Medical Physics
Real-time tissue-equivalent measurement of individual clinical radiotherapy pulses
Fernanda C. Rodrigues-Machado, Katherine Szabo, Jingyi Bian et al. (+5 more)
We apply the precision tools of cavity-enhanced absorption sensing to clinical oncology, demonstrating a dosimeter paradigm in which a centimeter-scale volume of water serves as a tissue-equivalent sensing medium. Our proof-of-concept, all-optical scheme achieves real-time readout of clinical radiation pulses with a nominal single-pulse resolution of 90 $\mu$Gy. This demonstration paves the way toward fiber-integrated, micron-scale devices for $\textit{in situ}$ universal absolute dosimetry during treatment.
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All authors Fernanda C. Rodrigues-Machado, Katherine Szabo, Jingyi Bian, Simon Bernard, Tanner Connell, Shirin A. Enger, Lilian Childress, Jack C. Sankey
Chemical Physics
Adaptive Inference and Convergence of Free Energy Landscapes Using Non-parametric Bayesian Enhanced Sampling
Daisy Kamp, Sinai Lee, Ronald Phung et al. (+4 more)
Enhanced sampling techniques are central to the study of statistically rare events in the computer modeling and simulation of molecular phenomena. In this work, we report the development and integration of a Gaussian process model, adaptive, uncertainty-driven sampling scheme for enhanced sampling. The framework trains a Gaussian process model on an iteratively improving estimate of the free energy landscape. Regions of high uncertainty within the reaction phase space are increasingly sampled, and the uncertainty is computed on-the-fly during free energy reconstruction, serving as a convergence metric. This approach provides a generalizable strategy that can be extended to complex molecular processes.
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All authors Daisy Kamp, Sinai Lee, Ronald Phung, Xavier Garcia, Joni Spencer, Alvin Yu, Elizabeth M.Y. Lee
Biological Physics
Cell intrinsic dynamics guide neuroblast ingression independent of tissue fluidity
David Green, Ermia Etemadi, Lauren Enright et al. (+3 more)
Morphogenesis involves the coordination of multiple cellular processes that occur simultaneously within developing tissues. During early Drosophila embryogenesis, neuroblast (NB) ingression occurs concurrently with germ band extension (GBE), yet whether these processes interact mechanistically remains unclear. Here, we combine mathematical modelling with quantitative live imaging to investigate whether tissue-level mechanics during GBE influence NB ingression dynamics. Mathematical modelling predicted that reducing tissue fluidity through impaired cellular rearrangements should slow NB ingression by increasing mechanical resistance. Experimental analysis of mutants in which
cell intercalation and GBE are disrupted revealed a dramatic reduction in tissue fluidity. However, NB ingression rates remained largely unaffected when tissue fluidity decreased. Incorporating
cell-intrinsic myosin anisotropy and endocytosis-contractility coupling into our mathematical model rescued the rate of neuroblast ingression in solid-like tissues. Thus, our findings suggest that
cell-intrinsic mechanisms, rather than tissue-level fluidity, maintain ingression kinetics. More broadly, these results illustrate how developmental systems can achieve robustness by insulating critical cellular events from tissue-level mechanical variability.
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All authors David Green, Ermia Etemadi, Lauren Enright, Rodrigo Fernandez-Gonzalez, Ulrich Tepass, Gonca Erdemci-Tandogan
Chemical Physics
A concentration-independent paradigm rendering weak interactions inherently quantifiable
Masahiko Yoshimura, Fuyuki Matsuda, Yoshiki Ikeda et al. (+9 more)
A vast class of weak, millimolar-affinity molecular interactions governs cellular function, yet their quantitative characterization has remained largely beyond conventional methods. For over a century, biochemistry has worked within a concentration-based framework where molarity scales with molecular number per volume (N/V), and experiments have usually, often implicitly, changed concentration by moving N while holding V fixed. The weak-interaction measurement bottleneck arises from this paradigm: reading weak binding through bulk concentration requires concentrations beyond practical limits, a framework constraint rather than one of instrumental sensitivity. Here we show that shifting experimental control from N to accessible volume V overcomes this bottleneck and opens previously intractable affinity ranges through nanoscale spatial confinement. Controlling V means controlling what biochemists have called "local concentration" and "proximity effects," recasting these long-ambiguous notions as quantitative variables grounded in first principles. Implemented in DNA nanocavities, the approach showed that
geometric arrangement alone can override solution-phase binding hierarchies. The same spatial control quantified a
protein-peptide interaction of order 10 mM from femtomoles per well, totalling under a picomole per titration. Even so, a standard plate reader gave a signal-to-noise ratio near 10^3, leaving headroom for still weaker interactions. The affinity-and-geometry readout also enabled rational screening for
protein-
protein-interaction modulators, identifying compounds that enhance weak associations by reweighting local encounters rather than binding tightly on their own or forming a stable ternary complex. Together, this volume-based paradigm and its implementation provide a general strategy for probing and modulating previously inaccessible biochemical phenomena.
