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Thursday 6 August

Astrophysics of Galaxies

A Detailed Analysis of Intermediate-scale Structure in Optical Extinction Curves: Expanded Census and Two-family Classification

C. M. Gunasekera, M. Decleir, K. D. Gordon et al. (+4 more)

The features of interstellar extinction curves serve as powerful diagnostics for interstellar dust, revealing information about its composition, size distribution, and the physical and chemical processes that shape it. D. Massa et al. reported three faint but wide extinction features, termed intermediate-scale structures (ISS) at 4370, 4870, 6300 Å. Since then, three additional ISS features have been reported in the literature at 7700, 5400, 8500 Å, all with widths greater than any known diffuse interstellar band. We present new optical and UV Hubble Space Telescope/STIS spectra for a sample of 24 early-type OB stars. We used these data combined with 50 literature targets for a systematic, homogeneous analysis of ISS features, with the aim of investigating their observational behavior to help constrain their carriers. This analysis revealed nine more candidate ISS features. We also find that ISS features can be arranged into two main families, which we call $\alpha$ and $\beta$, according to correlations between the feature strengths. Finally, we find strong correlations between the 2175 Å bump strength and ISS features at 4353, 4847, 6443, 7710 Å, suggesting their possible carbonaceous origin.
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All authors C. M. Gunasekera, M. Decleir, K. D. Gordon, G. C. Clayton, B. Günay, D. V. De Putte, P. Yanchulova

Nuclear Theory

Revised analysis of the strengths of the contact potential at N4LO through nuclear and neutron matter

Francesca Sammarruca and Tomiwa Ajagbonna

We examine the contact three-nucleon force at N4LO expressed as a density dependent potential. In Ref. [1], the necessary couplings (13, including two that appear in the leading three-nucleon force), were extracted from nd scattering observables. The contact strengths obtained through the three-nucleon continuum, without ?ts to the triton, seem incompatible with the energy of nuclear and neutron matter. We take the opportunity to revisit the role of the cD, cE couplings of the leading three-nucleon force in nuclear matter and nuclei. We close with a discussion about recent ?ttings of three-nucleon scattering observables using a spectroscopic basis for the subleading contact three-nucleon force. Using the errors given for the couplings in the spectroscopic basis, we derive uncertainty bands for the strengths in the operator basis and their contributions to the leading and subleading three-nucleon contact interactions.
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Physics and Society

Baseline-referenced spatial early warning signals for tipping points on heterogeneous networks

Tharusha Bandara, Shilong Yu and Naoki Masuda

Anticipating tipping points in complex systems is difficult because many early warning signals require long time series, which are often unavailable in practice. Spatial early warning signals offer an alternative by using a single snapshot across many interacting elements, or nodes. However, their performance in heterogeneous systems is often inconsistent because raw node states reflect both dynamical changes associated with an approaching transition and static heterogeneity induced by network structure. Here, we propose a baseline-referenced framework for spatial early warning signals. The method compares each node's state with its own baseline far from the tipping point before computing a spatial statistic, thus reducing network-structure-induced variation. We evaluate baseline-referenced variants of five classical spatial early warning signals across diverse tipping scenarios and networks, and find that baseline referencing markedly improves variance-based spatial signals. The best variants increase consistently and progressively toward tipping points across different scenarios, outperform a single-node temporal variance that requires long time series, and retain high performance even when up to 80% of nodes are omitted from observation. These results provide a practical route for using spatial early warning signals in heterogeneous networked systems when dense temporal monitoring or complete network-wide observation is infeasible, as is often the case in real applications.
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Fluid Dynamics

A Symplectic Theory of Turbulence Closure: Hidden Reservoir Dynamics, Endogenous Stochastic Transport, and Kraichnan Dual Cascades

Mickaël D. Chekroun and James C. McWilliams

The equations of fluid motion are known; retaining their physics after removing most degrees of freedom remains a fundamental problem. Closure must preserve the geometry of the dynamics it replaces. We introduce Symplectic Geometric Closure (SGC), a prognostic stochastic field theory carrying Euler's Hamiltonian, area-preserving transport into two-dimensional and $\beta$-plane turbulence. SGC couples resolved vorticity to a hidden stochastic reservoir. The coupling conserves augmented enstrophy while permitting bidirectional energy transfer. This yields a compact random attractor in the hyperviscous Navier–Stokes–$\beta$ realization. Numerically, SGC sustains jets, vortices and filaments in high-Reynolds-number turbulence with high fidelity to filtered DNS at an inertial-range cutoff, preserving geometric identities to machine precision. The induced transport folds, stretches and rearranges vorticity: cross-gradient coupling selects interactions through resolved–reservoir gradient misalignment, retaining geometric selectivity and memory. The same geometry addresses spurious sweeping decorrelation, a longstanding obstacle to Eulerian closure. The interaction vertex excludes uniform translation and is Random Galilean compatible. Eliminating the reservoir generates finite memory, stochastic backscatter and a Dyson–Volterra equation for the dressed propagator. Its one-loop, line-renormalized self-energy reproduces Kraichnan-type Direct-Interaction Approximation architecture with fourth-order infrared suppression of sweeping. Deformation-controlled memory and conservative triad constraints yield the $k^{-5/3}$ inverse-energy and $k^{-3}$ forward-enstrophy cascades under standard assumptions. SGC thus realizes Kraichnan's program through Eulerian field dynamics, opening a route to data-driven closures that learn admissible geometric interactions rather than unconstrained forces.
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High Energy Physics (Theory)

