Applied Physics · Cross-listed from cond-mat.mtrl-sci
A van der Waals material exhibiting room temperature broken inversion symmetry with ferroelectricity
Fabia F. Athena, Cooper A. Voigt, Mengkun Tian et al. (+8 more)
Since the initial synthesis of van der Waals two-dimensional indium selenide was first documented in 1957, five distinct polymorphs and their corresponding polytypes have been identified. In this study, we report a unique phase of indium selenide via Scanning Transmission Electron Microscopy (STEM) analysis in the synthesized large-area films – which we have named the $\beta^\text{p}$ phase. The quintuple layers of the $\beta^\text{p}$ phase, characterized by a unique zigzag atomic configuration with unequal indium-selenium bond lengths from the middle selenium atom, are distinct from any other previously reported phase of indium selenide. Cross-sectional STEM analysis has revealed that the $\beta^\text{p}$ layers exhibit intralayer shifting. We found that indium selenide films with $\beta^\text{p}$ layers display electric-field-induced switchable polarization characteristic of ferroelectric materials, suggesting the breaking of the inversion
symmetry. Experimental observations of nonlinear optical phenomena – Second Harmonic Generation (SHG) responses further support this conclusion. This study reports a $\beta^\text{p}$ phase of indium selenide showing ferroelectricity over large areas at room temperature in a low-dimensional limit.
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All authors Fabia F. Athena, Cooper A. Voigt, Mengkun Tian, Anjan Goswami, Emily Toph, Moses Nnaji, Fanuel Mammo, Brent K. Wagner, Sungho Jeon, Wenshan Cai, Eric M. Vogel
Optics
Equilateral triangular waveguides, modal structure, attenuation characteristics and quality factor
Francis Emenike Onah and Julio C. Gutiérrez-Vega
Equilateral triangular waveguides are one of the very few special kind of waveguides, whose field solutions can be constructed without necessarily solving the Maxwell's equations. Solutions can be obtained simply by superposing some plane wave solutions and requiring the solutions to obey the necessary boundary conditions for each modes, as would be expected of any Maxwell equation's solution or that of any Helmholtz equation resulting from the problem of Heat flow, membrane vibrations, etc. In fact, this was how one of the earlier solutions or eigen functions found by Gabriel Lamé, were obtained. Julian Schwinger, performed the same analysis, but used the superposition of complex exponential functions, in order to obtain the eigen functions of an equilateral triangular waveguide. The solutions exhibit other special symmetric properties that leave their solutions invariant and these special
symmetries and applications, are what we investigate in this work, particularly as it relates to their attenuation characteristics and quality factors. Finally, by employing the number theory of Eisenstein integers or
primes we have obtained a well ordered and more rigorous
eigenvalues of the equilateral triangular waveguides, which is definitely something missing in the literature.
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Physics and Society
Strategic Communication Protocols for Interstellar Objects Using a Threat-Communication Viability Index and the Information-Communication Paradox
David R. Gruber
Strategic Communication Protocols provide a structured approach for first contact with interstellar objects that demonstrate technological characteristics and high levels of threat. The protocols find their starting point in an ISO Information-Communication Paradox, namely, as our knowledge of an ISO's threatening capabilities increases, the probability of successful communication decreases while the urgency of communication attempts simultaneously intensifies. From this paradox, a Threat-Communication Viability Index is created to describe when the value of communication attempts outweighs strategic silence. The index scores the situation and operates as a decision-making tool for stakeholders tracking an ISO. The communication protocols subsequently outline several diplomatic strategies in cases where the index recommends communication.
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Fluid Dynamics
Dynamics of small bubbles in turbulence in non-dilute conditions
Xander M. de Wit, Hessel J. Adelerhof, André Freitas et al. (+3 more)
Turbulent flows laden with small bubbles are ubiquitous in many natural and industrial environments. From the point of view of numerical modeling, to be able to handle a very large number of small bubbles in direct numerical simulations, one traditionally relies on the one-way coupling paradigm. There, bubbles are passively advected and are non-interacting, implicitly assuming dilute conditions. Here, we study bubbles that are four-way coupled, where both the feedback on the fluid and excluded-volume interactions between bubbles are taken into account. We find that, while the back-reaction from the bubble phase onto the fluid phase remains energetically small under most circumstances, the excluded-volume interactions between bubbles can have a significant influence on the Lagrangian statistics of the bubble dynamics. We show that as the volume fraction of bubbles increases, the preferential concentration of bubbles in filamentary high-vorticity regions decreases as these strong vortical structures get filled up; this happens at a volume fraction of around one percent for $\textrm{Re}_\lambda=O(10^2)$. We furthermore study the influence on the Lagrangian velocity structure function as well as pair dispersion, and find that, while the mean dispersive behavior remains close to that obtained from one-way coupling simulations, some evident signatures of bubble collisions can be retrieved from the structure functions and the distribution of the dispersion, even at very small volume fractions. This work not only teaches us about the circumstances under which four-way coupling becomes important, but also opens up new directions towards probing and ultimately manipulating coherent vortical structures in small-scale
turbulence using bubbles.