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All authors Masahiko Yoshimura, Fuyuki Matsuda, Yoshiki Ikeda, Chihiro Mori, Tomoko Yoneda, Minako Kikukawa, Rie Murakami, Chiharu Nogami, Yukihiko Sugita, Yoshiko Nakada-Nakura, Masahiko Tsujimoto, Daishi Fujita
Chemical Physics
Experimental access to molarity's blind spot in macroscopic assays
Fuyuki Matsuda, Masahiko Yoshimura, Shiro Ikeda et al. (+1 more)
Chemical kinetics has long inferred local molecular behaviour through the flask-and-molarity pairing, where well-mixed concentrations serve as the experimental readout. Yet many biological reactions occur in structured environments. Researchers have long recognized that concentration may not carry the same operational meaning in such environments, but even local concepts such as effective molarity usually translate local effects back into a single value with units of concentration. What has been missing is the complementary path: a bench-compatible way to make local structure an experimental variable, rather than only a correction to molarity. Here we show a chemistry-geometry crossover that the flask-and-molarity interface could not make visible. In the micromolar-or-weaker affinity regime, inhibition can switch sharply out of the familiar concentration-and-affinity mode: chemical binding strength no longer determines the response, and the shape of the target's local space does. A bench-compatible interface made this switch measurable by separating bulk dose from local geometry. This blind spot arose from the hidden premise that macroscopic pooling makes a structured local state readable as a single local concentration. The chemistry-geometry crossover breaks that premise: in a structured target environment, a macroscopic assay can remain sensitive to the probability distribution of local states, so collapsing that distribution to one concentration-valued number removes the
geometric control axis from the readout. By preserving that axis in the experiment, the interface bypasses molarity's hidden bottleneck and provides a routine experimental route to remeasure and reinterpret molecular interactions in structured space.
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All authors Fuyuki Matsuda, Masahiko Yoshimura, Shiro Ikeda, Daishi Fujita
Instrumentation and Detectors
An Open Source RFSoC-based Readout Electronics System for Arrays of Kinetic Inductance Detectors and Superconducting Resonators
Cody Roberson, Nia McNichols, Jack Sayers et al. (+12 more)
We present a novel readout electronics system for large arrays of superconducting electromagnetic resonators, such as kinetic inductance detectors (KIDs), based on a
Radio Frequency System on Chip (RFSoC) architecture. Each channel in the readout system is designed for frequency division multiplexing of up to 1024 high quality factor resonances placed on a single microwave transmission line at unique frequencies within a 512 MHz bandwidth. We describe the design of the digital and analog signal processing chains for the implementation of a two-channel 2048-resonator system on the Xilinx ZCU111 RFSoC evaluation board in combination with a custom intermediate frequency (IF) system to convert the RFSoC band to higher frequencies up to 4 GHz. We also detail an associated software interface that provides a range of tools commonly utilized for characterizing KID resonators and for operating them as part of a photometric millimeter-wave imager. We additionally provide noise characterizations of the individual readout components, along with the complete readout system in isolation and in operation to readout KID resonators.
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All authors Cody Roberson, Nia McNichols, Jack Sayers, Sean Bryan, Daniel Cunnane, Peter K. Day, Fabien Defrance, Simon Hempel-Costello, Tracee Jamison-Hooks, Bradley R. Johnson, Maya Lee, Philip Mauskopf, Adrian Sinclair, Liam C. Walters, Eric Weeks
Computational Physics
Computing with traceable tensor networks
Sarah Ellwein and Daniele Venturi
We introduce a new SVD-based tensor decomposition method for tensor networks with arbitrary graph
topologies, extending classical hierarchical SVD-based techniques to networks with cycles and general connectivity. We also introduce addition and rounding procedures for traceable tensor graphs, enabling step-rounding time integration of high-dimensional PDEs directly in graph format, with rank truncation controlled to a prescribed tolerance at every time step. We demonstrate the new method on the decomposition of multivariate functions and on the numerical solution of the Fokker-Planck equation, and find that the graph-format representation attains comparable or better accuracy than the classical tensor train and hierarchical Tucker tensor formats, while using substantially fewer degrees of freedom at lower computational cost.