Superselected ghost theory: real spectrum

Bob Holdom

Quantum field theories with ghosts can be unitary and perturbatively stable, yet the negative-norm states of their conserved indefinite inner product obstruct a probabilistic interpretation. This problem is especially relevant to renormalizable quantum gravity. The focus of this paper is the real-spectrum regime, in which the interacting Hamiltonian has an exact $\mathbb{Z}_2$ symmetry $Q$, called exact ghost parity. Its eigenvalue on each energy eigenstate equals the sign of the norm, and it reduces to free ghost parity at zero coupling. Imposing $Q$ as a superselection charge defines a new theory in which the physical states have definite ghost parity and the observables commute with $Q$. The native Born rule then yields non-negative probabilities, while the optical theorem acquires a direct probabilistic interpretation. The propagator decomposes into $Q$-sector spectral representations with fixed-sign spectral functions and no complex poles on the physical sheet. Finally, a similarity transformation yields a Hermitian perturbation theory that preserves free ghost parity order by order, making the exact superselection structure perturbatively manifest.
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Solar and Stellar Astrophysics

The Maunder Model and Catalog: Stellar Rotation, Bimodal Activity, and Magnetic Braking in Kepler Main-Sequence Stars

Ilay Kamai, Lavi Somers and Hagai B. Perets

We present The Maunder, a machine learning pipeline and resulting catalog of rotation periods for 148,746 main-sequence stars in the Kepler field. To overcome single-catalog systematics and the simulation-to-reality gap, our architecture employs a hybrid training objective: a joint-embedding self-supervised loss applied to all light curves, combined with a supervised loss trained strictly on cross-catalog consensus labels. By processing multi-scale time- and frequency-domain inputs over rolling windows, the model leverages conformalized quantile regression to output calibrated predictive intervals, providing statistically robust per-star rotation uncertainty metrics. This rolling-window inference reveals that 31,953 stars (21.5$\%$) exhibit bimodal rotational signals. By incorporating APOGEE $v \sin i$ measurements, we demonstrate that for distinct (non-harmonic) bimodals, the longer mode represents the true rotation, exposing a systematic failure mode wherein classical single-pass periodograms lock onto shorter aliases. Filtering by our calibrated confidence intervals yields a highly reliable subset of 119,428 stars. The catalog resolves various rotation-related phenomena: the metallicity dependence of rotation at fixed stellar mass, pointing on the role of metallicity in magnetic braking processes; tracing equatorial velocity and specific angular momentum directly across the Kraft break; recovery of empirical gyrochronology sequences and identification of hierarchical triple candidates among the synchronized-binary population. The Maunder provides reliable rotation periods for the largest main-sequence population in Kepler, allowing for population-level studies of rotation-based phenomena.
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Optics

Grape expectations: direct thermographic imaging of electric fields in microwave Mie resonators

Kallan K. Ronholm, Yuchen Song and Aaron D. Slepkov

Internal electromagnetic fields determine the behaviour of dielectric nano-resonators, yet they remain exceptionally difficult to measure directly because subwavelength scales place them beyond conventional optical measurement, and any probe capable of local sensing perturbs the field it seeks to measure. We circumvent this limitation using water's high refractive index at microwave frequencies, which lets centimetre-scale aqueous spheres—grapes—serve as directly measurable, scale-invariant analogs of high-index nanophotonic resonators. Using polarization-controlled free-space excitation and infrared thermography, we show that internal heating patterns in grapes closely track simulated electric-, but not magnetic-, field distributions for both the fundamental magnetic- and electric-dipole Mie resonances. Extending this approach to grape dimers, we demonstrate that the massively sub-wavelength inter-object hotspot associated with microwave-induced sparking forms only under axial polarization, thus providing both a clue to its origin and a means for its control.
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Superconductivity

Determination of the properties of a superconducting single crystal FeSe using an EPR spectroscopy

S.I. Bondarenko, A.A. Prokhorov, N.N. Galtsov et al. (+3 more)

Using an EPR spectrometer, the properties of single-crystal FeSe were studied in a magnetic field up to 6000 Oe at temperatures from 3.5 K to 8 K in the superconducting state and at temperatures above 8K and up to 25K in the normal state. It was shown that by measuring non-resonant spectrometer signals in zero and weak magnetic fields up to 30 Oe, it is possible to determine critical temperature Tc, the superconducting transition width, and the value of the first critical magnetic field Hc1 in FeSe single-crystal. Resonant EPR signals are observed in fields at 1400 Oe and 3400 Oe, which corresponds to the paramagnetism of doubly ionized iron atoms (Fe2+) in the FeSe crystal. Non-resonant EPR signals in a magnetic field up to 6000 Oe at temperatures from 3.5K to 8K are a nonlinear function of the field, and correspond to the superconducting mixed state of the FeSe, but at temperatures above 8K (up to 25K) they are field independent.
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All authors S.I. Bondarenko, A.A. Prokhorov, N.N. Galtsov, V.P. Timofeev, V.P. Koverya, A.V. Krevsun

Earth and Planetary Astrophysics

Alkali Metallicity, Mineral Clouds, and Deep Atmospheric Variability on Jupiter

Xi Zhang, Jiheng Hu, Cheng Li et al. (+1 more)

The bulk elemental abundances of Jupiter provide critical insights into its formation history and interior structure. Recent observations by the Juno Microwave Radiometer (MWR) reveal a deep Jovian atmosphere significantly depleted in electrons, implying an alkali metal (Na, K) abundance of 10^-1 - 10^-5 times solar. This depletion stands in sharp contrast to the supersolar volatile enrichments measured by the Galileo probe. We propose that this apparent depletion arises from mineral cloud-induced processes deep in the atmosphere. We explore two physical mechanisms using thermochemical and microphysical modeling. In the "chemical sequestration" scenario, vigorous vertical mixing lofts deep refractory condensates (e.g., spinel) into the 1000-2000 bar region, where they react to form alkali feldspars (albite) and feldspathoids (leucite), efficiently sequestering gaseous Na and K. In the "dust-catalyzed recombination" scenario, the bulk alkali inventory remains gaseous, but the free electron density is suppressed by dust-plasma interactions. Thermally emitted alkali ions from the surfaces of micron-sized iron and silicate grains significantly increase the cation density, driving rapid recombination of free electrons. Both mechanisms allow for a bulk solar or even supersolar alkali inventory while suppressing the electron density to match Juno observations. Analyzing an extended dataset of MWR observations with 61 perijoves, we detect spatial variability in the deep atmosphere that suggests modulation by mineral clouds. Our findings challenge the traditional rainout framework, unveiling a deep "mineralogical zone" in Jupiter shaped by dynamics and heterogeneous chemistry, resembling the photospheres of hot exoplanets and brown dwarfs.
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All authors Xi Zhang, Jiheng Hu, Cheng Li, Quentin Williams