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All authors Xander M. de Wit, Hessel J. Adelerhof, André Freitas, Rudie P. J. Kunnen, Herman J. H. Clercx, Federico Toschi
Plasma Physics
An Explicit Energy-Conserving Particle Method for the Vlasov-Fokker-Planck Equation
Jiyoung Yoo, Jingwei Hu and Lee F. Ricketson
We propose an explicit particle method for the Vlasov-Fokker-Planck equation that conserves energy at the fully discrete level. The method features two key components: a deterministic and conservative particle discretization for the nonlinear Fokker-Planck operator (also known as the Lenard-Bernstein or Dougherty operator), and a second-order explicit time integrator that ensures energy conservation through an accuracy-justifiable correction. We validate the method on several
plasma benchmarks, including collisional Landau damping and two-stream instability, demonstrating its effectiveness.
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Optics
Super-resolution image projection over an extended depth of field using a diffractive decoder
Hanlong Chen, Cagatay Isil, Tianyi Gan et al. (+2 more)
Image projection systems must be efficient in data storage, computation and transmission while maintaining a large space-bandwidth-product (SBP) at their output. Here, we introduce a hybrid image projection system that achieves extended depth-of-field (DOF) with improved resolution, combining a convolutional neural network (CNN)-based digital encoder with an all-optical diffractive decoder. A CNN-based encoder compresses input images into compact phase representations, which are subsequently displayed by a low-resolution (LR) projector and processed by an analog diffractive decoder for all-optical image reconstruction. This optical decoder is completely passive, designed to synthesize pixel super-resolved image projections that feature an extended DOF while eliminating the need for additional power consumption for super-resolved image reconstruction. Our pixel super-resolution (PSR) image projection system demonstrates high-fidelity image synthesis over an extended DOF of ~267xW, where W is the illumination wavelength, concurrently offering up to ~16-fold SBP improvement at each lateral plane. The proof of concept of this approach is validated through an experiment conducted in the THz spectrum, and the system is scalable across different parts of the electromagnetic spectrum. This image projection architecture can reduce data storage and transmission requirements for display systems without imposing additional power constraints on the optical decoder. Beyond extended DOF PSR image projection, the underlying principles of this approach can be extended to various applications, including optical metrology and microscopy.
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All authors Hanlong Chen, Cagatay Isil, Tianyi Gan, Mona Jarrahi, Aydogan Ozcan
Applied Physics · Cross-listed from quant-ph
Metasurface-Based Dual-Basis Polarization Beam Splitter for efficient entanglement witnessing
Mohamed ElKabbash
Entanglement witnessing is essential for
quantum technologies such as computing, key distribution, and networking. Conventional bulk-optics methods require sequential reconfiguration across multiple polarization bases, limiting efficiency and scalability. We propose a metasurface-based analyzer that performs dual-basis (\sigma_z and \sigma_y) projections simultaneously by mapping them to orthogonal spatial modes. This allows direct access to the commuting two-
photon correlators \langle \sigma_z \otimes \sigma_z \rangle and \langle \sigma_y \otimes \sigma_y \rangle required for
entanglement witnessing. The metasurface design employs meta-atoms engineered to impart independent linear and circular phase delays through anisotropy and
geometric control, resulting in polarization-dependent beam deflection that separates H/V and R/L components. This approach halves the measurement overhead compared to sequential analysis while offering a compact, integrable platform for chip-scale
quantum photonics. The proposed scheme provides a path toward efficient
entanglement verification with applications in
quantum key distribution,
quantum repeaters, and scalable
quantum networks.
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Atomic Physics
Dual-frequency Doppler-free crossover resonance with suppressed magnetic-field sensitivity for compact optical frequency standards
D. S. Chuchelov, M. I. Vaskovskaya, E. A. Tsygankov et al. (+3 more)
We report the observation and characterization of a high-contrast dual-frequency Doppler-free ground-state crossover resonance in the D1 line of 87Rb.The crossover appears at a two-
photon detuning exceeding the natural linewidth of the excited state and is formed by the optical pumping effect. Unlike the previously proposed resonance at zero two-
photon detuning, which we show becomes sensitive to
magnetic-field fluctuations due to residual ellipticity of the optical fields-resulting in frequency shifts and profile asymmetry-the crossover resonance is largely immune to this effect. Our theoretical analysis attributes the observed sensitivity to the dispersive contribution of ground-state coherences to absorption. Stability measurements under
magnetic-field fluctuations demonstrate that using the crossover resonance provides more than an order-of-magnitude improvement, making it a promising reference for frequency stabilization in compact, field-deployable optical standards.
