Medical Physics · Cross-listed from eess.IV
Efficient Image Registration for Ultrasound Localization Microscopy by Obtaining Gradients via Integration Across Iterations
Jipeng Yan, Chang Liu, Hengchang Liu et al. (+4 more)
Tissue motion correction through image registration is essential for ultrasound localization microscopy (ULM). Parametric image registration is commonly formulated as an optimization problem where motion parameters are iteratively updated to maximize image similarity, and used optimization
algorithms typically rely on gradient information, the explicit evaluation of which can become computationally demanding. This work investigates Extremum Seeking Control (ESC) as an alternative to explicit derivative evaluation in image registration. By obtaining descent information via integrating perturbed and demodulated image similarity metric across iterations, ESC avoids differentiation of the image similarity metric with respect to motion parameters in each iteration. The classical ESC, whose optimization behavior approximates that of classical gradient descent (GD), is first compared with GD for affine image registration using simulated ground-truth motions derived from a beating ex vivo porcine heart
dataset. The results show that ESC achieves registration accuracy and convergence behavior comparable to GD while reducing per-iteration computational cost by approximately 3.5-fold. ESC is subsequently employed in a two-stage motion correction pipeline, where affine registration compensates for global tissue motion and B-spline registration corrects residual local deformation. The proposed method is applied to ULM imaging of a beating ex vivo porcine heart and achieves a spatial resolution of 219 um, substantially below the half-wavelength diffraction limit of 321 um associated with 2.4 MHz diverging-wave imaging. These results demonstrate that ESC provides an effective alternative to explicit derivative evaluation in ULM image registration, enabling accurate motion correction and high-quality super-resolution imaging.
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All authors Jipeng Yan, Chang Liu, Hengchang Liu, Biao Huang, Meng-Xing Tang, Yingxiang Liu, Ying Tan
Applied Physics · Cross-listed from quant-ph
Sensitive endoscopic diamond magnetometer for non-contact sensing in confined environments
Johannes Wesseler and Roland Nagy
Transitioning
quantum magnetometry from laboratory environments to real-world applications has been limited by a persistent trade-off between sensor miniaturization and
magnetic sensitivity. While bulky systems can achieve high sensitivity, endoscopic probes commonly suffer from inefficient fluorescence collection and reduced performance. Here we resolve this trade-off and present a miniaturized diamond
quantum magnetometer with a 6 mm diameter endoscopic sensor head, achieving a
magnetic-field sensitivity of 91 pT/sqrt(Hz) with a 2 kHz measurement bandwidth in a magnetically unshielded environment. The fluorescence collection bottleneck is overcome by separating excitation and collection into different cores of a fused multi-core fiber bundle, coupled to the diamond through a custom high-numerical-aperture micro-objective. A compact FPGA-based backend performs microwave control, lock-in detection and real-time resonance tracking, enabling robust operation during
magnetic-field imaging. To demonstrate the practical utility of the miniaturized sensor, we image the
magnetic field of a commercial lithium-ion pouch
cell during charge and discharge and reconstruct depth-integrated current-density maps of the current flow. These results show that endoscopic diamond magnetometers can combine high sensitivity with a probe geometry suitable for confined, unshielded measurements, opening new avenues in battery technology and beyond.
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Atmospheric and Oceanic Physics · Cross-listed from cs.LG
Investigating Inductive Biases for Machine Learning Emulation of Sudden Stratospheric Warmings in Idealised Isca Simulations
Oskar Bohn Lassen, Simon Driscoll, Stephen I. Thomson et al. (+2 more)
Machine-learning emulators are increasingly used for weather prediction and have the potential to extend skill on subseasonal-to-seasonal timescales by learning dynamically important sources of predictability. A key challenge is whether the models can exploit predictability anchors, such as stratospheric variability, that influence tropospheric circulation beyond short lead times. We test how architectural inductive bias affects emulation of sudden stratospheric warming (SSW) dynamics using paired idealised Isca simulations that differ only in an imposed wave-2 heating perturbation. Across convolutional,
transformer, and graph-based architectures trained for one-step prediction, model differences are modest when the stratosphere is dynamically quiet but widen substantially when SSW-like variability is active. Our results identify explicit three-dimensional vertical coupling as a key inductive bias for machine-learning emulation of stratospheric dynamics. However, Eliassen-Palm flux diagnostics show that low forecast error does not guarantee physically faithful wave-mean-flow interaction, with coherent errors remaining in stratospheric wave-driving structure.
