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f72fd93ef3d61661e12d76d28278cff9d34f05eb3172f21f47da240f149e88a3
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2026-01-13T00:00:00-05:00
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Co-doping of silicate bioceramics as a potential strategy to further enhance mono-doping consequences
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arXiv:2601.06099v1 Announce Type: new Abstract: Silicate bioceramics have attracted significant attention in medical applications, particularly in hard tissue regeneration, because of their controllable chemical, physical, and biological functionalities, while ensuring biocompatibility. The coordination of silicate bioceramics with mono-dopants has been extensively studied to enhance their osteogenesis, angiogenesis, and antibacterial activity. However, the concept of employing dual or multiple co-doping to further enhance these biomaterials still demands more attention. This review paper originally focuses on the effect of chemical interactions among co-dopants and the principal constituents of the silicates, on the bio-behavior of these bioceramics. Additionally, future prospects of co-doped silicate bioceramics are outlined, including in vivo studies, clinical trials, and potential commercialization.
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https://arxiv.org/abs/2601.06099
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Academic Papers
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96d216c8d58cddb9d2692fdc79631db992c32a70f51f3cd3cca72b4d77778617
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2026-01-13T00:00:00-05:00
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CR-39 track detector signatures of slow neutron like signals in Heavy-water electrolysis
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arXiv:2601.06155v1 Announce Type: new Abstract: We report reproducible track-detector signals consistent with slow neutron capture events, recorded in D$_2$O electrolysis involving D-Pd deposited on Pt cathode. Sensitivity to slow neutrons was achieved using boron-coated CR-39 (BCR) detectors, which register charged particle tracks arising from the $^{10}$B$(n,\alpha)^{7}$Li reaction. These detectors were positioned adjacent to identically prepared uncoated CR-39 control detectors (CCR), which are effectively insensitive to slow neutrons and serve to quantify background contributions from charged particles and fast neutrons under the present experimental conditions. A reproducible differential detector signature (BCR $>$ CCR) would thus indicative of slow neutron fluences. Across multiple independent D$_2$O electrolysis experiments in $0.25~\mathrm{T}$ field, the BCR exhibited significantly excess track signals relative to CCRs. Under these conditions, the observed differential response corresponds to an inferred detector-equivalent slow neutron flux of approximately $(6.7 \pm 0.2)~\mathrm{cm^{-2},s^{-1}}$. Removal of the magnetic field resulted in a reduction of the differential signal by a factor of $\sim6$, indicating a strong empirical dependence on the applied field. In contrast, H$_2$O electrolysis performed under otherwise identical conditions produced no measurable differential detector response, establishing the necessity of deuterated electrochemical conditions for the observed effect. The results are reported strictly as detector signatures consistent with slow neutron capture and do not assert any theoretical explanation. Instead, this work establishes a control verified and detector validated experimental protocol for detecting low flux slow neutrons, and provides empirical constraints relevant to slow neutron studies in experiments involving metal-deuteride systems.
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https://arxiv.org/abs/2601.06155
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Academic Papers
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57e149b581ee0d8a1c2a0a13fec926c2efbdcd22a9311f9608517e721af87aed
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2026-01-13T00:00:00-05:00
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Dynamics of Unemployment with Discouraged Workers: A Nonlinear Mathematical Model
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arXiv:2601.06184v1 Announce Type: new Abstract: In this article, we formulate and analyze a new non-linear mathematical model to describe the dynamics of unemployment with a discouraged working population. We consider five dynamic variables, namely, unskilled unemployed individuals, skilled unemployed individuals, discouraged individuals, employed persons, and job vacancies. Furthermore, we determine the equilibrium points of the dynamic system and investigate their local stability. To demonstrate the results, we conduct numerical simulations by presenting solution trajectories and analyzing how variations in key parameters influence the states of the dynamical variables.
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https://arxiv.org/abs/2601.06184
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Academic Papers
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39b8cd672faed908b37cdd5c55c339e7523f85d95d1a10b560714016680d1dc8
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2026-01-13T00:00:00-05:00
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Theoretical investigation of non-F\"{o}rster exciton transfer mechanisms in perylene diimide donor, phenylene bridge, and terrylene diimide acceptor systems
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arXiv:2601.06190v1 Announce Type: new Abstract: The rates of exciton transfer within dyads of perylene diimide and terrylene diimide connected by oligophenylene bridge units have been shown to deviate significantly from those of F\"{o}rster's resonance energy transfer theory, according to single molecule spectroscopy experiments. The present work provides a detailed computational and theoretical study investigating the source of such discrepancy. Electronic spectroscopy data are calculated by time-dependent density function theory and then compared with experimental results. Electronic couplings between exciton donor and acceptor are estimated based on both transition density cube method and transition dipole approximation. These results confirm that the delocalization of exciton to the bridge parts contribute to significant enhancement of donor-acceptor electronic coupling. Mechanistic details of exciton transfer are examined by estimating the contributions of the bridge electronic states, vibrational modes of the dyads commonly coupled to both donor and acceptor, inelastic resonance energy transfer mechanism, and dark exciton states. These analyses suggest that the contribution of common vibrational modes serves as the main source of deviation from F\"{o}rster's spectral overlap expression.
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https://arxiv.org/abs/2601.06190
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Academic Papers
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888e3c7d3fa69cbd8cc6b470c7fdd0657a2fb7316335a515388a950024cf5795
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2026-01-13T00:00:00-05:00
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Managing Situations of Complexity and Uncertainty : The Contribution of Research and Development
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arXiv:2601.06203v1 Announce Type: new Abstract: The second industrial revolution saw the development of management methods tailored to the challenges of the times: firstly, the need for mass production, and then, the pursuit of improved quality and customer satisfaction, followed by a push to improve operational performances in response to market globalization. If these approaches were initially inspired by rational mechanistic thinking, they have since gradually broadened to integrate other dimensions such as psychology, sociology and systemic analysis. Business enterprises underwent a profound rethink in the 1990s introducing increasingly refined modi operandi, only to find their environment disrupted by the appearance of two new parameters: complexity and uncertainty. Enterprises of the third industrial revolution were able to integrate these parameters at the outset, introducing new styles of management. However, these may well be deficient with regard to activities where an error may be fatal, or a failure intolerable. Caught between the precautionary principle and the principle of experimentation, the third industrial revolution falters to find the right approach, whereas the fourth industrial revolution is almost already upon us, bringing its lot of upheavals. In this regard, faced with increasing complexities and uncertainties, Research and Development is of particular interest since its vocation consists precisely in confronting the complex and the uncertain. This article examines the fundamental principles of the R&D process, and analyses how these may act as a benchmark for contemporary management by providing sources of inspiration.
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https://arxiv.org/abs/2601.06203
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Academic Papers
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44b4a8206e9466d144e4b43183c1560d493772a9cec3290ba8358ad3d429d73d
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2026-01-13T00:00:00-05:00
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Reliability is a new science: we are on the right way
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arXiv:2601.06206v1 Announce Type: new Abstract: Reliability has long been treated as an engineering practice supported by testing, statistics and standards, yet its status as a scientific discipline remains unsettled. From a philosophical perspective, scientific truth is characterized by a dual-structure that links empirical truth and mathematical truth, which requires an axiomatic system that is symbolically expressible and verifiable by universally repeatable controlled experiments. Building on this criterion, this paper examines whether reliability satisfies the dual-structure of scientific truth. Firstly, we analyze the philosophical foundations of the reliability problem, tracing its transition from experiential confidence and engineering practice toward scientific inquiry. Then, reliability science principles are introduced as an axiomatic system consisting of margin, degradation and uncertainty, which define reliability as the repeatability of system performance across time and space. Next, we present reliability science experiments as the empirical aspect of the dual-structure, where controlled and repeatable interventions are designed to verify the causal relations implied by the axioms. Furthermore, we develop the mathematical framework of reliability as the symbolic aspect of the dual-structure, articulating reliability laws through distance, relation and change, and developing a time-dependent measure, Biandong Statistics, to represent varying uncertainty beyond static descriptions. Accordingly, we argue that reliability is indeed a scientific discipline. The applicability of reliability science is demonstrated across engineering, living and social systems, and a unified logic for guiding engineering activities across the entire product lifecycle is provided, linking reliability to the conceptual, development, procurement, production and operation phases within a model-based structure.
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https://arxiv.org/abs/2601.06206
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Academic Papers
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6763952b2bcc65c717fb6b2de15b1920e3d4adeee2a705ffcd65e7de5c5e6fd4
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2026-01-13T00:00:00-05:00
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Improving TauFinder Reconstruction at a 10 TeV Muon Collider with the MAIA Detector Concept
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arXiv:2601.06215v1 Announce Type: new Abstract: This study aims to improve the TauFinder reconstruction algorithm for the MAIA detector concept. Through this work, we seek to increase the reconstruction efficiency and identification of hadronically decaying tau leptons. Through our work, we introduce a dynamic signal cone, known as a shrinking cone, which adjusts its size based on the transverse momentum of the tau candidate. In addition to the already studied one charged hadron and three charged hadron decay modes we extend TauFinder to include decays that consist of one charged hadron and up to two neutral pions. Furthermore, we have developed a tagger that prevents electrons being misidentified as one-prong tau candidates. Applying this tagger results in near-perfect electron rejection with negligible decrease in one-prong tau reconstruction efficiency.
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https://arxiv.org/abs/2601.06215
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8da8f24f4f57fd1d4a7cfa1f2ed325f1009a6136dc3b43cfea06fa797787ccda
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2026-01-13T00:00:00-05:00
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Introducing the Physics of Complex Systems through Videogames
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arXiv:2601.06230v1 Announce Type: new Abstract: The purpose of this work is to explore a teaching methodology aimed at communicating topics and subjects not typically studied and analyzed in the (Italian) secondary school. We focused specifically on the use of videogames as a recreational and educational tool, grounding our approach in a broadened conceptual view in which engagement and attentional allocation interact with motivational and affective components of play. Within this perspective, the playful format is considered not only to enhance motivation and enjoyment, but also to attenuate learners' counter-arguing tendencies when confronted with unfamiliar or abstract material. Building on this framework, we developed or adapted several videogames whose central scientific topics are phase transitions, sensitivity to initial conditions, and synchronization. We had a certain number of high school students playing the games, and we asked them several questions to guide them and determine whether the communication was successful. At the end of the activity, we administered a questionnaire about the enjoyment and the difficulties encountered in each game, and the relevant critics.
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https://arxiv.org/abs/2601.06230
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Academic Papers
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36e67d425cdb927ce2c5b2819166ff18819a48ea32d33662f54ae64581e30b34
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2026-01-13T00:00:00-05:00
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Crossing the Functional Desert: Critical Cascades and a Feasibility Transition for the Emergence of Life
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arXiv:2601.06272v1 Announce Type: new Abstract: The origin of life poses a problem of combinatorial feasibility: How can persistent functional organization arise in exponentially branching assembly spaces when unguided exploration behaves as a memoryless random walk? We show that nonlinear threshold-cascade dynamics in connected interaction networks provide a minimal, substrate-agnostic mechanism that can soften this obstruction. Below a critical connectivity threshold, cascades die out locally and structured input-output response mappings remain sparse and transient-a "functional desert" in which accumulation is dynamically unsupported. Near the critical percolation threshold, system-spanning cascades emerge, enabling persistent and discriminative functional responses. We illustrate this transition using a minimal toy model and generalize the argument to arbitrary networked systems. Also near criticality, cascades introduce structural and functional persistence, directional bias, and weak dynamical path-dependence into otherwise memoryless exploration, allowing biased accumulation over short coherence timescales. This connectivity-driven transition-functional percolation-requires only generic ingredients: interacting units, nonlinear thresholds, influence transmission, and non-zero coherence times. The mechanism does not explain specific biochemical pathways, but it identifies a necessary dynamical regime in which structured functional organization can emerge and persist, providing a physical foundation for how combinatorial feasibility barriers can be crossed through network dynamics alone.
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https://arxiv.org/abs/2601.06272
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Academic Papers
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0b132107018f10ef2df49aaeb7c9bab55faa7d271c47890ce8a7d0af5daa523e
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2026-01-13T00:00:00-05:00
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Building blocks of topological band theory for photonic crystals
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arXiv:2601.06293v1 Announce Type: new Abstract: We derive a framework for classifying topological bands in three-dimensional photonic band structures, where the zero frequency polarization singularity implied by Maxwell's equations complicates the direct application of existing symmetry-based approaches. Building on recent advances in the regularization of photonic bands, we use the recently introduced concept of stable real-space invariants (SRSIs) to show how photonic band structures can be unambiguously characterized in terms of equivalence classes of band representations. We classify topologically trivial photonic bands using SRSIs, treating them as the fundamental building blocks of 3D photonic band structures. This means that if certain bands cannot be constructed from these building blocks, they are necessarily topological. Furthermore, we distinguish between photonic and electronic band structures by analyzing which SRSI values are allowed in systems with and without polarization singularity. We also explore the impact of the polarization singularity on the behavior of Wilson loops, providing new insights into the topological classification of 3D photonic systems.
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https://arxiv.org/abs/2601.06293
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76ed8e5b5802bf94ef1f9eca5d913fcdf48b5d69ce9c921d7441c3e08309c8cd
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2026-01-13T00:00:00-05:00
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Localization of sources in weakly nonlinear fluid systems using linear and quadratic sensitivity analysis
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arXiv:2601.06304v1 Announce Type: new Abstract: We develop a framework for localized source detection in dynamical systems governed by nonlinear partial differential equations based on first and second-order sensitivity analysis. Building on the standard adjoint formulation, which relates multiple measurements to external sources through a linear duality relation, we first introduce a linear positional embedding that identifies the source location by aligning the measurement vector with the embedding. To capture weakly nonlinear effects that arise when the source intensity is finite, we then incorporate a quadratic correction represented as a symmetric bilinear operator and approximated via a truncated eigen-expansion obtained with Krylov subspace iterations. This yields quadratic positional embeddings that augment the linear adjoint field, enabling measurement data to be projected onto a higher-dimensional hyperplane, spanned by the linear and quadratic embeddings. A source search algorithm is formulated based on principal angle minimization between this hyperplane and the observation vector, providing a natural probabilistic interpretation of source location. The method operates in a one-shot fashion without iterative updates of candidate source positions, and it can be readily extended to scenarios involving multiple sources. Demonstrations on benchmark inverse problems include perturbation-source identification in the viscous Burgers equation and heat-source detection in a two-dimensional laminar stratified channel. The results with quadratic embeddings show significant improvements in localization accuracy compared with linear adjoint-based sensitivity methods, especially in the region where linear adjoint sensitivity vanishes.
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https://arxiv.org/abs/2601.06304
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0ab93927131afa8230afcab80a86085c89096c9cf8260b734830320c2530ab7d
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2026-01-13T00:00:00-05:00
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Creation and precise spectroscopy of $^{86}$Sr$_2$ halo molecules
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arXiv:2601.06319v1 Announce Type: new Abstract: We report on the creation of $^{86}$Sr$_2$ molecules in the halo state and neighboring weakly bound states. Efficient molecule production via one-photon photoassociation relies on sufficient wavefunction overlap between the target vibrational states in the electronic excited- and ground-state potentials. Using Autler-Townes spectroscopy, transition strengths are measured to identify optimal pathways for production of weakly bound molecules. Vibrational splittings for the three least-bound vibrational states are measured, and dominant systematic uncertainties are evaluated with uncertainties below 100 Hz. From these splittings, absolute binding energies for these weakly bound vibrational states are determined. The results pave the way to a molecular isotope shift measurement with Sr$_2$.
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https://arxiv.org/abs/2601.06319
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4df38e94551b463c700916e5607ed02c1a41dcadb68b3110edb65dbf406a2169
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2026-01-13T00:00:00-05:00
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Hierarchical metamaterials with tunable flat bands, zero-frequency, and wavenumber gaps
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arXiv:2601.06323v1 Announce Type: new Abstract: Metamaterials are arrangement of basic building blocks that repeat in space, time, or both. These material systems serve as an excellent platform for controlling waves, such as engineering wavenumber band gaps, flat bands, and zero-frequency band gaps. However, combining one or more of these exotic features within the same unit cell design remains a challenge. Moreover, once a metamaterial is realized, its dispersive properties are usually fixed. In this work, we present a tunable passive hierarchical metamaterial capable of exhibiting wavenumber band gaps, flat bands, and zero-frequency band gaps within the same dispersion curve. Our metamaterial is composed of magnetic elements confined within a fixed magnetic boundary. The metamaterial can be tuned by adjusting the magnetic boundary, which in turn can alter the lattice periodicity. We open wavenumber band gaps by incorporating magnetic coupling within the unit cell elements, resulting in negative physical stiffness. The tunability of the magnetic coupling also enables complete flattening of the dispersion bands. Moreover, the ground stiffness within our unit-cell design causes the opening of zero-frequency band gaps. We present our approach through a combination of analytical, numerical, and experimental methods. The analytical framework provides a blueprint for obtaining each of these exotic dispersion characteristics. The numerical analysis, using both linear and nonlinear models, validates our analytical predictions, which we further confirm through experimental demonstrations. Our work opens the door to exploring magnetic tunability and hierarchy in engineering metamaterial systems with exotic properties that can be harnessed in advanced acoustic and mechanical devices.