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All authors D. S. Chuchelov, M. I. Vaskovskaya, E. A. Tsygankov, V. V. Vassiliev, S. A. Zibrov, V. L. Velichansky
History and Philosophy of Physics
Comment on "Comment on Galina Weinstein's article entitled 'Convergences and Divergences: Einstein Poincaré and Special Relativity' "
Galina Weinstein
This paper provides a systematic response to the criticisms raised by Jean-Marc Ginoux in response to my review of his book on the history of relativity. Whereas my review was written in a strictly academic manner, Ginoux's commentary intermingles mathematical objections with ad hominem insinuations about both Einstein and me. The purpose of this reply is twofold: first, to clarify the historiographical and conceptual issues at stake in the interpretation of Einstein's 1905 paper and Poincaré's contributions of 1905–1906; and second, to demonstrate why the conflation of algebraic form with conceptual content leads to distorted conclusions.
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Physics and Society
Cooperation in public goods game on square lattices with agents changing interaction groups
Jarosław Adam Miszczak
The emergence of cooperation in the groups of interacting
agents is one of the most fascinating phenomena observed in many complex systems studied in social science and ecology, even in the situations where one would expect the
agent to use a free-rider policy. This is especially surprising in the situation where no external mechanisms based on reputation or punishment are present. One of the possible explanations of this effect is the inhomogeneity of the various aspects of interactions, which can be used to clarify the seemingly paradoxical behaviour. In this work we demonstrate that the diversity of interaction networks helps to some degree explaining the emergence of cooperation. We extend the model of spatial interaction diversity by enabling the evaluation of the interaction groups. We show that the process of the reevaluation of the interaction group facilitates the emergence of cooperation. Furthermore, we also observe that a significant participation of
agents switching their interaction neighbourhoods has a negative impact on the formation of cooperation. The introduced scenario can help to understand the formation of cooperation in the systems where no additional mechanisms for controlling
agents are included.
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Geophysics · Cross-listed from cs.LG
HydroFusion-LMF: Semi-Supervised Multi-Network Fusion with Large-Model Adaptation for Long-Term Daily Runoff Forecasting
Qianfei Fan, Jiayu Wei, Peijun Zhu et al. (+2 more)
Accurate decade-scale daily runoff
forecasting in small watersheds is difficult because signals blend drifting trends, multi-scale seasonal cycles, regime shifts, and sparse extremes. Prior deep models (DLinear, TimesNet, PatchTST, TiDE, Nonstationary
Transformer, LSTNet, LSTM) usually target single facets and under-utilize unlabeled spans, limiting regime adaptivity. We propose HydroFusion-LMF, a unified framework that (i) performs a learnable trend-seasonal-residual decomposition to reduce non-stationarity, (ii) routes residuals through a compact heterogeneous expert set (linear refinement, frequency kernel, patch
Transformer, recurrent
memory, dynamically normalized
attention), (iii) fuses expert outputs via a hydrologic context-aware gate conditioned on day-of-year phase, antecedent precipitation, local variance, flood indicators, and static basin attributes, and (iv) augments supervision with a semi-supervised multi-task objective (composite MSE/MAE + extreme emphasis + NSE/KGE, masked reconstruction, multi-scale contrastive
alignment, augmentation consistency, variance-filtered pseudo-labeling). Optional adapter / LoRA layers inject a frozen foundation time-series encoder efficiently. On a ~10-year daily
dataset HydroFusion-LMF attains MSE 1.0128 / MAE 0.5818, improving the strongest baseline (DLinear) by 10.2% / 10.3% and the mean baseline by 24.6% / 17.1%. We observe simultaneous MSE and MAE reductions relative to baselines. The framework balances interpretability (explicit components, sparse gating) with performance, advancing label-efficient hydrologic
forecasting under non-stationarity.
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All authors Qianfei Fan, Jiayu Wei, Peijun Zhu, Wensheng Ye, Meie Fang
Optics
Advancing Plasmonic Computing with Single-Beam Logic Primitives
Komal Gupta, Anand Hegde and Chen-Bin Huang
Plasmonic logic
circuits combine ultrafast operation with nanoscale integration, making them a strong candidate for next-generation optical computing. Realizing this potential, however, requires overcoming practical challenges such as bulky interferometric designs and reliance on secondary control signals. This work advances plasmonic logic by introducing a single-global threshold mechanism in plasmonic two-wire transmission lines, empowered with polarization modal selectivity and
geometric tuning to enable versatile
circuit functionality. The scheme embeds the control signal with a single
laser beam, supporting six deterministic polarization states and eliminating the need for auxiliary inputs. With this framework, we experimentally demonstrate advanced logic operations, including a 2-bit comparator, parity checkers, and encoder/decoder
circuits. The approach reduces
circuit footprint by 67% and power consumption by 50% relative to state-of-the-art systems, while maintaining low latency and high stability. By unifying thresholding, polarization, and geometry into a compact, source-free scheme, this work pushes plasmonic nanocircuitry from device-level novelty toward scalable, energy-efficient architectures for next-generation optical processors.