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All authors Oskar Bohn Lassen, Simon Driscoll, Stephen I. Thomson, Sebastian Schemm, Francisco C. Pereira
Plasma Physics
Wake Perturbations in Laser- and Beam-Driven Plasma Wakefield Accelerators: A Symmetry-Based Multipole Classification
Andrei C. Berceanu and Alessio Del Dotto
We review beam-quality physics in
laser-driven (LWFA) and beam-driven (PWFA)
plasma wakefield accelerators through the
symmetry group of the idealised blowout wake – axisymmetry $\mathrm{SO}(2)_\phi$, adiabatic longitudinal translation, and propagation-direction parity. Transverse perturbations of the wake are classified by an integer azimuthal multipole order $m$ labelling the irreducible representations of $\mathrm{SO}(2)_\phi$, with the lowest beam-quality observables coupling at a specific multipole: the bunch centroid at $m=1$, cross-plane emittance coupling at $m=2$. A
symplectic analogy relates transverse matching to longitudinal beam loading. Several phenomena common to LWFA and PWFA – hose instabilities, pulse-front-tilt jitter, spot-asymmetry emittance growth, polarisation-dependent centroid motion, resonant cross-plane mixing – populate the two lowest non-trivial $m$-channels and admit a unified discussion. The positron-witness problem reorganises in the same
language: each known mitigation abandons one specific feature of the uniform-density blowout, drawn from a finite set. The classification also raises the possibility of an $m=3$ response channel whose magnitude remains open. We note the connection to
symmetry-equivariant
Bayesian optimisation of
plasma accelerators.
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Fluid Dynamics
On the governing mechanism of unsteadiness in bow shock-induced three-dimensional separation
S. Vayala, K. Ramachandra, K. Abhishek et al. (+2 more)
We investigate the driving mechanism of low-frequency unsteadiness in bow shock-turbulent boundary layer interactions due to protuberances. Wind tunnel experiments are conducted at a freestream Mach number of 2.87 with protuberances of different shapes and sizes. From time-resolved surface pressure measurements and schlieren imaging, the unsteadiness is characterized by low-frequency shock oscillations, with a Strouhal number of $St_{\delta}\sim 0.01$ based on the boundary layer thickness ($\delta$), while the separated region exhibits predominantly mid-frequency pressure oscillations, with $St_{\delta} \sim 0.1$. Mid-span separation length, $L_{sep}$, is identified as a key parameter in determining time and length scales of shock oscillations. Further details of the interaction are examined through compressible adaptive detached eddy simulations for one particular case, viz.,the cubical protuberance of side 15 mm. A detailed modal analysis using proper orthogonal decomposition (POD) is performed with the 3-D data from computations. Flapping of shock-foot about mid-span was apparent, over and above the coherent to-and-fro oscillations, with the dominance of anti-symmetric mode in the POD of wall pressure fluctuations. The motion of the shock foot is initiated near mid-span, while the shock foot at other spanwise locations lags behind. The flap and asymmetries are related to the spanwise extent of reverse flow. From the reconstructed 3-D flow field using low-frequency modes, along with corroborating observations from the two-point correlations, it is inferred that the imbalance and time lag between the mass injected into the separated region at reattachment and the mass leaving spanwise at the horseshoe
vortex core govern the observed shock motion.
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All authors S. Vayala, K. Ramachandra, K. Abhishek, N. R. Vadlamani, R. Sriram
Computational Physics · Cross-listed from cond-mat.stat-mech
Classical dissipative search of unstructured database
A.E. Allahverdyan and Y. Bisharyan
We propose a physical realization of the unstructured database search that works via classical, dissipative model of spherical
spins. The database is implemented via
spin-
spin couplings, where the selected coupling refers to a larger
ferromagnetic interaction between two selected
spins. The low-temperature
equilibrium of this model leads to magnetization strongly concentrated on the selected
spins, which means that the search is complete. The search time refers to the relaxation time to
equilibrium from a homogeneous initial state, and is described via Langevin equations. This time scales as ${\cal O}(M^a)$ with $a<1/2$, where $M$ is the database volume. This is faster than Grover's search, showing how a dissipative, classical analog computer can overcome the
quantum unitary computer.