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https://arxiv.org/abs/2601.06323
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Academic Papers
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a3f2cb5bb4fe1eef0f01adce0abd641db6707bc032ab3a82793967443c232e2d
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2026-01-13T00:00:00-05:00
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Simulation package for solving dynamic diffraction problems in deformed crystals. Bragg, Laue geometry, asymmetric reflections, bend crystals, dislocations, crystals with arbitrary shapes, strain distributions and time dependent problems
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arXiv:2601.06340v1 Announce Type: new Abstract: We demonstrate the use of the Fast Fourier Transform Beam Propagation Method (FFT BPM) to simulate dynamic diffraction effects, including scattering from deformed crystals with arbitrary shapes in Bragg, Laue, and asymmetric geometries. The method's straightforward algorithm, combined with FFT, enables fast computation and is easy to implement in Python. It successfully reproduces literature results for bent crystals, dislocations, and finite-shaped crystals simulated using the Takagi-Taupin equations. Python implementations for each case are provided in a public GitHub repository, with the code structured for parallel computing.
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https://arxiv.org/abs/2601.06340
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Academic Papers
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e37e811d2efb149dc7dd1e9c6c9e5b3cf056dd5c13023b4400d9b40f3c8e2140
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2026-01-13T00:00:00-05:00
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Controlling Rydberg atom-polariton interactions: from exceptional points to fast readout
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arXiv:2601.06345v1 Announce Type: new Abstract: Rydberg atoms represent a platform underpinning many recent developments in quantum computation, simulation, sensing, and metrology. They further facilitate optical nonlinearity at the single-photon level when coupled to photons propagating in atomic clouds, which form collective atomic excitations called Rydberg polaritons, strongly interacting with each other. Here, we experimentally explore interactions between a Rydberg polariton in an atomic ensemble and a single, adjacent, Rydberg atom. We discover three different regimes of quantum dynamics corresponding to polariton blockade, coherent exchange, and probabilistic hopping, which are defined by their distinct transmission characteristics, with a transition through an exceptional point occurring between blockade and coherent exchange. We investigate the applications of such interactions for fast, non-destructive detection of Rydberg atoms and present proof-of-principle demonstrations for their potential application in nonlinear photonic networks.
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https://arxiv.org/abs/2601.06345
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b0e388c109885cfe24cd6a38fa5fabb98739ca77fdcb81ccae8e824c6a4c076f
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2026-01-13T00:00:00-05:00
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Scaling of Rainfall Intensity and Frequency with Rising Temperatures
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arXiv:2601.06408v1 Announce Type: new Abstract: Global warming is projected to intensify the hydrological cycle, amplifying risks to ecosystems and society. While extreme rainfall appears to exhibit stronger sensitivity to global warming compared to mean rainfall rates, a unifying physical mechanism capable of explaining this systematic divergence has remained elusive. Here, we integrate theory and data from a global network of nearly 50,000 rain-gauge stations to unravel the rainfall intensity and frequency response to rising temperatures. We show that the distributions of wet-day rainfall depth exhibit self-similar shapes across diverse geographical regions and time periods. Combined with the temperature response of rainfall frequency, this consistently links mean and extreme precipitation at both local and global scales. We find that the most probable change in rainfall intensity follows Clausius-Clapeyron (CC) scaling with variations shaped by a fundamental hydrological constraint. This behavior reflects a dynamic intensification of updrafts in space and time, which produces localized heavy precipitation events enhancing atmospheric moisture depletion and hydrologic losses through runoff and percolation. The resulting reduction in evaporative fluxes slows the replenishment of atmospheric moisture, giving rise to the observed trade-off between rainfall frequency and intensity. These robust scaling laws for rainfall shifts with temperature are essential for climate projection and adaptation planning.
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https://arxiv.org/abs/2601.06408
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Academic Papers
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d37ad9a497de3dc6e07be1cf2554ab2f4072506e56fecc05c9460afe86c68875
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2026-01-13T00:00:00-05:00
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Slowdown and saturation of internal time according to the statistics of information input: a minimal model of response systems
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arXiv:2601.06433v1 Announce Type: new Abstract: We consider a response system that updates its internal state in accordance with information input arriving from outside. In this paper, we define as internal time the ``number of kinds'' of codes that have been observed at least once up to a given time, and analyze how the way internal time advances is determined by the statistics of information input (arrival rate and code distribution). When arrivals follow a Poisson process, the average advancing speed of internal time decreases monotonically with time, and if the number of kinds of codes is finite, it eventually approaches an upper limit and saturates. As a result, on long time scales, internal time becomes relatively shorter than physical time. For a uniform code distribution, we provide a closed form for the correspondence between internal time and physical time, and show that the physical time required to ``advance internal time by one step'' increases in later stages. As an ancillary quantity, we quantify by conditional entropy the remaining uncertainty of ``which codes have been observed'' when only internal time is known, and we give unimodality and the maximization time in the uniform case, and upper bounds, equality conditions, and expressions of the difference from the upper bound in the non-uniform case. Finally, we also present a generalization that assigns weights (description lengths) to each code so that internal time is ticked according to the amount of information in the input.
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https://arxiv.org/abs/2601.06433
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Academic Papers
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e2e8e2b8485737de092702151df352bb0b4db852d260c9be7254e5be28ef54d5
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2026-01-13T00:00:00-05:00
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Physics-guided foundation model for universal speckle removal in ultrathin multimode fiber imaging
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arXiv:2601.06448v1 Announce Type: new Abstract: Ultrathin multimode fibers (MMFs) promise endoscopes with hair-scale diameters for accessing sub-millimeter anatomy, but in MMF far-field imaging the required small collection aperture drives speckle-dominated measurements that rapidly degrade image fidelity. Here we present Speckle Clean Network (SCNet), a physics-guided foundation model for universal speckle removal that makes photon-limited, single-fiber collection compatible with high-fidelity reconstruction across diverse scattering conditions without target-specific retraining. SCNet combines a Mixture of Experts (MoE) architecture with material-aware routing, wavelet-based frequency decomposition to separate structure from speckle across sub-bands, and a curriculum-style optimization that progressively enforces spectral consistency before spatial fidelity. Using an ultrathin dual-fiber holographic probe, we deliver wavefront-shaped illumination through one s and collect backscattered photons through a parallel MMF. We validate SCNet on 3D plastic objects over varying working distances, resolve 5.66 lp/mm on a paper USAF target, and restore fine structures on leaves and metal surfaces. On rabbit heart and kidney tissues, SCNet improves recovery of low-contrast anatomical texture under the same ultrathin collection constraint. We further compress SCNet through multi-teacher distillation to reduce computation while preserving reconstruction quality, enabling inference at 60 FPS. This work effectively decouples image quality from probe size, establishing a speckle-free ultrathin endoscopy for stand-off imaging in confined spaces.
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https://arxiv.org/abs/2601.06448
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e2a3ec2f7db2dc9a0916e02035a05a0bd70a6b209c2a65666062d60bf57cfb41
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2026-01-13T00:00:00-05:00
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Optimized Broadband Cryogenic Ferromagnetic Resonance Spectrometer using a Closed Cycle Refrigerator
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arXiv:2601.06449v1 Announce Type: new Abstract: We present a vector network analyzer (VNA) based broadband cryogenic ferromagnetic resonance (FMR) spectrometer, operating up to 20 GHz over a temperature range of 11 to 350 K. A cost effective architecture is implemented through the integration of a closed cycle refrigerator (CCR) and a custom fabricated grounded coplanar waveguide (GCPW), designed for broadband transmission and reliable cryogenic operation. The VNA calibration is performed prior to measurements to account for microwave background and transmission losses, enabling reliable extraction of FMR spectra across the full temperature / frequency range. The sensitivity of the spectrometer is benchmarked using a yttrium iron garnet (YIG) thin film, yielding well resolved resonances with narrow linewidths and high sensitivity.
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https://arxiv.org/abs/2601.06449
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9a003804aef490ac7daae38cf4a055c2c294817808a081e299bfe3de96a2d892
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2026-01-13T00:00:00-05:00
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A High-Speed CGH Calculation Method for Mirror Images on B\'ezier Surfaces using Optical Path Length Minimization
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arXiv:2601.06459v1 Announce Type: new Abstract: Rendering reflections in curved mirrors is crucial for enhancing the realism in computer-generated hologram (CGH), yet it poses a fundamental challenge due to the unique computational principles of CGH. Conventional methods using B\'ezier clipping are computationally prohibitive, and a previously proposed mirror surface subdivision method suffered from the computation time increasing with mirror curvature. To address these limitations, this paper proposes a novel calculation method based on Fermat's principle that directly and efficiently determines the reflection point by minimizing the optical path length from a point light source to a hologram pixel via the mirror surface, using Newton's method for optimization. Experimental results demonstrate that this method significantly reduces computation time compared to previous approaches. Furthermore, it enables the rendering of multiple reflections from several mirrors, a capability that was challenging for conventional techniques.
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https://arxiv.org/abs/2601.06459
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553f91b05122d6532d2f9ee0f57d1642cc1e7477ae1d85b443be67ee9f0e2eeb
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2026-01-13T00:00:00-05:00
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Spectral Distribution of one-dimensional Photonic Quasicrystals: The Role of Irrational Numbers
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arXiv:2601.06482v1 Announce Type: new Abstract: In this paper, we construct a one-dimensional photonic quasicrystal by combining two incommensurate spatial harmonics, where the ratio of their periods is the irrational number \beta. We evaluate the photonic quasicrystal accurately by a generalized spectral method that embeds the quasiperiodic structure into a higher-dimensional periodic system. We study the spectral distribution of one-dimensional photonic quasicrystals and find some interesting phenomena. As the computational resolution N increases, there are more eigenvalues within finite frequency bandwidths, and the maximum localization always occurs at spectral gap edges for states near index N + 1. By varying \beta within the range of (0,1), we present a butterfly-shaped spectral structure with abundant band gaps. We find that the spectral structure factor Q (defined as I_{mg}/N, where I_{mg} is the maximum gap index) exhibits different linear patterns as \beta changes: Q = 1 - \beta when \beta \beta c, where \beta c \approx 0.424 is the transition point. This linear relationship holds robustly in the strong quasiperiodic regime (\beta away from 0 or 1) and is independent of the specific type of irrational number used. The relationship disappears (weak quasiperiodic regime) near \beta = 0 or \beta = 1. It demonstrates that the intrinsic spectral properties of one-dimensional photonic quasicrystals are fundamentally governed by the magnitude of the irrational parameter \beta.
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https://arxiv.org/abs/2601.06482
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7b3b3307ae3a38f28d7b867954afd382a0c2d66a7b24843863462b09bdfdf6e1
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2026-01-13T00:00:00-05:00
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Constellation: The Autonomous Control and Data Acquisition System for Dynamic Experimental Setups
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arXiv:2601.06494v1 Announce Type: new Abstract: The operation of instruments and detectors in laboratory or beamline environments presents a complex challenge, requiring stable operation of multiple concurrent devices, often controlled by separate hardware and software solutions. These environments frequently undergo modifications, such as the inclusion of different auxiliary devices depending on the experiment or facility, adding further complexity. The successful management of such dynamic configurations demands a flexible and robust system capable of controlling data acquisition, monitoring experimental setups, enabling seamless reconfiguration, and integrating new devices with limited effort. This paper presents Constellation, a flexible and network-distributed control and data acquisition software framework tailored to laboratory and beamline environments, that addresses the limitations of existing solutions. The framework is designed with a focus on extensibility, providing a streamlined interface for instrument integration. It supports efficient system setup via network discovery mechanisms, promotes stability through autonomous operational features, and provides comprehensive documentation and supporting tools for operators and application developers such as controllers and logging interfaces. At the core of the architectural design is the autonomy of the individual components, called satellites, which can make independent decisions about their operation and communicate these decisions to other components. This paper introduces the design principles and framework architecture of Constellation, presents the available graphical user interfaces, shares insights from initial successful deployments, and provides an outlook on future developments and applications.
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https://arxiv.org/abs/2601.06494
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4cbe6447b060d6f8b26cec28c76fa0f5e0ead775cd42989e859f79487454b123
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2026-01-13T00:00:00-05:00
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A Response to "Application of Gauss's Principle to the Classical Airfoil Lift Problem"
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arXiv:2601.06495v1 Announce Type: new Abstract: The classical theory of lift is confined to sharp edged airfoils. The search for a more general closure condition in potential flow remained elusive for over a century. Recently, a variational theory of lift, inspired by Gauss's principle of least constraint, was proposed as a remedy. The theory was shown to recover the Kutta condition as a special case for sharp-edged airfoils. However, recent criticism of the variational theory has asserted fundamental issues and discontinuities in its predictions. The present paper demonstrates that these assertions are incorrect and arise from inconsistencies with basic principles of analytical mechanics, the calculus of variations, and ideal-flow aerodynamics, as well as from misapplications of the variational theory itself. To resolve such misunderstandings, we review foundational concepts from analytical mechanics, including least action, Gauss's principle, and Hertz's principle; the definitions of impressed and constraint forces; and the distinction between actual work and virtual work. We then place these concepts in the context of incompressible fluid mechanics, utilizing the geometric interpretation of Helmholtz decomposition. In particular, we demonstrate that, for incompressible flows subject to the no-penetration boundary condition, the pressure force is orthogonal to the entire space of kinematically admissible flows and therefore performs no virtual work. The pressure force, thus, acts as the constraint force required to ensure the continuity constraint. From an aerodynamic perspective, we show that the classical and variational theories of lift, as well as any theory based on steady, irrotational motion, are necessarily reversible and therefore inapplicable to reversed-flow configurations.
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https://arxiv.org/abs/2601.06495
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Academic Papers
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4a13deaeb57c4d25006a45bec1bf50c1c9df6102c8c84674547855ee41d14fe4
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2026-01-13T00:00:00-05:00
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Rapid Prediction of Three-Dimensional Scour Flow around Bridge Piers via Body-Fitted Coordinate-Based U-Net
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arXiv:2601.06506v1 Announce Type: new Abstract: Predicting three-dimensional (3D) turbulent flows around bridge piers is a prerequisite for assessing local scour, a primary cause of infrastructure failure. While Computational Fluid Dynamics (CFD) captures complex flow features - such as horseshoe vortices - its high cost hinders real-time risk assessment. This study presents a physics-aware deep learning surrogate using a Body-Fitted Coordinate (BFC) system, BFC-UNet, designed to rapidly reconstruct 3D Reynolds-Averaged Navier-Stokes (RANS) solutions on curved domains. Unlike voxel-based Convolutional Neural Networks (CNNs) prone to staircase errors, the proposed architecture leverages a BFC system to predict the bed shear stress accurately. By transforming the physical O-grid into a canonical computational space, the model preserves the geometric integrity of the no-slip boundary. Trained on 2,304 simulations parameterized by inlet velocity and scour depth, BFC-UNet predicts velocity, pressure, and bed shear stress distributions with an R2 value of > 0.98. It infers a full 3D domain (200,000 cells) in just 8 milliseconds on a single Graphics Processing Unit (GPU) - achieving a speed-up of five orders of magnitude over the CFD solver. Crucially, the model captures the topological evolution of vortex structures, including wake expansion and diving flows. These findings position BFC-UNet as a promising foundation for real-time digital twins, bridging rigorous fluid mechanics with data-driven efficiency.