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Fluid Dynamics
Experimental investigation relating free-surface features to sub-surface turbulence
Omer M. Babiker, Jørgen R. Aarnes, Ali Semati et al. (+4 more)
Turbulent flows beneath a free surface play a central role in the Earth system, yet their coupling to observable surface features remains incompletely understood. Recent studies using Direct Numerical Simulations (DNS) have reported strong correlation between observable surface features and surface divergence as well as velocity statistics directly beneath, but were limited to Reynolds numbers ($Re$) far below those typical of natural flows, and do not carry the inherent challenges of measurement and flow fidelity that real flows present. We present a laboratory study in which free-surface
topology and sub-surface turbulent velocity are measured simultaneously in a jet-stirred tank, extending these numerical results to the physical domain. Using a novel combination of particle-image velocimetry (PIV) and free-surface profilometry, we access $Re$ up to two orders of magnitude higher than in the DNS. A computer
vision method developed for identifying turbulent imprints on the free surface is successfully applied to experimental data, enabling direct comparison with the DNS. The correlation between time series of mean-square surface divergence and surface features is found to persist as strongly at higher Reynolds numbers, despite the increased disparity of turbulent scales. Beyond the thin viscous layer, all surface-to-bulk correlations scale with the integral length scale across both experimental and numerical cases. The normalized cross-correlation between mean-square horizontal velocity divergence and surface area covered by structures decreases linearly with depth and remains significant even two integral scales beneath the surface, unlike point-to-point correlations which decay fast, illustrating how correlations are near-instantaneous but spatially non-local. These results demonstrate that visible surface features provide considerable... [truncated due to arXiv length constraint]
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All authors Omer M. Babiker, Jørgen R. Aarnes, Ali Semati, Amélie Ferran, Yi Hui Tee, R. Jason Hearst, Simen Å. Ellingsen
Biological Physics · Cross-listed from q-bio.PE
Scarce Data, Noisy Inferences, and Overfitting: The Hidden Flaws in Ecological Dynamics Modelling
Mario Castro, Rafael Vida, Javier Galeano et al. (+1 more)
Metagenomic data has significantly advanced microbiome research by employing ecological models, particularly in personalised medicine. The generalised Lotka-Volterra (gLV) model is commonly used to understand microbial interactions and predict ecosystem dynamics. However, gLV models often fail to capture complex interactions, especially when data is limited or noisy. This study critically assesses the effectiveness of gLV and similar models using
Bayesian inference and a model reduction method based on information theory. We found that ecological data often leads to non-interpretability and overfitting due to limited information, noisy data, and parameter sloppiness. Our results highlight the need for simpler models that align with the available data and propose a distribution-based approach to better capture ecosystem diversity, stability, and competition. These findings challenge current bottom-up ecological modelling practices and aim to shift the focus toward a Statistical Mechanics view of ecology based on distributions of parameters.
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All authors Mario Castro, Rafael Vida, Javier Galeano, José A. Cuesta
Chemical Physics
Tracking Electron, Proton, and Solvent Motion in Proton-Coupled Electron Transfer with Ultrafast X-rays
Abdullah Kahraman, Michael Sachs, Soumen Ghosh et al. (+24 more)
Proton-coupled electron transfer (PCET) is foundational to catalysis, bioenergetics, and energy conversion, yet capturing and disentangling the coupled motions of electrons,
protons, and solvent has remained a major experimental challenge. We combine femtosecond optical spectroscopy, site-specific ultrafast soft X-ray absorption spectroscopy, and time-resolved X-ray scattering with advanced calculations to disentangle the elementary steps of PCET in solution. Using a ruthenium polypyridyl model complex, we directly resolve photoinduced electron redistribution, ligand-site protonation within 100 ps, and the accompanying solvent reorganization. This unified multi-modal approach provides an orbital-level, atomistic picture of PCET, showing how electronic,
nuclear, and solvation degrees of freedom can be separated experimentally. Our results establish a general X-ray framework for understanding and ultimately controlling PCET in catalysis, artificial photosynthesis, and biological energy flow.
