General Relativity and Quantum Cosmology
Can the gravitational waves emitted by Eta Carinae be detected?
Odylio D. Aguiar
In this article, we propose a search for gravitational waves emitted by Eta Carinae using the PTA technique, not to detect a background, but rather a strong, isolated source (a task not yet accomplished). We suggest including
pulsars PSR J0952-0607, PSR J1719-1438, PSR J2322-2650, and PSR J1909-3744 in the search network, as they exhibit relatively high residual-to-pulse-width ratios and spatial positions that favor the detection of tensor polarizations. The high eccentricity (0.9) of the Eta Carinae binary orbit may facilitate signal identification within the data due to the presence of harmonics in the emitted gravitational waves. It is possible that some of the raw data have already been recorded and are available; the remaining step is to analyze them against a model of the gravitational wave signal arriving at Earth from Eta Carinae.
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Optics
Digital twin for full field-of-view Fraunhofer holographic patterning
Antoni J. Wojcik, Dilawer Singh, Hannah J. Joyce et al. (+1 more)
Computer-generated holography allows for nearly complete dynamic control of optical fields, but discrepancies between idealised propagation models and physical hardware limit its performance, particularly across large fields of view. We present a compact differentiable model of a Fraunhofer
holographic projector which describes the complete propagation chain, from a phase-only spatial light modulator (SLM) to the camera recording the focal plane of a
Fourier lens. It uses physically interpretable parameters for the SLM, illumination, pupil, coherent stray light, and camera. The model is identified in situ from noise-probed hologram-image pairs without additional hardware, system modification, or camera-in-the-loop refinement. The recovered digital twin is used to generate holograms for patterns spanning the entire first diffraction order of the SLM at its spatial-bandwidth limit. This full-field capability is enabled by measuring field-dependent pupil aberrations and compensating severe inter-pixel crosstalk by operating at the $4\pi$ phase modulation range. The stray light responsible for residual zeroth-order artefacts is recovered in amplitude and phase, allowing its physical origin to be investigated, and its contribution suppressed during hologram synthesis. The work establishes a framework for calibration-aware field synthesis in
holographic systems operating in the Fraunhofer regime for applications such as maskless lithography and optical tweezer arrays.
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All authors Antoni J. Wojcik, Dilawer Singh, Hannah J. Joyce, Timothy D. Wilkinson
Plasma Physics
IGNITE Tokamak World Model Architecture
Peter Steiner, Azarakhsh Jalalvand, Nathaniel Chen et al. (+4 more)
We introduce IGNITE, a generative world foundation model for fusion
plasma behavior simulation trained in a self-supervised manner from over a decade of unlabeled experimental data at the DIII-D National Fusion Facility. The core of IGNITE is a dynamics model that can simulate DIII-D discharges from a given set of actuator trajectories. These trajectories can be supplied or generated on-the-fly from a textual
prompt or from desired experimental outcomes. The model architecture consists of several spatio-temporal tokenizers that embed the different input modalities, including time-series like spatio-temporal measurement data, image sequences, and high-resolution spectrograms, each of which collected at vastly different time scales. The backbone is composed of an auto-regressive dynamics model that has the capacity to predict entire DIII-D discharges given initial latent
plasma states and actuator trajectories over a theoretical infinite horizon. IGNITE paves the way towards efficient AI-driven experimental planning and world modeling for
nuclear fusion.
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All authors Peter Steiner, Azarakhsh Jalalvand, Nathaniel Chen, Kouroche Bouchiat, Ricardo Shousha, SangKyeun Kim, Egemen Kolemen
Mesoscale and Nanoscale Physics
Quantum materials QED with van der Waals crystals
Suheng Xu, Brian Vermilyea, Ran Jing et al. (+19 more)
A central goal of the emerging field of materials QED is to harness subwavelength electromagnetic confinement in engineered cavities to tailor light-matter interactions. Here, we demonstrate that van der Waals multilayer cavities composed of stacked
graphene and hexagonal boron nitride (hBN) provide unprecedented control over hybridization between their electromagnetic resonances. By magnetically tuning
graphene inter-Landau-level transitions (ILTs) into resonance with hBN
phonons, we witness broadband, mode-selective strong coupling in the mid-infrared. Our
quantum-material QED framework shows that cavity geometry and layer placement jointly control both coupling strength and modal selectivity. For experimentally realistic cavity parameters, the predicted mode splitting exceeds the width of the hBN Reststrahlen band, providing a direct route to the ultrastrong coupling regime. Together, these results establish van der Waals multilayer cavities as a scalable platform for tunable multimode QED and broaden the design space for reconfigurable
quantum materials.