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History and Philosophy of Physics
The orientation of historic churches in Las Palmas de Gran Canaria and its surroundings: preliminary results
Alejandro Gangui, Jose Ricra, Joaquin Pallares et al. (+1 more)
We present preliminary results of the analysis of the precise spatial orientation of colonial Christian churches located in the city of Las Palmas, capital of the island of Gran Canaria (Spain), and its surroundings. Our sample consists of 27 churches, 15 of which belong to the city proper while the rest are situated within roughly 12 km away inland. Most of these churches were constructed between the first decades after the Castilian conquest of the island, and the end of the 19th century. In our analysis we examine whether these orientations respond to calendrical coincidences, to the main features of the landscape, or whether the standard tradition was followed regarding the orientation of the churches' apses eastwards. We find that no church in the sample is oriented towards points of the horizon on which the Sun rises on the day of the patronal feasts. Furthermore, we find no correlation between the global orientation pattern and the orography of the island which, near the local prominent Guiniguada ravine, could have been an important factor at the time of the construction of the churches. What we do find is that most of the orientations fit within the
solar range, mainly to the east but also with a few historic churches oriented towards the west, while less than 20% have astronomical declinations outside of this range. In the statistical analysis, the declination histogram for the sample shows a pattern where the apses of the churches point consistently to the north of due east. This might signal constructions that were oriented to the rising Sun on dates close to Easter. We briefly discuss the implications these findings may have for a future study of the rest of Gran Canaria, which includes several dozens of historic churches scattered throughout the valleys, slopes, and volcanic calderas of the island.
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All authors Alejandro Gangui, Jose Ricra, Joaquin Pallares, Juan Antonio Belmonte
Chemical Physics
The Existence Regions for Transcomplex Recombination of Heavy Ions. Two-Dimensional Recombination Regions and Surroundings Indices
V. M. Akimov, V. M. Azriel, E. V. Ermolova et al. (+4 more)
In this paper, we examine transcomplex recombination RCs$^+$ + Br$^-$ $\to$ CsBr + R (R = Kr, Xe, Hg) for collision energies from 0.1 to 2.5 eV. Within the framework of the quasiclassical trajectory method on semiempirical diabatic potential energy surfaces, we have considered the existence regions for recombination in the space of kinematic parameters. Two-dimensional "slices" of the existence regions for recombination (on the sphere where the coordinates are the orientation angles of the initial direction of the axis of the ionic complex RCs$^+$) sometimes exhibit a chaotic structure. We have proposed a quantitative measure of chaoticity of two-dimensional existence regions for recombination (on the basis of the combinatorics of
matrices of zeros and ones) and have presented examples of chaotic regions. We have introduced the surroundings index of recombinative trajectories and have explored its connection with the integration time of the trajectory and with the total internal energy of the product molecule CsBr.
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All authors V. M. Akimov, V. M. Azriel, E. V. Ermolova, D. B. Kabanov, L. I. Kolesnikova, L. Yu. Rusin, M. B. Sevryuk
Data Analysis and Statistics · Cross-listed from astro-ph.SR
The Bimodal Mass Ratio Distribution of the Hyades
Henri M.J. Boffin
The distribution of
stellar mass ratios, q, in binary systems provides critical insights into the dynamical history and
star-formation processes of open clusters. Here, I re-evaluate the recently published mass ratio distribution (MRD) of a sample of spectroscopic binaries in the Hyades cluster, which was based on
stellar positions in colour-magnitude diagrams. I demonstrate that the mass ratios derived in that work are statistically inconsistent with a random distribution of orbital inclinations. Furthermore, several systems yielded non-physical results. By applying a Richardson-Lucy deconvolution to the spectroscopic mass functions and assuming a random distribution of inclinations, I re-derive the MRD for this sample, showing that it is statistically different from a uniform distribution. I further find a significant dependence on the primary mass: systems with lower-mass primaries exhibit a peak near q~1, whereas more massive primaries show a distribution heavily skewed toward low mass ratios (q~0.15). These findings highlight the potential pitfalls of photometric mass ratio derivations and underscore the need for further verification with future data releases such as
Gaia DR4.
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Computational Physics · Cross-listed from gr-qc
Integral Hilbert spaces and the dynamics of loop quantum cosmos
Janek Kozicki and Tomasz Pawłowski
Polymer quantization program applied in Loop
Quantum Gravity/Cosmology leads to nonseparable
Hilbert spaces. Commonly, one sidesteps this problem by singling out and working with a separable superselection sector. This is however often no longer accessible in more involved models beyond isotropic ones. In an alternative approach one builds a separable
Hilbert space as an integral over all available sectors. Here we test the dynamics following from the latter on the example of a flat isotropic Universe admitting negative cosmological constant and a massless scalar field. There, numerical
evolution of (initially) semiclassical states shows that there is no relevant difference in their long term semiclassicality properties in comparison to those in a single sector approach. Further, the older (problem-specific) numerical methods are compared against an application of more common and more efficient standard tools (eigen library).