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Optics
EDoF-NeRF: extended depth-of-field neural radiance fields using a coded aperture camera
Yoshiyuki Shirasaki and Ryoichi Horisaki
We propose a method for extending the depth-of-field (DoF) to construct high-fidelity neural radiance fields (NeRF) – an emerging technique for rendering photorealistic novel views from a
dataset of images captured at different viewpoints, based on implicit neural representations. The trade-off between DoF and light quantity is inherent not only in conventional cameras but also in NeRF, since the
datasets used by NeRF are captured by these cameras. To address this issue, we introduce a coded aperture placed at the camera pupil, preserving spatial frequency components under defocused conditions. We develop a camera model incorporating coded apertures into NeRF, allowing direct input of coded images and enabling the generation of novel views with an extended DoF. We validate the proposed method, termed extended DoF-NeRF (EDoF-NeRF), through simulations and experiments, demonstrating its superior performance compared to conventional aperture cameras.
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Instrumentation and Detectors
Track and energy reconstruction algorithms for a time projection chamber with orthogonal fields
Martin Vít Vavřík, Babar Ali, Hugo Natal da Luz et al. (+2 more)
In this work, we describe the development of track- and energy-reconstruc-tion
algorithms for atypical Time Projection Chambers (TPCs) that will be used at the Institute of Experimental and Applied Physics, Czech Technical University in Prague, to search for the anomalous internal pair creation reported by the ATOMKI group. These chambers operate with an inhomogeneous toroidal
magnetic field oriented orthogonally to the electric field; we therefore refer to them as Orthogonal-Field TPCs (OFTPCs). Although this configuration distorts the drift of ionization electrons and complicates the resulting electron and positron trajectories, it also offers several practical advantages. We present the most effective of several tested approaches, which employs a simulated ionization-electron drift map for track reconstruction and a Runge–Kutta-based fit for energy reconstruction. Using simulations, we demonstrate that – under idealized conditions, namely an ideal charge readout with no amplification and no noise and with known initial track positions and directions – it is possible to achieve a fitted Gaussian width (sigma) better than 1% in relative energy for both electrons and positrons, after applying corrections for systematic effects that depend on the track parameters.
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All authors Martin Vít Vavřík, Babar Ali, Hugo Natal da Luz, Olivier Rousselle, Tomáš Sýkora
Optics
Magnetic-polarization-dependent spectroscopy of lanthanide-doped anisotropic crystals
Zoe Liestmann, Luca Koldeweyh, Moritz Badtke et al. (+3 more)
We experimentally demonstrate that absorption and emission spectra of trivalent lanthanide-doped anisotropic
crystals can exhibit a significant
magnetic-polarization dependence, which has been largely overlooked in spectroscopic studies to date. Focusing on the uniaxial
laser host LiYF4 (YLF) doped with Yb3+, Tm3+, Er3+, and Ho3+, we measure
magnetic-polarization-dependent absorption and emission spectra for transitions with strong
magnetic-dipole (MD) contributions predicted by theory. Our results reveal that MD-induced spectral anisotropy, i.e., spectral differences for the same electric field orientation but for different
magnetic field orientations, is present even in these well-established
laser materials. A complete spectroscopic characterization of uniaxial
crystals requires three polarizations, including the $\alpha$-polarization, with both the electric field vector E and the
magnetic field vector H perpendicular to the c-axis (E $\perp$ c, H $\perp$ c), in addition to the commonly used two polarizations $\pi$ (E $\parallel$ c, H $\perp$ c) and $\sigma$ (E $\perp$ c, H $\parallel$ c). We further discuss the observed MD-induced spectral anisotropy and calculated MD branching ratios, the impact of the anisotropy on emission cross-section calculations, and the relevance of our results to other uniaxial and biaxial
crystals.
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All authors Zoe Liestmann, Luca Koldeweyh, Moritz Badtke, Sascha Kalusniak, Christian Kränkel, Hiroki Tanaka
Optics
Volumetric nanoscale localization using engineered point spread functions in light sheet microscopy
R. E. Bautista Gonzalez, R. Mouthaan, A. Upadhya et al. (+3 more)
Nanoscale three-dimensional localization across large biological volumes remains an outstanding challenge in optical microscopy, with existing approaches typically limited by imaging speed, volumetric field of view and localization precision when required simultaneously. Here, we overcome these limitations by combining a twin Airy engineered point spread function with two-
photon light sheet fluorescence microscopy, enabling nanoscale localization throughout large volumetric fields of view. Our framework explicitly incorporates the broadband fluorescence emission characteristic of biological fluorophores, ensuring accurate localization under realistic imaging conditions. We achieve localization precisions of $<20$~nm laterally and 42~nm axially over volumes measuring 295~$\mu$m x 330~$\mu$m x 100~$\mu$m , with a projected path to sub-10-nm localization in millimeter-scale specimens. Experiments in fluorescent bead phantoms and live mammalian oocytes confirm robust performance in both controlled and biologically complex environments. These results establish a scalable strategy for localization-based super-resolution imaging across biologically relevant volumes, bridging the gap between nanoscale precision and large-scale volumetric microscopy.