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https://arxiv.org/abs/2601.06506
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Academic Papers
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6e3691b1f637b6ba2a48e17a8fe6f5c0203481df87c6c02354f1a6729788065e
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2026-01-13T00:00:00-05:00
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Transition from classical to ultimate melting
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arXiv:2601.06517v1 Announce Type: new Abstract: Melting is omnipresent in nature and technology, with applications ranging from metallurgy, biology, food science, and latent thermal energy storage to oceanography, geophysics, and climate science, and occurring on all scales from sub-millimeter to global scales. The key objective is to understand the rate at which an object melts as a function of its size and of the ambient conditions. To achieve this it is important to be able to extrapolate from small scale experiments and observations to large or even global scales. This is done by scaling laws. However, these are only meaningful if there is no transition from one scaling relation to another one. Here we show, however, that for both fixed and freely-advected melting objects immersed in a turbulent flow a melting transition does exist, namely from slow melting at the small scales to fast melting at the large scales. We do so by controlled melting experiments and corresponding direct numerical simulations, covering four orders of magnitude in scale. The transition corresponds to the transition from a laminar-type boundary layer around the melting object to a turbulent-type boundary layer, i.e., from so-called classical turbulence to ultimate turbulence, with its enhanced transport properties. Our results thus provide a quantitative understanding of the flow physics of the melting process and thereby enable a better extrapolation and prediction of melt rates on large scales such as relevant in geophysics, oceanography, and climate science.
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https://arxiv.org/abs/2601.06517
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Academic Papers
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2e83b03bd4750aba3b94f88c196f70cce6465acd674d82a30fc7e7c62794b5e7
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2026-01-13T00:00:00-05:00
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Unsteady flow predictions around an obstacle using Geometry-Parameterized Dual-Encoder Physics-Informed Neural Network
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arXiv:2601.06561v1 Announce Type: new Abstract: Machine learning-based flow field prediction is emerging as a promising alternative to traditional Computational Fluid Dynamics, offering significant computational efficiency advantage. In this work, we propose the Geometry-Parameterized Dual-Encoder Physics-Informed Neural Network (GP-DE-PINN) with a dual-encoder architecture for effective prediction of unsteady flow fields around parameterized geometries. This framework integrates a geometric parameter encoder to map low-dimensional shape parameters to high-dimensional latent features, coupled with a spatiotemporal coordinate encoder, and is trained under the Navier-Stokes equation constraints. Using 2D unsteady flow past petal-shaped cylinders as an example, we evaluate the model's reconstruction performance, generalization capability, and hyperparameter sensitivity. Results demonstrate that the GP-DE-PINN significantly outperforms the PINN with direct geometric input in flow field reconstruction, accurately capturing vortex shedding structures and pressure evolution, while exhibiting superior generalization accuracy on unseen geometric configurations. Furthermore, sensitivity analyses regarding geometric sampling and network width reveal the model's robustness to these hyperparameter variations. These findings illustrate that the proposed framework can serve as a robust and promising framework for predicting unsteady flows around complex geometric obstacles.
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https://arxiv.org/abs/2601.06561
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Academic Papers
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a47cf3e65a1c628176c23926304b0e9d8613b8327169cc0e45e2df6d0f3f6f0c
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2026-01-13T00:00:00-05:00
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Spontaneous Brillouin Scattering in a Few-Mode Optical Fiber
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arXiv:2601.06569v1 Announce Type: new Abstract: We report a comprehensive experimental study of spontaneous Brillouin scattering in a few-mode optical fiber, resolving both forward and backward scattering processes for intra- and inter-modal interactions. Using heterodyne detection, Stokes and anti-Stokes components without external acoustic excitation are observed and quantitatively extracted Brillouin shifts, linewidths, and gain coefficients. Forward scattering is mediated by guided torsional-radial acoustic modes with frequencies ranging from MHz to GHz, while backward scattering involves longitudinal core-guided modes at frequencies of tens of GHz. These results provide calibrated benchmarks for Brillouin interactions in few-mode fibers, offering insights relevant to phonon-based quantum applications and mode-selective optomechanics.
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https://arxiv.org/abs/2601.06569
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Academic Papers
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4cd9edf7a57c8c0442a741d59a3a85d2574d848a8c81581bf0e588fb99c9a99c
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2026-01-13T00:00:00-05:00
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Non-volatile Programmable Photonic Integrated Circuits using Mechanically Latched MEMS: A System-Level Scheme Enabling Power-Connection-Free Operation Without Performance Compromise
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arXiv:2601.06578v1 Announce Type: new Abstract: Programmable photonic integrated circuits (PPICs) offer a versatile platform for implementing diverse optical functions on a generic hardware mesh. However, the scalability of PPICs faces critical power consumption barriers. Therefore, we propose a novel non-volatile PPIC architecture utilizing MEMS with mechanical latching, enabling stable passive operation without any power connection once configured. To ensure practical applicability, we present a system-level solution including both this hardware innovation and an accompanying automatic error-resilient configuration algorithm. The algorithm compensates for the lack of continuous tunability inherent in the non-volatile hardware design, thereby enabling such new operational paradigm without compromising performance, and also ensuring robustness against fabrication errors. Functional simulations were performed to validate the proposed scheme by configuring five distinct functionalities of varying complexity, including a Mach-Zehnder interferometer (MZI), a MZI lattice filter, a ring resonator (ORR), a double ORR ring-loaded MZI, and a triple ORR coupled resonator waveguide filter. The results demonstrate that our non-volatile scheme achieves performance equivalent to conventional PPICs. Robustness analysis was also conducted, and the results demonstrated that our scheme exhibits strong robustness against various fabrication errors. Furthermore, we explored the trade-off between the hardware design complexity of such non-volatile scheme and its performance. This study establishes a viable pathway to a new generation of power-connection-free PPICs, providing a practical and scalable solution for future photonic systems.
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https://arxiv.org/abs/2601.06578
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Academic Papers
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44325c5216baf92d037ebefaa54f1574c8fefe2988de25266eecb9b7a8573fda
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2026-01-13T00:00:00-05:00
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Transfer of Orbital Angular Momentum in Vortex Light through Four-Wave Mixing and the Manipulation of Slow and Fast Light
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arXiv:2601.06579v1 Announce Type: new Abstract: Vortex light, a unique optical field that carries orbital angular momentum (OAM), has attracted considerable attention in recent years. In this paper, we present a detailed theoretical analysis of OAM transfer from the input field to the generated signal field in a four-level double-Lambda system via the four-wave mixing (FWM) process, showing that their OAMs follow a specific algebraic relationship. We identify the optimal conditions for efficient vortex light transmission, analyze the influence of detuning on transmission efficiency and phase distortion, and specifically examine the scenario where the control field carries OAM the latter being essential for a complete characterization of OAM conservation in the FWM process, while all three aspects have been largely overlooked in the existing literature. Furthermore, we investigated the tunability of the group velocity between the probe and signal fields by modulating the Rabi frequencies of the two control fields and the relative phase between the probe and signal fields during the FWM process. We demonstrate that the conversion between matched vortex slow and fast light can be realized an effect that has not been widely explored in dual-Lambda-type systems. These results may hold promise for applications in quantum information storage and processing, quantum computing, and ultrasensitive detection.
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https://arxiv.org/abs/2601.06579
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Academic Papers
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1495fad92aaba9a9673cc5f59805ef09a419bb41691df197a8aa84b5cceba2f6
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2026-01-13T00:00:00-05:00
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Mati\`ere noire et (ou) gravitation modifi\'ee : une approche historique et \'epist\'emologique
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arXiv:2601.06592v1 Announce Type: new Abstract: The current standard model of cosmology assumes that the majority of matter in the Universe is made of dark matter, and that the latter is fundamentally different from ordinary matter. Dark matter can in principle explain the rotation of galaxies, the gravitational lensing from galaxy clusters or the appearance of the cosmic microwave background, the oldest light in the Universe. But does dark matter really exist? Here, we review the history of this concept and its implications for the formation and evolution of galaxies. We also consider the questions that remain, the limitations of the model, and present alternative theories, in particular modifications to the gravitional law that would -- perhaps -- make it possible to do without it.
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https://arxiv.org/abs/2601.06592
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3faf4635bd5e0abfd6c1625fe1412f1b20fbee6aa85ba9e84dba541ae3f6a26c
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2026-01-13T00:00:00-05:00
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Single-exposure holographic 3D printing via inverse-designed phase masks
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arXiv:2601.06614v1 Announce Type: new Abstract: Additive manufacturing using light is commonly constrained by serial voxel-by-voxel or layer-by-layer processing, which fundamentally limits fabrication speed and scalability. Here, we introduce a single-exposure holographic three-dimensional (3D) printing approach that synthesizes an entire volumetric dose distribution optically in one step. The method combines inverse-designed microstructured phase masks with photopolymer resins engineered for controlled optical absorption. By precisely tailoring the phase-mask topography, we generate arbitrary 3D light-intensity distributions within the resin, including intentionally encoded dark regions that define hollow internal features. Simultaneously, the resin formulation is designed to balance optical penetration with sufficient local energy deposition to achieve high-fidelity polymerization throughout the volume. Using this approach, millimeter-scale architectures comprising more than $10^{6}$ addressable voxels are fabricated in a single 7.5~s exposure, corresponding to a volumetric throughput of $\sim$1~mm$^{3}$/s ($>10^{5}$~voxels/s). The demonstrated performance is presently limited by resin kinetics and illumination geometry rather than by the phase-mask framework itself. Because the volumetric information capacity scales with the space--bandwidth product of the phase mask, this approach provides a clear pathway toward substantially higher throughput, enabling scalable fabrication of micro-optical components, biomedical scaffolds, and other precision-engineered mesoscale systems.
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https://arxiv.org/abs/2601.06614
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d906d16c990b10f64f4172ecc2ae295497eeb2b1767bb1258c69ac1914730679
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2026-01-13T00:00:00-05:00
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Wave Function Realism and the Mathematization of Nature. A Phenomenological Perspective
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arXiv:2601.06618v1 Announce Type: new Abstract: This chapter reexamines wave function realism (WFR) through the lens of phenomenology. We begin by situating WFR within the broader debate about the ontology of the quantum state and the temptation to "read off" metaphysics from mathematical formalism. Against this background, we turn to the London-Bauer interpretation (LBI), the most explicit attempt to interpret quantum mechanics through phenomenological categories. On this view, the measurement transition is not a physical discontinuity but a reflective articulation of objectivity, and the wave function formally encodes the horizonal structure of world-givenness. We develop this idea by reconfiguring the notion of realism itself: not as objectivist, but as correlational and transcendental. The resulting picture suggests that quantum mechanics, rather than depicting a world "minus observers," mathematically articulates the very correlation through which a world becomes manifest at all.
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https://arxiv.org/abs/2601.06618
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Academic Papers
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c1a1624570e654b3ef9245f0a23a62c143dfa581d63b30249bfe848cb5fc9040
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2026-01-13T00:00:00-05:00
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CFD study of particle back-flow in pneumatic conveying systems due to triboelectrification
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arXiv:2601.06651v1 Announce Type: new Abstract: In industrial plants, pneumatic conveying systems are often used to convey particles from one location to another. Surprisingly, in bench-scale experiments, clusters of particles sometimes flow backward or upstream in the conveying channel. In this paper, the effect of electrostatic charge and forces on particle back-flow was investigated. Different conveying conditions with varying particle charges were simulated using computational fluid dynamics (CFD), and the resulting flow patterns were compared with CFD simulations of uncharged particles. In a channel flow with periodic boundary conditions in the streamwise and spanwise directions, it was found that electrostatic forces drive particles into low-velocity regions but do not reverse their flow. When transporting particles through a finite-length duct, electrostatic forces cause particles to settle close to the duct's inlet. Finally, when particles were injected into the duct in a pulse, back-flow was observed once particles obtained a charge of 5.04 femto-coulombs or more. The electrostatic forces decelerated the particles at the tail of the pulse and ultimately reversed their direction, whereas the particles at the head of the pulse were accelerated. Thus, it was concluded that electrostatic forces can cause particle back-flow in pneumatic conveying systems if particles are fed discontinuously.
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https://arxiv.org/abs/2601.06651
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Academic Papers
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ab9af3bb94b8058e3e38b4b2c99ce5e9899482784cf1b0bcd2d44695104b0eba
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2026-01-13T00:00:00-05:00
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The effect of discontinuous injection on particle back-flow in pneumatic conveying systems
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arXiv:2601.06653v1 Announce Type: new Abstract: Pneumatic conveying is used in many process industries to transport dry, granular, and powdered solids. The triboelectrification of particles during conveying causes particle agglomeration, spark discharges, and disruptions in particle flow, making particles move upstream against the fluid flow. The effect of frequency of particle injection on particle backflow is studied using CFD-DEM simulations. Conveying flow in a square-shaped duct with fluid frictional Reynold's number equal to 180, particle Stokes number equal to 8, and individual particle charge equal to 504 fC, is simulated with different particle injection frequencies. The proportion of particles moving upstream is found to increase as the delay period between injections increases, and the effect of the length of the injection period is minimal. Further, particles moving upstream are situated in low-drag zones at the corners of the duct where the electrostatic force dominates. In conclusion, the delay period between discontinuous injections plays a major role in particle backflow. The findings of the article are important for industrial processes with discontinuous injection of particles with a risk of particle accumulation within the conveying boundary.
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https://arxiv.org/abs/2601.06653
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Academic Papers
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51bb39f929554b2d395a1730867e0c627221e1d60e51d40e2fc56ff355c8e1b3
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2026-01-13T00:00:00-05:00
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Chip-integrated metasurface-enabled single-photon skyrmion sources
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arXiv:2601.06657v1 Announce Type: new Abstract: Skyrmions, topologically stable field configurations, have recently emerged in classical optics as structured light for high-density data applications. Achieving controllable on-chip generation of single-photon skyrmions, while being highly desirable for quantum information technologies, remains challenging due to the nanoscale confinement of quantum emitters (QEs). Here we demonstrate a metasurface-integrated quantum emitter (metaQE) platform enabling room-temperature on-chip generation of single-photon skyrmions. Near-field coupling between QEs and propitiously designed surface arrays of meta-atoms mediates spin-orbit interaction, transforming nanoscale-localized dipole emission into free-propagating topologically structured photonic modes. By exploiting this approach for structuring quantum emission from different color centers in nanodiamonds, we realize diverse skyrmionic states, including high-order anti-skyrmions and skyrmionium, and thereby demonstrate its universality across QEs. Our work establishes a unified framework for on-chip structured quantum light sources, offering versatile control of high-dimensional topological states, such as skyrmions, and advancing scalable quantum photonic technologies.
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https://arxiv.org/abs/2601.06657
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Academic Papers
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1cb9317f47a5b95513ce5c8952233d4f8575a1c6d88aa233268a29e2bbc61610
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2026-01-13T00:00:00-05:00
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Bystander effect emerges from individual psychological prospects
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arXiv:2601.06709v1 Announce Type: new Abstract: The bystander effect is a social psychological phenomenon in which individuals are less likely to help a person potentially in need if there are others present. Sociologists and psychologists have proposed multiple plausible reasons for the bystander effect, from situational ambiguity and social contagion to diffusion of responsibility and mutual denial. We build a new model of an individual's decision to intervene in a bystander situation based on these social psychological hypotheses, along with ideas borrowed from prospect theory. This model shows, for the first time, that the bystander effect emerges from social risk perception among non-coordinating individuals in ambiguous bystander situations. Expanding upon this static model, we explore the effect of social learning, where individuals update their perceived risk of intervening after experiencing or witnessing the social repercussions of previous interventions. A novel result of this model is that social learning exacerbates the bystander effect. We validate these models using a new database of 42 experimental and observational studies across a wide range of bystander situations, demonstrating a straightforward and generalizable explanation for the observed phenomenon, which may suggest effective interventions tailored to specific bystander situations.
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https://arxiv.org/abs/2601.06709
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Academic Papers
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d12359e61604ebb3d07a32f6c815b1027f7af1e654319f3408b1438de4a94804
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2026-01-13T00:00:00-05:00
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Digitally Controlled Mechatronic Metamaterials for Actively Induced Targeted Bandgaps
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arXiv:2601.06714v1 Announce Type: new Abstract: This paper presents an experimental framework for inducing and tuning vibration bandgaps in digitally controlled mechatronic metamaterials. A slender-beam structure instrumented with collocated piezoelectric sensor-actuator pairs distributed periodically along the length is used as the host medium, with decentralized second-order low-pass resonant filter with negative position feedback controllers implemented in real time on an FPGA platform. Unlike conventional approaches that assess bandgap formation through tip displacement, this study relies on bending strain minimization of piezoelectric sensors as the principal indicator of control-induced bandgaps. This reflects more accurately the moment-based phase cancellation dynamics similar to resonator behavior. We derive analytical expressions for transmissibility in an n x n decentralized feedback architecture and verify them experimentally using a 7 x 7 unit-cell configuration. The findings show that resonant controllers with negative feedback applied at the unit-cell level can be systematically tuned through controller gain and damping to open targeted low-frequency bandgaps and significantly improve vibration attenuation. By shifting the focus to localized dynamics, this work deepens the understanding of how control-induced bandgaps emerge and demonstrates a scalable pathway for designing programmable mechatronic metamaterials based on unconventional resonator behavior.