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Optics
Real-time quasi-distributed fiber optic sensor based on resonance frequency mapping
Gyeong Hun Kim, Sang Min Park, Chang Hyun Park et al. (+3 more)
Distributed optical fiber sensors (DOFS) based on Raman, Brillouin, and Rayleigh scattering have recently attracted considerable
attention for various sensing applications, especially large-scale monitoring, owing to their capacity for measuring strain or temperature distributions. However, ultraweak backscatter signals within optical fibers constitute an inevitable problem for DOFS, thereby increasing the burden on the entire system in terms of limited spatial resolution, low measurement speed, high system complexity, or high cost. We propose a novel resonance frequency mapping for a real-time quasi-distributed fiber optic sensor based on identical weak fiber Bragg gratings (FBG), which has stronger reflection signals and high sensitivity to multiple sensing parameters. The resonance configuration, which amplifies optical signals during multiple round-trip propagations, can simply and efficiently address the intrinsic problems in conventional single round-trip measurements for identical weak FBG sensors, such as crosstalk and optical power depletion. Moreover, it is technically feasible to perform individual measurements for a large number of quasi-distributed identical weak FBGs with relatively high signal-to-noise ratio (SNR), low crosstalk, and low optical power depletion. By mapping the resonance frequency spectrum, the dynamic response of each identical weak FBG is rapidly acquired in the order of kilohertz, and direct interrogation in real time is possible without time-consuming computation, such as fast
Fourier transformation (FFT). This resonance frequency spectrum is obtained on the basis of an all-fiber electro-optic configuration that allows simultaneous measurement of quasi-distributed strain responses with high speed (>5 kHz), high stability (approximately 2.4 microstrain), and high linearity (R^2 = 0.9999).
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All authors Gyeong Hun Kim, Sang Min Park, Chang Hyun Park, Hansol Jang, Chang-Seok Kim, Hwi Don Lee
Optics
Phase-Locked Time-Stretch Optical Coherence Tomography for Contrast-Enhanced Retinal Microangiography
Gyeong Hun Kim, Seongjin Bak, Hyung-Hoi Kim et al. (+4 more)
Optical coherence
tomography angiography has transformed retinal vascular imaging by providing non-invasive, high-resolution visualization. However, achieving an optimal balance between field of view, resolution, and three-dimensional microvasculature contrast, particularly in deeper retinal layers, remains challenging. A phase-locked time-stretch optical coherence
tomography microangiography system is developed to address these limitations with a 5-MHz A-line rate and sub-nm phase sensitivity. Utilizing a dual chirped fiber Bragg grating architecture, the swept-source
laser achieves an extended coherence length of approximately 10 mm and a 102-nm bandwidth. A time-stretch analog-to-digital converter overcomes the limitations of conventional multi-MHz optical coherence
tomography systems, ensuring a 2-mm imaging depth in the air with high spatial resolution. The proposed system enables high-contrast, depth-encoded mapping of key retinal structures, including the superficial and deep capillary plexuses and the choriocapillaris. Compared to a state-of-the-art system, the proposed approach demonstrates enhanced resolution, improved contrast, and faster imaging speeds, enhancing its potential for diagnosing and monitoring retinal and systemic diseases like age-related macular degeneration, diabetic retinopathy, and Alzheimer's disease.
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All authors Gyeong Hun Kim, Seongjin Bak, Hyung-Hoi Kim, Jun Geun Shin, Tae Joong Eom, Chang-Seok Kim, Hwidon Lee
Fluid Dynamics
Jean-Régis Angilella and S. Ravichandran
We study the motion of inertial particles in two-dimensional inviscid and viscous
vortex crystals, where
vortices are placed at the tips of a regular polygon, and determine the conditions under which long-term trapping of particles can occur. In
crystals with a central
vortex, we find that trapping points in addition to those found in a previous analysis may exist finding, furthermore, that particle trajectories may approach a limit-cycle which can be described by means of asymptotic methods. We show that these newly discovered fixed points persist temporarily in the presence of viscosity, and study the different transitions following viscous
vortex mergers. We find that for moderate Reynolds numbers, the annular merger of the
vortex crystal form an annular
vortex layer that can keep particles trapped within a disk centered at the origin. For larger Reynolds numbers, pairwise
vortex merger leads to
crystals with a smaller number of
vortices, with particles clustering at the fixed points of the newly formed
vortex crystal.