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All authors R. E. Bautista Gonzalez, R. Mouthaan, A. Upadhya, D. J. X. Chow, K. R. Dunning, K. Dholakia
Chemical Physics
Giant Nonequilibrium Fluctuations at a Reactive Surface
Hyun Tae Jung, Hyungjun Kim, Alejandro L. Garcia et al. (+4 more)
We investigate whether
giant fluctuations in a gas can induce corresponding fluctuations on a reactive surface in contact with the gas. Numerical simulations of a minimal heterogeneous catalytic reactor demonstrate that such fluctuations indeed emerge on the surface, with spatial correlations extending over micrometer scales. These fluctuations originate from the dependence of the adsorption rate on the reactant partial pressure. As a result, the surface-coverage structure factor mirrors that of the partial pressure, exhibiting similar enhancement and roll-off behavior across wave numbers.
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All authors Hyun Tae Jung, Hyungjun Kim, Alejandro L. Garcia, Andrew J. Nonaka, John B. Bell, Ishan Srivastava, Changho Kim
Computational Physics
Extension of a multi-region free-surface MHD solver beyond the inductionless approximation
Min Ki Jung, Brian Wynne, Francisco Saenz et al. (+4 more)
Free-surface
liquid metal flows are a leading candidate for the
plasma-facing components of future fusion reactors, but existing transient, three-dimensional, free-surface MHD solvers rely on the inductionless approximation, in which the induced
magnetic field is neglected. This paper extends the open-source solver FreeMHD [B. Wynne et al., Phys.
Plasmas 32, 013907 (2025)] beyond that approximation, resolving the induced field self-consistently with a vector-potential formulation that enforces $\nabla\cdot\boldsymbol{B}=0$ by construction while preserving the original multi-region, two-phase framework. It is verified against the analytical Shercliff and Hunt duct flows, against flows driven by a time-varying applied field, and against the deformation of a free
liquid metal jet crossing a non-uniform field, and validated against free-surface height measurements from the LMX-U experiment. The experiment validates the overall free-surface solution rather than finite-$R_m$ effects, which the transient-field cases verify. To our knowledge this is the first open-source, fully three-dimensional free-surface
liquid metal solver to resolve the
evolution of the induced
magnetic field, providing a basis for modeling the finite
magnetic Reynolds number conditions expected in large-scale, transient fusion events.
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All authors Min Ki Jung, Brian Wynne, Francisco Saenz, Yufan Xu, Jabir Al-Salami, Yong-Su Na, Egemen Kolemen
Computational Physics · Cross-listed from cs.LG
Trainable Photonic Measurement for Physics-Informed PDE Learning
Jiale Linghu, Hao Dong and Yangshuai Wang
Photonic
quantum machine learning offers a route to trainable physical representations built from phase, interference and measurement. However, its role in scientific machine learning remains largely unexplored. Physics-informed neural fields provide a natural setting, because differential equations require trial spaces that preserve phase, frequency and derivative structure. Here we introduce a photonic
quantum neural field in which coordinates become trainable optical phases, are mixed by multi-
photon Fock-space interference and are decoded from
photon-number measurements. The photonic
circuit is optimized as the neural-field representation itself, not as a fixed feature map or hardware accelerator. Photonic measurement is therefore a trainable representation on which the physics-informed residual is minimized. Across seven
elliptic, wave, nonlinear dispersive and inverse PDE
benchmarks, we observe a phase-complexity transition: classical coordinate and
Fourier-feature networks suffice in smooth regimes, whereas the photonic field is most accurate when residual derivatives amplify phase mismatch. In the hardest regimes it gives the lowest errors, with margins reaching an order of magnitude and about one quarter of the trainable parameters of classical baselines. Frozen and shuffled controls, together with noise stress tests, attribute this gain to learned interference and stable Fock-probability readout under compound perturbations. These results identify photonic
quantum measurement as a representation-learning principle for scientific machine learning.