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https://arxiv.org/abs/2601.06714
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Academic Papers
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9ab3a6e3850fa32b414071a5cf652b32bfbccae0cd2fac595cc952d13faeb45d
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2026-01-13T00:00:00-05:00
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Plasma Discharge Undulator: a novel concept for plasma-based radiation sources
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arXiv:2601.06717v1 Announce Type: new Abstract: Plasma discharge devices have recently emerged as compact and versatile tools for particle beam manipulation. Building upon the Active Plasma Lens (APL) and its curved extension, the Active Plasma Bending (ABP), this work introduces the concept of the Plasma Discharge Undulator (PDU). In a PDU, a high-current discharge within a capillary generates an azimuthal magnetic field providing strong linear focusing ($O(1)$ (kT/m)), while a controlled and periodical spatial modulation of the discharge axis acts as a geometric driving term. The resulting beam dynamics can be modeled as a forced harmonic oscillator, yielding a well-defined oscillation at wavelength $\lambda_{\mathrm{PDU}}$, distinct from the natural betatron wavelength $\lambda_\beta$ related to APL focusing. Proper injection conditions result in the suppression of collective betatron oscillations, significantly reducing the intrinsic undulator strength spread typical of conventional plasma undulators, while allowing for matched beam transport thanks to APL strong focusing. Analytical models for particle trajectories and radiation emission are developed, and the one-dimensional requirements for free-electron laser (FEL) emission are evaluated, providing scaling relations and feasibility criteria for FEL operation in the proposed scheme. Theoretical estimates and multi-particle simulations indicate that the PDU can operate in the short-period regime ($\lambda_{\mathrm{PDU}} = $ mm-cm) with tunable undulator strength $K_{\mathrm{PDU}}$, supporting narrow-band radiation emission. The PDU thus provides a pathway toward miniaturized, tunable, fully-plasma-based light sources with enhanced control over focusing and spectral properties.
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https://arxiv.org/abs/2601.06717
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2f0f46ec7fc4ee8f5e5610b121e74d89169a1b238cfe6e0b2f031ae4a83a16a8
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2026-01-13T00:00:00-05:00
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Imaginary Gauge-steerable Edge Modes In Non-Hermitian Aubry-Andr\'e-Harper Model
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arXiv:2601.06746v1 Announce Type: new Abstract: We investigate a non-Hermitian Aubry-Andr\'e-Harper lattice exhibiting quasiperiodicity, featuring an imaginary gauge field that varies spatially but averages to zero. In the presence of open boundary conditions, this system is precisely mapped, through a nonunitary gauge transformation, to the Hermitian AAH model with balanced hopping terms. The mapping leaves the spectrum unchanged but reshapes each eigenfunction by a realization-dependent random-walk envelope. In a parameter regime where the Hermitian counterpart hosts spectrally isolated in-gap boundary modes, we identify two such modes with sharply different responses to the envelope: one stays anchored at the boundary, while the other is controllable via the gauge, allowing its peak intensity to be relocated solely by altering the gauge setup without modifying the associated eigenenergy. Additionally, we demonstrate that this steerable mode can be preferentially enhanced and generated from an initial bulk wavefunction by introducing mild site-specific amplification at a location determined exclusively from the Hermitian model using the biorthogonal function. These findings offer pathways for both static and dynamic manipulation of spatially adjustable in-gap states in quasiperiodic non-Hermitian lattices.
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https://arxiv.org/abs/2601.06746
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Academic Papers
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02e64f1b5f0fe452b6154218c238e22e7edeacdaa16e415d8733a4389d28123d
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2026-01-13T00:00:00-05:00
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Coherent power combining of four-way injection-locked 5.8-GHz magnetrons based on a five-port hybrid waveguide combiner
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arXiv:2601.06775v1 Announce Type: new Abstract: A high-efficiency power-combining method for four-way 5.8-GHz magnetrons based on the external injection-locking technique is presented in this article. The method uses a nonisolated, lossless five-port hybrid waveguide combiner for power combining. Meanwhile, the injection-locking technology has been applied to magnetrons for achieving coherent power combining. The phase fluctuation of the injection-locked magnetron, without the presence of a phase-locked loop, measured nearly 2.5 degree. In contrast, when a phase-locked loop was introduced, the phase fluctuation reduced significantly to approximately 0.5 degree. This phase accuracy can fully meet the requirements of combining experiments. Four magnetrons worked in injection-locked states without phase-locked loop. The proposed power-combining system is designed, measured, and analyzed. Measurement results show that a high-power-combining efficiency of over 95% is achieved by injection-locked magnetron without PLL, with the best efficiency reaching up to 97.7% with phase control of the injected signals. Experimental results reveal that the magnetron phase-pushing effects and the ripple in high-power dc voltage and current have a minor impact of approximately 4% on the combining efficiency.
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https://arxiv.org/abs/2601.06775
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b68beda05962bc8761bdaa1eb12853807668f6c6a8ec08bd4881bc338867b342
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2026-01-13T00:00:00-05:00
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Performance evaluation of Luxium Solutions BCF-XL wavelength-shifting fibers
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arXiv:2601.06784v1 Announce Type: new Abstract: We evaluate the performance of single-clad wavelength-shifting fibers newly developed by Luxium Solutions, BCF-92XL, BCF-9929AXL, and BCF-9995XL and compare them with the multi-clad Kuraray Y-11 fiber. The BCF-XL fibers exhibit faster decay times (92XL: $2.10\pm0.01$ ns, 9929AXL: $2.10\pm0.02$ ns, 9995XL: $2.41\pm0.03$ ns) than Y-11 ($7.44\pm0.06$ ns). The attenuation lengths are comparable to that of Y-11 within the measurement range up to 3.2 m. When coupled to an EJ-204 plastic scintillator, the BCF-XL fibers achieve superior time resolution while maintaining light yields comparable to those expected for a single-clad Y-11 fiber.
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https://arxiv.org/abs/2601.06784
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dc3f1803ee24af98530f03a595a93a375e9905c1a16f6fe16893710cb5f54e87
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2026-01-13T00:00:00-05:00
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Two-dimensional FrBD friction models for rolling contact
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arXiv:2601.06811v1 Announce Type: new Abstract: This paper develops a comprehensive two-dimensional generalisation of the recently introduced Friction with Bristle Dynamics (FrBD) framework for rolling contact problems. The proposed formulation extends the one-dimensional FrBD model to accommodate simultaneous longitudinal and lateral slips, spin, and arbitrary transport kinematics over a finite contact region. The derivation combines a rheological representation of the bristle element with an analytical local sliding-friction law. By relying on an application of the Implicit Function Theorem, the notion of sliding velocity is then eliminated, and a fully dynamic friction model, driven solely by the rigid relative velocity, is obtained. Building upon this local model, three distributed formulations of increasing complexity are introduced, covering standard linear rolling contact, as well as linear and semilinear rolling in the presence of large spin slips. For the linear formulations, well-posedness, stability, and passivity properties are investigated under standard assumptions. In particular, the analysis reveals that the model preserves passivity under almost any parametrisation of practical interest. Numerical simulations illustrate steady-state action surfaces, transient relaxation phenomena, and the effect of time-varying normal loads. The results provide a unified and mathematically tractable friction model applicable to a broad class of rolling contact systems.
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https://arxiv.org/abs/2601.06811
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0d78aaeeb05cf02eabbe40b5837debacdedefb9bf40942445366e27654d006d8
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2026-01-13T00:00:00-05:00
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Tunneling of Elastic Waves in a Tapered Waveguide
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arXiv:2601.06855v1 Announce Type: new Abstract: Understanding how evanescent modes mediate energy transfer in tapered elastic waveguides is of paramount interest, as it unlocks new strategies for wave control and manipulation. Evanescent modes play a crucial role in energy localization and in the emergence of thickness resonances. We report the first unambiguous experimental evidence of Lamb mode tunneling near turning points, revealing how energy can traverse an evanescent barrier and recover its propagative nature after a finite transit time. Focusing on waveguides with linearly varying thickness, we show that the $S_2$ mode becomes evanescent over a narrow frequency band, enabling a tunnelinglike phenomenon. Our study demonstrates that the barrier width is governed by the elastic properties of the material, particularly the Poisson's ratio, within a confined range bordering the Dirac cone. Numerical results exhibit excellent agreement with predictions from the Wentzel-Kramers-Brillouin approximation. These findings provide compelling evidence that, for a specific barrier width, evanescent modes mediate energy transfer across regions classically forbidden to propagating waves, revealing the mechanisms governing transmission, localization, and mode conversion in structured or corrugated elastic waveguides.
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https://arxiv.org/abs/2601.06855
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4badf688804ca537becaa7fa7cdfb228794aae47f9a60ff74ada064855556395
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2026-01-13T00:00:00-05:00
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Coherent Control of the Goos-H\"{a}nchen Shift in Polariton Optomechanics
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arXiv:2601.06876v1 Announce Type: new Abstract: We propose a theoretical scheme for controlling the Goos-H\"{a}nchen shift (GHS) of a reflected probe field in a polariton optomechanical system. The system comprises an optical mode, a molecular vibrational mode, and $N$ excitonic modes, where excitons couple to molecular vibrations via conditional displacement interactions and to photons through electric dipole interactions. We show that the effective exciton-vibration coupling provides a powerful mechanism for coherent GHS control: in its absence, the system exhibits a pronounced GHS at resonance, while activating it strongly suppresses the shift. The effective cavity detuning and the cavity length serve as additional tunable parameters for GHS manipulation. Furthermore, increasing the collective exciton-optical coupling enhances the GHS. Our results establish a framework for probing the GHS in polariton optomechanical systems and offer new avenues for designing optical devices that exploit beam-displacement phenomena.
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https://arxiv.org/abs/2601.06876
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Academic Papers
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63097dbfed67854d30ce4876fee2ce52c848d041809069f36e876aaa9814178f
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2026-01-13T00:00:00-05:00
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Interfacial standing wave-patterns disentangle dilatational and shear surface viscous effects
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arXiv:2601.06881v1 Announce Type: new Abstract: Dilatational and shear surface viscosities are highly correlated parameters, making their individual contributions difficult to disentangle in Stokes flow, linearised flow models, or two-dimensional flows. We therefore investigate the three-dimensional interfacial standing waves as a means to decouple the influence of dilatational and shear surface viscosities. Two dimensionless controlling parameters are introduced: $Bq$, the total Boussinesq number, which quantifies the the relative importance of surface viscous stresses compared with bulk viscous stresses, and $\tan \chi$, which quantifies the ratio of surface dilatational viscosity to surface shear viscosity. The growth rates and threshold accelerations are independent of $\chi$, consistent with previous theoretical predictions. Nonlinear analyses of square and hexagonal patterns reveal that Fourier decomposition of wave-patterns can effectively decouple the intricate dynamics into axial modes, where the waves are weakly dependent on $\chi$, and oblique modes, where additional damping occurs in the shear surface viscous dominant interface. These results demonstrate that Faraday wave-patterns provide a route for identifying and quantifying the distinct roles of dilatational and shear surface viscosities.
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https://arxiv.org/abs/2601.06881
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88d911bc4ed86519dfa58066574d92821d9a509af53edbad8c07065cdc98bf04
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2026-01-13T00:00:00-05:00
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Influence of bending parameters on crystalline undulator radiation peak stability for 530 MeV positron channelling
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arXiv:2601.06921v1 Announce Type: new Abstract: We investigate the stability of crystalline undulator radiation (CUR) peaks emitted by 530 MeV positron channelling in periodically bent C(110) crystals with varying bending amplitudes and bending periods. Relativistic molecular dynamics simulations were performed to quantify how these parameters affect the intensity and position of the CUR peak. The continuous potential approximation was used to identify isolines of constant peak energy, providing a reference for regions of spectral stability. MD results show that increasing the bending amplitude shifts the CUR peak to lower photon energies, while decreasing the period shifts it to higher energies, with both trends accompanied by enhanced dechannelling. For crystal parameters similar to recent experiments conducted at the MAinz MIkrotron (MAMI), the simulated CUR peak appears near 0.515 MeV. These results demonstrate that the CUR peak remains stable across a broad range of bending amplitudes and periods, establishing estimates of manufacturing tolerances for the design of gamma-ray crystal-based light sources.
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https://arxiv.org/abs/2601.06921
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c3425ba3a16cfd6892033a7b12bddd1a9795d4c71e59fa63e25803f9ccc86181
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2026-01-13T00:00:00-05:00
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Toward Meshless Turbulent Flow Simulation: LES-Integrated Vortex Particle Method
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arXiv:2601.06942v1 Announce Type: new Abstract: Recent developments in vortex particle methods for simulating three-dimensional incompressible flows are presented. A lightweight, dynamic Large-Eddy Simulation model is tested, featuring a dynamic procedure that relies solely on Lagrangian information and requires minimal auxiliary computation to update the model constant. The method employs a high-order algebraic kernel which enables direct, analytical expressions for conservation laws, the strain-rate tensor, and quadratic velocity diagnostics. Viscous diffusion is modeled using the core-spreading technique. The particle method is assessed with respect to kinematics and the conservation of energy, helicity, and enstrophy in vortex ring and leapfrogging vortex ring scenarios, both unperturbed and perturbed. The results indicate that the kinematics and flow diagnostics are accurately captured using relatively sparse particle distributions, effectively resolving the dynamics of the unstable flow phase. However, after the onset of instabilities, the sub-grid-scale methodology becomes strongly dependent on particle regularization to stabilize the flow solution.
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https://arxiv.org/abs/2601.06942
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201cb179b1f5d5984bb3d549beaef4d8a0dc5719f4dce4cb4b78dee394228387
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2026-01-13T00:00:00-05:00
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Hidden free energy released by explicit parity-time-symmetry breaking
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arXiv:2601.06952v1 Announce Type: new Abstract: It is shown that the familiar two-stream instability is the result of spontaneous parity-time (PT)-symmetry breaking in a conservative system, and more importantly, explicit PT-symmetry breaking by viscosity can destabilize the system in certain parameter regimes that are stable when viscosity vanishes. This reveals that complex systems may possess hidden free energies protected by PT-symmetry and viscosity, albeit dissipative, can expose the systems to these freed energies by breaking PT-symmetry explicitly. Such a process is accompanied by instability and total variation growth.
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https://arxiv.org/abs/2601.06952
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e52b4b41a004af6e58f6ccbc44297037d0bf4ee690462d47afd1ce80b44ac05c
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2026-01-13T00:00:00-05:00
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Identifying skin-friction generation structures in turbulent channel flows via canonical correlation decomposition
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arXiv:2601.06955v1 Announce Type: new Abstract: Flow structures directly responsible for local skin-friction generation in turbulent channel flows are identified using the newly developed Canonical Correlation Decomposition (CCD) method. The dominant structures take the form of streamwise streaks that are spanwise-localised around the position where the skin-friction is targeted and exhibit significantly shorter streamwise extent than those revealed using POD. The resulting CCD spectrum shows a clear low-rank behaviour; flow reconstruction using only the first 4 CCD modes recovers more than 80\% of the examined skin friction, as opposed to 2\% recovered by the leading 4 POD modes. When the opposition control technique is used to reduce drag, the application of CCD shows that drag reduction is achieved by lifting the original streak structures and generating smaller streaks with opposite phases underneath. These findings demonstrate that CCD isolates the causally relevant flow structures governing skin-friction generation and modification, which is expected to find use in various drag control applications in wall-bounded turbulence.
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https://arxiv.org/abs/2601.06955
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ffb52f0a36c70b56e334eeb9e7172dfdb8d6f625dc4f7a8dca2080d16f3c7227
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2026-01-13T00:00:00-05:00
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Hybrid Bound States in the Continuum beyond Diffraction Limit
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arXiv:2601.06983v1 Announce Type: new Abstract: Bound states in the continuum (BICs) have greatly impacted our ability to manipulate light-matter interaction at the nanoscale. However, in periodic structures, BICs are typically realized below the diffraction limit, thus leaving a broad spectral domains largely unexplored. Here, we introduce a new type of at-$\Gamma$ BICs of photonic crystal (PhC) slabs supporting higher diffraction orders, which we call hybrid BICs (h-BICs), whereby symmetry protection and parameter tuning are utilized to suppress light emission in the zeroth- and higher-diffraction orders, respectively. By tuning certain structural parameters of the PhC slab, we fully characterize the dynamics of the topological structure of these h-BICs, including the generation, merging, splitting, and annihilation of circularly polarized states. We further show that the relative amount of light radiated in the first-order diffraction channels can be effectively controlled by simply breaking the $C_{4v}$ symmetry of the PhC slab. Our findings reveal a versatile approach to realize new types of BICs above the diffraction limit, and could potentially inspire new efforts towards development of novel photonic nanodevices, such as multi vortex-beam generators, frequency converters, and lasers.