Statistical Mechanics

Cascading Through the Hierarchy: Regularizer-Induced Feature Detection as Phase Transitions in Deep Linear Neural Networks

Björn Ladewig, Ibrahim Talha Ersoy and Karoline Wiesner

A scientific theory of deep learning, comprising learning dynamics and statistical properties of learned models, is rapidly gaining attention. One of the corner stones of this development are analytically solvable toy models, allowing for the fully tractable analysis of the learning dynamics. Here we analytically investigate such a toy model using the regularization strength as a tunable external parameter - akin to external fields in statistical physics. In previous studies, (i) an onset of learning transition was predicted analytically and (ii) it was phenomenologically/numerically established that tuning the regularization strength can result in a cascade of phase transitions. The number of those transitions was linked to the geometry of the loss landscape determined by the model complexity. Setting up a rigorous framework underpinning the previous numerical observations, our investigation reveals a precise connection between those cascades of phase transitions, learnable features and the underlying geometry. We provide analytic predictions of these phase transitions as well as tractable order parameters related to learned features. At the level of the minimal model, we connect this macroscopic perspective (that can be condensed into an effective description) to the microscopic perspective in terms of the geometry of the loss landscape characterized by the Hessian spectrum. Thus, the presented model provides a platform to explore and sharpen advances made in the scientific theory of deep learning rooted in statistical physics concepts.
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Instrumentation and Methods for Astrophysics

Optomechanical Design of the MANTIS SmallSat: An Extreme-, Far- and Near-Ultraviolet Spectrograph for Exoplanet Host Stars

Brian Fleming, Briana Indahl, Dmitry Vorobiev et al. (+16 more)

The MANTIS (Monitoring Activity of Nearby sTars with uv Imaging and Spectroscopy) observatory is a compact, multi-instrument small satellite designed for simultaneous extreme- (EUV; 100 - 560 Angstrom), far- (FUV; 1150-1800 Angstrom) and near-ultraviolet/visible (NUV/VIS; 2000-6400 Angstrom) spectroscopy of low-mass stars. The EUV optical system consists of a first-of-its-kind Hettrick-Bowyer grazing incidence telescope contributed by the Italian National Institute for Astrophysics (INAF) feeding an advanced e-beam lithographic etched variable line spacing grating developed at Pennsylvania State University (PSU). The resulting low-resolution spectrum is imaged on an advanced microchannel plate detector with a potassium iodide (KI) photocathode for extremely low background noise, resulting in a limiting sensitivity for MANTIS that exceeds that of the last EUV-sensitive astrophysics point-source spectrograph, the Deep Survey/Spectrometer (DS/S) on EUVE. The FUV and NUV/Optical channels are fed by a compact rectangular telescope that focuses onto a series of point-source apertures. The diverging beam is refocused and the FUV band dispersed by a holographic grating, then folded back onto the same detector as the EUV channel by a toroidal fold mirror. The zero-order light is picked off by a flat NUV grating, with the NUV/Optical spectrum recorded on an e2v CCD 42-10 detector. The MANTIS spacecraft is a custom build that leverages the experience derived from prior University of Colorado - LASP SmallSats for avionics, power, communications, and mechanical structure. MANTIS is projected to be completed in 2027 with an anticipated 2028 launch as an ESPA-class payload on a rideshare opportunity.
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All authors Brian Fleming, Briana Indahl, Dmitry Vorobiev, Kristina Davis, Kevin France, David Wilson, Nicholas Kruczek, Timothy Hellickson, Emily Farr, Marta Civitani, Davide Sisana, Kotish Grover, Laura Proserpio, Stefano Basso, Vincenzo Cotroneo, Fabien Grise, Randall McEntaffer, Oswald Siegmund, Adrian Martin

High Energy Astrophysical Phenomena

Measuring the electric dipole moment of the neutron using neutron star spin-down

Abriana Lyda

The neutron electric dipole moment (nEDM) is a sensitive probe of CP violation beyond the Standard Model. We develop a source-specific framework for constraining CP-odd neutron structure using the nearby millisecond pulsar PSR J0437-4715. Mass and radius measurements are used to construct a stellar-structure model and estimate the polarized inner-crust neutron reservoir. Wideband radio polarimetry provides a propagation-informed surface-field posterior that is not obtained from the conventional $P\dot P$ magnetic-field estimate, while published NICER hot-region constraints are used to test low-order surface-field geometries and isolate the dipolar component entering the electromagnetic torque. These inputs are propagated through a present-day spin-down budget including electromagnetic and gravitational-wave losses. The remaining positive residual is first interpreted as an unscreened electric-dipole-radiation benchmark. Crustal and magnetospheric screening then motivate an effective CP-odd magnetic-quadrupole channel. Conditional on the adopted screening, coherence, and effective-mode-frequency prescriptions, the positive-residual branch gives a 90th-percentile bound $|M_n^0|<7.47\times10^{-38}$ e cm$^2$. With the adopted QCD conversion coefficients, this corresponds to $|\bar{\theta}|<2.99\times10^{-9}$ and an equivalent $|d_n|<4.42\times10^{-25}$ e cm. Although weaker than laboratory nEDM limits, the result demonstrates how source-specific neutron-star structure, radio propagation, magnetic geometry, and spin-down energetics can be combined to test nonstandard CP-odd radiation channels.
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Quantum Physics