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All authors Suheng Xu, Brian Vermilyea, Ran Jing, Lukas Wehmeier, Jihoon Park, Rafael A. Mayer, Xinzhong Chen, Samuel L. Moore, Fuyang Tay, Boyi Zhou, Wenjun Zheng, Dihao Sun, Birui Yang, Cory R. Dean, Daniel Cazorla, Xu Du, Milan Delor, Andrew J. Millis, Angel Rubio, Michael M. Fogler, Mengkun Liu, D. N. Basov
Earth and Planetary Astrophysics · Cross-listed from cs.LG
Post-Training Quantization of Autoregressive Weather Models
Ananyo Bhattacharya, Swastik Bhattacharya and Christiane Jablonowski
Advancements in high-resolution numerical weather prediction (NWP) and data assimilation (DA) have shaped the developments in deep learning (DL) architectures emulating atmospheric dynamics. Emulators for weather
forecasting exhibit forecast quality comparable to physics based models at forecast horizon scaling from few days to subseasonal time scales. The emulators are driven by hardware-accelerated
matrix multiplication in autoregressive inferences, significantly reducing the computation time and resources required for NWP. Optimization of the
matrix multiplication processes in GPU architectures provides opportunities to scale towards high-resolution domain, and offers implementation of out of the box solutions. Post-training quantization (PTQ) has been demonstrated across multiple DL architectures to accelerate and increase the number of computations in unit time while consuming less power, enabling applications on edge hardware. In this study, we investigate the effect of PTQ on pre-trained AI emulators for global-scale weather
forecasting. We implement PTQ
algorithms in Deep Learning Weather Prediction (DLWP) and FourCastNet (FCN) models as a proof of concept for geophysical fluid dynamics applications. We systematically investigate the effect of PTQ on emulator inferences over short-range forecast horizons. Evaluation of PTQ configurations using simulated quantization hints at qualitatively meaningful forecasts over short-time horizons. These results provide a first
benchmark of PTQ for autoregressive weather emulators and a basis for quantization-based optimization of DL models for dynamical systems.
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Disordered Systems and Neural Networks
Quantum transmission in 1D disordered stealthy hyperuniform Kronig–Penney-like models
Shaobing Yuan, Carlo Vanoni and Salvatore Torquato
Disordered stealthy hyperuniform (SHU) systems are emerging as platforms for controlling classical and
quantum transport due to vanishing single-scattering contributions in the stealthy regime. Here, to our knowledge, we present the first perturbation theory of one-dimensional
quantum transport through a continuum of identical point scatterers with SHU positional disorder. Our perturbation theory indicates the exact cancellation of all the lower-order terms due to the
Fourier-space stealthy condition $S(q)=0$, and the further suppression of the lowest non-vanishing fourth order in the Lyapunov exponent $\lambda(k)$ due to the real-space hyperuniform constraint $\lim\limits_{D\to\infty}\sigma_D^2=c<\infty$. Our findings presents universal implications of the general wave-propagation phenomena in disordered SHU systems.
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Mesoscale and Nanoscale Physics
Magnetic-field response of generalized Wigner crystals in twisted MoTe$_2$
F. K. Wolff, S. Jiao, H. Park et al. (+9 more)
We report a magnetotransport study of fractional hole-filling states in the layer-polarized regime of a twisted MoTe$_2$ homobilayer. A perpendicular
magnetic field suppresses the resistance peak at the two-thirds filling while enhancing the one-third peak by several orders of magnitude. Both remain near their commensurate densities. We argue that these commensurate states are generalized Wigner
crystals whose distinct charge configurations define different
magnetic lattices, leading to contrasting responses to
spin polarization. Near half filling, we observe a qualitatively different state whose resistance maximum shifts approximately quadratically with field and exhibits pronounced transport anisotropy consistent with a stripe phase. These results reveal a strong dependence of magnetotransport on fractional filling and open a route to
magnetic control of transport in moiré charge-ordered states.
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All authors F. K. Wolff, S. Jiao, H. Park, J. Cai, E. Anderson, X. Liu, C. Wang, T. Taniguchi, K. Watanabe, X. Xu, D. Xiao, S. Vaitiekėnas
Soft Condensed Matter
How Does Hard Magnetic Soft Matter Deform?
Daniel Katusele, Carmel Majidi, Liping Liu et al. (+2 more)
Hard
Magnetic Soft Materials, i.e., elastomers seeded with hard
magnetic particles, convert
magnetic energy into complex motion and have become central to the design of untethered soft
robots, biomedical devices, and, in general, for enabling fast, wireless actuation. Their behavior depends critically on how the surrounding soft
matrix deforms and transmits torque to each magnetized inclusion, yet there is no consensus on the correct mapping between macroscopic strain and microscopic motion. Competing models predict conflicting particle rotations and
magnetic responses under identical loads. Here, we construct counterexamples that show the key shortcomings in these models, and then establish a first-principles framework that leads to an optimal deformation mapping. The resulting closed-form law unifies conflicting models and shows that they are, in fact, simply different limits of our general approach. Our work permits the rational design of magnetically actuated soft devices and a unified view of deformation in
magnetic soft matter, and broadly, in similar architectured materials.