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Plasma Physics
Radial transport of electric current by electromagnetic microturbulence in tokamaks
Haomin Sun, Toby Adkins, Justin Ball et al. (+1 more)
The turbulent transport of toroidal angular momentum helps determine the rotation profiles of tokamak
plasmas, and thereby their confinement and stability. The electron contribution therein has an additional consequence: even a modest electron momentum flux can correspond to a substantial turbulent flux of toroidal current, whose divergence could in principle modify the safety-factor profile. Here, using nonlinear gyrokinetic simulations, we show that electromagnetic fluctuations qualitatively alter turbulent momentum transport. In microtearing-mode-driven
turbulence, the total momentum transport is inefficient relative to that of heat, yet an electron contribution associated with the turbulent Maxwell stress dominates the momentum flux. We show that this contribution exceeds an estimated scale required for turbulent current redistribution to compete with the collisional processes maintaining the bootstrap current. In the case of kinetic-ballooning-mode-driven
turbulence considered, the momentum transport is found to be stronger and remains dominated by the electrostatic ion contribution; nevertheless, retaining the Maxwell stress is essential for the electron momentum flux to exceed this bootstrap-based reference scale. To enable this study, we independently implemented complete electromagnetic momentum-flux diagnostics in the gyrokinetic codes GENE and CGYRO, and verified them through linear and nonlinear cross-code
benchmarks. Taken together, these results suggest that electromagnetic momentum transport may potentially be important for the coupled
evolution of the rotation, current, and safety-factor profiles in high-beta tokamak
plasmas.
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All authors Haomin Sun, Toby Adkins, Justin Ball, Yann Camenen
Physics and Society
What Is Sonification? Toward a Philosophy of Sonification
Rubén García-Benito
Sonification operates across scientific, artistic, and design contexts, yet its identity remains conceptually ambiguous: is it music, a scientific method, or a hybrid practice? This paper presents a philosophical framework that treats sonification as a coherent, transcategorical practice. Drawing on Gustavo Bueno's materialist gnoseology, we identify its operative core through systematic data-to-sound relationships that define its technical identity. Complementing this with Gilbert Simondon's philosophy of individuation, we show conceptually how sonification adapts across contexts while preserving its operative structure. By distinguishing between technical identity and pragmatic use, this framework clarifies the relationship between sonification, music, and aesthetics, providing researchers and practitioners with a philosophical framework to navigate the field's diversity while maintaining its epistemic and operational integrity.
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Applied Physics · Cross-listed from cond-mat.mtrl-sci
Investigation of GeSn aspect ratio trapping growth up to 8% Sn
Hryhorii Stanchu, Quang Minh Thai, Fernando M. de Oliveira et al. (+10 more)
Aspect ratio trapping (ART) growth of germanium-tin (GeSn) is a promising approach to target important objectives on the quest towards commercialization of complementary metal-
oxide-
semiconductor (CMOS)-compatible GeSn optoelectronics devices. Its local growth on patterned substrate allows for versatile device integration into photonics integrated
circuit or for stand-alone structure like focal plane array imager. Additionally, high aspect ratio from nano-sized window can terminate early threading dislocation propagation on the
oxide sidewalls, leaving subsequent growth defect-free and potentially improving the device performance. Knowledge remains missing regarding GeSn ART growth kinetics, morphology and how they evolve from thin film growth, with successful growth itself yet to be demonstrated. In this work, we report GeSn ART growth up to 8% Sn. Two configurations – self-induced Ge core/GeSn shell for Sn content between 6% and 8%, and bulk GeSn ART for Sn content below 1% – are observed. We present a comprehensive study on GeSn ART growth kinetics through different growth rounds and designs, showing a link between pyramid shape of ART island and successful Sn incorporation, as well as the role of growth selectivity and local heating.
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All authors Hryhorii Stanchu, Quang Minh Thai, Fernando M. de Oliveira, Mourad Benamara, Stephen Margiotta, Matthew Cook, Xiaoxin Wang, Jifeng Liu, Perry C. Grant, Baohua Li, Wei Du, Gregory Salamo, Shui-Qing Yu
Accelerator Physics
A diagnostic system of 5.7 keV muon beam for muon accelerator
M. Wada, M. Kimura, S. Aritome et al. (+28 more)
Realization of a low-emittance
muon beam through the acceleration of keV-scale
muons requires the injection of a suitably matched beam into an accelerator, since beam mismatch can lead to emittance growth and reduced acceleration efficiency. In one such scheme,
muons are first thermalized to room temperature and then injected into a linear accelerator. Non-destructive diagnostics are challenging because of the low energy and low intensity. We developed a compact low-energy
muon diagnostic system compatible with the accelerator under construction at J-PARC. The system is designed to evaluate beam conditions required for precise tuning prior to acceleration. Commissioning with low-energy
muon sources shows the system's capability to identify low-energy
muon signals and measure beam profiles.