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All authors Abdullah Kahraman, Michael Sachs, Soumen Ghosh, Benjamin I. Poulter, Estefanía Sucre-Rosales, Elizabeth S. Ryland, Douglas Garratt, Sumana L. Raj, Natalia Powers-Riggs, Subhradip Kundu, Christina Y. Hampton, David J. Hoffman, Giacomo Coslovich, Georgi L. Dakovski, Patrick L. Kramer, Matthieu Chollet, Roberto A. Mori, Tim B. van Driel, Sang-Jun Lee, Kristjan Kunnus, Amy A. Cordones, Robert W. Schoenlein, Eric Vauthey, Amity Andersen, Niranjan Govind, Christopher Larsen, Elisa Biasin
Applied Physics
Seal Whisker-Inspired Sensor for Amplifying Wake-Induced Vibrations in Underwater Marine Animal Monitoring
Yuyan Wu, Sanjay Giridharan, Leixin Ma et al. (+1 more)
Underwater marine animal monitoring is essential for assessing biodiversity, evaluating ecosystem health, and understanding the effects of offshore structures. Traditional approaches such as tagging, sonar, and camera systems are often invasive, energy-intensive, or limited by poor visibility and water turbidity. Inspired by the hydrodynamic sensing of seal whiskers, wavy whisker vibration sensors have been developed for flow velocity and angle-of-attack detection. However, most prior work has focused on sensor characterization and only forward modeling, with limited exploration of the inverse problem of inferring animal movement. Moreover, current sensor sensitivity to
vortex street wakes generated by swimming animals remains insufficient for practical monitoring. To address this gap, we develop a whisker-inspired sensor with a spiral-perforated base that amplifies vibrations within frequency ranges relevant to animal-induced wakes. We further characterize the influence of spiral parameters on the sensitive frequency band, enabling adaptation of the design to specific species. We evaluated the amplification effect of the spiral-perforated design using frequency response simulations of the whisker-base structure under harmonic water pressure. Results show up to 51x enhancement in root mean squared displacement at the target sensor location within frequency bands associated with animal-induced wakes compared to the baseline design, confirming the effectiveness of the amplification.
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All authors Yuyan Wu, Sanjay Giridharan, Leixin Ma, Hae Young Noh
Atmospheric and Oceanic Physics · Cross-listed from astro-ph.EP
Effect of a Fine-Scale Layered Structure of the Atmosphere on Infrasound Signals from Fragmenting Meteoroids
Igor P. Chunchuzov, Oleg E. Popov, Elizabeth A. Silber et al. (+1 more)
We investigate the influence of a fine-scale (FS) layered structure in the atmosphere on the propagation of infrasound signals generated by fragmenting meteoroids. Using a pseudo-differential
parabolic equation (PPE) approach, we model broadband acoustic signals from point sources at altitudes of 35-100 km. The presence of FS fluctuations in the stratosphere (37-45 km) and the lower thermosphere (100-120 km) modifies ray trajectories, causing multiple arrivals and prolonged signal durations at ground stations. In particular, meteoroids fragmenting at 80-100 km can produce two distinct thermospheric arrivals beyond 150km range, while meteoroids descending to 50 km or below yield weak, long-lived arrivals within the acoustic shadow zone via antiguiding propagation and diffraction. Comparison with observed infrasound data confirms that FS-layered inhomogeneities can account for multi-arrival "N-waves," broadening potential interpretations of meteoroid signals. The results also apply to other atmospheric-entry objects, such as sample return capsules, emphasizing how FS structure impacts shock wave propagation. Our findings advance understanding of wavefield
evolution in a layered atmosphere and have broad relevance for global infrasound monitoring of diverse phenomena (e.g., re-entry capsules, rocket launches, and large-scale explosions).
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All authors Igor P. Chunchuzov, Oleg E. Popov, Elizabeth A. Silber, Segey N. Kulichkov
Instrumentation and Detectors
A Novel, Steerable, Low-Energy Proton Source for Detector Characterization
Nicholas Macsai, August Mendelsohn, David Harrison et al. (+7 more)
We report on the conversion of the Manitoba II mass spectrometer into a versatile low-energy
proton beam facility. This infrastructure is adaptable to any detector-under-test (DUT), and has proven itself effective with the characterization of silicon detectors used in subatomic beyond-the-StandardModel (BSM) searches, namely the Nab experiment. A pencil beam of monoenergetic
protons can be produced in a range from 25 keV to 35 keV, achieving a beamcurrent of ~1x10-18 A. Electrostatic steering plates were constructed to direct the Gaussian-profile
proton beam over a 117mm diameter areaof-interest with full-width at half-maxima (FWHM) ranging from 0.6 mm to 1.26 mm. This work discusses the modifications and subsequent tests to confirm the beam specifications met the demands of the aforementioned detectors.