Matrix Product State Theory of Few-Photon Squeezed Pulses Interacting with a Two-Level Emitter in a Waveguide

Sofia Arranz Regidor, Matthew Kozma and Stephen Hughes

Squeezed light states have a special place in quantum optics with potentially profound applications in emerging quantum technologies. We present a numerically-exact matrix product states (MPS) approach to model quantum pulses of squeezed light, at the few-photon level, interacting with a two-level system in a waveguide environment. We represent the squeezed state as a coherent superposition of Fock states and explore the nonlinear population dynamics as well as multi-photon correlation functions that emerge. We show how the squeezed pulse can create quantum correlations that are unique to squeezed pulses, including $\langle b(t) b(t+t')\rangle$ for transmitted fields as well as $\langle b^\dagger(t) b^\dagger(t+t') b(t+t') b(t) \rangle$. We also demonstrate how $\langle b(t) b(t+t') \rangle$, a first-order correlation function, shows nonlinear photon correlations that are similar to those known and measured for two-photon scattering states. Finally, we also study the squeezed spectra of the pulse before and after interacting with the two-level system, and highlight the role of the spectral bandwidth of the incident pulse. The MPS theory allows the modeling of arbitrary bandwidth squeezing without making any Markov and Born approximations for the light-matter interaction processes, and can easily be extended to waveguide systems with multiple emitters and time-delayed feedback.
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Earth and Planetary Astrophysics

Juno Microwave Observations Reveal Jupiter's Deep Alkali-Chlorine Relation

Xi Zhang, Jiheng Hu, Cheng Li et al. (+2 more)

The longest-wavelength channel of the Juno Microwave Radiometer (MWR) probes Jupiter's kilobar atmosphere through free electrons produced by sodium and potassium ionization. Under equilibrium chemistry the electron abundance is the small residual of the charge balance between alkali cations and the anions Cl- and HS-. Chlorine is not directly measurable in Jupiter's deep atmosphere because gaseous HCl is removed from the observable atmosphere by NH4Cl condensation, whereas sulfur has been measured by the Galileo probe. The MWR-derived electron measurement therefore constrains the alkali-to-chlorine ratio rather than the alkali abundance alone. We combine the MWR observations with equilibrium chemistry and microwave radiative transfer in a Bayesian framework, finding that the deep gas-phase elemental alkali-to-chlorine abundance ratio is (Na+K)/Cl = 0.05 over 0.3-5 times solar in chlorine, about 180 times below the protosolar ratio of 8.7. At 3 times solar chlorine, the inferred alkali metallicity is 1.6 x 10^-2 times solar (1 sigma: 1.2 x 10^-2 - 2.7 x 10^-2 times solar), while at low chlorine abundance HS- sets an alkali floor near 10^-3 times solar. The inferred gas-phase alkali abundance exceeds the ~10^-5 times solar threshold by more than two orders of magnitude and rules out the long-proposed global kilobar radiative zone. Because sodium and potassium are refractory whereas chlorine is volatile, the inferred ratio provides a new diagnostic of the rock-to-ice balance in the solids accreted by Jupiter. This compositional interpretation assumes equilibrium chemistry; if lofted mineral clouds instead control the electron abundance under disequilibrium conditions, the inferred alkali-chlorine relationship need not hold.
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All authors Xi Zhang, Jiheng Hu, Cheng Li, Louis Siebenaler, Yury Aglyamov

Earth and Planetary Astrophysics

The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems VIII: patchy forsterite and enstatite clouds in the atmosphere of VHS 1256 b, retrieval lessons learned and outlook to the future

Niall Whiteford, Jacqueline K. Faherty, Ben Burningham et al. (+123 more)

JWST defines a new era for the data-driven approach of retrieval modelling, which has become a cornerstone tool for the statistical inference of exoplanetary and brown dwarf properties. The Early Release Science program #1386 observations of VHS 1256 b represent a huge jump in data quality, data quantity and spectral coverage for such objects. VHS 1256 b is a young, planetary mass and extremely variable companion that populates the enigmatic L/T cohort of substellar atmospheres. In this first retrieval analysis of the full 1 - 18 micron dataset, we apply the Brewster retrieval framework to the NIRSpec and MIRI spectroscopic observations of VHS 1256 b, exploring a variety of cloud species and structures. Using Delta(BIC) we find that the data is best described by a forsterite (Mg$_{2}$SiO$_{4}$) and enstatite (MgSiO$_{3}$) cloud combination. Our analysis shows a strong preference for patchy silicate cloud coverage, which aligns with VHS 1256 b's extensive and well documented spectral variability. Our retrieval is able to place constraints on the abundances of H$_{2}$O, CO, CO$_{2}$, CH$_{4}$ as well as NH$_{3}$. We also show that the retrieved parameters are sensitive to the data used and the relative signal-to-noise ratios between data from different instruments. We conclude with the next steps for the wider retrieval community to better understand young and cloudy exoplanetary atmospheres.
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All authors Niall Whiteford, Jacqueline K. Faherty, Ben Burningham, Johanna M. Vos, Simon Petrus, Polychronis Patapis, Beth A. Biller, Andrew Skemer, Sasha Hinkley, Emily Calamari, Genaro Suárez, Kelle L. Cruz, Brittany E. Miles, Aarynn L. Carter, Francisco A. Martinez, Melanie J. Rowland, Olivier Absil, Arthur D. Adams, William O. Balmer, Anthony Boccaletti, Mariangela Bonavita, Mickaël Bonnefoy, Mark Booth, Brendan P. Bowler, Zackery W. Briesemeister, Marta L. Bryan, Per Calissendorff, Faustine Cantalloube, Benjamin Charnay, Gaël Chauvin, Christine H. Chen, Elodie Choquet, Valentin Christiaens, Gabriele Cugno, Thayne Currie, Camilla Danielski, Matthew De Furio, Trent J. Dupuy, Samuel M. Factor, Michael P. Fitzgerald, Jonathan J. Fortney, Kyle Franson, Julien H. Girard, Eileen C. Gonzales, Carol A. Grady, Thomas Henning, Dean C. Hines, Callie E. Hood, Kielan K. W. Hoch, Alex R. Howe, Markus Janson, Paul Kalas, Jens Kammerer, Grant M. Kennedy, Pierre Kervella, Minjae Kim, Daniel Kitzmann, Adam L. Kraus, Masayuki Kuzuhara, Pierre-Olivier Lagage, Anne-Marie Lagrange, Kellen Lawson, Cecilia Lazzoni, Jarron M. Leisenring, Ben W. P. Lew, Michael C. Liu, Pengyu Liu, Jorge Llop-Sayson, James P. Lloyd, Anna Lueber, Bruce Macintosh, Mathilde Mâlin, Elena Manjavacas, Sebastián Marino, Mark S. Marley, Christian Marois, Raquel A. Martinez, Elisabeth C. Matthews, Brenda C. Matthews, Dimitri Mawet, Johan Mazoyer, Michael W. McElwain, Stanimir Metchev, Michael R. Meyer, Maxwell A. Millar-Blanchaer, Paul Mollière, Sarah E. Moran, Caroline V. Morley, Sagnick Mukherjee, Paulina Palma-Bifani, Eric Pantin, Marshall D. Perrin, Laurent Pueyo, Sascha P. Quanz, Andreas Quirrenbach, Shrishmoy Ray, Isabel Rebollido, Jea Adams Redai, Bin B. Ren, Emily Rickman, Steph Sallum, Matthias Samland, Benjamin Sargent, Joshua E. Schlieder, Karl R. Stapelfeldt, Jordan M. Stone, Ben J. Sutlieff, Motohide Tamura, Xianyu Tan, Christopher A. Theissen, Pascal Tremblin, Taichi Uyama, Malavika Vasist, Arthur Vigan, Kevin Wagner, Jason J. Wang, Kimberly Ward-Duong, Schuyler G. Wolff, Kadin Worthen, Mark C. Wyatt, Marie Ygouf, Alice Zurlo, Xi Zhang, Keming Zhang, Zhoujian Zhang, Yifan Zhou