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https://arxiv.org/abs/2601.06983
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5d5c057231825d8d2531219a081f0a776efc4d5bf8f3133ac032b17a969494dd
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2026-01-13T00:00:00-05:00
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Structural Cointegration of the Paleoclimate: Estimating Earth System Sensitivity
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arXiv:2601.06986v1 Announce Type: new Abstract: Understanding the long-term relationship between atmospheric $CO_2$ and global temperature is fundamental to assessing Earth's climate sensitivity. This study applies a Structural Vector Error Correction Model (SVECM) to paleoclimate records from the EPICA Dome C and Vostok ice cores, spanning the last 800,000 years. By leveraging the statistical property of cointegration, we identify a robust, long-term equilibrium relationship between temperature and log-transformed $CO_2$ concentrations while controlling for orbital forcing ($N60J$). Our results, based on 854 observations, reveal a strong causal link with a long-term coefficient ($\beta$) of 17.30, characterized by a high level of statistical significance ($z = -3.82$). This corresponds to an Earth System Sensitivity (ESS) of approximately 12.0$^\circ$C per doubling of $CO_2$. Forecast Error Variance Decomposition (FEVD) further demonstrates that $CO_2$ shocks account for approximately 40\% of the long-term temperature variance.
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https://arxiv.org/abs/2601.06986
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2e8feb25c05fa6b1f97ecf35f75ddc633bb755fe13efc3e408cfeba06c78aa58
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2026-01-13T00:00:00-05:00
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Cation Dominated but Negatively Charged Na2SO4,aq-Graphene Interfaces
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arXiv:2601.06995v1 Announce Type: new Abstract: The distribution of ions and their impact on the structure of electrolyte interfaces plays an important role in many applications. Interestingly, recent experimental studies have suggested the preferential accumulation of $SO_4^{2-}$ ions at the $Na_2SO_{4,aq}$-graphene interface in disagreement with the generally known tendency of cations to accumulate at graphene-electrolyte interfaces. Herein, we resolve the atomistic structure of the $Na_2SO_{4,aq}$-graphene interfaces in the 0.1-2.0 M concentration range using machine learning interatomic potential-based simulations and simulated sum frequency generation (SFG) spectra to reveal the molecular origins of the conundrum. Our results show that Na+ ions accumulate between the outermost and second water layers whereas $SO_4^{2-}$ ions accumulate within the second interfacial water layer indicating cation dominated interfaces. We find that the interfacial region (within ~10 ${\AA}$ of the graphene sheet) is negatively charged due to sub-stoichiometric $Na^+$/$SO_4^{2-}$ ratio at the interface. Our simulated SFG spectra show enhancement and a red-shift of the spectra in the hydrogen bonded region as a function of $Na_2SO_4$ concentration similar to measurements due to $SO_4^{2-}$-induced changes in the orientational order of water molecules in the second interfacial layer. Our study demonstrates that ion stratification and ion-induced water reorganization are key elements of understanding the electrolyte-graphene interface.
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https://arxiv.org/abs/2601.06995
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2247542f067ce8e91bf6dd884f5c159aaa366f9c53e5cdc9c146b1e3e19289bc
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2026-01-13T00:00:00-05:00
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Multiscale geometric analysis of dynamic wettability on complex, fractal-like, anisotropic surfaces
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arXiv:2601.06999v1 Announce Type: new Abstract: This study introduces novel insights into the development of procedures for identifying the most relevant scales for observing the interactions of dynamic wettability and surface complexities. The experimental procedures presented for measuring dynamic contact angle hysteresis in multiscale correlation with the geometric characteristics of anisotropic surfaces contribute to a new perspective on measurement practice. In this study, microtexturing with a pyramidal structured abrasive belt is applied for precisely forming area- and length-scale fractal anisotropic surface complexities, and consequently, topographically dependent functional feature. The significant role of anisotropic topographies in modeling dynamic wettability behavior is highlighted through multiscale measurement-based analysis. These studies verify the relationship between dynamic wettability and the finest surface microgeometry (microroughness) and also the coarsest texture components (waviness). The size of topographic features, ranging from microroughness to waviness, significantly influences droplet pinning and liquid entrapment. Furthermore, the influence of material hydrophilicity and hydrophobicity on the calculated multiscale relationships is assessed. The results indicated specific scales that best correlate with dynamic wettability, with length- and area-scale complexities of 6.9 um and 28 um2, respectively. A novel measurement-based approach to scale-dependent surface-functionality interactions offers new insights for designing dynamic wettability on anisotropic surfaces.
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https://arxiv.org/abs/2601.06999
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f29f35796613b9c5d43fb707d052d2bbda8ca4156b89d032516223fd087c1d98
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2026-01-13T00:00:00-05:00
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PANDA-film: an automated system for electrodeposition of polymer thin films and their wetting analysis
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arXiv:2601.07043v1 Announce Type: new Abstract: Thin polymer films are widely used as functional and protective coatings. However, determining the composition and processing conditions that produce a desired function is a tedious process due to the large number of factors that must be considered and the manual nature of most synthesis and characterization methods. Self-driving labs (SDLs), or robotic systems that prepare and test materials samples, are designed to overcome this bottleneck by enabling the efficient exploration of complex parameter spaces. In this paper, we report the development and testing of the polymer analysis and discovery array (PANDA)-film, a modular SDL for electrochemically synthesizing polymer films and then determining their water contact angle as a measure of surface energy. The system is designed to be highly modular and based upon a lowcost gantry platform to facilitate adoption. In addition to validating fluid handling and electrochemical tasks, we introduce two novel modular capabilities that enable PANDA-film to run sustained campaigns to study the wetting properties of films: (1) an electromagnetic capping/decapping system to mitigate fluid evaporation, and (2) a top-down optical method to determine water contact angle based upon reflectance. These capabilities are validated by depositing and characterizing a poly(allyl methacrylate) (PAMA) film using electrodeposition of polymer networks (EPoN). Comprehensive details for replicating the hardware and software of PANDA-film are included.
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https://arxiv.org/abs/2601.07043
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Academic Papers
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d51647fb6ad55aab1bff68ae049179419513679d5280a10c6118c57009eac608
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2026-01-13T00:00:00-05:00
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Ab Initio Characterization of C2H4N2 Isomers: Structures, electronic energies, spectroscopic parameters and formation pathways
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arXiv:2601.07078v1 Announce Type: new Abstract: This work presents a comprehensive theoretical investigation of key isomers of C2H4N2 using state-of-the-art quantum chemical methods. The objective is to characterize their molecular structures, spectroscopic constants, and electronic energies, and to elucidate plausible formation and destruction pathways, providing data critical for astrochemical and atmospheric detection. High-accuracy ab initio methods were employed, notably CCSD(T)-F12/cc-pVTZ-F12 for optimized geometries. Additional calculations were performed at the CCSD(T)/aug-cc-pVTZ, CCSD(T)/cc-pVTZ, MP2/aug-cc-pVTZ, and CIS levels. Intrinsic reaction coordinate (IRC) calculations were performed at the B3LYP/6-31G(d,p) level to explore reaction pathways. Zero-point energy corrections were determined for all isomers considered. Six low-energy C2H4N2 isomers were identified, all within 1 eV of the global minimum. Among them, methylcyanamide (MCA) exhibits the lowest relative energy (~0.2 eV) and a significant electric dipole moment of 5.00 D, making it a strong candidate for gas-phase detection. The rotational constants for MCA, computed at the CCSD(T)-F12/cc-pVTZ-F12 level, are Ae = 34932.44 MHz, Be = 4995.31 MHz, and Ce = 4520.30 MHz. The V3 torsional barrier was found to be 631.19 cm^{-1}. Centrifugal distortion constants were computed up to sextic order for all isomers. Formation pathways for MCA, such as CH3N + HCN -> CH3NHCN and related isomers, were characterized. The combination of large dipole moments and distinct rotational signatures supports the detectability of methylcyanamide and related C2H4N2 isomers via radioastronomy, infrared, and microwave spectroscopy. Isomerization and reaction pathways involving radical-neutral and neutral-neutral processes were found to be key to their formation in gas-phase environments. These results provide a robust foundation for future observational and modeling efforts.
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https://arxiv.org/abs/2601.07078
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2fbcc67a5263863ef4bf218f71c57bdd87a9467d7d073751f54bd4e79028963f
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2026-01-13T00:00:00-05:00
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SMARTHEP: training PhD students in real-time analysis at the LHC and in industry
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arXiv:2601.07089v1 Announce Type: new Abstract: In this invited Editorial for Software and Computing for Big Science, we describe the SMARTHEP Innovative Training Network funded via the Marie Sk{\l}odowska-Curie Actions between 2021 and 2025. SMARTHEP trained 12 PhD students to advance machine learning and real-time analysis in high-energy physics experiments and industrial applications. We present the perspective of students, supervisors, and external observers of the network, concerning the work done within the network, the added value compared to ``typical'' PhD positions, and the emerging themes and directions from our experiences in the past four years.
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https://arxiv.org/abs/2601.07089
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94cbf23c4c2f3dc9cca69830fbe474135e4fa8a421f18bbedd8503169ee31d00
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2026-01-13T00:00:00-05:00
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Electric field gradient in accurate quantum chemical calculations
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arXiv:2601.07098v1 Announce Type: new Abstract: The electric field gradients (EFGs) at the (non-spherical) nucleus contribute to atomic and molecular hyperfine structure and govern Nuclear Quadrupole Resonance (NQR) and M\"ossbauer spectra. EFGs provide a highly sensitive probe of local bonding, symmetry, and crystal defect geometry and electronic structure. The EFGs can be obtained from electronic structure calculations and can also be extracted from spectroscopic measurements, thus linking electronic structure theory and spectroscopic observables. In this work, we present a methodological study of EFGs for a range of molecules and crystalline materials, using both periodic boundary conditions and embedded cluster models, and compare the results with reported experimental data. We analyze the sensitivity of EFG values to details of the calculations, such as the selection of the model Hamiltonians, basis sets, and the geometries of molecules and crystals. We also address persistent differences in EFG sign conventions and tensor definitions employed in the literature and in widely used quantum chemistry codes. While the EFG sign does not affect zero B-field NQR spectra, they can become critical in Mossbauer spectroscopy or when the quadrupolar interactions are combined with other interactions of the nucleus with the environment. Together, our systematic study results provide practical guidelines for computing, interpreting, and exploiting EFGs as quantitative descriptors of electronic structure and chemical environment.
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https://arxiv.org/abs/2601.07098
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4ec0317c7944ebf56a157627e404ac2ea10e21a96d0c25854550f8bb83b38cc3
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2026-01-13T00:00:00-05:00
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Guiding-center dynamics in a screw-pinch magnetic field
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arXiv:2601.07109v1 Announce Type: new Abstract: The guiding-center dynamics of charged particles moving in a doubly-symmetric screw-pinch magnetic field is investigated. In particular, we verify that Kruskal's adiabatic-invariant series expansion of the radial action integral associated with the reduced full-orbit radial motion matches the perturbation expansion of the magnetic-moment gyroaction up to first order in magnetic-field non-uniformity. Because the radial action integral is an exact invariant of the full-orbit dynamics, the magnetic moment is therefore represented as non-perturbative integral expression, which can be used to test the validity of the guiding-center approximation.
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https://arxiv.org/abs/2601.07109
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ec74aecbe05cf38a97a0b1b424b77c6541ce434495a817e14c5a9ae0246217ba
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2026-01-13T00:00:00-05:00
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Living in the tensions: Investigations of gender performativity in STEM
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arXiv:2601.07126v1 Announce Type: new Abstract: In this work, we present the results of semi-structured interviews with four women to explore how they perceive themselves with respect to three gender constructs (femininity, masculinity, androgyny), and how they believe others perceive them. All the women highlighted the performative nature of gender in science, technology, engineering, and mathematics (STEM), citing (1) stereotypes that women are not analytical thinkers, or femininity being associated with "being stupid"; (2) the pressure to conform to the masculine norms of STEM, and (3) a pressure to perform to prove that they belong in STEM. Some of these women aligned their own perceptions of their gender with these norms, while others expressed frustration with the tension between their gender and how that is perceived by peers in STEM. This work suggests that conceptualizing gender as performance is a useful lens for understanding the oppression and underrepresentation of women and gender minorities in STEM.
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https://arxiv.org/abs/2601.07126
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f57a860665238b2866bc36b3d1fec513a81a823e39edc45cfad763ebbff755ee
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2026-01-13T00:00:00-05:00
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Dynamics of Multi-Agent Actor-Critic Learning in Stochastic Games: from Multistability and Chaos to Stable Cooperation
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arXiv:2601.07142v1 Announce Type: new Abstract: Achieving robust coordination and cooperation is a central challenge in multi-agent reinforcement learning (MARL). Uncovering the mechanisms underlying such emergent behaviors calls for a dynamical understanding of learn processes. In this work, we investigate the dynamics of actor-critic agents in stochastic games, focusing on the impact of entropy regularization. By leveraging time-scale separation, we derive the system's evolution equations, which are then formally analyzed using dynamical systems theory. We find that in the constant-sum game of Matching Pennies, the system exhibits chaotic behavior. Entropy regularization mitigates this chaos and drives the dynamics toward convergence to fair cooperation. In contrast, in the general-sum game of the Prisoner's Dilemma, the system displays multistability. Interestingly, the three stable equilibria of the system correspond to the well-known ALLC (Always Cooperate), ALLD (Always Defect), and GRIM (Grim Trigger) strategies from evolutionary game theory (EGT). Entropy regularization strengthens system resilience by enlarging the basin of attraction of the cooperative equilibrium. Our findings reveal a close link between the mechanism of direct reciprocity in EGT and how cooperation emerges in MARL, offering insights for designing more robust and collaborative multi-agent systems.
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https://arxiv.org/abs/2601.07142
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f8739ab34cd286e3def6675a1405d91a09216d90f8e1d0403b2acdc9f9085ce5
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2026-01-13T00:00:00-05:00
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Dynamic Water-Wave Tweezers
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arXiv:2601.07166v1 Announce Type: new Abstract: Following a recent demonstration of stable trapping of floating particles by stationary (monochromatic) structured water waves [Nature 638, 394 (2025)], we report dynamic water-wave tweezers that enable controllable transport of trapped particles along arbitrary trajectories on the water surface. We employ a triangular lattice formed by the interference of three plane waves, which can trap particles, depending on parameters, either at intensity maxima or at intensity zeros (vortices). By introducing small frequency detunings between the interfering waves, we control 2D motion of the lattice and trapped particles. This approach is robust and effective over a relatively broad range of particle sizes and wave frequencies, offering remarkable new possibilities for noncontact manipulation of floating (e.g., biological and soft-matter) objects in fluidic environments.
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https://arxiv.org/abs/2601.07166
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677958de95f5994c6b88046a2adcf55aa045f19cf9b15a314bc1ba8e13d893eb
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2026-01-13T00:00:00-05:00
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Discharge characteristics and parameter diagnosis of dielectric barrier discharge patterns in double-gap configuration
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arXiv:2601.07167v1 Announce Type: new Abstract: Pattern discharge is a common mode in dielectric barrier discharge (DBD) and has broad application prospects in various industrial fields, such as material surface treatment, environmental monitoring, and biomedical applications. In this work, a mixed gas of 75% argon and 25% air is used to generate a pattern discharge. A double-gap boundary composed of hexagonal configuration and square configuration is employed, and the gas pressure is fixed at 20 kPa. By varying the applied voltage amplitude, single-ring pattern, square-point-line pattern, square lattice pattern, and annular-lattice pattern are obtained for the first time. The discharge characteristics and their temporal correlation are studied using both optical method and electrical method. The results show that the discharge patterns exhibit multiple discharges in each half of the voltage cycle, and these discharges are temporally correlated with each other. Time-resolved discharge images of the square lattice pattern are captured using an enhanced charge-coupled device (ICCD). The experimental results reveal that multiple discharges in a half-voltage cycle correspond to the ignition process of the pattern in the radial direction from the outside to the inside. The morphology of the square lattice pattern observed by the naked eye is actually the result of the temporal superposition of luminescence from points at different positions in the evolution process.