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All authors Nicholas Macsai, August Mendelsohn, David Harrison, Russell Mammei, Michael Gericke, Leah Broussard, Erick Smith, Grant Riley, Glenn Randall, Mark Makela
Instrumentation and Detectors · Cross-listed from astro-ph.IM
CCAT: Magnetic Sensitivity Measurements of Kinetic Inductance Detectors
Benjamin J. Vaughan, Yuhan Wang, Cody J. Duell et al. (+15 more)
The CCAT Observatory is a ground-based submillimeter to millimeter experiment located on Cerro Chajnantor in the Atacama Desert, at an altitude of 5,600 meters. CCAT features the 6-meter Fred Young Submillimeter
Telescope (FYST), which will cover frequency bands from 210 GHz to 850 GHz using its first-generation science instrument,
Prime-Cam. The detectors used in
Prime-Cam are feedhorn-coupled, lumped-element superconducting microwave kinetic inductance detectors (KIDs). The
telescope will perform wide-area surveys at speeds on the order of degrees per second. During
telescope operation, the KIDs are exposed to changes in the
magnetic field caused by the
telescope's movement through Earth's
magnetic field and internal sources within the
telescope. We present and compare measurements of the
magnetic sensitivity of three different CCAT KID designs at 100 mK. The measurements are conducted in a dilution refrigerator (DR) with a set of room temperature Helmholtz coils positioned around the DR. We discuss the implications of these results for CCAT field operations.
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All authors Benjamin J. Vaughan, Yuhan Wang, Cody J. Duell, Jason Austermann, James R. Burgoyne, Scott Chapman, Steve K. Choi, Abigail T. Crites, Eliza Gazda, Ben Keller, Michael D. Niemack, Darshan A. Patel, Anna Vaskuri, Eve M. Vavagiakis, Michael Vissers, Samantha Walker, Jordan Wheeler, Ruixuan Xie
Biological Physics
X-ray resonance therapy with parametric X-ray radiation (PXR) for sulfur-containing tumor tissues
N. Q. San, O. D. Skoromnik, A. U. Leonau et al. (+2 more)
We investigate the possibility of usage of the parametric X-ray radiation (PXR) for the selective therapy of superficial sulfur-containing tumor tissues. In these tissues, the concentration of sulfur atoms is significantly higher than in healthy ones. Accordingly, the destruction of cancer
cells is caused by the ionization of sulfur atoms. The selective nature of the therapy is determined by the narrow spectral-angular distribution of the PXR
photon beam and the resonant absorption of radiation by sulfur atoms. This leads to a significant decrease in the total dose required to achieve the desired effects compared to irradiation with conventional X-ray tubes or electron accelerators.
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All authors N. Q. San, O. D. Skoromnik, A. U. Leonau, V. Q. Nha, I. D. Feranchuk
Optics
XG-Attention-WGAN PIC: Utilizing XGboost-Attention-WGAN for Photonics Integrated Circuit Design
Mahmood Hasani, Atena Shircharandabi, Masiha Rabiei et al. (+4 more)
Photonic Integrated
Circuits (PICs) are fundamental for optical computing, communication,
quantum information processing, and precision sensing. However, traditional numerical simulations for designing PIC components are computationally intensive and struggle with high-dimensional parameter spaces. This paper introduces XG-
Attention-WGAN PIC, a novel framework that synergistically combines Wasserstein Generative
Adversarial Networks (WGANs) with eXtreme Gradient Boosting (XGBoost) to enhance parameter prediction and inverse design in PICs. We utilize Finite-Difference Time-Domain simulations to generate high-fidelity training data, which is augmented by WGAN-generated synthetic data, yielding a root mean squared error (RMSE) of 0.26089. When integrated with XGBoost, this error is reduced to 0.008. The integration of a 64-head self-
attention mechanism within the WGAN generator significantly improves data quality and model efficiency over 1000 training epochs. Demonstrated on microring resonators, our approach not only achieves superior prediction accuracy and design optimization but also autonomously discovers a novel, experimentally realizable geometry with enhanced Q-factor performance. The proposed framework provides a scalable, data-driven strategy for developing high-performance PIC components, with promising implications for
quantum computing and advanced optical systems.
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All authors Mahmood Hasani, Atena Shircharandabi, Masiha Rabiei, Mobin Motaharifar, Mehrdad Ghasemi, Yaser Mike Banad, Sarah Sharif
Computational Physics
Uncertainty quantification of reacting fluids interacting with porous media using a hybrid physics-based and data-driven approach
Diba Behnoudfar and Kyle E. Niemeyer
Accurately simulating coupled physical processes under uncertainty is essential for reliable modeling and design in performance-critical applications such as combustion systems. Ablative heat shield design, as a specific example of this class, involves modeling multi-physics interactions between reacting flows and a porous material. Repeatedly evaluating these models to quantify parametric uncertainties would be prohibitively computationally expensive. In this work, we combine physics-based modeling using a single-domain approach with data-driven reduced-order modeling to quantify uncertainty via the operator inference method. The detailed physics-based simulations reproduce the measured surface temperature of an object exposed to high-enthalpy flow in a
plasma wind tunnel experiment within 5%. We further use the model to demonstrate the effect of complex flow situations on the dynamic interactions between the porous heat shield material and the surrounding gas. The parametric reduced-order model, built on physics-based simulation data, successfully captures variations in quantities of interest resulting from changes in the permeability and heat transfer coefficient of the porous material in two separate studies: solid-fuel combustion with emission of buoyant reacting plumes in quiescent air, and ablation in a wind tunnel.