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All authors Daniel Katusele, Carmel Majidi, Liping Liu, Pradeep Sharma, Kaushik Dayal
Space Physics
A Student Sounding Rocket Experiment to Probe Electron Density in the Lower Ionosphere
Joshua Goodwill, Timothy Tomaszewski, Jarrod Bieber et al. (+17 more)
Earth's ionosphere is primarily generated by the Sun's ionization of atoms in the upper atmosphere. This
plasma environment is highly dynamic, exhibits strong spatial and temporal, variations and significantly impacts power systems,
navigation, and satellite and ground communications. The University of Delaware Ionospheric Probe (UDIP) was developed as a hands-on learning experience for University of Delaware students on the ionosphere itself and on the development of space technology. Students (mostly undergraduates) have led all aspects of the experiment including mission planning, electronics development, mechanical development, software development, and scientific data analysis. The present study is intended as a guide to readers on how the development of space and near-space flight missions can be successfully incorporated into an undergraduate physics curriculum. The fourth version of the experiment (UDIP-4) flew along with student experiments from across the USA on the 2024 RockSat-C sounding rocket, which was launched from NASA Wallops Flight Facility. During the flight, UDIP-4's Langmuir probe successfully measured the ionosphere's density profile – electron density as a function of altitude – up to an apogee of 114 km. Though the measured density profile agrees well overall with the predictions of theoretical models, UDIP-4 identified a thin layer of enhanced electron density at an altitude of approximately 110 km that is consistent with a sporadic E layer.
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All authors Joshua Goodwill, Timothy Tomaszewski, Jarrod Bieber, Carson P. Brown, Ashton Southwick, Samuel Auerbach, Sreenidhi Banda, Alex Bruce, Marisol Catalan Olais, Markos Duey, Ranyah Khan, Connor McCleery, Jonathan Rosado, Amanda Swenson, Matthew Ward, Jarod Dagney, David Sundkvist, John W. Bonnell, William H. Matthaeus, Bennett A. Maruca
High Energy Astrophysical Phenomena
Suppression of spiral density waves in collisionless accretion flows
Stephen Majeski, Matthew W. Kunz and Jason Dexter
Spiral density waves are ubiquitous phenomena in differentially rotating flows. They are non-modal, non-axisymmetric perturbations that, due to shear in the background flow, possess time-evolving wavenumbers, frequencies, and amplitudes. In global simulations of optically thin, low-luminosity black-hole
accretion flows, the excitation of such waves leads to spiral patterns in the
plasma density that influence the morphology of the emission region. As such, the observed variabilities of such
accretion flows are expected to be affected by the behavior of spiral density waves. Thus far, investigations of spiral density waves in
accretion flows have exclusively used the assumption that the
accretion-flow
plasmas are in local thermodynamic
equilibrium (LTE) at all times. In reality, hot and diffuse
accretion-flow
plasmas are expected to deviate far from LTE, and should be modeled accordingly. Here, we employ a combination of kinetic and fluid models to describe spiral density wave propagation, damping, and excitation in a collisionless shearing sheet, which more accurately represents the
plasma conditions of low-luminosity
accretion flows than do models that assume LTE. We find that micro-physical
plasma instabilities are especially important in determining how spiral density waves behave, because the weak particle scattering that they induce leads to appreciable viscous damping. Observational implications of these results include reduced emission-region variability, which may improve agreement between Event Horizon
Telescope (EHT) observations and simulation/theory, as well as a reduction in emission-region pattern speeds compared to simulations employing LTE, which bears on the interpretation of eventual EHT movies.
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Fluid Dynamics
Linear stability of electroconvection in a viscoelastic electrolyte: polymeric-work pathways and eigenmode selection
Minyoung Kim
Electroconvective (EC) instability near ion-selective surfaces plays a key role in electro-chemical transport beyond the
diffusion-limited regime. While EC instability in Newtonian electrolytes has been extensively investigated, the influence of viscoelasticity on the instability mechanism remains less understood. In the present study, we investigate the viscoelastic modulation of EC instability using linear stability, eigenspectrum, and mechanical-work analyses, supported by asymptotic pathway ordering. The analysis reveals a non-monotonic dependence on the Weissenberg number Wi, with the maximum growth rate and minimum critical voltage occurring near Wi ~ O(1). The mechanical-work balance separates electric, solvent-viscous, and polymeric contributions, and further decomposes the polymeric work into normal-stress-difference and shear-stress pathways according to their constitutive origins. For Wi << 1, the
polymer stress recovers Newtonian viscous dissipation at leading order. As Wi approaches unity, the phase efficiencies of the Newtonian-like polymeric pathways decrease substantially, causing the negative polymeric work to collapse and the instability to intensify. At intermediate Wi, an additional minimum in the critical voltage appears at low wavenumbers. Eigenspectrum analysis attributes this feature to the selection of a slowly propagating mode that retains substantial negative polymeric work. At large Wi, this mode no longer determines the instability threshold, and the low-wavenumber minimum disappears. The normal-stress-difference and shear-stress work then nearly cancel, accompanied by stronger ESC-localized shear deformation and predominantly solvent-viscous dissipation. Thus, the non-monotonic response is governed by stress-deformation phase relations, solvent dissipation, and eigenmode selection rather than stress magnitude or a single polymeric contribution.
