolved Atomic Interferences
Marc Bröckel, Johannes Gierschner, Alfred J Meixner et al. (+1 more)
Raman spectroscopy is commonly reduced to molecular fingerprint sensing, neglecting Raman intensities. Atomic Raman intensity contributions trace Raman intensities back to their microscopic origin and act as local electronic structure descriptors; however, a both physical but intuitive framework is missing by now. Therefore, in this work, we combine the two main lines of decomposing Raman intensities: atomic Raman tensors and atomic Raman Intensity Densities (RIDs). The former are used to define atomic Raman intensities which quantify both the magnitude and the phase of each atom's contribution to the global Raman signal, demonstrating that weak Raman bands may arise from destructive interference of individually strong atomic contributions. The latter build on redefined atomic Raman Polarizability Densities, RPDs, and are defined in analogy to our atomic Raman intensities. They show how the motion of an individual atom modulates the polarizability of the entire molecule. Atomic RIDs thus show local interferences of different atomic contributions. They integrate to the atomic Raman intensities bridging the two main lines. Additional (atomic) Charge Density Differences (CDDs) extend the RIDs to electronic structure effects. Finally, we apply the methodology to experimental surface-enhanced Raman spectra of substituted 2-mercaptobenzothiazole derivatives and discuss substituent-induced Raman intensity changes. We show that such changes do not necessarily stem from globally altered polarizabilities but from changes in the relative phase of atomic contributions. However, this method is not limited to SERS but widely applicable to all kinds of Raman, SERS or picocavity TERS experiments offering a basis for atomically resolved investigations of molecular processes such as adsorption, catalysis, and chemical reactions
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All authors Marc Bröckel, Johannes Gierschner, Alfred J Meixner, Kai Braun
Biological Physics · Cross-listed from cond-mat.soft
Persistence length of short homopolymeric single-stranded DNA sequences in polyvalent cations
Balaka Mondal and D. Thirumalai
We used simulations of short single stranded DNA (ssDNA) homopolymers, based on the sequence dependent Three Interaction Site (TIS) model, to calculate the persistence length ($l_p$) in polyvalent cations. The TIS model accounts for stacking interactions and electrostatic interactions are treated using the Coulomb potential. We find that $l_p$ for $\mathrm{dT_{30}}$ (T is thymine) and $\mathrm{dA_{30}}$ (A is adenine) is quantitatively fit using $l_p = l_p^0 + \lambda \kappa^{-1}$ ($l_p^0$ is the bare persistence length, $\lambda$ is a dimensionless constant, and $\kappa$ is the inverse Debye length) in the divalent cations $\mathrm{Mg^{2+}}$ and $\mathrm{Ca^{2+}}$. The dependence of $l_p$ on $\kappa$ is surprising because it was derived for long flexible polyelectrolytes in which the charges interact via the Debye-Hückel potential. The $l_p^0$ values are 0.4 nm and 1.1 nm for polyT and polyA, respectively. Strikingly, $l_p$ is almost independent of the tetravalent spermine concentration. There is no clear theoretical explanation although simulations suggest that the number of spermine molecules that bind to the ssDNA saturates at a small value. A qualitative picture, based on the restrictions of access to the phosphate groups due to volume exclusion of the anisotropic structure of $\mathrm{Spm^{4+}}$, rationalizes the simulation results. The predicted dependence of $l_p$ in spermine awaits experimental test.
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Computational Physics
Rapidly Convergent Finite-Element Domain Decomposition Method With Two-Channel Transmission Conditions
Furkan Ş{\i}k, Fernando L. Teixeira and Balasubramaniam Shanker
A novel dual-primal finite element tearing and interconnecting (FETI-DP) domain decomposition method (DDM) is introduced for solving Maxwell's equations. The proposed method is built upon a two-channel transmission condition (TC) enforcing both tangential-field and normal-flux continuity across subdomain interfaces. Two interface channels are separately constructed from the Faraday and Ampere-Maxwell equations. Simultaneously enforcing tangential-field and normal-flux continuity reduces interface jumps by several orders of magnitude relative to the widely used Robin TC. The resulting global interface equation exhibits markedly improved iterative convergence. Numerical experiments across different partitioning strategies, subdomain counts and volumes, mesh resolutions, and geometries demonstrate drastic reductions in iteration counts, while accuracy, massive parallelism, and scalability are preserved.
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Accelerator Physics
High-charge collimated and energy-selected laser-driven MeV electron beams produced by magnetic selection
I. Cohen, I. Slabu, Q. Peysson et al. (+16 more)
We have developed a compact passive energy-selector for MeV-range electrons produced by irradiating solid targets by ultra-intense short-pulse
lasers. The device allows for generating electron beams with a variable energy spread over a broad range of energies, from tens of keV to tens of MeV. Here we have demonstrated its use by producing electrons from solid targets in the MeV range and with a ~10% bandwidth, thereby compensating the intrinsic broadband nature of the electrons produced from such source. Coupled with a pulsed
magnetic field to further compensate the intrinsic large divergence of this source, it allows to produce a highly-collimated beam of narrow-band and ultra-fast electrons, suitable for a wide range of applications, e.g. radiation therapy or time-resolved electron probing.