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Optics
Integration of diamond nanobeams with SnVs on Al2O3 waveguides for scalable quantum photonic chip application
Yeting Yang, Ryota Kitagawa, Tetsuya Miyatake et al. (+14 more)
Tin vacancy (SnV) centers in diamond are promising solid state
qubits for integrated
quantum photonics. Here, we fabricate and characterize a diamond on Al2O3 dual taper waveguide structure containing SnV centers, demonstrating optical coupling between the diamond nanobeam and the underlying Al2O3 waveguide. The devices are realized using a
bilayer fabrication approach compatible with wafer scale lithography. Clear guided SnV- emission is observed in all optically active devices, indicating effective optical coupling in the integrated structure. These results demonstrate a scalable fabrication approach toward integrating diamond color centers with photonic waveguides.
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All authors Yeting Yang, Ryota Kitagawa, Tetsuya Miyatake, Masaharu Hida, Naoki Fushimi, Koki Kaminaka, Takuto Yamaguchi, Toshiki Iwai, Itsuki Takagi, Hidetsugu Matsukiyo, Satomi Ishida, Satoshi Iwamoto, Manabu Ohtomo, Toshiyuki Miyazawa, Kenichi Kawaguchi, Ryoichi Ishihara, Shintaro Sato
Applied Physics
Unified 1D Theory and Design Principles for Harmonic Electrothermal Characterization of Nanoscale Conductors
Chuyue Peng, Joshua Ginzburg, Annika Shah et al. (+1 more)
Electrothermal characterization based on the third or other harmonics of an ac Joule heating current is widely deployed for the thermal analysis of solid conductors and their environment, including solid substrates and fluids. However, a unified theory that bridges heat transfer in two archetypal experimental geometries - suspended vs. substrate-supported conductor - has been missing. Here, we present and validate such a theory that explicitly accounts for finite conductor length, thermal mass, and environmental coupling through a unified thermal transfer function. This framework enables the prediction of voltage responses at all harmonics of the driving current (dc, 1$\omega$, 2$\omega$, 3$\omega$) and the formulation of design principles for the characterization of nanoscale conductors. The conductor length $l$ is the primary parameter controlling the frequency regime at which the conductor's thermal mass dominates the thermal response, with the characteristic frequency $\omega_\mathrm{c}=\alpha/l^2$, where $\alpha$ is the conductor's thermal diffusivity - closely related to a criterion previously reported for suspended wires free from environmental coupling. Our unified framework generalizes this result, revealing that sufficiently weak environmental coupling is a necessary condition for $\omega_\mathrm{c}$ to govern the onset of thermal-mass-dominated response. Optimization of interfacial thermal resistance and environmental thermal impedance may further improve temperature resolution and facilitate on-substrate implementations.
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All authors Chuyue Peng, Joshua Ginzburg, Annika Shah, Matthias Kuehne
Physics and Society · Cross-listed from q-bio.PE
Effects of spatial environmental noise on evolution of cooperation
Janguk Kim, Seung-Woo Son and Hye Jin Park
We investigate the effects of environmental noise on cooperation in a spatial evolutionary game model with variable population size. Building on a one-dimensional
lattice model in which vacancies promote cooperation through spatial selection, we add random noise to the environmental quality parameter and consider two distinct types: annealed noise, where the environmental quality fluctu ates independently at each site and each time step, and quenched noise, where each site is assigned a permanently fixed random value. For annealed noise, we develop a mean-field theory by replacing the noise-dependent death probabilities with their distribution averages, and find that increasing the noise intensity shifts both the cooperator-defector phase boundary and the absorbing boundary upward in the parameter space, simultaneously expanding the cooperative regime and the extinc tion region. These predictions are confirmed by numerical simulations. In contrast, quenched noise leaves the phase boundary nearly unchanged across all noise levels, exerting only a weak effect on cooperator frequency. Together, these results demonstrate that temporal fluctuations, rather than static spatial heterogeneity, are the primary driver of noise-induced shifts in the cooperative phase structure.