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Quantum Physics
Single-photon addition to multimode quantum fields at telecom wavelengths using lithium niobate and its doped variants
Naveen V, Nicolas Treps, Raghavan G et al. (+2 more)
Multimode spectro-temporal non-Gaussian
quantum states of light play a crucial role in continuous-variable
quantum information processing. In particular, the non-Gaussian
quantum states generated through a single-
photon addition (SPA) to multimode
quantum fields at telecommunication wavelengths constitute a useful resource for
quantum technologies. We present a detailed theoretical analysis and numerical simulations of single-
photon addition (SPA) and mode-selective single-
photon addition (MSSPA) to a multimode
quantum field at telecommunication wavelengths. The analysis is performed for congruently grown lithium niobate (LN), $5\%$ MgO-doped lithium niobate (MgO:LN) and various concentrations of ZnO-doped lithium niobate (ZnO:LN) bulk
crystals. We investigate MSSPA using type-II parametric down-conversion (PDC) and SPA using the type-I PDC processes. We further present spectro-temporal mode-selective SPA at the telecom wavelength using $5\%$ MgO:LN for temperatures ranging from $0^\circ C$ to $15^\circ C$. In addition, we perform simulations to investigate SPA based on the noncollinear type-I PDC configuration. These theoretical results identify optimal experimental conditions and phase-matching parameters to achieve SPA and mode-selective SPA for LN-based
crystals, providing a potential platform for non-Gaussian
quantum state engineering at telecommunication wavelengths, mainly at $1550$ nm.
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All authors Naveen V, Nicolas Treps, Raghavan G, Valentina Parigi, Srinivasan K
Quantum Physics
Robust constrained optimization of nonequilibrium Casimir repulsion in a biased-semiconductor cavity
Mohamed R. Khodja and Belkacem E. Khodja
Nonequilibrium electromagnetic fluctuations offer a route to repulsive Casimir–Lifshitz forces. However, designs optimized only at nominal conditions may be fragile. We formulate repulsion in a planar PEC–
vacuum–biased-GaAs–
vacuum–PEC stack as a robust constrained optimization problem. The smaller of the outward pressures on the two conductors is maximized under fabrication and drive uncertainties. In the optically thick-slab limit, we prove that identical boundaries admit a symmetric optimizer, so equality of the optimal gaps emerges from the model rather than being imposed. At $300~\mathrm{K}$, with gap uncertainty of $\pm10~\mathrm{nm}$ and drive uncertainty of $\pm0.005$, the optimized design sustains a worst-case outward pressure of $2.257~\mathrm{mPa}$ and exceeds the corresponding far-field radiation-pressure plateau by $0.1812~\mathrm{mPa}$. At the nominal and active worst-case points, a full finite-slab scattering calculation agrees with the reduced model to within $1.60\times10^{-3}\%$. These results provide a design bound for cavity-enhanced nonequilibrium Casimir–Lifshitz repulsion and show how robust optimization can distinguish cavity enhancement from ordinary far-field radiation pressure.
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Astrophysics of Galaxies
X-ray Characterization of Galaxy Groups and Hickson Groups in COSMOS-Web to z~3.8 I. X-ray Luminosity Function Evolution
Ghassem Gozaliasl, Günther Hasinger, Gavin Leroy et al. (+35 more)
Galaxy groups are the dominant
halo environment in the Universe and a sensitive laboratory for feedback and gas-cycling physics, yet a uniform, intermediate-
redshift X-ray characterization of the group population has been limited by the availability of deep, wide-area imaging. We present a uniform X-ray characterization of the COSMOS-Web
galaxy group population: 1,678 groups (CW-All) identified with the AMICO
algorithm applied to the JWST-selected COSMOS-Web photometric catalog ($0.08 \lesssim z \lesssim 3.7$), and a parallel sample of 993 Hickson compact groups (CW-HCG; $0.08 \lesssim z \lesssim 3.82$) over $0.45~\mathrm{deg}^2$. We apply a uniform aperture-photometry X-ray pipeline to the combined Chandra and XMM-Newton COSMOS mosaic, measuring fluxes, luminosities, temperatures, and
halo masses and radii for every group, together with detections, upper limits, and quality flags. We detect X-ray emission from 499 CW-All groups (29.7%) and 332 CW-HCG groups (33.4%) at SNR~$\geq 2.0$, and present the X-ray luminosity function in four
redshift bins. The characteristic luminosity $L^\star$ rises monotonically by $\sim$1.9–2.1~dex from the lowest to highest
redshift bin in both catalogs, a trend that persists under two independent cross-check binning schemes and is not explained by mass or richness selection of the detected population. A targeted search for diffuse X-ray emission from the AmicOne protocluster candidate at $2.50 \lesssim z < 3.09$ finds no statistically significant signal at the current depth. We publicly release the X-ray measurements and derived properties for both catalogs.