Instrumentation and Methods for Astrophysics

Visible-Light High-Contrast Polarimetry with MagAO-X: Characterization and Initial Results

Miles Lucas, Laird Close, Jared R. Males et al. (+22 more)

MagAO-X is a visible-light extreme adaptive optics instrument on the 6.5 meter Magellan Clay Telescope, recently upgraded to enable high-contrast polarimetric differential imaging (PDI) in r', i', and z' filters. Polarimetry is a powerful technique for suppressing unpolarized starlight and isolating the faint, polarized signal scattered by circumstellar dust, but it demands precise calibration of instrumental polarization effects introduced by the telescope and instrument optics. We present an overview of the MagAO-X polarimeter and characterize its polarimetric response using a purpose-built polarization generator that injects light of a known polarization state. From these measurements, we fit a Mueller-matrix model of the instrument and quantify its polarimetric efficiency and instrumental polarization as a function of the k-mirror image rotator angle and observing filter. The initial characterization revealed significant, dynamic inefficiencies driven by the image rotator, motivating the deployment of a dual rotating quarter-wave plate (DQWP) compensator that dynamically reorients the input polarization to the instrument's eigenpolarization. Following installation of the DQWP, we measured an average increase in polarimetric efficiency of +17.5% (to 87.4%) and a reduction in instrumental polarization of -5.4% (to 8.3%) across all filters. Finally, we demonstrate the on-sky performance of the polarimeter with i' imaging of the debris disk around HR 4796, producing one of the closest inner-working-angle views of the bright, forward-scattering side of the disk. These results help pave the way for polarimeters on future extremely large telescopes such as GMT and ELT.
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All authors Miles Lucas, Laird Close, Jared R. Males, Tiago Gualberto Bezerra de Souza, Rodrigo Pereira, Jialin Li, Joseph D. Long, Jaren N. Ashcraft, Kyle Van Gorkom, Olivier Guyon, Sebastiaan Y. Haffert, Alexander D. Hedglen, Rob G. van Holstein, Parker T. Johnson, Maggie Kautz, Jay Kueny, Briley L. Lewis, Joshua Liberman, Jennifer Lumbres, Eden McEwen, Avalon L. McLeod, Maxwell A. Millar-Blanchaer, Lauren Schatz, Katie Twitchell, Manxuan Zhang

Soft Condensed Matter

The structural relaxation time of a polymer glass during deformation

Pradip K. Bera, Grigori A. Medvedev, James M. Caruthers et al. (+1 more)

In order to determine the structural relaxation time of a polymer glass during deformation, a strain rate switching experiment is performed in the steady-state plastic flow regime. A lightly cross-linked poly (methyl methacrylate) (PMMA) glass was utilized, and simultaneously the segmental motion in the glass was quantified using an optical probe reorientation method. After the strain rate switch, a non-monotonic stress response is observed, consistent with previous work. The correlation time for segmental motion, in contrast, monotonically evolves towards a new steady-state, providing an unambiguous measurement of the structural relaxation time during deformation, which is found to be approximately equal to the segmental correlation time. The Chen-Schweizer model qualitatively predicts the changes in the segmental correlation time and the observed non-monotonic stress response. In addition, our experiments are reasonably consistent with the material time assumption used in polymer deformation modeling; in this approach, the response of a polymer glass to a large deformation is described by combining a linear-response model with a time-dependent segmental correlation time.
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All authors Pradip K. Bera, Grigori A. Medvedev, James M. Caruthers, Mark D. Ediger

Optics · Cross-listed from eess.IV

Implicit Neural Speckle Denoising

Matthew R. Ziemann, Casey J. Pellizzari, Tyler J. Hardy et al. (+1 more)