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Atmospheric and Oceanic Physics
Understanding the Evolution of Global Atmospheric Rivers with Vapor Kinetic Energy Framework
Aidi Zhang, Da Yang, Hing Ong et al. (+1 more)
Atmospheric rivers (ARs) often cause damaging winds, rainfall, and floods. However, the physical mechanisms governing their
evolution remain poorly understood. To close this gap, we perform a global Vapor Kinetic Energy (VKE) budget analysis. Using two formulations of VKE, we show that ARs are governed by similar mechanisms regardless of ocean basins. ARs intensify primarily through the conversion of potential energy to kinetic energy (PE-to-KE), with horizontal convergence of vapor kinetic energy providing a secondary contribution in some regions. ARs decay mainly through condensation and turbulent dissipation, while their propagation is governed by the downstream convergence and upstream divergence of vapor kinetic energy. We also find PE-to-KE conversion varies spatially and strengthens in regions of greater baroclinic instability or enhanced topographic lifting, e.g., along North America's west coast. Collectively, these findings demonstrate that the VKE framework provides a powerful diagnostic for how physical processes shape AR
evolution and regional variability.
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All authors Aidi Zhang, Da Yang, Hing Ong, Zhihong Tan
Optics · Cross-listed from quant-ph
Broadband Quantum Photon Source in Step-Chirped Periodically Poled Lithium Niobate Waveguide
Xiao-Xu Fang, Guoliang Shentu and He Lu
Broadband nonlinear optical devices play a critical role in both classical and
quantum optics. Here, we design and fabricate a 6.82-mm-long step-chirped periodically poled lithium niobate~(CPPLN) waveguide on lithium niobate on
insulator, which enables quasi-phase matching over a broad bandwidth for second-harmonic generation~(SHG) and spontaneous parametric down-conversion~(SPDC). The SHG achieves an average efficiency of 54.4%/W/cm$^2$ over the first-harmonic wavelength range of 1510~nm-1620~nm, paving the way for realizing SPDC across a wide range of pump wavelengths. For SPDC, by tuning the pump wavelength to 775~nm, 780~nm, and 785~nm, we achieve broadband
photon-pair generation with a maximum full bandwidth and brightness up to 99~THz~(846~nm) and 20~GHz/mW/nm, respectively. Our findings provide an efficient and experiment-friendly approach for generating broadband
photon pairs, which holds significant promise for advancing applications in
quantum metrology.
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Optics
Curving the Trajectory of Light in Refraction Index Gradients
Oliver Polachini and Fabricio Marques
This work seeks to present an investigation about the trajectories followed by rays of light passing through refractive index gradients that was entirely carried by high school students. Such trajectories are curved, therefore contradicting the common sense that light should always travel along straight lines. This fact causes the formation of distorted and striated images, similarly to a type of mirage known as Fata Morgana. Using a rectangular aquarium containing solutions with different gradients of sugar or water with a temperature gradient, we analyzed the conditions for image inversion to occur. Also, we were able to reconstruct a distorted image through our theoretical predictions.
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Atmospheric and Oceanic Physics
Atmospheric rivers and winter sea ice drive recent reversal in Antarctic ice mass loss
Marlen Kolbe, Jose Abraham Torres Alavez, Ruth Mottram et al. (+3 more)
Since about 2000, the total mass of the Antarctic Ice Sheet (AIS) has declined at a near-linear rate, increasing global sea levels. Since 2016, however, satellite gravimetry data reveal a slowdown in net AIS mass loss and a net mass gain since 2020, despite increases in dynamically-driven ice loss by discharge from outlet glaciers. Here we use a suite of reanalyses and regional
climate models to show that this reversal is caused by increased precipitation and positive surface mass balance anomalies linked to increased atmospheric river (AR) activity, strengthening westerlies, and loss of sea ice. ARs have become more frequent and intense since 2020, particularly over the Antarctic Peninsula, Queen Maud Land, and Wilkes Land, resulting in strong regional positive mass balance anomalies. High-resolution regional
climate model simulations with modified sea ice extent show that the effect of sea ice on enhancing precipitation through increased evaporation accounts for around 10% of the winter increase, but is overall minor compared to remote large-scale processes. Combined, these factors result in accumulation increases that currently offset the mass loss from accelerated ice discharge in Antarctica and point to processes important for future projections.