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https://arxiv.org/abs/2601.07167
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f3953dcfbfb99eeb1565284640dc63b03849942306a76225f0df0590c49c1fa7
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2026-01-13T00:00:00-05:00
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Critical Shortfall in NIH Support for Medical Physics Research
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arXiv:2601.07187v1 Announce Type: new Abstract: This report summarizes changes in federal research funding to the medical physics community between FY24 and FY25. By linking the AAPM membership database with NIH RePORTER records, we quantified the distribution of NIH funding for projects led by AAPM researchers. Although total NIH funding to AAPM members remained relatively stable across the two years, the composition of that funding shifted substantially. Competing (new and renewal) awards declined 50%, driven largely by an 80% collapse in new R01 grants from the National Cancer Institute (NCI). In contrast, noncompeting continuation awards increased by 10%, following a shift in how NIH funds multi-year projects. These changes occurred in the context of widespread disruptions to NIH review and grantmaking, including delayed study sections and more stringent administrative requirements. Federal funding is essential to sustaining innovation, supporting early-stage investigators, and ensuring that patients receive the best possible care. The trends identified here raise concerns about the long-term vitality and stability of the medical physics research pipeline.
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https://arxiv.org/abs/2601.07187
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5a673a8d282104735ad17c23624242ad44c70bccee9d05c2d2cfc28bedb07af7
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2026-01-13T00:00:00-05:00
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Full symmetry-breaking of electronic and nuclear dynamics for low attosecond timescale electronic chirality reversal
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arXiv:2601.07193v1 Announce Type: new Abstract: Attosecond science is an emerging topic where chirality plays a central role. Here we demonstrate that subjecting iodoacetylene,a geometrically achiral molecule, to a pair of simulated non-ionizing ultrafast circularly polarized laser pulses induces the fastest reversals of the continuously-valued S and R electronic chirality assignments to date, by two orders of magnitude (3.87 attoseconds). We partner the only vector-based quantum chemical physics theory enabling full symmetry-breaking with electronic and nuclear dynamics simulations: the former does not require charge density differences or special symmetry positions. The resulting 'easy' and 'hard' directions of the total electronic charge density motion are quantified as a cardioid-like morphology for the duration of the simulated laser pulses and toroidal afterwards. Future research directions include determination of the underlying mechanism governing chiral induced spin selectivity, in addition to application to chiral spin selective phenomena in opto-spintronics and exotic superconductors, partnered with orbital-free density functional theory (OF-DFT).
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https://arxiv.org/abs/2601.07193
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34942c04abe0a816c8ef42ef1f29baa83e5a12cec08e4fccc39008202ec1c382
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2026-01-13T00:00:00-05:00
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Effect of LH and ECR waves on plasma parameters in ADITYA Upgrade tokamak
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arXiv:2601.07205v1 Announce Type: new Abstract: The plasma discharges in ADITYA Upgrade Tokamak are produced by means of transformer action, in which Ohmically created plasma is driven by means of a secondary loop voltage. Due to reduction of plasma resistivity after a certain level of plasma temperature, Ohmic heating becomes poor and further achievement of temperature needs other heating techniques. ADITYA-U tokamak is facilitated with a 42 GHz-500 kW Electron Cyclotron Resonant Heating (ECRH) system. Also, there is a Lower Hybrid Current Drive (LHCD) system installed and operated at 3.7 GHz for driving non-inductive plasma current followed by the Ohmic current drive. Though an eventual impact in the rise of plasma temperature and plasma current due to the application of ECRH and LHCD respectively are very obvious, their energy coupling with the plasma results in several interesting outcomes in a number of experimentally measured plasma parameters. The present work addresses such impactful observations that are noticed and reported for the first time in ADITYA-U Tokamak.
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https://arxiv.org/abs/2601.07205
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eeec3713ec9dea266bce85f4091d6fa6c39a9d056d768a7dfc3b6ab675ef3786
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2026-01-13T00:00:00-05:00
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Programmable radio-frequency calculations in electromagnetic-wave domain
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arXiv:2601.07213v1 Announce Type: new Abstract: Information metasurfaces have emerged as pivotal components in next-generation electronic systems, with significant progress in their applications to communication, radar, and sensing. However, the current researches are mainly focused on their physical structures and system functions, while radio-frequency (RF) signal processing and calculation remain constrained to digital-domain operations. This reliance on digital conversion inherently increases hardware complexity and power consumption. To address this challenge, we propose a programmable RF calculation system based on a space-time-coding metasurface (STCM), which can control the wave-matter interactions through space-time-coding (STC) strategies and achieve direct RF calculations in the electromagnetic (EM) space in a reprogrammable way. Particularly, the fundamental signal operations - Fourier transform and convolution - are implemented in the EM-wave domain successfully. We validate the RF calculation capabilities in radar scenarios, facilitating the accurate detection of target velocity and range. Theoretical analysis, numerical simulations, and experimental results collectively demonstrate that the STCM-based RF calculation system exhibits superior precision, enhanced operational efficiency, and notable cost-effectiveness, highlighting its significant potentials for the next-generation electronic system deployments.
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https://arxiv.org/abs/2601.07213
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c43ad2ae5e6810df994d9d3eaac3cced7ae3b3882325a9ab4c241df3e839bc9e
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2026-01-13T00:00:00-05:00
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What is a Schiff moment anyway?
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arXiv:2601.07217v1 Announce Type: new Abstract: Schiff moments of atomic nuclei are of considerable interest to experiments searching for undiscovered new physics that breaks time-reversal symmetry. I develop a simple picture of the Schiff moment of a charge distribution, and discuss the interaction of the Schiff moment of a nucleus with the field produced by an electron in an atom.
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https://arxiv.org/abs/2601.07217
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72100092cb84a3e431521e3db858bed4b222de7370c86ab64716a0166d764f24
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2026-01-13T00:00:00-05:00
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On optimization of Paganin's method for propagation-based X-ray phase-contrast imaging and tomography
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arXiv:2601.07225v1 Announce Type: new Abstract: Paganin's method for image reconstruction in propagation-based phase-contrast X-ray imaging and tomography has enjoyed broad acceptance in recent years, with over one thousand publications citing its use. The present paper discusses approaches to optimization of the method with respect to simple image quality metrics, such as signal-to-noise ratio and spatial resolution, as well as a reference-based metric corresponding to the relative mean squared difference between the reconstructed image and the "ground truth" image that would be obtained in a setup with perfect spatial resolution and no noise. The problem of optimization of the intrinsic regularization parameter of Paganin's method with respect to spatial resolution in the reconstructed image is studied in detail. It is also demonstrated that a combination of Paganin's method with a Tikhonov-regularized deconvolution of the point-spread function of the imaging system can provide significantly higher image quality compared to the standard version of the method. Analytical expressions for some relevant image quality metrics are obtained and compared with results of numerical simulations. Advantages and shortcomings of optimization approaches using a number of different image quality metrics are discussed. The results of this study are expected to be useful in practical X-ray imaging and training of deep machine learning models for image denoising and segmentation.
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https://arxiv.org/abs/2601.07225
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41cd109182985fdc39fd8610f695d0aac181361ff1953ba7ceebd2272f0b5818
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2026-01-13T00:00:00-05:00
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Physics-embedded neural computational electron microscopy for quantitative 4D nanometrology
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arXiv:2601.07311v1 Announce Type: new Abstract: The fusion of rigorous physical laws with flexible data-driven learning represents a new frontier in scientific simulation, yet bridging the gap between physical interpretability and computational efficiency remains a grand challenge. In electron microscopy, this divide limits the ability to quantify three-dimensional topography from two-dimensional projections, fundamentally constraining our understanding of nanoscale structure-function relationships. Here, we present a physics-embedded neural computational microscopy framework that achieves metrological three-dimensional reconstruction by deeply coupling a differentiable electron-optical forward model with deep learning. By introducing a Vision Field Transformer as a high-speed, differentiable surrogate for physical process analysis simulations, we establish an end-to-end, self-supervised optimization loop that enforces strict physical consistency with hardware geometry. This synergy enables single-shot, quantitative three-dimensional nanometrology with precision comparable to atomic force microscopy but at orders of magnitude higher throughput. Furthermore, we demonstrate the capability for four-dimensional (3D real space plus time) in situ characterization by tracking the dynamic evolution of surface nanostructure during copper redox, revealing hidden crystallographic kinetics invisible to conventional imaging. Our work not only redefines the limits of scanning electron microscopy but also establishes a generalizable archetype for solving ill-posed inverse problems across physical sciences, unlocking the full potential of simulation as a third pillar of discovery.
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https://arxiv.org/abs/2601.07311
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0516600fa965fdddc3d341adc044f1ddbeca035d345c589fde4a3fa02c50344f
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2026-01-13T00:00:00-05:00
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Ultralow-noise microwave oscillator via optical frequency division with a co-self-injection-locked miniature Fabry-Perot reference
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arXiv:2601.07319v1 Announce Type: new Abstract: Optical frequency division (OFD) provides the purest microwaves by down-converting the stability of optical cavity references. State-of-the-art references typically rely on electronic co-Pound-Drever-Hall locking to ultrahigh-Q microresonators-a complex approach that introduces servo bumps and increases footprint. Alternatively, optical co-self-injection-locking (co-SIL) offers inherent simplicity but is limited by the large thermo-refractive noise and confined mode volumes of integrated cavities. Here, we demonstrate a two-point OFD-based microwave oscillator that combines an ultrahigh-Q miniature Fabry-Perot cavity with optical co-SIL. Leveraging its low relative phase noise optical reference and combing with an integrated soliton microcomb, the system generates a microwave with phase noise of -147 dBc/Hz at 4 kHz offset (scaled to 10 GHz)-performance rivalling most electronically stabilized systems. This work marries the superior noise floor of ultrahigh-Q cavities with the simplicity of optical locking, providing a compact, cost-effective, and field-deployable path to pure microwaves for next-generation communications, radar and metrology.
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https://arxiv.org/abs/2601.07319
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183f3c4d2263d26d214f49fb19e4777c6c8b670a26945f8680878110232eba11
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2026-01-13T00:00:00-05:00
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Endcap-Type Paul Trap for Precision Spectroscopy and Studies of Controlled Interactions
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arXiv:2601.07328v1 Announce Type: new Abstract: We present the design and fabrication of an endcap-type Paul trap. The trap is designed for studies with Ca$^{+}$ and Yb$^{+}$. The design, fabrication process, and characterization are presented in detail with a focus on trapping a single compensated ion at the rf node. A custom-built imaging system of $NA = 0.14$ and magnification $\approx 22 \times$ performs close to diffraction-limit and resolves multi-ion clusters. Controlled ion loading and characterization of the trap are performed using $^{40}$Ca$^{+}$. The experimentally determined quadrupole coefficient of the trap is $\approx 0.3$, which is very close to the design value. The relative frequency shift along the spectroscopy beam due to excess micromotion (EMM) is at the level of $3.5\times 10^{-18}$ for $^{40}$Ca$^{+}$. Applications of this trap encompass single-ion-based optical frequency standards, tests of fundamental physics, the study of mesoscopic Coulomb clusters, and the controlled interaction of a single ion with co-trapped atoms.
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https://arxiv.org/abs/2601.07328
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5542da8cd40c4ddd7768a590e2e21ebeb69e0d5c435c2435749ae57bfef6771e
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2026-01-13T00:00:00-05:00
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Monitoring of structural changes in materials under the exposure of ionization radiation using a vibrating wire
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arXiv:2601.07330v1 Announce Type: new Abstract: Ionizing radiation (X-rays, proton beams) causes structural changes in materials. If a vibrating metallic wire is subjected to such radiation, the natural frequency of the wire is affected as a result of changes in the elastic characteristics of the material. This paper presents the results of experiments on the impact of X-ray radiation in the range of 100-165 keV and a proton beam with energy 18 MeV on the structure of stainless steel wire. In case of proton irradiation an irreversible change in the wire frequency was observed, which indicated residual changes in the structure of the wire material. X-ray diffractometry methods were used to analyze the structural changes.
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https://arxiv.org/abs/2601.07330
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ddb5d6b48b60a493cd99e0ec9d44522f62156e3cf7c5b04cd45bbee4bd4baf6d
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2026-01-13T00:00:00-05:00
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Mud-Standoff Effect Correction Based on Open-Short Calibration and Resistivity Consistency-Constrained Iterative Inversion for Oil-Based Mud Imagers
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arXiv:2601.07343v1 Announce Type: new Abstract: We propose a mud-standoff effect correction method and a set of approximate apparent resistivity inversion methods suitable for oil-based mud micro-resistivity imaging logging. To calibrate the influence of the mud layer on electrode measurement signals, this study integrates the Open-Short calibration(OSC) method with the three-layer impedance model of the oil-based mud resistivity imager. By treating the electrode and the mud layer as an integrated whole and simulating the open/short-circuit states via the finite element method, the independent extraction of the mud layer impedance signal is achieved, and the formation impedance signal is separated from the total impedance. For fast inversion of formation resistivity, standoff thickness (mud layer thickness), and relative permittivity of formation, a resistivity consistency-constrained iterative inversion method is further proposed. In this method, the formation impedance is first converted into resistivity, and then the consistency residual of the resistivity at different frequencies is used as the objective function to invert the approximate apparent resistivity of the formation through an iterative optimization algorithm. The effectiveness of the finite element-simulated OSC method, the objective function construction scheme, and the consistency inversion method is verified through both numerical models and an example of field data.
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https://arxiv.org/abs/2601.07343
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e8d84768df8a673dbff953c3a28680ca20f626d8223807e0167d5267043f059f
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2026-01-13T00:00:00-05:00
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A Pilot Kinematic Study on the Forehand Reverse Flick: Feasibility of a Novel Short Return Technique in Table Tennis
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arXiv:2601.07363v1 Announce Type: new Abstract: Background Following changes in table tennis ball materials, offensive returns have become more important for initiating sustained topspin offense. However, using the backhand flick (BF) to return forehand short balls often increases the difficulty of recovery and continuity, revealing a technical gap. This study preliminarily verified a novel forehand short return technique, the forehand reverse flick (FRF), and analyzed its similarities and differences with the BF. Methods Four elite athletes completed seven consecutive days of FRF specific training. Infrared motion capture and ultra-high-speed cameras were used to collect data on racket kinematics, movement duration, and ball performance. Results The success rate of the FRF increased steadily, reaching 86%. Racket trajectories of the two techniques were highly similar along the X (r = 1) and Y (r = 0.99) axes but differed along the Z (r = -0.04) axis. Racket and ball velocities were comparable between techniques, whereas the FRF showed lower resultant acceleration (approximately 265.57 m/s) and required about 0.03 s more for movement duration. Ball velocity was comparable between techniques, for the ball spin, the FRF generated lower spin (approximately 76.61 r/s) about 64% of the BF value (approximately 120.13 r/s). The highest participant mean spin rate reached 93 r/s, about 77% of the BF mean. Conclusion Overall, the FRF was found to have favorable learnability and training value, with potential for further optimization and competitive application.
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https://arxiv.org/abs/2601.07363
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d4f403031395e37651bd86f01cc08f8a65494b9a7e5b7696bc22b688e280b3d9
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2026-01-13T00:00:00-05:00
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Intraresonance frequency combs in Kerr microresonators
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arXiv:2601.07378v1 Announce Type: new Abstract: For more than 20 years, optical microresonators have served as the backbone of integrated nonlinear photonics, exploiting Kerr nonlinearity to generate octave-spanning frequency combs, enable quantum effects, and drive optical parametric oscillators. Since the inception of microresonator-based nonlinear optics, related studies have focused primarily on regimes in which photons with distinct resonant modes can interact. Although multiple comb lines can occupy a single resonance during the Kerr comb formation process, their mutual interactions have remained largely unexplored. Here we demonstrate a Kerr comb formation that is confined to a single resonance of a microresonator via dual-pumping. MHz-scale comb-line spacing reveals previously unobserved Kerr-comb dynamics, featuring parametrically driven phase multistability that can be observed directly in the temporal domain. Two laser pumps serve as phase-coupled references for heterodyne read-out, simplifying the measurements.
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https://arxiv.org/abs/2601.07378
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eb578d2c358815aebaa001ba71ea322a7f76fb5d0c680def5255f7b84d798e18
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2026-01-13T00:00:00-05:00
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Control of Electron Energy Distribution Functions by Current Waveform Tailoring in Inductively Coupled Radio Frequency Plasmas
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arXiv:2601.07386v1 Announce Type: new Abstract: Based on two-dimensional particle-in-cell simulations a novel approach towards Electron Energy Probability Function (EEPF) and plasma chemistry control by Current Waveform Tailoring (CWT) in the coil of inductively coupled discharges is proposed. Varying the shape of this current waveform provides electrical control of the dynamics of the electric field in the plasma. Using sawtooth instead of sinusoidal waveforms allows breaking and controlling the temporal symmetry of the electric field dynamics. In this way CWT allows controlling the EEPF, the ionization-to-excitation rate ratio, and the plasma chemistry.