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All authors M. Wada, M. Kimura, S. Aritome, E. Cicek, K. Futatsukawa, K. Hirai, M. Hoshiai, T. Iijima, Y. Imai, K. Inami, K. Ishida, S. Kamioka, Y. Kawase, A. Kondo, Y. Kondo, M. Lyu, T. Mibe, Y. Nagatani, Y. Nakazawa, S. Ogawa, Y. Oishi, M. Otani, N. Saito, K. Shimomura, K. Suzuki, T. Takayanagi, K. Ueda, S. Uetake, S. Yamamoto, T. Yamazaki, M. Yang
Optics · Cross-listed from astro-ph.IM
CCAT: Optical Design of the 410 GHz Prime-Cam Module
Tilak M. Patel, Tanner Buck, Anthony Huber et al. (+7 more)
Prime-Cam is a first-generation instrument for the Fred Young Submillimeter
Telescope (FYST), enabling wide-field, multi-frequency observations for cosmology, line-intensity mapping, and
galaxy studies. We present an optical performance study for a candidate 410 GHz broadband module designed to field approximately 21,000 polarisation-sensitive kinetic inductance detectors (KIDs). The three-lens silicon design was adapted from the SO LATR design and used for the existing 280 and 350 GHz
Prime-Cam instrument modules, as well as this study. At 410 GHz, a shorter wavelength places tighter demands on wavefront quality and beam shape. Using Ansys Zemax OpticStudio and Huygens PSF analysis, we evaluate candidate module positions, compare 350 and 410 GHz performance, and assess field-dependent Strehl ratio, ellipticity, and encircled-energy behaviour. A preliminary tolerancing study, using inverse increment and Monte Carlo methods, tests sensitivity to selected
alignment perturbations.
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All authors Tilak M. Patel, Tanner Buck, Anthony Huber, Eve M. Vavagiakis, James Burgoyne, Scott Chapman, Ben Keller, Jenna E. Moore, Michael D. Niemack, CCAT Collaboration
Optics · Cross-listed from cond-mat.mes-hall
Magnetic Skyrmion Interacting with Optical Skyrmion
Lan Bo, Jian Chen, Xichao Zhang et al. (+3 more)
Magnetic skyrmions (MSks) and optical skyrmions (OSks) embody
topology in matter and in light, respectively. Here we investigate the interaction between a single MSk and an OSk beam. Three distinct nonlinear dynamical modes are identified: rotation, skipping, and trochoidal motion. By decomposing the optical driving force into gradient, orbital-angular-momentum, and
spin-angular-momentum contributions, we clarify their respective roles of radial confinement, azimuthal drift, and precessional modulation. The skipping motion arises from the azimuthal asymmetry of the OSk beam and exhibits spatial selectivity originating from the magnetization-polarization coupling between the MSk and OSk. In three dimensions, the coupling acquires a propagation-dependent phase dominated by the differential Gouy phase, which yields $z$-asymmetric skipping trajectories. These results bridge topological particles and topological fields within a unified framework, offering helicity-selective and phase-programmable routes to optomagnonic control.
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All authors Lan Bo, Jian Chen, Xichao Zhang, Yan Zhou, Chengwei Qiu, Masahito Mochizuki
History and Philosophy of Physics
Gauge and Metaphysics of Spacetime
Álvaro Mozota Frauca
Some authors have argued that spacetime in general relativity should be given a radically different interpretation from the ones given to spacetime in other theories in virtue of it being a gauge theory. In this article I review this sort of argument and argue against this view. That is, I argue that spacetime in general relativity can be understood analogously to spacetime in other models and that the argument from the diffeomorphism invariance of the theory misapplies the concepts of gauge theory to a context in which they are of limited application.
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Chemical Physics
Committors and Reaction Rates from Trial Functions That Violate the Boundary Conditions
Magnus Petersen, Simon Lichtinger and Roberto Covino
The committor is the optimal reaction coordinate for a rare transition: it pinpoints the transition state and fixes the rate, and it governs events from
protein folding to
crystal nucleation. It minimises a Dirichlet energy, whose value at the minimum is the reactive flux, over functions that vanish on the reactant state and equal one on the product state. In high dimensions such a trial space is very hard to build. Here we rewrite the variational principle so that the boundary conditions are replaced by a normalisation of one boundary observable, the fidelity. Any trial function is then admissible, including functions that cannot satisfy the boundary values at all. On this basis we estimate the high-dimensional committor and rates from one-dimensional profiles along projected coordinates, taking as input only pre-existing
equilibrium or reweighted configurations, a
diffusion constant estimate, and the two state definitions. The optimum has a closed form that is cheap to evaluate. We obtain committors for AIB9 and villin HP-35 in full torsion space, and folding and unfolding rates for chignolin from umbrella sampling alone.