Speckle fundamentally limits coherent imaging by introducing multiplicative, spatially correlated noise that obscures scene structure. Removing speckle noise from dynamic scenes–that do not benefit from conventional speckle averaging–is particularly challenging. We introduce a training-free framework that combines a spatiotemporal implicit neural representation with an aperture-aware maximum-likelihood formulation to recover dynamic, speckle-free imagery directly from noisy observations. The coherent likelihood explicitly models the aperture-dependent spatial covariance of speckle, enabling adaptation to arbitrary pupil geometries without retraining. A matrix-free implementation based on FFT-accelerated operators, stochastic approximations, and conjugate gradients makes optimization practical for realistic image sizes. Meanwhile, a blind holdout criterion provides automatic early stopping without clean reference data. Simulated and laboratory results demonstrate improved spatial fidelity, temporal consistency, and robustness to varying speckle statistics relative to classical, unsupervised, and supervised baselines.
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All authors Matthew R. Ziemann, Casey J. Pellizzari, Tyler J. Hardy, Christopher A. Metzler

Quantum Physics

Exact quantum circuits for a lattice Boltzmann realization of the Dirac equation

Nilesh Sawant, Ethan Young, Kevin Patrick Griffin et al. (+1 more)

The quantum lattice Boltzmann scheme of Succi and Dellar advances a four-component Dirac spinor on a lattice by a fixed sequence of local, exactly norm-preserving operations: a basis rotation, a collision, a streaming shift, and the inverse rotation. While this correspondence has been noted qualitatively, it has remained unclear whether it can be realized exactly and unitarily as a gate-model quantum circuit. This unitarity is a structural property of the scheme, which should, in principle, enable an operator-by-operator port onto quantum hardware. We give a gate-level construction of every operation of the three-dimensional Dirac QLB scheme: the fixed rotation gates, the collision gate, the streaming shift as a controlled increment on a position register, the position-dependent potential as a phase oracle, and periodic and reflecting boundary conditions as unitary circuits. Together, these constructions provide the first complete demonstration that the scheme is exactly representable in the gate model without any approximation beyond the classical method itself. We then compose them into single-axis, two- and three-dimensional time steps. On a state-vector emulator the resulting circuits reproduce the classical QLB solver to machine precision, thus verifying our quantum implementation. Our aim is representability and correctness rather than computational speedup; questions of state preparation, asymptotic cost, and hardware noise are identified as open avenues for future work. Appendices restore physical units, derive the scheme's Zitterbewegung in closed form and compare it with a trapped-ion simulation, and execute a reduced two-site instance on a Rigetti superconducting processor, where choosing the qubits from the live calibration lowers the state-preparation error. All operators, circuits, and figures are reproducible from the open-source quantumKineticMethods library.
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All authors Nilesh Sawant, Ethan Young, Kevin Patrick Griffin, Michael Martin

Mesoscale and Nanoscale Physics

Observation of metastable chiral domain walls in a topological magnet

Richen Xiong, Chenxin Qin, Zhaoyu Han et al. (+17 more)

The interplay between topology and correlation can give rise to exotic collective excitations. The integer and fractional quantum anomalous Hall (QAH) magnets recently discovered in two-dimensional (2D) flatband systems are predicted to host spin excitations distinct from those in conventional magnets. Experimentally, nevertheless, these new excitations remain largely unexplored. Here we investigate spin-valley excitations in a twisted MoTe2 moiré superlattice using resonant ultrafast pump-probe spectroscopy. We observe a metastable spin-valley excitation in the QAH magnet below T ~ 3.7 K that survives reverse magnetic field several times larger than the saturation field. The behavior of this excitation is sharply distinct from ordinary domain walls and magnons, indicating a new type of spin-valley textures unique to topological magnets. We propose that these textures are chiral domain walls with an in-plane winding of the pseudospin order parameter along the domain wall. Their metastability arises from the interplay between the topological winding in real space and the quantum geometry of the parent bands in momentum space through a universal mechanism. These chiral domain walls govern the nonequilibrium dynamics of QAH magnets and may play a central role in their stability. Our study highlights intrinsic quantum geometry effects on spin excitations in topological magnets; and provides key insights into the fundamental mechanism limiting stability of topological protection.
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All authors Richen Xiong, Chenxin Qin, Zhaoyu Han, Nisarg Chadha, Qiang Gao, William Holtzmann, Weijie Li, Jiaqi Cai, Yi Guo, Weihanzhang Guo, Qi Chen, Samuel L. Brantly, Sam Bonkowsky, Chen Huang, Kenji Watanabe, Takashi Taniguchi, Andrea F. Young, Xiaodong Xu, Eslam Khalaf, Chenhao Jin

Materials Science

Nonreciprocity reversal of magnetoacoustic attenuation in NiFe alloy thin films

Mingran Xu, Kei Yamamoto, Kouta Kondou et al. (+8 more)

Nonreciprocity, the asymmetry of transport, underlies technologies from the diode to the microwave isolator. In a ferromagnet, a surface acoustic wave generates an elliptical effective field with propagation-locked handedness, breaking the reciprocity of its propagation. Despite decades of study on this phenomenon, a method for controlling the sign of the nonreciprocity has remained elusive. Here we observe a sign reversal in Ni$_x$Fe$_{100-x}$ films. A 0.8 at.% change across Permalloy's zero-magnetostriction composition, where the magnetoelastic coefficient $b$ changes sign, reverses the handedness of the elliptical effective field and thereby the nonreciprocity, from 78.6% to -61.8%. Angle-dependent measurements and spin-wave-ellipticity modelling show that reversing the sign of $b$ reverses the handedness of the elliptically polarized effective field. Aided by cubic frequency scaling, we resolve the sign of $b$ down to -0.05 MPa in a 10-nm film, establishing nonreciprocity as a nanoscale probe of magnetoelastic coupling.
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All authors Mingran Xu, Kei Yamamoto, Kouta Kondou, Zheng Zhu, Liyang Liao, Kiyohiro Adachi, Tomoka Kikitsu, Daisuke Hashizume, Dirk Grundler, Sadamichi Maekawa, Yoshichika Otani