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https://arxiv.org/abs/2601.07386
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45aa0547c3fc52fd73cb2e36badd291eef64f22e9fb6137a6c88d04fc454cb5b
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2026-01-13T00:00:00-05:00
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Effect of directionality on extreme wave formation during nonlinear shoaling
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arXiv:2601.07399v1 Announce Type: new Abstract: Recent studies have shown that, in coastal waters where water depth decreases significantly due to rapid bathymetric changes, the non-equilibrium dynamics (NED) substantially increases the occurrence probability of extreme (rogue) waves. Nevertheless, research on depth-induced NED has been predominantly confined to unidirectional irregular waves, while the role of directionality remains largely unexplored. The scarce studies on multidirectional waves mainly rely on numerical simulations and have yielded conflicting results. In this work, we report on an experimental investigation of wave directionality on the depth-induced non-equilibrium wave statistics. High-order statistical moments, skewness and kurtosis, are used as proxies for the non-equilibrium wave response. Our results indicate that the directional spreading has a minor effect on decreasing the maximum values of these statistical moments. In contrast, the incidence direction plays a significant role in the non-equilibrium wave response, which is attributed to the effective bottom slope.
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https://arxiv.org/abs/2601.07399
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b5854f26334a99a682198b82aa098081567e0424c0c0b75633d2b549f97fb01f
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2026-01-13T00:00:00-05:00
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Universal scaling between precursory duration and event size across mechanically driven geohazards
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arXiv:2601.07404v1 Announce Type: new Abstract: Many catastrophic events, including landslides, rockbursts, glacier breakoffs, and volcanic eruptions, are preceded by an observable acceleration phase that offers a critical window for early warning and hazard mitigation; however, the duration of this precursory phase remains poorly constrained across sites, scales, and hazard types. This limitation arises because the onset of acceleration is often identified using heuristic thresholds or empirical criteria. Here, we introduce a physics-based framework that objectively constrains the precursory duration from accelerating dynamics, without prescribing the onset a priori or being tied to any specific observable. We analyse a global dataset of 109 geohazard events across seven continents over the past century, quantifying their precursory durations in a consistent manner. For mechanically driven instabilities, we identify a robust scaling between precursory duration and failure volume spanning more than ten orders of magnitude. When expressed in terms of a characteristic system size, this relationship is close to linear, consistent with finite-size scaling near a dynamical critical point. This behaviour indicates that precursory duration reflects the progressive growth of correlated deformation up to system-spanning scales, rather than local rupture kinetics. The resulting universality points to common organising mechanisms governing the approach to catastrophic failure across mechanically driven geohazards.
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https://arxiv.org/abs/2601.07404
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3556ea4ff55f6fc4bcf722a9eec78f0b65e330ec01d177643770c4151a2b719e
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2026-01-13T00:00:00-05:00
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The design and expected performance of the ALICE ITS3 upgrade
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arXiv:2601.07405v1 Announce Type: new Abstract: During the LHC Long Shutdown 3 (2026-29) ALICE will replace its three innermost tracking layers by a new detector, the "ITS3". It will be based on newly developed, wafer-scale monolithic active pixel sensors, which are bent into truly cylindrical layers and held in place by light mechanics made from carbon foam. Unprecedented low values of material budget (0.09\% $X_0$ per layer) and proximity to the interaction point (19 mm) lead to a factor two improvement in pointing resolutions for particles from very low $p_{\mathrm{T}}$ (O(100 MeV/$c$)), achieving, for example, 20 $\mu$m and 15 $\mu$m in the transversal and longitudinal directions, respectively, for 1 GeV/$c$ particles. After a successful R&D phase (2019-2023), which demonstrated the feasibility of this innovative detector and led to the Technical Design Report (https://cds.cern.ch/record/2890181/), the final sensor and mechanics are being developed right now. This contribution will review the conceptual design and the main R&D achievements, as well as the current activities and road to completion and installation. It includes a projection of the improved physics performance, in particular for heavy-flavor mesons and baryons, as well as for thermal dielectrons that will come into reach with this new detector installed.
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https://arxiv.org/abs/2601.07405
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b595f667e378b73222554957eb6816027b17230969372273675fa38665ad6b4d
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2026-01-13T00:00:00-05:00
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Extending the Biswas--Chatterjee--Sen model with nonconformists and inflexibles
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arXiv:2601.07432v1 Announce Type: new Abstract: Originally, the Biswas--Chatterjee--Sen model exhibits an order/disorder phase transition for a sufficiently large number of negative interactions among actors. In this paper, the model is extended by the nonconformists and inflexibles. Nonconformists are actors who do not follow the original model rules, but in different ways do something opposite. We introduce inflexibles as actors who does not change their opinions. Both discrete and continuous opinions are considered. With direct Monte Carlo simulations and mean-field calculations, we check the influence of fractions of nonconformists and inflexibles on mean opinion in the system. With the mean-field calculations we identify ranges of fractions of nonconformists where ordered phase of the system is available. The results of the mean-field calculations perfectly match the results of the Monte Carlo simulations. We consider inflexibles adhered: (i) to extreme opinions; (ii) to specific opinions and (iii) chosen independently of their initial opinion. For inflexibles adhered to specific and extreme opinions they play a role of effective bias suppressing disorder phase in the system. The qualitative results of introducing nonconformists (inflexibles) in various ways (discrete/continuous opinions and annealed/quenched disorder) are roughly the same. However, for the model extended by inflexibles, we can observe a systematic shift of the mean order parameter to its higher values for quenched disorder compared with annealed disorder.
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https://arxiv.org/abs/2601.07432
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508f3cc761307e24f8c9e86d61f2896f05934b85d197795e70e0b6dce7a025e4
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2026-01-13T00:00:00-05:00
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Observation of anomalous exciton polariton bands in PEPI perovskite based microcavity at room temperature
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arXiv:2601.07438v1 Announce Type: new Abstract: Recently anomalous energy bands with negative mass attract intensive attention where non Hermiticity plays an important role. In this work we observe anomalous exciton polariton bands in PEPI perovskite based microcavity at room temperature. We simulate the anomalous band structure using a non-Hermitian coupled oscillator model which agree with experiments very well. Our results offer to study non-Hermitian polariton wave dynamics at room temperature.
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https://arxiv.org/abs/2601.07438
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8042c527064e9fd8268c508ee56e7dfc9a5cab92e0186e5d064d2d1dd8b27863
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2026-01-13T00:00:00-05:00
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Noise enhances odor source localization
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arXiv:2601.07445v1 Announce Type: new Abstract: We address the problem of inferring the location of a target that releases odor in the presence of turbulence. Input for the inference is provided by many sensors scattered within the odor plume. Drawing inspiration from distributed chemosensation in biology, we ask whether the accuracy of the inference is affected by proprioceptive noise, i.e., noise on the perceived location of the sensors. Surprisingly, in the presence of a net fluid flow, proprioceptive noise improves Bayesian inference, rather than degrading it. An optimal noise exists that efficiently leverages additional information hidden within the geometry of the odor plume. Empirical tuning of noise functions well across a range of distances and may be implemented in practice. Other sources of noise also improve accuracy, owing to their ability to break the spatiotemporal correlations of the turbulent plume. These counterintuitive benefits of noise may be leveraged to improve sensory processing in biology and robotics.
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https://arxiv.org/abs/2601.07445
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2ee08d0df32333c43b80304c9b18c6e9a0e9736687fca36c1a3e00531978c082
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2026-01-13T00:00:00-05:00
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High-Speed Non-Volatile Barium Titanate Field Programmable Photonic Gate Array
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arXiv:2601.07456v1 Announce Type: new Abstract: Programmable integrated photonics aims to replicate the versatility of field-programmable gate arrays in the optical domain. However, scaling these systems has been prevented by the high power consumption and thermal crosstalk of conventional volatile phase shifters. Here, we demonstrate the first non-volatile field-programmable photonic gate array, implemented on a hybrid silicon-barium titanate platform. Unlike traditional thermo-optic devices that require constant power to maintain a state, our device utilizes ferroelectric domain switching to provide non-volatile memory, allowing optical circuits to be programmed and retained without any holding power or electrical bias. The hexagonal waveguide mesh integrates 58 programmable unit cells and 116 actuators, achieving nanosecond-scale switching speeds of 80 nanoseconds while reducing static power consumption to negligible levels (560 nanowatts per {\pi} phase shift). To validate this platform, we configured the mesh to perform diverse signal processing functions, including tunable filtering, 4x4 linear unitary transformations, and optical routing. This work establishes non-volatile ferroelectric silicon photonics as a scalable, heat-free platform essential for the next generation of energy-efficient photonic computing.
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https://arxiv.org/abs/2601.07456
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f08df6da2e28513905f9012ea4c8175bec19185fad554c37c410967deb4d9e20
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2026-01-13T00:00:00-05:00
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Overcoming the limitations of NMR Field Probes: A Novel Integrated Sensor Utilizing Pre-Polarization for (Ultra) Low Field MRI
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arXiv:2601.07458v1 Announce Type: new Abstract: Access to magnetic resonance imaging (MRI) remains severely limited in low- and middle-income countries, especially in sub-Saharan Africa, despite rising rates of non-communicable diseases. Low-field MRI presents an affordable, locally developable diagnostic solution, but its performance is constrained by magnetic field instability. We present a novel NMR field probe designed to overcome these challenges using a rapid non-adiabatic switch-off of a pre-polarization field resulting in precessing spin magnetization. Achieved by first use of high-voltage silicon carbide transistors operating in controlled avalanche breakdown, it measures the Larmor frequency without prior field knowledge, unlike conventional probes. This capability is crucial during magnet development with often unknown fields, allowing early detection of magnet issues, and offering an urgently needed tool for magnet design and image-quality improvement. Validated from 1 mT to 45 mT (up to 1,000 times stronger than similar systems) its low-cost, modular design supports replication, upgrades, and enhanced field control, helping expand global MRI access.
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https://arxiv.org/abs/2601.07458
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11c2c8c148ebf409e38a9179487ab869815ff83aeaef57c1c59d2b218be357ef
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2026-01-13T00:00:00-05:00
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A radiation two-phase flow model for simulating plasma-liquid interactions
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arXiv:2601.07486v1 Announce Type: new Abstract: In laser-produced plasma (LPP) extreme ultraviolet (EUV) sources, deformation of a tin droplet into an optimal target shape is governed by its interaction with a pre-pulse laser-generated plasma. This interaction is mediated by a transient ablation pressure, whose complex spatio-temporal evolution remains experimentally inaccessible. Existing modeling approaches are limited: Empirical pressure-impulse models neglect dynamic plasma feedback, while advanced radiation-hydrodynamic codes often fail to resolve late-time droplet hydrodynamics. To bridge this gap, we propose a radiation two-phase flow model based on a diffuse interface methodology. The model integrates radiation hydrodynamics for the plasma with the Euler equations for a weakly compressible liquid, extending a five-equation diffuse interface formulation to incorporate radiation transport, thermal conduction, and ionization. This formulation enforces pressure and velocity equilibrium across the diffuse interface region, with closure models constructed to ensure correct jump conditions at interfaces and asymptotically recover the pure-phase equations in bulk regions. Then, we apply the model to simulate a benchmark pre-pulse scenario, where a 50 micron tin droplet is irradiated by a 10 ns laser pulse. The simulations capture the rapid plasma expansion and subsequent inertial flattening of the droplet into a thin, curved sheet over microsecond timescales. Notably, the model reproduces experimentally observed features (such as an axial jet) rarely replicated in prior simulations. Quantitative agreement with experimental data for sheet dimensions and velocity validates the approach. The proposed model self-consistently couples laser-plasma physics with compressible droplet dynamics, providing a powerful tool for fundamental studies of plasma-liquid interactions in LPP-EUV source optimization.
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https://arxiv.org/abs/2601.07486
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69a5af53eb528185a2ef5ea5ac082e41ccc587d270bce8ef4b2e6e4d6d5c4e1a
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2026-01-13T00:00:00-05:00
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Standardized Images and Evaluation Metrics for Tomography
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arXiv:2601.07531v1 Announce Type: new Abstract: Advances in instrumentation and computation have enabled increasingly sophisticated tomographic reconstruction methods. However, existing evaluation practices -often based on simple phantoms and global image metrics- are limited in their ability to differentiate among modern high-fidelity reconstructions. A standardized, quantitative framework capable of revealing subtle yet meaningful differences is therefore required. We introduce such a framework, built upon two core components. The first is a set of four standardized reference images - Source, Detector, Ideal, and Realistic - each derived from physical modeling and representing a distinct stage in the imaging and reconstruction chain. The second is a suite of diagnostic and quantitative tools that remain sensitive in regimes where conventional metrics (e.g., SSIM, PSNR, NMSE, CC) tend to saturate. These include pixel-wise $\chi^2$ and difference maps, their quantitative characterization, spectral decomposition of intensity distributions, and Region-of-Interest (RoI)-based metrics. Application of this framework to MLEM and RISE-1 reconstructions using software phantoms demonstrates its ability to expose discrepancies that might elude detection by conventional global metrics. While developed in the context of SPECT, the methodology generalizes to other tomographic modalities, providing a reproducible, interpretable, and physically grounded basis for evaluating reconstruction fidelity in the high-performance regime.
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https://arxiv.org/abs/2601.07531
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490b2e5ed5018a74cc1297d3c673ca5f8af64b9e47a9cc487d5c9d9a34e372c2
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2026-01-13T00:00:00-05:00
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Exciton coherence propagation measured with non-local four-wave mixing micro-spectroscopy
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arXiv:2601.07549v1 Announce Type: new Abstract: Coherence transfer is a multi-disciplinary topic of interest, including chemistry, biology and physics. In quantum technologies, achieving non-local coherent coupling between solid-state qubits is of the utmost importance. Here, we demonstrate that excitons - i.e. electron-hole pairs bound by the Coulomb force within a quantum well - can act as a medium for mesoscopic optical coherence transfer in semiconductors. To this end, we use a femtosecond laser pulse to resonantly generate excitons within the light cone. These excitons can then either recombine radiatively or scatter out of the light cone, gaining an in-plane momentum in the process. In samples without disorder, such as the CdTe quantum wells used here, the resulting fast excitons can diffuse over mesoscopic distances before recombining radiatively. Using coherent nonlinear micro-spectroscopy, we carry out exciton time-of-flight measurements. Specifically, we monitor the spatio-temporal propagation of launched exciton wave packets, selectively observing their coherence or density on a scale of up to 10$\,\mu$m. Our proof-of-principle experiment demonstrates that free excitons inherit a phase modulation from the optical pulsed excitation and can generate coherent links within excitonic circuits, offerring a higher level of miniaturisation and compactness than photonic or polaritonic architectures.
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https://arxiv.org/abs/2601.07549
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1a2e2b2d2e5d2b3697a58421fffb4b86602748e6bcb8af217960bcd2ec5827d3
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2026-01-13T00:00:00-05:00
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Self-optimizing multichannel optical computing
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arXiv:2601.07574v1 Announce Type: new Abstract: Optical computing offers ultrafast, energy-efficient alternatives to conventional digital processors, yet most implementations remain confined to single-channel processing, severely underutilizing light's information capacity. Here we demonstrate a self-optimizing multichannel optical computing architecture based on multi-plane light conversion that natively processes RGB images and structured numerical data throughout the optical domain. We introduce two complementary optimization strategies that enable autonomous performance adaptation without differentiable forward models. First, Bayesian optimization tunes channel mixing coefficients to minimize crosstalk and enhance feature separability at the input level. Second, a hardware-in-the-loop protocol based on self-organized criticality leverages avalanche dynamics to autonomously navigate the high-dimensional phase landscape, enabling the system to self-optimize through stochastic multi-scale perturbations. Across medical imaging, natural image classification, and regression tasks, multichannel processing with random phase masks improves accuracy by 26--58 percentage points over raw pixel baselines, with RGB systematically outperforming grayscale by 5--6 percentage points. Self-optimization strategies provide additional gains of 6--7 percentage points through autonomous adaptation at complementary system levels. Our work establishes self-optimizing multichannel optical computing as a practical platform for real-world machine learning applications.