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Chemical Physics · Cross-listed from quant-ph
Thermalization of open quantum systems with pseudomodes
R. Kevin Kessing, Thibaut Lacroix, Susana F. Huelga et al. (+1 more)
Pseudomode approaches allow for an exact and unapproximated description of a
quantum system interacting arbitrarily strongly with a bath. In general, a system coupled to pseudomodes will not thermalize to the system's Gibbs state: This is to be expected when the system-bath coupling is non-perturbative, but conflicts with common thermodynamic intuition when the system-bath coupling is asymptotically weak. We explore under which circumstances pseudomode models satisfy detailed balance (and subsequently thermalize to the system Gibbs state) and how specific choices of parameters can force "weak" detailed balance that is restricted to a limited frequency range. A combination of Hermitian and non-Hermitian pseudomodes that yields a flat effective-temperature profile is also considered. The results and criteria established here are relevant for the construction of pseudomode models in contexts where thermodynamic consistency is required.
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All authors R. Kevin Kessing, Thibaut Lacroix, Susana F. Huelga, Martin B. Plenio
Applied Physics
Reduced Dark Current in Cd0.9Zn0.1Te Detector Arrays by Aluminium Oxide Passivation
Sudarshan Singh, Luc Montpetit, Eloïse Rahier et al. (+3 more)
Contrary to the prevailing view that processing cadmium zinc telluride (CZT)
semiconductors above 150 {\deg}C leads to irreversible device degradation, here we show that Al2O3 passivation layer deposited by atomic layer deposition at 250 {\deg}C not only preserves CZT detector performance but also substantially improves it. Pixelated metal-
semiconductor (MS) and metal-
insulator-
semiconductor (MIS) CZT detectors were passivated with a thin atomic-layer-deposited Al2O3 film and characterized electrically. The passivated devices exhibited no measurable degradation, even under a high-bias operation of 1000 V. Instead, the dark current decreased by approximately a factor of five, while the interpixel leakage current was reduced by nearly one order of magnitude, from ~41 nA to ~2-3 nA at -200 V. Passivation also produced highly uniform dark-current characteristics across adjacent pixels and completely eliminated current-voltage hysteresis, indicating suppression of defect-assisted charge transport. Furthermore, no significant difference in dark current was observed between the MS and MIS detectors after passivation, suggesting that the Al2O3 layer dominates the surface electrical behavior. These results demonstrate that optimized Al2O3 passivation at 250 {\deg}C is fully compatible with high-performance CZT detector processing and provides a practical route toward lower-noise, higher-spectral-resolution X-ray imaging systems.
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All authors Sudarshan Singh, Luc Montpetit, Eloïse Rahier, Mahmoud R. M. Atalla, Sebastian Koelling, Oussama Moutanabbir
Space Physics · Cross-listed from astro-ph.EP
The Length of Martian Crater Rays and Their Relation to Lunar Cold Spots
Trevor P. Erwin, Brandon C. Johnson, David Minton et al. (+1 more)
Impact-generated crater rays are well-documented on the Moon, with most appearing as high-albedo streaks extending radially from a crater's center. On Mars, however, crater rays are significantly rarer and discernible only through thermal imaging due to their lower thermal inertia compared to surrounding terrain. This study presents the first comparative analysis between the lengths of Martian and lunar crater rays, including lunar albedo rays and cold spots, which are ray-like thermal anomalies associated with many of the youngest lunar craters. Our findings indicate that both Martian crater rays and lunar cold spots extend significantly farther than lunar albedo rays, with lengths an order of magnitude greater for craters of equivalent diameter. Furthermore, we propose a connection between the formation mechanisms of Martian crater rays and lunar cold spots based on their thermal properties. By integrating thermal rays into existing ejecta models, we refine the understanding of crater-ray formation and suggest that Martian crater rays and lunar cold spots may share a similar formation mechanism via secondary cratering processes. Advancing knowledge of these features has implications for impact dynamics and surface
evolution across planetary bodies.
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All authors Trevor P. Erwin, Brandon C. Johnson, David Minton, Alexandria V. Johnson
Optics · Cross-listed from quant-ph
Salini Rajeev and Mayukh Lahiri
The goal of
quantum process
tomography is to fully characterize an operation performed on a
quantum state. By considering high-dimensional
quantum states (qudit), we show that it is possible to fully reconstruct an arbitrary operation without performing any measurement on the transformed qudit. Our method is interferometric and conceptually different from existing techniques of
quantum process
tomography that must perform a measurement on the transformed qudit.