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All authors Ghassem Gozaliasl, Günther Hasinger, Gavin Leroy, Alexis Finoguenov, Fatemeh Abedini, Hollis B. Akins, Rafael C. Arango-Toro, Arif Babul, Caitlin M. Casey, Nicole E. Drakos, Andreas L. Faisst, Carter Flayhart, Maximilien Franco, Zohreh Ghaffari, Santosh Harish, Hossein Hatamnia, Olivier Ilbert, Jeyhan S. Kartaltepe, Ali Ahmad Khostovan, Maarit Korpi-Lagg, Ronaldo Laishram, Daizhong Liu, Matteo Maturi, Henry Joy McCracken, Jed McKinney, Nicolas McMahon, Lauro Moscardini, Mahdiyar Mousavi-Sadr, Jason Rhodes, Brant E. Robertson, Louise Paquereau, Rasha M. Samir, Mark Sargent, Diana Scognamiglio, Marko Shuntov, Greta Toni, Francesco Ubertosi, Eleni Vardoulaki
Astrophysics of Galaxies
Separating the Optical to Near-Infrared Light of AGN and Their Host Galaxies
Callum Dewsnap, Pauline Barmby and Sarah C. Gallagher
The properties of
galaxies that host active
galactic nuclei (AGNs) offer clues to the conditions that enable
accretion onto supermassive black holes. A
galaxy's morphology can provide significant information on the evolutionary processes underway. By modeling the surface-brightness profiles of
galaxies that host AGN, we can characterize physical properties of the host
galaxy. With a sample of sources across a wide range of
redshifts, we can investigate how both the supermassive black hole and
galaxy evolve over time. Applying the best practices from previous work, we perform Sersic + point source fits of 96 X-ray-selected AGN in the Extended Groth Strip across up to 13 bands of James Webb Space
Telescope and Hubble Space
Telescope imaging using AstroPhot. We examine both parametric (Sersic) and nonparametric methods in tandem to best determine the physical properties of the host
galaxy. After separating the light of the host
galaxy and the AGN, we perform independent CIGALE model fits to photometric spectral energy distributions to estimate physical properties including the host
galaxy stellar mass and
star formation rate, and AGN disk luminosity. In the
stellar-mass/
star-formation-rate plane, the AGN host
galaxies align with the population of massive non-AGN
galaxies in the control sample across all
redshifts. The AGN disk luminosities result in ratios of bolometric to X-ray flux within the expected range, 5-20:1. We provide an evaluation of the limitations of Sersic modeling to obtain
galaxy properties and provide recommendations on best practices for multi-band AGN+host
galaxy image decomposition with James Webb Space
Telescope imaging.
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High Energy Physics (Phenomenology)
$SU(\mathcal{N})$ baryon formation in the early Universe and dark matter
Luca Di Luzio, Samuele Di Valeriano and Enrico Nardi
We study the formation of $\mathcal{N}$-
quark baryons during the confinement crossover of an $SU(\mathcal{N})$ gauge theory containing
quarks in the fundamental representation, with masses around or below the confinement scale. We assume stepwise
baryon formation through the successive fusion of pairs of
quark-clusters, with color interaction rates obeying quadratic Casimir scaling. We include the complete set of reactions between $SU(\mathcal{N})$ antisymmetric clusters dressed with their specific
spin-
flavor multiplicities. We show that at large $\mathcal{N}$,
baryon formation is hindered by a Casimir bottleneck, such that fusion of few-
quark clusters in the initial steps of the
baryon assembly chain is strongly outweighed by cluster destruction processes. We find that for $\mathcal{N}=12\,(18)$ the
baryon-to-
meson yield ratio is suppressed down to $10^{-12}\,(10^{-23})$ of its value at $\mathcal{N}=3$. We embed the mechanism in a vectorlike three-
flavor model whose lightest
baryon can be electrically neutral, while axial-anomaly-induced couplings and dimension-six operators induce decays of the unstable
mesons and charged
baryons safely before big-bang nucleosynthesis. The relic density of cosmologically stable neutral $\mathcal{N}$-
baryons is thus set during confinement at values so small that, for sufficiently large $\mathcal{N}$, the
baryon masses required to saturate the dark matter energy density exceed by several orders of magnitude the unitarity bound on annihilation cross sections.
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Disordered Systems and Neural Networks
Universal energy barrier for plastic flow in a network glass
Ibrahim Ghanem, Richard Jana, Wolfram G. Nöhring et al. (+2 more)
Shear transformations are the elementary events of plasticity in glasses and underpin many mesoscopic models of plastic flow, yet their atomic origin and energetics remain difficult to establish. Here we use a machine-learned interatomic potential to show that, in amorphous carbon as a representative network glass, a shear transformation corresponds to the breaking or formation of a single covalent bond. The simplicity of the associated reaction coordinate, the bond length, enables us to extract energy landscapes and barriers. Despite the intrinsic structural disorder, we find that all energy landscapes collapse onto a universal barrier shape. What remains bond-specific is a single scale, the bond-jump distance, which fixes the barrier height through a cubic law. Combined with the activation statistics of shear transformations, this yields a model that predicts the plastic flow stress from independently determined bond-level quantities. Our results provide microscopic support for phenomenological models of plastic flow in glasses and suggest a route towards a quantitative description of amorphous plasticity.
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All authors Ibrahim Ghanem, Richard Jana, Wolfram G. Nöhring, Michael Moseler, Lars Pastewka
Quantum Physics
Investigating entanglement dynamics with dynamical decoupling together with initial qubit-reservoir correlations
Rifzah Shahid, Amna Qadeer and Ali Raza Mirza
We study the exact
entanglement dynamics of two
qubits coupled to a common bosonic reservoir through a pure dephasing interaction. We ask how this dynamics changes when the
qubits and the reservoir already share correlations before the
qubit state is prepared. In that case the system and reservoir first interact for a long time and settle into a joint
equilibrium state. Only afterward is the
qubit pair projected onto the desired state by a local measurement. For an Ohmic spectral density we obtain the exact reduced two
qubit dynamics. Using the Wootters concurrence we show that initial correlations always speed up
entanglement sudden death relative to the factorized case, and that this gap grows quadratically with the coupling strength in the weak-to-moderate coupling regime. Finally we show that a symmetric sequence of periodic {\pi} pulses applied to both
qubits extends the
entanglement lifetime close to a factor of seven over the range of pulse numbers studied.