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All authors Marlen Kolbe, Jose Abraham Torres Alavez, Ruth Mottram, Marwan Katurji, Richard Bintanja, Eveline C. van der Linden
Medical Physics
Human brain high-resolution diffusion MRI with optimized slice-by-slice B0 field shimming in head-only high-performance gradient MRI systems
Patricia Lan, Sherry S. Huang, Chitresh Bhushan et al. (+6 more)
The purpose of this study is to propose a
brain tissue-selective, optimized slice-by-slice B0 field shimming for high-resolution
brain diffusion MRI. We incorporated actual gradient fields of X, Y, and Z gradient coils in the calculation of the shimming coefficients in dynamic slice-by-slice B0 field shimming to minimize B0 field inhomogeneity (i.e., Delta B0) in deep-learning segmented
brain tissues.
Diffusion MRI with oscillating gradient
spin echo (OGSE) at 55 Hz and pulsed gradient
spin echo (PGSE) (approximated at 0 Hz) were obtained in phantoms and healthy volunteers using a head-only high-performance gradient 3T MRI system. In each
diffusion MRI acquisition, standard static volumetric shimming and the proposed shimming method were applied separately, and mean/axial/radial diffusivities (MD/AD/RD) and fractional anisotropy (FA) were estimated. In phantom, the root-mean-square of Delta B0 in areas with high gradient nonlinearity was reduced by 7 Hz when incorporating actual gradient field in dynamic shimming. Compared to static shimming, dynamic shimming reduced root-mean-square of voxel displacement of each slice by a maximum of 5-10 voxels in single-shot EPI acquisition at 1-2 mm in-plane resolution in phantom, and a maximum of 3 voxels in human
brains. Improved accuracy of MD/AD/RD/FA in the superior region of the
brain, brainstem, and cerebellum were observed by applying dynamic shimming and/or two-shot EPI acquisition. MD(55 Hz)-MD(0 Hz) showed higher values in T2 FSE hypo-intensity region by applying dynamic shimming. We concluded that
diffusion MRI with
brain tissue-selective, dynamic slice-by-slice B0 effectively improves the accuracy of diffusivity characterization in high-resolution images.
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All authors Patricia Lan, Sherry S. Huang, Chitresh Bhushan, Xinzeng Wang, Seung-Kyun Lee, Raymond Y. Huang, Jerome J. Maller, Jennifer A. McNab, Ante Zhu
Optics
Reversing Annealing-Induced Optical Loss in Diamond Microcavities
Vinaya K. Kavatamane, Natalia C. Carvalho, Ahmas El-Hamamsy et al. (+2 more)
A key challenge for
quantum photonic technologies based on
spin qubits is the creation of optically active defects in photonic resonators. Several of the most promising defects for
quantum applications are hosted in diamond, and are commonly created through ion implantation and annealing at high temperatures and high
vacuum. However, the impact of annealing on photonic resonator quality factor, a critical parameter governing their coupling to defects, has not been reported. In this work, we characterize the effect of annealing at temperatures >1200{\deg}C in high
vacuum on the quality factors of diamond microdisk resonators. We investigate the optical losses associated with a non-diamond layer formed during annealing, and use Raman spectroscopy to analyze the resonator surface morphology and demonstrate that tri-acid cleaning can restore their optical quality factors. These results show the viability of creating defects in pre-fabricated diamond resonators without degrading their optical properties.
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All authors Vinaya K. Kavatamane, Natalia C. Carvalho, Ahmas El-Hamamsy, Elham Zohari, Paul E. Barclay
Atmospheric and Oceanic Physics
Deep learning the sources of MJO predictability: a spectral view of learned features
Lin Yao, Da Yang, James P.C. Duncan et al. (+4 more)
The Madden-Julian oscillation (MJO) is a planetary-scale, intraseasonal tropical rainfall phenomenon crucial for global weather and
climate; however, its dynamics and predictability remain poorly understood. Here, we leverage deep learning (DL) to investigate the sources of MJO predictability, motivated by a central difference in MJO theories: which spatial scales are essential for driving the MJO? We first develop a deep convolutional neural network (DCNN) to forecast the MJO indices (RMM and ROMI). Our model predicts RMM and ROMI up to 21 and 33 days, respectively, achieving skills comparable to leading subseasonal-to-seasonal models such as NCEP. To identify the spatial scales most relevant for MJO
forecasting, we conduct spectral analysis of the latent feature space and find that large-scale patterns dominate the learned signals. Additional experiments show that models using only large-scale signals as the input have the same skills as those using all the scales, supporting the large-scale view of the MJO. Meanwhile, we find that small-scale signals remain informative: surprisingly, models using only small-scale input can still produce skillful forecasts up to 1-2 weeks ahead. We show that this is achieved by reconstructing the large-scale envelope of the small-scale activities, which aligns with the multi-scale view of the MJO. Altogether, our findings support that large-scale patterns–whether directly included or reconstructed–may be the primary source of MJO predictability.
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All authors Lin Yao, Da Yang, James P.C. Duncan, Ashesh Chattopadhyay, Pedram Hassanzadeh, Wahid Bhimji, Bin Yu