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Optics
Cavity optomechanics with a suspended resonant mirror
Trishala Mitra, Gurprret Singh, Søren Peder Madsen et al. (+1 more)
We investigate optomechanical effects in cavities consisting of a plane-plane arrangement of a broadband reflectivity mirror and an ultrathin, suspended resonant mirror possessing a high-Q internal optical resonance. We first investigate dispersive optomechanics in such cavities on the basis of a generic analytical model as well as finite element method simulations of realistic structures. We then report on experimental optical spring measurements using a suspended silicon nitride membrane patterned with a subwavelength grating. While the observed optical spring variations qualitatively match those expected from the dispersive cavity optomechanics model, their magnitude is more than two orders of magnitude larger than predicted. We surmize that this strong optomechanical interaction is due to photothermal effects and put forward a phenomenological model that plausibly supports the observations.
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All authors Trishala Mitra, Gurprret Singh, Søren Peder Madsen, Aurélien Dantan
Instrumentation and Detectors · Cross-listed from quant-ph
Nanohertz Pendulum toward Macroscopic Entanglement under Structural Damping
Azusa Sawada, Hina Nakano, Kanta Watanabe et al. (+3 more)
Pendulums are attractive for macroscopic
quantum control because
gravity dilution reduces mechanical loss, while the $1/f$ force-noise spectrum associated with structural damping allows nearly lossless trapping to suppress the thermal noise sampled at an upward-shifted resonance. The same $1/f$ spectrum, however, produces a low-frequency tail that penalizes
entanglement. With $10\%$ detection loss, we find that this tail raises the required back-action-to-thermal force-noise ratio by about $50\%$, corresponding to a required suspension gain $G_{\rm req}=1.49$. To overcome this structural-noise penalty, we realize a $7$-mg pendulum suspended by a stepped fused-silica fiber, with an energy-decay rate $\Gamma/2\pi=361(39)$ nHz ($Q\equiv\omega_0/\Gamma=7.3(8)\times10^6$) at $\omega_0/2\pi=2.63$ Hz. The reduction in $\omega_0\Gamma$ yields a measured gain $G_q\simeq2.5$ relative to the previous monolithic device, exceeding the requirement.
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All authors Azusa Sawada, Hina Nakano, Kanta Watanabe, Gaku Ohashi, Shota Okumura, Nobuyuki Matsumoto
Optics · Cross-listed from quant-ph
Detecting high-dimensional entanglement with simple measurements
Suraj Goel, Alexander Bernal, Gabriele Cobucci et al. (+3 more)
The standard
benchmark for high-dimensional
entanglement is the number of dimensions in which
entanglement must be present in order to generate the state. This is called the Schmidt number and its detection is usually based on implementing an appropriate set of local basis measurements. However, as
quantum technology brings increasingly large physical dimensions within reach, the implementation of such measurements typically becomes more costly. Here, we develop a scheme for detecting Schmidt numbers based only on sequences of single-
qubit observables. These measurements are simpler to implement as they require only low-depth
quantum circuits. Using up to sixteen-dimensional photonic spatial mode
entanglement and multi-plane light conversion technology, we demonstrate how it simplifies setup complexity and successfully detects the maximal (or close-to-maximal) Schmidt number. Our results reveal that simple and more scalable measurements are sufficient to detect high-dimensional
entanglement properties.
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All authors Suraj Goel, Alexander Bernal, Gabriele Cobucci, Will McCutcheon, Mehul Malik, Armin Tavakoli
Atomic Physics
Measurement and control of the interaction frequency shift in bosonic optical lattice clocks
J. P. Salvatierra, M. Barbiero, G. Bertaina et al. (+3 more)
We report precise measurements of inter-level interactions in a bosonic optical
lattice clock based on $^{88}$Sr atoms. We observe a nonlinear density dependence of the clock shift, even without reaching
quantum degeneracy. In a 2D
lattice, the Rabi line shape exhibits an interaction sideband consistent with a collective
spin model, while in a 1D
lattice the shift is modified by density-induced dephasing. These findings, combined with a careful choice of interrogation detuning and atomic density, can enable operation at a net-zero systematic density shift in $^{88}$Sr
lattice clocks. We discuss the implications of these findings in many-body physics,
quantum simulation, and precision isotope shift measurements, which provide a powerful probe for new physics beyond the Standard Model.
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All authors J. P. Salvatierra, M. Barbiero, G. Bertaina, D. Calonico, F. Levi, M. G. Tarallo