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https://arxiv.org/abs/2601.07574
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Academic Papers
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79f6526b1257d21d219178971e14d7d56d35c106fd642d45bb84c29754cd05de
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2026-01-13T00:00:00-05:00
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Performance of the Pair Spectrometer in Hall D at Jefferson Lab
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arXiv:2601.07587v1 Announce Type: new Abstract: This article describes the performance of the pair spectrometer installed in experimental Hall D at Jefferson Lab and its operation in multiple experiments with the GlueX detector. The primary purpose of the pair spectrometer is the precise determination of the flux of beam photons incident on the GlueX target, a critical input for physics analyses such as absolute cross-section measurements. The photon energy spectrum is determined by reconstructing electron-positron pairs produced in a thin converter inserted into the photon beam. The spectrometer is integrated into the GlueX trigger system, enabling continuous real-time monitoring of the photon flux and the recording of $e^+e^-$ pair candidates for offline analysis. In addition, the pair spectrometer provides a versatile test facility for evaluating calorimeter prototypes using leptons with well-defined energies produced via electromagnetic pair production.
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https://arxiv.org/abs/2601.07587
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Academic Papers
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1d75a2fa6f824607be847d0c2142289db274be50270063cce4cdc79a73070ffb
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2026-01-13T00:00:00-05:00
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Coordinate Systems and Transforms in Space Physics: Terms, Definitions, Implementations, and Recommendations for Reproducibility
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arXiv:2601.07605v1 Announce Type: new Abstract: In space physics, acronyms for coordinate systems (e.g., \texttt{GEI}, \texttt{GSM}) are commonly used; however, differences in their definitions and implementations can prevent reproducibility. In this work, we compare definitions in online resources, software packages, and frequently cited journal articles and show that implementation differences can lead to transformations between same-named coordinate systems and ephemerides values from different data providers to differ significantly. Based on these comparisons and results, and to enable reproducibility, we recommend that (a) a standard for acronyms and definitions for coordinate systems is developed; (b) a standards body develops a citable database of reference data needed for these transforms; (c) a central authority maintains the SPICE (Spacecraft, Planet, Instrument, C-matrix, Events) kernels used by space physics spacecraft missions to generate data products in different coordinate systems; and (d) software developers provide explicit comparisons of their implementations with the results of (b) and documentation on implementation choices. Additionally, we provide recommendations for scientists and metadata developers to ensure that sufficient information is provided to enable reproducibility if these recommendations are not implemented.
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https://arxiv.org/abs/2601.07605
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Academic Papers
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9f921af76cbdaf9a5e76256048345dd174d1b41c7ce43b3a2e0b8a2f187e3380
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2026-01-13T00:00:00-05:00
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A directly observable, Zeeman-insensitive nuclear spin coherence in solution
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arXiv:2601.07614v1 Announce Type: new Abstract: Clock transitions are well known in atomic and solid-state systems, but are largely unexplored in molecular liquids. Here we demonstrate a clock-like, nuclear-spin avoided crossing in [1--$^{13}$C]-fumarate that supports long-lived and directly observable coherences at ultralow magnetic field: a three-spin transition $|S_0\alpha\rangle \leftrightarrow |T_{+1}\beta\rangle$ near 400 nT exhibits a shallow crossing with a frequency minimum of 2 Hz. The transition is first-order immune to magnetic field perturbations and displays a lifetime of 25 s, around three times the longest single-spin $T_2^*$. Sensitivity to effective pseudo-fields is also demonstrated, including the internal dipolar field of the sample.
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https://arxiv.org/abs/2601.07614
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Academic Papers
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4a866e4979261ff289cabec9827bc5bd29228c484410d5cf8b1dda8c3c377c99
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2026-01-13T00:00:00-05:00
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A note on thermodynamics of the production processes
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arXiv:2601.07616v1 Announce Type: new Abstract: The process of creating goods and services, measured by their value, is considered as a process of creating complexity. This makes it possible to consider the production system as an open thermodynamic system, and to develop a simple heuristic model for the production process. The model includes three production factors: the index of complexity of production equipment (physical capital $K$), human activity (labour $L$), and the substitutive capacity of equipment (substitutive work $P$). The latter is a contribution to economic theory from the thermodynamic approach, which also requires the introduction of technological characteristics of production equipment, such as labor requirement ($\overline{\lambda}$) and energy requirement ($\overline{\varepsilon}$), which indicate the amounts of labor and energy required to operate production equipment. By applying thermodynamic principles to the theory of production, we can understand how labour can be replaced by capital, and derive the production function in four equivalent but different formulations. Two of them are known and used by economists for interpretation the production phenomena; the thermodynamic approach gives some foundation for economic theory. The production function allows an unambiguously decompose of the growth rate of output according to the growth rates of production factors and technological level. The introduction of substitute work as a factor of production and technological features of capital expands planning and analyse of production processes.
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https://arxiv.org/abs/2601.07616
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Academic Papers
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6894fba612ade3d6e78b5e2aae038e98d8b7c372aa7305cade7ba37f4f06b57e
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2026-01-13T00:00:00-05:00
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Performance Benchmarks for 2-View and 3-View Fiber-Projection Fine-Grained Particle Detectors
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arXiv:2601.07633v1 Announce Type: new Abstract: Fine-grained scintillator detectors are critical for precision measurements in nuclear and particle physics, where accurate reconstruction of interaction vertices and secondary particle directions enables separation of signal from background events. A well-known design choice is the fiber readout geometry: traditional 2-View systems use orthogonal X and Y fibers, while next-generation 3-View designs add a third Z-fiber layer that provides unambiguous 3D voxel identification. The 2-View approach suffers from combinatorial ghost hits, that the false 3D candidates arising from fiber projection ambiguities, degrading reconstruction performance in high-multiplicity events. This paper presents comprehensive simulation benchmarks quantifying the performance difference between 2-View and 3-View geometries across key metrics. We find that the 3-View geometry reduces ghost hits by 30--90\% depending on event topology, provides robust vertex resolution across complex topologies, and maintains superior angular resolution for shower direction reconstruction. These benchmarks inform the design optimization of future detectors and provide quantitative guidance for reconstruction algorithm development across a broad range of experiments including neutrino physics, rare kaon/pion decays, and collider calorimetry.
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https://arxiv.org/abs/2601.07633
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Academic Papers
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ab5b22efc5b2a42206c49cc8340693c589b671f6e507801935f0876fc44e98e8
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2026-01-13T00:00:00-05:00
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Multi-pathline flow visualization using PIV images
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arXiv:2601.07643v1 Announce Type: new Abstract: One of the oldest flow visualization techniques is through multiple pathlines generated by the movement of seeding particles spatially distributed in the flow. In the computerized era, particle images are used in quantitative measurements, such as particle image and particle tracking velocimetry (PIV and PTV). Here, we present several methods for post-processing raw particle images to generate enhanced flow visualization without a need for conducting additional experiments. Three post-processing methods will be shown: 1) controlling the exposure time, 2) color-coding temporal information, and 3) changing the frame of reference. We showcase how employing these three methods can highlight different flow features in three canonical flow cases: vortex ring, leading edge vortex, and turbulent boundary layer. In addition to the quantitative flow field, the multi-pathline visualization is expected to augment our ability to observe fluid flow from many different perspectives.
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https://arxiv.org/abs/2601.07643
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Academic Papers
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4b4c6f673e0e30d559b645438f1837c644b00c37f50abe929a403fc39b2c3903
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2026-01-13T00:00:00-05:00
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Mind the Temperature Gap: The Role of Pit Thermal Energy Storage in a Sector-Coupled Energy System with High-Temperature District Heating
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arXiv:2601.07647v1 Announce Type: new Abstract: Pit thermal energy storage (PTES) provides large-scale thermal storage capacity in district heating systems, supporting flexibility on both daily and seasonal scales. Most existing large-scale energy system studies on PTES do not account for temperature differences between storage and the network. Neglecting these temperature differences can result in less efficient PTES integration, since they affect usable energy capacity and introduce additional costs for discharge requiring temperature boosting. To explore how temperature constraints shape the system-level value of PTES, we use PyPSA-DE, an open-source sector-coupled capacity expansion model of Germany and neighboring countries in a scenario with net zero carbon emissions for 2045. To isolate PTES effects, we examine counterfactual scenarios: systems without PTES, idealized systems with PTES but without temperature constraints, and feasible systems with boosting. We find that PTES reduces German annual system costs by 135-345 M EUR per year relative to systems relying solely on tank storage. Lowering maximum forward temperatures from 124 degrees C to 95 degrees C decreases district heating costs by 7.6 percent without PTES and 10 percent with PTES. Idealized scenarios without temperature constraints yield district heating cost savings of up to 15 percent, indicating that temperature-agnostic modeling overestimates PTES benefits. PTES provides economic value even under current high temperatures, though temperature misalignment limits its contribution during peak demand due to the need for boosting. The findings highlight the role of PTES in leveraging low-price electricity through electrified heating while emphasizing the importance of explicitly accounting for temperature constraints.
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https://arxiv.org/abs/2601.07647
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Academic Papers
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1998ae3f454c337d4efc122b806985b26c5d80e71937b8dd6f203337f3870b76
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2026-01-13T00:00:00-05:00
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Role of Shafranov shift, zonal structures on the behavior of TAEs, AAEs and microinstabilities in the presence of energetic particles
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arXiv:2601.07652v1 Announce Type: new Abstract: In future nuclear fusion reactors, even a small fraction of fusion-born energetic particles (EP) about 100 times hotter than the thermal bulk species, contributes substantially to the kinetic pressure and therefore affect the MHD equilibrium, mainly via the Shafranov shift. In this work, we perform first-principles numerical simulations using the gyrokinetic, electromagnetic, global code ORB5 to study the effect of a self-consistent finite $\beta$ equilibrium on the arising Alfv\'en Eigenmodes (destabilized by EPs), Ion Temperature Gradient (ITG), and Kinetic Ballooning Modes (KBM) microturbulence (destabilized by thermal species). Linearly, we explore the complex interplay between EP fraction, bulk gradients and a self-consistent Shafranov shift on the plasma stability. We choose single toroidal mode numbers to represent the system's instabilities and study the characteristic nonlinear evolutions of TAEs, KBMs and ITGs separately and including the axisymmetric field response to each mode separately. This study focuses on the impact of Shafranov shift equilibrium consistency, as well as the self-generated zonal ${E \times B}$ flows, the saturation levels and resulting heat and particle fluxes. In the ITG cases including the $n=0$ perturbations reduces turbulent fluxes, as expected, however, for the TAE cases including the $n=0$ perturbations is shown to enhance the fluxes. We show for the first time that Axisymmetric Alfv\'en Eigenmodes (AAEs) play a role in this mechanism.
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https://arxiv.org/abs/2601.07652
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Academic Papers
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7b5dbbf12fcd705b55170e444a42e679b16620158a863ca5c8110c82dc09ddbc
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2026-01-13T00:00:00-05:00
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Landau damping of disturbances in nearly inviscid inflectional shear flows
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arXiv:2601.07656v1 Announce Type: new Abstract: We investigate the structure of damped two-dimensional perturbations in unstable plane-parallel shear flows with an inflection point. In inviscid flows within the stable wavenumber region $k$, no regular eigenmodes exist -- the frequency spectrum $\omega$ consists of a continuous set of singular van Kampen modes with real frequencies. Nevertheless, initial perturbations of the total vorticity integrated across the flow decay exponentially, resembling the behavior of an eigenmode with complex eigenfrequency ${\rm Im}\,\omega<0$ (Landau damping). However, the vorticity itself does not decay but becomes increasingly corrugated across the flow. We demonstrate that accounting for arbitrarily small viscosity transforms this exponentially decaying perturbation into a true eigenmode in which the vorticity preserves its spatial form. We numerically trace the transformation of the vorticity structure of this mode and its disappearance as viscosity approaches zero. We discuss similarities and differences between the behavior of damped perturbations in the transition from inviscid to nearly inviscid flows in hydrodynamics and their behavior in plasma and homogeneous stellar systems during the analogous transition from collisionless to very weakly collisional systems.
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https://arxiv.org/abs/2601.07656
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Academic Papers
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2821ecf2236ab357d4354f5ee0a099ba78e4d63836e66ad25d4f9d794c308723
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2026-01-13T00:00:00-05:00
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Inversion of Sea Ice Spectral Albedo to Estimate Under-Ice Transmittance
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arXiv:2601.07672v1 Announce Type: new Abstract: Sunlight radiation under snow-covered sea ice obtained from remote sensing could help assess under-ice primary production at pan-Arctic scale. Yet, the current remote sensing methods to estimate sunlight transmittance under sea ice is limited by its reliance on imprecise snow depth products and its inability to sense microstructure-driven variations in snow and ice light scattering properties. Based on Monte-Carlo simulations of radiative transfer, we developed an inversion method relying solely on spectral albedo to estimate transmittance under snow-covered sea ice. The method analyses albedo spectral information to derive the vertically resolved scattering properties of snow and sea ice above the freeboard. Assuming fixed columnar ice physical and optical properties, transmittance is then estimated. At ground level, our spectral albedo inversion method is more precise than the current approaches. We argue this is because it implicitly accounts for the variability in snow scattering properties. This method could significantly improve the satellite estimation of photosynthetically available radiation under sea ice, especially because it does not need snow depth.
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https://arxiv.org/abs/2601.07672
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Academic Papers
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125ff1d43cb20d514a3450135d8db3b472bd025f2ea39a1b5c47840fa50789fc
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2026-01-13T00:00:00-05:00
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Sub-Pixel Electron Beam Alignment for Machine Learning Characterization of Hybrid Pixel Detectors
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arXiv:2601.07682v1 Announce Type: new Abstract: Due to their radiation hardness, kilohertz frame rates, and high dynamic range, hybrid pixel detectors have recently expanded their application range to electron diffraction and recently also electron imaging. However, these detectors typically have pixel sizes about ten times larger than those of direct electron detectors commonly used for imaging and more prominent electron multiple scattering effects. To overcome these limitations, machine learning approaches can be utilized to reconstruct the electron entrance point and achieve super-resolution. As this process is inherently stochastic, and machine learning relies on suitable training data, high-quality, representative training data are essential for developing models that achieve the best possible resolution. In this work, we present two novel experimental methods for generating such training data. The first method employs precise microscope alignment to scan the detector plane using a finely focused electron beam of 2 {\mu}m diameter, enabling controlled sub-pixel mapping. The second method utilizes specially designed aperture masks with sub-pixel-sized holes to accurately localize electron entry points. We developed and validated two experimental strategies for collecting training data at acceleration voltages of 60, 80, 120, and 200 keV, which enable sub-pixel labeling for hybrid pixel detectors. Notably, our methodology is broadly applicable to a wide range of hybrid pixel detectors.
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https://arxiv.org/abs/2601.07682
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Academic Papers
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dfc797199119ce16e6330df8a493bfb460497f83cdb7e9a51794c154c673921f
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2026-01-13T00:00:00-05:00
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Single-Chip 1.024 Tb/s Optical Receiver for High-Speed Optical links
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arXiv:2601.07709v1 Announce Type: new Abstract: Integrated optical transceivers, utilizing wavelength-division-multiplexing, offer a path forward for implementation of compact, high-bandwidth and energy-efficient interconnects for future data centers. Here we report the demonstration of a monolithically integrated optical receiver in 45nm CMOS, where efficient multi-layer optical demultiplexing with capacitive tuning, energy efficient electronics and wideband inverse designed grating couplers enable implementation of a 32-channel receiver chip based on wavelength-division multiplexing. The chip operates at an aggregate data-rate of 1.024 Tb/s with all channels operating simultaneously at a data-rate of 32 Gb/s/channel achieving a record energy efficiency of 71 fJ/b, including the power consumption of both the electronic circuitry and the tuning and control of photonic devices, and a record bandwidth density of 4 Tb/s/mm2. The receiver achieves a bit-error-rate below 1E-12 without requiring equalization, error correction or digital processing. Inverse-designed broadband grating couplers provide efficient, low-loss optical coupling into the chip. An on-chip demultiplexer, composed of Mach-Zehnder interferometers (MZIs) and ring resonators, offers a large channel-to-channel isolation sufficient for error-free operation. Capacitive phase shifters embedded within the ring resonators of the demultiplexer are used for wavelength alignment at a zero static power consumption. MZIs and ring-resonators are periodically selected and autonomously locked to the wavelength of the corresponding optical carrier. The implemented monolithic receiver offers a scalable, energy-efficient and reliable solution for the beyond Tb/s optical interconnects.
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https://arxiv.org/abs/2601.07709
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Academic Papers
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