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Instrumentation and Methods for Astrophysics
Learning Approximate Isometric Embeddings for Efficient Template Placement
Alexandra Wernersson, Jessica Irwin, Melissa Lopez et al. (+1 more)
The sphere covering problem has broad applications in science however, exact solutions are computationally infeasible on curved, high-dimensional
manifolds because distances must be evaluated using a position-dependent metric. We present $\texttt{isobank}$, a normalizing flow that learns an approximately isometric coordinate transformation, such that Euclidean distances in the latent space approximate metric-induced proper distances in the physical parameter space. This enables template placement using Euclidean distance checks in the latent space, avoiding repeated metric evaluations during placement. We evaluate $\texttt{isobank}$ in the context of gravitational wave template bank construction, where the sphere covering problem corresponds to the template placement problem. On a five-dimensional eccentric binary parameter space, $\texttt{isobank}$ reaches 97% coverage at a maximum mismatch of $\mu=0.03$ with 23% fewer templates than the state-of-the-art
stochastic placement code $\texttt{mbank}$, which reaches 94% coverage. Coverage is measured on independent injections drawn uniformly over the masses,
spins and eccentricity, using the exact waveform match rather than the metric approximation. Training the flow takes about 2.5h and placing the bank under 1h on 32 CPU cores. $\texttt{isobank}$ is publicly available on Github https://github.com/Alexandra-Wernersson/isobank
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All authors Alexandra Wernersson, Jessica Irwin, Melissa Lopez, Sarah Caudill
Physics and Society
Measuring Diversity and Segregation with Convex Functions
Philip S. Chodrow
The problem of segregation measurement is to quantitatively describe the interaction of a population's attributes (such as race, ethnicity, education level, or income) with a separating distinction (such as organizational rank, school district, or spatial location). This primarily expository article gives an opinionated tour of one mathematical approach to measuring segregation. We begin with some basic intuitions about diversity and unify these through the framework of convex functions on the probability simplex. Formalizing segregation as a local-to-global comparison of diversity measures, resulting in the general class of Jensen informations as segregation measurements. We describe and computationally illustrate three ways to incorporate spatial structure into segregation measurements: spatial smoothing, aggregation, and local Jensen information. We close with several suggestions for future work.
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Pattern Formation and Solitons
Bacterial aggregation in the presence of directed motion
Timothy Power, Hildur Knutsdottir, Leah Edelstein-Keshet et al. (+1 more)
We model directed motion of
cells that aggregate into a cluster in the presence of chemotaxis or fluid transport. Starting from a
stochastic agent-based model (ABM) of Galante & Levy (2013), Chavy-Waddy & Kolokolnikov (2016), we consider two model variants, with (I) directed motion of individuals, or (II) implicit individual bias in one direction. In both cases, we derive fourth order nonlinear PDEs representing the continuum limits of the models as a generalization of Chavy-Waddy & Kolokolnikov (2016). An exact analytic solution then describes cluster density profile as well as the group velocity, and we identify the regimes where the travelling cluster exists. Excellent agreement is observed between the discrete models and the exact solutions of the PDEs in both models, including the existence and speed of the travelling cluster.
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All authors Timothy Power, Hildur Knutsdottir, Leah Edelstein-Keshet, Theodore Kolokolnikov
Earth and Planetary Astrophysics
TOI-1408: the limb darkening models, photometric and Doppler noises, and the exoplanetary system
Roman V. Baluev
We perform a self-consistent analysis of Doppler and photometric TESS and ground-based transit observations available for TOI-1408, known to host a system with two
planets orbiting near 2:1 mean-motion commensurability and a distant companion. In general we confirm its orbital configuration derived in previous studies, however we found that the likelihood function contains multiple local maxima spread over a wider parametric domain, thus making some model uncertainties significantly larger than deemed before. In particular, the
planet b radius still appears poorly constrained (from $\sim 1.2$~$R_{\rm Jup}$ to $\sim 3.5$~$R_{\rm Jup}$) because of the near-tangential transit geometry. We also show that the derived model is very prior-dependent regarding the astrophysical (spectrum-derived) constraints on the
stellar mass $M_\star$ and radius $R_\star$. While such estimations may potentially contribute a significant information to the fit, their prior distribution must be accurately specified to be useful. Presently so accurate characterization (e.g. the correlation between $M_\star$ and $R_\star$) is not available in the literature.