Quantum Physics

Generalized Loschmidt echoes associated with operational quantum non-Markovianity

Cecilia Cormick and Adrián A. Budini

Non-Markovianity can be characterized by performing a series of successive measurements and analyzing departures of the corresponding outcome statistics from a Markovian probabilistic structure. Considering a system coupled with its environment via a dephasing interaction, we show that joint outcome probabilities can be written in terms of a set of two-time environment correlations. Their definition involves forward and backward propagators with different Hamiltonians, associated with a recently introduced generalization of standard Loschmidt echoes [Cormick and Budini, Phys. Lett. A 593, 132011 (2026)]. This result establishes a solid connection between quantum non-Markovianity defined in an operational (measurement-based) way and complex quantum dynamics studied through their sensitivity to dynamical perturbations. We find conditions that guarantee a Markovian (system) behavior and also determine how the generalized echoes can identify information exchanges between the system and its environment. We illustrate our ideas considering examples of spin environments that realize these different dynamical regimes.
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Quantum Physics

Detecting quantumness with generalized Loschmidt echoes

Cecilia Cormick and Adrián A. Budini

Loschmidt echoes are a well-established method to characterize dynamical properties such as quantum chaos and sensitivity to perturbations. Here we present a straightforward generalization that identifies non-classical dynamical behavior. The generalized echoes involve four forward-backward time propagators. If these propagators do not commute, one can readily identify signatures of this property in the relations between echoes. As an example, detection of intrinsic non-commuting quantum features is analyzed in critical dynamics of a spin chain. Interestingly, this phenomenon is also observed for Gaussian dynamics and high temperature limits which are generally regarded as classical.
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Fluid Dynamics

Effect of Chordwise Flexibility Distribution on Wave-Assisted Flapping Foil Performance

Lokesh Silwal, Neel Karani and Anchal Sareen

This study investigates the influence of the spatial distribution of flexibility along a propulsor on thrust generation and propulsive efficiency in wave-assisted flapping foils. While flexibility is known to enhance propulsive performance, the role of its chordwise placement remains poorly understood. Here, the effective flexible length is systematically varied by shifting the flexure location along the tail while maintaining constant flexural rigidity and total chord length. Experiments are conducted in quiescent flow at heave frequencies of 0.8 Hz and 1.25 Hz, and non-dimensional heave amplitudes of h* = 0.13 and 0.22. Simultaneous measurements of hydrodynamic forces, flow fields, and tail kinematics are used to quantify performance and elucidate the underlying fluid-structure and fluid-particle interactions. The fully flexible configuration consistently achieves higher propulsive efficiency (up to approximately 164%) across all conditions, which is attributed to enhanced jet persistence and increased streamwise vortex spacing, indicative of a more coherent and sustained momentum jet. In contrast, the mid-flexible configuration yields substantially higher thrust (up to approximately 66%) at the largest heave frequency and amplitude, driven by a pronounced increase in near-wake jet velocity and momentum flux. These results demonstrate that the chordwise distribution of flexibility governs the trade-off between thrust and propulsive efficiency by modulating wake coherence and momentum transfer. The findings establish flexibility placement as a key design parameter in flapping propulsion and provide physics-based guidelines for enhancing the performance and endurance of wave-driven unmanned surface vehicles.
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Earth and Planetary Astrophysics

Estimating Harmonic Coefficients of Asteroids through LiAISON Navigation

Jun Maruyama and Simone Servadio

This paper evaluates the Linked Autonomous Interplanetary Satellite Orbit Navigation (LiAISON) method in near two-body asteroid systems. While LiAISON's usefulness has been proven in multibody environments such as the cislunar region, the application of a two-body system with gravity perturbations has not been sufficiently demonstrated. Vesta and Ceres are good candidates to test LiAISON, because the asteroids have sufficiently strong perturbations to use LiAISON method. The study utilizes a Multi-Model Adaptive Estimation (MMAE) framework integrated with Unscented Kalman Filters (UKF) to estimate the spacecraft states and perturbations using only range and range rate measurements. Results from the Monte Carlo analysis indicate that the proposed framework makes accurate and consistent estimates of position, velocity, and the perturbations for cases of Ceres and Vesta.
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Mesoscale and Nanoscale Physics

Temperature-tunable spin-wave refraction using superconducting control elements

Pim H. Vree, Merel A. Bouma, Michael Borst et al. (+3 more)

Spin waves are promising signal carriers for microwave control at the micrometer scale. However, realizing low-damping, tunable control of spin-wave propagation remains a central challenge. Here we use magnetic shielding by superconducting control elements to tune the local spin-wave dispersion and realize temperature-controlled refraction of spin waves in a thin-film magnetic insulator. Using magnetic imaging based on spins in diamond, we characterize the refractive index and demonstrate both positive and negative refraction as well as wavefront shaping by the superconductors. The observed refraction is explained by a geometrical analysis of the superconductivity-induced modification of the hyperbolic spin-wave dispersion. Our results demonstrate that superconductors enable tunable spin-wave optical elements, opening new opportunities for microwave control in classical or quantum information devices.
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All authors Pim H. Vree, Merel A. Bouma, Michael Borst, Tomas T. Osterholt, Rembert A. Duine, Toeno van der Sar

Quantum Physics · Cross-listed from cs.LG

Newton-Schulz Retraction-Based Inference Enables Hidden Quantum Markov Models to Outperform Classical HMMs