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Computational Physics
Deep Research in Physical Sciences: A Multi-Agent Framework and Comprehensive Benchmark
Yigeng Jiang, Tengchao Yang, Taoyong Cui et al. (+25 more)
Deep research
agents are Large
Language Model (LLM)-based systems designed for autonomous, multi-step scientific
reasoning, and they hold immense potential for accelerating research in the physical sciences. However, comprehensive and in-depth evaluations of their capabilities within this domain remain lacking. To address this gap, we introduce PhySciBench, a
benchmark highly relevant to physical science research, comprising 200 expert-curated questions, balanced between physics and chemistry, across six task categories that reflect real-world scientific workflows. Evaluations of state-of-the-art models and
agent systems on PhySciBench reveal limited performance; even the strongest baseline, Gemini Deep Research, achieves an accuracy of only 33.5%. Analysis of failure cases identifies three recurrent deficiencies: fragility in extended
reasoning chains, limited knowledge transfer across steps, and a lack of physics-grounded self-verification. Motivated by these findings, we develop DelveAgent, a modular multi-
agent framework equipped with an adaptive planning loop, dual-granularity
memory, and a hierarchical physics-grounded reflection mechanism. Across four scientific
benchmarks, DelveAgent improves accuracy by up to 7.5 percentage points while reducing inference costs to approximately one-third of the strongest baseline. These results establish the significance of PhySciBench as a critical
benchmark for evaluating AI systems in the physical sciences and demonstrate that architectural specialization can effectively enhance the reliability of autonomous scientific research. Our data and code are publicly available at https://github.com/yigengjiang/physci-deepresearch.
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All authors Yigeng Jiang, Tengchao Yang, Taoyong Cui, Jiaxing Wan, Yuan Wang, Weida Wang, Zhiyu Liu, Chuyi Peng, Binzhao Luo, Maoli Gao, Huaihai Huang, Yuqianer Zeng, Ziyang Zheng, Dongchen Huang, Chao Chen, Zichao Liu, Weiping Shen, Shuchen Pu, Siyu Zhou, Runmin Ma, Yusong Hu, Fei Chao, Bo Zhang, Xiawu Zheng, Zifu Wang, Lei Bai, Yunqi Cai, Shufei Zhang
Chemical Physics · Cross-listed from cond-mat.soft
Dynamics of monohydroxy alcohols with chain-like structures: Hydrogen bonding lifetime, chain swapping, and Debye process
Shiwang Cheng and Shalin Patil
By assuming reversible H-bonding association and dissociation, this work provides a description of the supramolecular structure and dynamics of monohydroxy alcohols (MAs) within the framework of a recently proposed living chain model (LCM). Structurally, reversible H-bonding leads to a single exponential distribution of the molar concentration of the supramolecular chain with length N. Dynamically, reversible H-bonding enables supramolecular chain breakage and recombination, which modifies the relaxation time of the supramolecular chains. In addition to the structural relaxation, tau_a, and the Debye relaxation, tau_D, two other relaxation times are revealed: the chain breakage time, tau_B, and the H-bonding lifetime, tau_H. The interplay among these four-time scales defines five distinct dynamics regimes. In Regimes I and V, no supramolecular chains form. In Regimes II and IV, supramolecular chains form and give a Debye relaxation. The characteristic chain length scales as Nc~tau_D/tau_a. In these two regimes, the H-bonding lifetime controls the Debye process. In Regime III, large supramolecular chains form. In all regimes with supramolecular chain formation, the Debye relaxation comes from the overall chain end-to-end dipole reorientation and scales with Nc. Excellent agreements between experiments and LCM have been observed, leading to quantitative descriptions of the dielectric and linear viscoelastic properties of MAs. These results thus establish a theoretical framework linking reversible H-bonding interactions to supramolecular structures, dynamics, and macroscopic properties of MAs.
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Fluid Dynamics
Distinguished Scaling and UTSD Structure in Weak Shock Reflection at Nearly Glancing Incidence
Justin Kin Jun Hew
We study weak shock reflection from a rigid wall in the joint limit of weak shock strength and nearly glancing incidence. In the distinguished scaling $\Mach=1+\lambda\alpha^2$, the inner reflection region is governed by the unsteady transonic small-disturbance (UTSD equation and is controlled, to leading order, by the single parameter $a_0=1/(2\sqrt{\lambda})$, independent of the ratio of specific heats $\gamma$. Thus the known UTSD detachment value $a_d=\sqrt2$ corresponds in this scaling to $\lambda_d=1/8$, with Guderley–Mach reflection for $\lambda>1/8$. The physical trajectory angle is obtained by multiplying the canonical UTSD trajectory function $g(a)$ by the Mach-number strength scale $\delta=\sqrt{2(\Mach^2-1)}$, so that $\chi_{\rm phys}=\delta g(a)+O(\delta^2)=2\sqrt{\lambda}\,\alpha g(a_0)+O(\alpha^3)$. We rederive the self-similar UTSD reduction, sonic parabola, and shock polar in order to make the convention and the detachment map self-contained. We also record a formal adjoint solvability expression for the first correction $H(a;\gamma)$, while specifying the free-boundary data required to evaluate it. Finally, a time-marching solver for the full leading-order canonical UTSD system is benchmarked at $a_0=0.5$: retaining the transverse compression $u>1$ gives a $u=0.5$ contour location consistent with the Hunter–Tesdall triple-point
benchmark. This computation is used only as a leading-order
benchmark, not as a substitute for an adaptive self-similar Guderley free-boundary solver.