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All authors I. Cohen, I. Slabu, Q. Peysson, S. Dorard, Y. Abe, J. Béard, T. Moraine, S.N. Chen, A. Chessa, K.Iida, P. Kempski, Y. Kuramitsu, H. Kusano, F. Nikaido, M. Ruszkowski, K. Sakai, N. Tamaki, O. Tesileanu, J. Fuchs
Instrumentation and Detectors
Aliased noise characterization and mitigation in BICEP Array 150, 220 and 270 GHz time-division multiplexed detectors
S. Fatigoni, P. A. R. Ade, Z. Ahmed et al. (+83 more)
Early observations with the BICEP Array 150 GHz (BA2-150) and 220/270 GHz (BA3-220/270) receivers revealed detector noise equivalent temperatures (NETs) higher than expected, together with substantial detector-to-detector and module-to-module scatter. Noise measurements acquired with multiplexing off and high frequency sampling demonstrate that this excess originates from elevated high-frequency detector noise that aliases into the science band during time-division multiplexing. We show that the excess high-frequency noise is correlated with anomalously large logarithmic TES transition slopes, {\alpha}, resulting in elevated electrothermal loop gain and operation near the detector stability boundary. Measurements of {\alpha} indicate values substantially larger than expected, consistent with the sharper superconducting transitions introduced by the inverted TES fabrication process adopted for BA2-150 and BA3-220/270 detectors. Operational mitigation strategies were investigated through both increased multiplexing rates and elevated focal-plane operating temperatures. Faster multiplexing reduces aliasing by shifting the multiplexing Nyquist frequency beyond the excess noise roll-off, while elevated bath temperatures reduce TES electrical power and loop gain, improving detector stability and reducing NET by approximately 10%. These results demonstrate the importance of balancing TES responsivity, electrothermal stability, and multiplexed readout performance in next-generation CMB polarimeters.
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All authors S. Fatigoni, P. A. R. Ade, Z. Ahmed, M. Amiri, D. Barkats, R. Basu Thakur, C. A. Bischoff, D. Beck, J. J. Bock, V. Buza, B. Cantrall, J. R. Cheshire IV, J. Connors, J. Cornelison, M. Crumrine, A. J. Cukierman, E. Denison, L. Duband, M. A. Echter, M. Eiben, B. D. Elwood, J. P. Filippini, A. Fortes, M. Gao, C. Giannakopoulos, N. Goeckner-Wald, D. C. Goldfinger, S. Gratton, J. A. Grayson, A. Greathouse, P. K. Grimes, M. Halpern, S. Henderson, T. D. Hoang, J. Hubmayr, H. Hui, K. D. Irwin, M. Izquierdo Poza, J. H. Kang, K. S. Karkare, S. Kefeli, J. M. Kovac, C. Kuo, K. Lasko, K. Lau, M. Lautzenhiser, T. Liu, S. C. Mackey, N. Maher, K. G. Megerian, L. Minutolo, L. Moncelsi, Y. Nakato, H. T. Nguyen, R. O'Brient, S. N. Paine, A. Patel, M. A. Petroff, A. R. Polish, T. Prouve, C. Pryke, C. D. Reintsema, T. Romand, M. Salatino, A. Schillaci, B. Schmitt, B. Singari, A. Soliman, T. St. Germaine, A. Steiger, B. Steinbach, R. Sudiwala, K. L. Thompson, C. Tucker, A. D. Turner, C. Vergès, A. G. Vieregg, A. Wandui, A. C. Weber, J. Willmert, W. L. K. Wu, H. Yang, C. Yu, L. Zeng, C. Zhang, S. Zhang
Optics · Cross-listed from cond-mat.str-el
High-harmonic fingerprints of sharp spin twists in a chiral soliton lattice
Atsushi Ono
A
magnetic field applied perpendicular to the helical axis of a monoaxial
chiral helimagnet compresses the
spin helix into a coplanar
chiral soliton lattice (CSL). We show that optically driven high-harmonic generation from itinerant electrons coupled to a frozen CSL resolves the
lattice-scale structure of the localized twist, rather than the continuum
soliton shape. High-order harmonics remain perturbative for the uniform helix. As the winding localizes at fixed
magnetic period, they grow by many orders of magnitude and acquire a nonperturbative dependence on the drive amplitude. The growth originates from a spatially nonuniform effective hopping that turns each
soliton into a localized dip in the hopping amplitude. When the degree of winding localization is held fixed, high-order intensities fall by many orders of magnitude as the
magnetic period increases toward the continuum limit, where the hopping modulation is spatially smoothed. High-order harmonics thus resolve a real-space characteristic of the coplanar CSL, even in the absence of scalar chirality and an emergent
magnetic field.
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