Ning Ning

Hidden Markov models (HMMs) are widely used probabilistic models for discrete sequential data but can be limited when hidden dynamics are complex. Hidden quantum Markov models (HQMMs) generalize HMMs by replacing probability vectors with density matrices and stochastic transitions with quantum operations, enabling richer latent representations. However, existing HQMM learning methods have not consistently outperformed Expectation–Maximization (EM)-trained HMMs on data not generated by quantum processes, limiting their practical applicability. We introduce NS-RIS, Newton–Schulz Retraction-based Inference on the Stiefel manifold, a scalable algorithm for learning trace-preserving HQMMs. NS-RIS uses Newton–Schulz orthogonalization to compute a polar-factor search direction while preserving Stiefel-manifold feasibility, avoiding costly matrix decompositions. We further establish a finite-time stationarity guarantee under standard assumptions on smoothness, stochastic gradients, and finite Newton–Schulz accuracy. Empirically, NS-RIS provides the first benchmark evidence that an HQMM can significantly outperform an EM-trained HMM on data not generated by a quantum model. On synthetic HMM-generated benchmarks, NS-RIS outperforms both EM and the state-of-the-art HQMM method COSM, improving the evaluation metric by an average of 38.5% and by up to 50.6%. On a synthetic HQMM benchmark, it improves the test metric over COSM by 18.9% while reducing runtime by 12.0%. On the real-world Splice classification benchmark, NS-RIS also surpasses both EM and COSM in higher-dimensional latent regimes, reducing mean classification error by 17.9% for latent dimension 6 and 14.9% for latent dimension 8 relative to COSM. These results move HQMMs beyond a theoretical generalization of HMMs and establish them as practical and expressive models for scientific sequence data.
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Superconductivity

Emergence of Bogoliubov Fermi Surfaces in hybrid Al/InAs heterostructures

S. Feyrer, V. Dimic, I. Lobato et al. (+15 more)

We investigate the microwave electrodynamics of a proximitized two-dimensional electron gas in hybrid superconductor/semiconductor heterostructures. Using lumped-element resonators with inductor wires oriented relative to an in-plane magnetic field, we directly probe the superfluid stiffness via the kinetic inductance. As the field increases, the resonance frequency exhibits a non-monotonic and strongly anisotropic evolution that cannot be explained by orbital pair breaking alone. We show that this behavior is consistent with the emergence of Bogoliubov Fermi surfaces, which selectively suppress the supercurrent response depending on the direction of the magnetic field. Microscopic calculations of the stiffness tensor capture the observed anisotropy driven by the interplay of Zeeman and orbital Fulde-Ferrell effects. Our results establish microwave stiffness measurements as a sensitive probe of anisotropic gapless superconductivity in hybrid systems.
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All authors S. Feyrer, V. Dimic, I. Lobato, A. Kirchner, P. Drexler, L. Rupp, D. Bougeard, T. Lindemann, S. Gronin, G. Gardner, M. J. Manfra, G. F. R. Ruiz, C. A. Balseiro, L. Arrachea, M. Aprili, N. Paradiso, C. Strunk, L. Tosi

Mesoscale and Nanoscale Physics

Anderson Orthogonality as Measurement Backaction in Coupled Quantum Dots

Will Grant, Sarath Sankar, Elena Cornick et al. (+9 more)

Measurement perturbs a quantum system by coupling it to external degrees of freedom, but detector backaction depends on the physical mechanism of measurement itself. In solid-state devices, detectors driven far from equilibrium to enable faster measurements produce backaction that can often be understood as classical noise. However, a strong measurement can also induce backaction from quantum many-body correlations in the detector that are intrinsic to the measurement, even without shot noise. Here, we probe this near-equilibrium backaction through the effect of a quantum-dot charge sensor on tunnelling between a second quantum dot and its reservoirs. The measurement realizes the Anderson Orthogonality Catastrophe (AOC): electrons in the detector leads reorganize in response to an abrupt change in local scattering potential, suppressing resonant tunnelling while enabling inelastic processes that exchange energy with the detector. Changing the detector energy level tunes the AOC backaction from negligible to dominant in the tunnelling dynamics. More broadly, these results establish detector-induced many-body correlations as a controllable influence on quantum dynamics.
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All authors Will Grant, Sarath Sankar, Elena Cornick, Vahid Movahed, Johann Drayne, Silvia Lüscher, Saeed Fallahi, Geoffrey C. Gardner, Michael J. Manfra, Eran Sela, Yigal Meir, Joshua Folk

Fluid Dynamics

Nonisothermal Shock Structure and Universal Flow-Index Thresholds in a Hyperbolic Power-Law Fluid

Tommaso Ruggeri

We investigate whether the two flow-index thresholds previously found for isothermal shock profiles persist when the full nonisothermal dynamics is taken into account in a hyperbolic power-law relaxation model of Rational Extended Thermodynamics. The nonisothermal profile problem is structurally different from its isothermal counterpart: restoring the energy balance determines the temperature along the traveling wave and feeds it back into the pressure, the relaxation production, the temperature-dependent consistency coefficient, and the characteristic structure. Under thermodynamic stability, $p_\theta\ge0$, and strict convexity of the reduced Hugoniot pressure, no nontrivial constant-temperature compressive profile can satisfy the full equations. We derive an exact global characteristic-ordering identity and prove that the positive nonequilibrium characteristic speed has its strict global minimum at the unperturbed upstream state. Consequently, a monotone continuous profile exists for $1<M_0<\Mst$, whereas for $M_0>\Mst$ the Boillat–Ruggeri theorem excludes a $C^1$ profile and any admissible piecewise-smooth connection must contain a subshock. Despite the thermomechanical coupling, the shock-thickness classification remains unchanged: $m=2$ is the weak-shock threshold and $m=1$ the near-critical threshold as $M_0\nearrow\Mst$. The corresponding exponents are constitutive-independent within the present class, while finite limiting values and prefactors depend on the equation of state, internal energy, and temperature-dependent consistency coefficient. For the Tait–Murnaghan example, increasing the reference temperature lowers the critical Mach number when the dimensional viscous–relaxation scale is fixed and, for the thermally thinning law considered, reduces the resolved shock thickness.
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