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Instrumentation and Detectors
A Search for Effects of Cosmic Rays with Multi-scale Entropy Metrics
William M. Campbell, Ben T. McAllister, Eugene N. Ivanov et al. (+4 more)
We report a comparison of frequency fluctuations in oven-controlled quartz bulk-acoustic-wave oscillators operated above ground and one kilometre underground in a low-
muon-background environment. The experiment is motivated by the possibility that
cosmic rays and other ionizing-radiation backgrounds produce rare, impulsive energy-deposition events that perturb high-Q mechanical resonators and appear as intermittent, non-Gaussian structure in oscillator frequency noise. Conventional power spectral density and Allan-deviation analyses show no statistically compelling separation between the two environments over the explored timescales. In contrast, multi-scale sample
entropy and its modified form reveal a pronounced divergence, with the underground data exhibiting increased predictability over a broad range of effective integration times. This result identifies a change in the temporal structure of the oscillator fluctuations that is largely hidden from standard second-order frequency-stability metrics. We therefore propose multi-scale sample
entropy as a new diagnostic for frequency control and timing, complementary to Allan deviation and spectral analysis, with particular sensitivity to intermittent structure, non-stationary contributions, and rare-event contamination. The observed
entropy separation also provides evidence that the above-ground
cosmic-ray environment influences oscillator frequency fluctuations, suggesting that radiation-linked disturbances may contribute to the
stochastic behaviour of precision mechanical oscillators. These findings introduce an
entropy-based methodology for oscillator metrology and provide a practical tool for future fundamental-physics experiments using cryogenic resonant sensors, where rare-event backgrounds and poorly understood low-frequency noise can limit sensitivity.
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All authors William M. Campbell, Ben T. McAllister, Eugene N. Ivanov, Michael E. Tobar, Mehran Mossammaparast, Mike Sawicki, Maxim Goryachev
Biological Physics
A symmetric relaxation method for entire two-dimensional cellular networks and its implications
Kai Xu, Lifan Weng, Zihan Wang et al. (+2 more)
To simulate the relaxation of an entire 2D cellular network, this study proposes a symmetric relaxation method for both inner and marginal vertices. The relaxations of these two types of vertices are determined by the central angle
symmetry of associated
cells and the angle
symmetry at each vertex, but with different major considerations. Trimmed Voronoi networks with varying irregularity are used as initial networks for the relaxation simulation. In particular, we propose a regular hexagon disordering method to generate Voronoi networks and find that the inner
cells of networks with an irregularity value of one exhibit a conserved edge number distribution, as found in other 2D cellular networks. Simulation results agree with the von Neumann-Mullins law for both inner and marginal
cells, and a modified equation including a
geometric correction term significantly improves prediction quality. The Aboav-Weaire law and Lewis law are also reproduced, with the latter showing that relaxed
cells tend to approach the ellipses' maximum inscribed polygons. Analysis of edge length, interior angle, and shape index reveals that symmetric relaxation inhibits T1 (neighbour exchange) topological transitions by reducing short edges while increasing area disparity among neighbouring
cells. The findings suggest that T1 events may be triggered when force disequilibrium overcomes the stabilising effect of symmetric relaxation, providing a possible mechanistic explanation for T1 in 2D foams.