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Lattice Field Theory
Towards Precision-Controlled Partonic Structures from First Principles
Jinchen He
The internal structure of
hadrons is governed by nonperturbative
Quantum Chromodynamics (QCD). This dissertation presents first-principles calculations of partonic observables using
lattice QCD and effective field theory, with controlled systematic uncertainties, advancing from collinear structure to transverse-momentum-dependent distributions (TMDs) that encode the three-dimensional partonic structure of
hadrons. Within the large momentum effective theory (LaMET) framework, this work presents state-of-the-art calculations of pion distribution amplitudes and systematic studies of nucleon parton distributions, with control of renormalization, excited-state contamination,
Fourier-transform systematics, and power corrections. A Coulomb-gauge formulation of quasi-distributions simplifies ultraviolet structure by avoiding Wilson-line related linear divergences, with Gribov-copy effects found to be negligible at current statistical precision. Building on these developments, this dissertation reports
lattice determinations of nucleon TMD parton distributions, the Collins-Soper kernel, the intrinsic soft function, and pion TMD observables. These results provide nonperturbative inputs for global QCD analyses and the precision
hadron-structure program, including the Electron-Ion
Collider. In parallel, this work explores machine-learning acceleration of
lattice gauge simulations through neural field transformations embedded in Hybrid Monte Carlo. In two-dimensional U(1) tests, the method reduces autocorrelation and improves performance toward finer
lattice spacing, suggesting potential applications to more efficient
lattice QCD simulations.
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High Energy Astrophysical Phenomena
Extending the Pulsar radio population through Quantum Vacuum Cherenkov Emission
Tales A. O. Gomes, Sergei V. Bulanov, Jaziel G. Coelho et al. (+3 more)
The presence of some
radio pulsars within and below the so-called “death valley” in the $P$–$\dot{P}$ diagram challenges the standard pair-cascade models based on
curvature radiation (CR) and resonant inverse Compton scattering (RICS) in
neutron star polar caps. We show that Cherenkov radiation from the
quantum vacuum, a strong-field
quantum electrodynamics (QED) phenomenon enabled by
vacuum polarization, constitutes a distinct pair-creation channel within the
vacuum gap model. Within this model, the acceleration length scale for Cherenkov
photon emission and the subsequent
photon mean free path are sufficiently short to ensure rapid conversion into $e^+e^-$ pairs. This process acts as a complementary pair-creation channel, remaining viable even in regimes where classical mechanisms become heavily suppressed. This leads to a new set of death lines in the $P$–$\dot{P}$ diagram that partially overlap with and extend beyond the CR and RICS death valleys, enlarging the viable parameter space for
radio-emitting
neutron stars. The result provides a physical basis for coherent
radio emission from long-period
neutron stars previously considered inactive, and offers a new window for testing non-linear QED with next-generation
radio facilities such as the Square Kilometre Array.
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All authors Tales A. O. Gomes, Sergei V. Bulanov, Jaziel G. Coelho, Martin Jirka, Alexander J. Macleod, J. A. Rueda
Disordered Systems and Neural Networks
Breakdown of material-time scaling in the microscopic dynamics of metallic glasses
Till Böhmer, Jie Shen, Jan Philipp Gabriel et al. (+6 more)
Physical aging in glasses is often described using the concept of material time, which assumes the underlying relaxation mechanism to remain the same as in
equilibrium, but with a rate that changes during aging. Whether material time also captures the microscopic dynamics of metallic glasses, which differ qualitatively between the glass and the
equilibrium supercooled
liquid, is unclear. Using simultaneous time-resolved X-ray diffraction and X-ray
photon-correlation spectroscopy, we follow the full equilibration of a metallic glass after small temperature jumps starting from
equilibrium. The time
evolution of the first sharp diffraction peak position exhibits the asymmetry between temperature up- and down-jumps characteristic of material-time aging and is quantitatively described by the Tool-Narayanaswamy-Moynihan model, which is based on this concept. By contrast, the microscopic density-density autocorrelation functions strongly violate material-time scaling. Compressed-exponential relaxation emerges even after temperature changes as small as 4K, irrespective of the direction of the temperature jump, and continuously evolves into a stretched-exponential relaxation shape following the equilibration of the average structure. This behavior is consistent with a transient stress-mediated contribution associated with volumetric frustration that disappears upon equilibration. Our results show that a material time can describe the
evolution of average structural properties even when the corresponding microscopic dynamics do not obey material-time scaling.
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All authors Till Böhmer, Jie Shen, Jan Philipp Gabriel, Rolf Zeißler, Federico Zontone, Fan Yang, Eloi Pineda, Beatrice Ruta, Thomas Blochowicz
High Energy Physics (Theory)
Note on the Pure State of Old Black Holes in Some Models of Asymptotically Flat Quantum Gravity
T. Banks
We analyze two old models of black holes to see whether they realize the AdS/CFT paradigm of “multiple representations of bulk data by boundary states that differ only in the expectation value of exponentially complex operators" . We find that the explanation of the firewall paradox in these models is much simpler and corresponds to the naive way
entanglement is resolved when small constituents escape from a complex chaotic
quantum system. The real issue is that the
quantum field theory (QFT) picture of the states near the boundary of a causal diamond is wrong. The phrase in quotes above is correct in our models because most of the states associated with any causal diamond cannot be associated with ANY states in
quantum field theory.
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Mesoscale and Nanoscale Physics
Highly Tunable Photon-Magnon Coupling Governed by Collective-Mode Profiles in Reconfigurable Dielectric-Resonator Arrays
Shihao Zhou, Edward Kwao, Junming Wu et al. (+7 more)
The spatial structure of a microwave
photon mode provides a degree of freedom for controlling its interaction with a localized
magnetic excitation. We demonstrate site-selective
magnon-
photon coupling in modular arrays of discrete dielectric resonators mounted on a common microstrip line. The resonators can be added, removed, or rearranged on the same completed PCB, enabling post-fabrication geometrical reconfiguration of the collective
photon modes and their nodal structure. A YIG sphere is positioned successively above individual resonators, while an in-plane
magnetic field tunes its Kittel mode through the collective
photon resonances. In a three-resonator array, modes with finite local microwave
magnetic fields hybridize with the
magnon at every measured site, whereas a mode containing a central field node exhibits no resolvable splitting when the sphere is positioned at that node. Full-wave simulations and a coupled-mode model show that the interaction is governed by the local amplitude of the collective
photon mode rather than by spectral resonance alone. Extending this local-node selection rule to a five-resonator array successfully predicts the measured position-dependent coupling patterns. These results establish post-fabrication control of spatial
magnon-
photon hybridization and provide a route toward reconfigurable magnonic interfaces in future hybrid
quantum microwave architectures.
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All authors Shihao Zhou, Edward Kwao, Junming Wu, Abhijit Shinde, Yin Lyu, Rene Lopez, Wencan Jin, Yi Li, Binbin Yang, Wei Zhang
High Energy Physics (Phenomenology)
High Energy Neutrinos, Gravitational Waves, and Dark Matter from a Cosmological First Order Phase Transition
James M. Cline, Savas Stoica and Yong Xu
We investigate high energy
neutrinos (HE$\nu$s) from the decay of superheavy dark matter (DM) produced during a cosmological first order phase transition. Adopting the filtered DM production mechanism, we revisit the relic abundance calculation by incorporating recent progress in determining the bubble wall velocity from hydrodynamics. We show that DM with mass $m_{\text{DM}}\simeq 4.4\times10^{8}~\text{GeV}$ can reproduce the observed relic abundance and accommodate ultra high energy
neutrino events such as KM3-230213A, while the same phase transition simultaneously generates a
stochastic gravitational wave (GW) background. Although the GW signal (which peaks at $10^{4}\,\text{Hz}$) is not yet observable in this example, at lower DM masses $m_{\text{DM}} \lesssim10^{6}~\text{GeV}$, the
neutrino spectrum shifts into the energy range relevant for IceCube observations, while the associated GW signal moves to lower frequencies and can reach the projected sensitivities of
Cosmic Explorer, BBO, and DECIGO. This gives a multimessenger connection between HE$\nu$s and GWs, with both signals connected to DM production in a first order phase transition.
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Materials Science · Cross-listed from cs.LG
The AI Theorist reveals excitonic structure in $\alpha$-RuCl$_3$
Hongjian Zhou, Xianfan Nie, Sean Wu et al. (+5 more)
Advances in experimental instrumentation and automation generate increasingly rich
datasets, but turning experimental observations into microscopic understanding remains a bottleneck in scientific discovery. To accelerate this process, we introduce AI Theorist, a system of artificial intelligence (AI)
agents for autonomous discovery of physical models through hypothesis generation, first-principles calculations and evidence-driven refinement. We apply the framework to $\alpha$-RuCl$_3$, a leading candidate material for realizing a Kitaev
quantum spin liquid, to investigate its electronic structure through optical spectra. AI Theorist develops a new interpretation of the optical and photocurrent observations, identifying distinct excitonic states with contrasting optical selection rules and real-space distributions. To our knowledge, this is the first demonstration of an AI system autonomously developing a physical model to explain previously unpublished experimental observations in a
quantum material, utilizing first-principles electronic-structure and many-body calculations. Our results establish a route to autonomous theoretical discovery in materials science, in which AI
agents use first-principles calculations to turn experimental observations into physical models and testable predictions.
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All authors Hongjian Zhou, Xianfan Nie, Sean Wu, Tarun Patel, Jinge Wu, Andrew Liu, Adam Wei Tsen, David A. Clifton
Nuclear Theory
The causal diamond of relativistic hydrodynamics
L. Gavassino
The convergence of hydrodynamics is commonly investigated by Taylor-expanding the gapless dispersion relations $\omega(k)$ around $k=0$. We show that this diagnostic can fail arbitrarily close to the hydrodynamic limit: sound modes can collide at arbitrarily small wave number, rendering $\omega(k)$ nonanalytic, while the relationship between densities and fluxes remains analytic there. We instead formulate the gradient expansion off-shell (i.e. in the presence of external forces), directly at the level of the constitutive relations. For causal theories with relaxational spectra, we establish convergence for $|i\omega|+w|ik|<1/\tau_g$, where $w$ is the maximal information speed and $1/\tau_g$ the nonhydrodynamic gap. On the naturally Lorentzian $\{i\omega,ik\}$ plane, this region is a causal diamond, whose boundary marks the first possible encounter with nonhydrodynamic modes. Beyond it, analytic continuation reveals the nonhydrodynamic spectrum through singularities of the resummed constitutive relations. Thus, hydrodynamics is aware of the degrees of freedom beyond hydrodynamics, but this information becomes fully accessible only off-shell.
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