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All authors Kai Xu, Lifan Weng, Zihan Wang, Yuyang Lian, Bin Huang
Fluid Dynamics
Response of a Turbulent Boundary Layer to a Synthetic Periodic Large-Scale Structure
Mitchell Lozier, Flint O. Thomas and Stanislav Gordeyev
The dynamic response of a zero-pressure gradient turbulent boundary layer (TBL) to a large-scale perturbation in the outer region was investigated experimentally. The baseline TBL had a moderate Reynolds number such that there was no naturally occurring energetic large-scale structure (LSS) present. An active
plasma-based actuator was then placed in the outer region of the TBL to introduce a periodic, spanwise-uniform, synthetic LSS. This novel actuation scheme provides a new tool by which to experimentally examine the `top-down' view of TBL dynamics/interactions. The TBL response to this synthetic structure was investigated using a combination of planar particle imaging velocimetry and spanwise offset hot-wires, over a large streamwise extent downstream of the actuator device. Phase-locked analysis was implemented to isolate and measure the streamwise development of large-scale motions and changes in
turbulence amplitude induced by this synthetic LSS. A strong correlation was observed between large-scale motions near the wall, linearly superimposed from the synthetic LSS, and a periodic modulation of
turbulence amplitudes. This periodic modulation was found to be linked to phase-dependent changes in both the production and transport of
turbulence driven by the induced large-scale motions. The phase speed of these induced large-scale motions, coupled with intermittent changes to spanwise coherence near the wall, revealed an additional, but transient, effect of the synthetic LSS on near-wall cycle dynamics. Overall, these results characterize the influences, and limitations, of top-down interactions on global TBL dynamics.
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Chemical Physics
Streamlining Analysis and Design of Two-Dimensional Electronic Spectroscopy using Machine Learning
Nicholas I. Hausman, Joseph Kelly, Michael S. Chen et al. (+5 more)
Two-dimensional electronic spectroscopy (2DES) offers unique insights into the coupling between electronic and
nuclear motion and dynamics, making it a key technique in diverse fields, including materials science and biology. Obtaining 2DES data requires a series of measurements that involve multiple pulses to construct the full picture – a time-consuming task that often necessitates working with limited or noisy data. Here we introduce a machine-learning based framework that aims to maximize the data that can be extracted from 2DES experiments and provides guidance towards the selection of additional experiments. We design a Gaussian mixture model to learn the underlying spectral density of a system, allowing the extraction of reorganization energies and the extrapolation of the 2DES spectra to other time delays beyond those measured, and demonstrate how our framework can be used to select additional measurements to further improve the accuracy. We show that our approach yields accurate results on a variety of systems, including simulations ranging from photoactive yellow
protein in the gas phase to Nile red in benzene to the anionic green fluorescent
protein chromophore in water, and experiments on Nile blue in ethanol. Our work provides an efficient route to extract maximum insights from 2DES while incurring minimal experimental costs.
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All authors Nicholas I. Hausman, Joseph Kelly, Michael S. Chen, Frank Hu, Angela Lee, Andrés Montoya-Castillo, Gabriela S. Schlau-Cohen, Thomas E. Markland
Atomic Physics · Cross-listed from quant-ph
Towards Entanglement-Enhanced Atom Interferometry Using Bow-Tie Cavities
Christian Mancini, Marco Malitesta, Tommaso Mariani et al. (+7 more)
Atom interferometers are among the most sensitive instruments for precision measurements and tests of fundamental physics. Their performance, however, is ultimately limited by
quantum projection noise when uncorrelated atomic ensembles are employed. Cavity-assisted generation of entangled states has proven to be a promising route toward
quantum-enhanced interferometry beyond the standard
quantum limit. In this work, we present the realization and characterization of a monolithic bow-tie cavity developed to achieve a strong collective atom-light coupling with strontium atoms. Unlike conventional standing-wave Fabry-Pérot resonators, the traveling-wave geometry of the bow-tie cavity provides homogeneous atom-light coupling over the entire atomic ensemble, making it particularly suitable for
entanglement-enhanced atom interferometry with freely falling atoms. The monolithic cavity architecture presents several scientifically relevant features such as high mechanical stability, high finesse, robustness against mirror misalignment, optical and atomic access and the option of generating squeezed states through different strategies. The cavity was realized for operation on the strontium $(5s^2) ^1S_0-(5s5p) ^3P_1$ transition at 689 nm and achieves a finesse of $\mathcal{F}=5.7\times 10^4$ while keeping the transmission of a single mirror sufficiently large to allow for efficient atomic information extraction. In this geometry, the cavity supports two foci with waists of 164 $\mu$m and 31 $\mu$m which gives access to different regimes of atom-cavity coupling. For ensembles containing up to $10^5$ atoms, the cavity is expected to enable a Wineland squeezing parameter $\xi^2$ of 24 dB through cavity-feedback squeezing, and 28 dB through
quantum non-demolition measurements, demonstrating its potential as a platform for next-generation
quantum-enhanced atom interferometers.
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All authors Christian Mancini, Marco Malitesta, Tommaso Mariani, Annalisa Pappalardo, Giuseppe Vinelli, Paolo Vezio, Gabriele Rosi, Enrico Meli, Leonardo Salvi, Guglielmo Maria Tino