Optics
Design of a Compact Monolithic Catadioptric Lens for CubeSat Hyperspectral Imaging Payloads
Iliya Shofman and Kenya He
Monolithic catadioptric lenses have emerged as a novel class of compact long-focal-length lenses. Fabricated from a single fused silica substrate with distinct optical prescriptions across annular zones, these systems fold the optical path within the substrate, achieving long effective focal lengths at a fraction of the track length of refractive equivalents. The monolithic architecture and low coefficient of thermal expansion provide inherent athermal performance and preserve optical
alignment under the thermal and vibrational loads of nanosatellite launch and orbital operation. Despite these advantages, commercial offerings of monolithic catadioptric lenses are limited and no comprehensive optical design literature review has been published for this lens class. We survey of monolithic catadioptric design variants, including Schmidt-Cassegrain-derived, annular folded, and gradient-index configurations. Building on this design space, we also present a novel monolithic catadioptric objective lens optimized for a CubeSat pushbroom hyperspectral Earth imaging payload. Pushbroom hyperspectral imagers require a precision entrance slit at the focal plane of the objective lens, and maintaining slit-to-focal-plane
alignment under launch shock and thermal cycling is a significant optomechanical challenge. The proposed design places the focal plane coincident with the back surface of the substrate, enabling the slit to be lithographically etched directly onto that surface. This approach eliminates the slit-to-objective
alignment degree of freedom, yielding an integrated, mechanically robust, and thermally stable objective-slit module for pushbroom imaging. We present the completed optical design of a near-diffraction-limited F/3 f=100mm VSWIR monolithic catadioptric lens, assess imaging performance, and discuss preliminary fabrication and tolerancing considerations.
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Quantum Physics
Multistage Rewinding Decoder for QLDPC Codes
Milad Taghipour, Dimitris Chytas and Bane Vasić
In this paper, we propose a multistage decoding framework that leverages internal information produced by an underlying message-passing decoder. The proposed method targets the failure dynamics caused by both classical trapping sets and degenerate errors supported on symmetric stabilizers, which are among the primary limitations of iterative decoding for QLDPC codes. To identify unreliable variable nodes, we introduce a heuristic metric that combines several dynamical features of the decoder, including variable-node log likelihood reliabilities, hard-decision oscillations, the number of adjacent unsatisfied checks, and the soft information contributed by unsatisfied checks. Based on this ranking metric, the decoder performs guided rewinds by selectively forcing the initial log likelihood ratio values of the most suspicious variable nodes and restarting the message-passing decoder under the corresponding forced configuration. To manage the combinatorial growth of candidate configurations, the search is formulated within a beam- search framework with controlled beam width. In addition, we introduce a
pruning metric based on the combination of the residual syndrome weight and a posteriori reliability of the decoder output, thereby retaining only the most promising search paths. Logical error rate results demonstrate that the proposed decoder significantly outperforms the normalized min- sum decoder and achieves competitive performance with belief propagation enhanced by order-10 ordered statistics decoding.
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Materials Science
Understanding the Oxygen Reduction Reaction and Oxygen Evolution Reaction in Metal Intercalated Biphenylene Bilayers
Henri G. Mendonça, Pedro H. Souza, Walter Orellana et al. (+1 more)
We conducted an ab initio study of the oxygen reduction reaction (ORR) and oxygen
evolution reaction (OER) in metal-encapsulated biphenylene
bilayers, B/M/B, with M = Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Ru, W, Os and Pt. In most systems, the intercalated metal sits at the square carbon sites (C$^{468}$) of the biphenylene
lattice. Using a computational hydrogen electrode approach, we evaluated the reaction energetics at these active sites. Several B/M/B systems show competitive ORR and OER performance. Among the investigated systems, Cu, Pt, Ru, and Mn exhibit the lowest ORR overpotentials of 0.42, 0.44, 0.50, and 0.56 V, respectively, while Fe is identified as the most active catalyst for OER with an overpotential of 0.44 V. To understand the catalytic trends, we looked at the electronic structure through the metal $d-$band centers, the C$^{468}$ $p_z-$band centers, and the corresponding orbital charge populations. The band centers did not give a simple
polynomial dependence on the overpotentials, though they did point to favorable electronic ranges for the best catalysts. The $d-$orbital charge population of the encapsulated metal, however, correlated most clearly with activity-especially for OER-yielding volcano-type plots. From these, B/Fe/B emerges as the best OER catalyst, while B/Mn/B lies closest to the ORR optimum. The $p-$orbital population at the active carbon site also captures the main trends, albeit less strongly. Overall, these results show that straightforward electronic descriptors can predict catalytic behavior in metal-encapsulated biphenylene
bilayers and guide the search for efficient catalysts where the carbon framework itself drives the reactivity.
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All authors Henri G. Mendonça, Pedro H. Souza, Walter Orellana, Roberto H. Miwa
High Energy Astrophysical Phenomena
A Systematic Study of Type Ia Supernova Remnants: Using Nucleosynthesis to Probe their Supernova Progenitors
Cole Treyturik, Samar Safi-Harb and Gilles Ferrand
We present the first systematic, spatially resolved X-ray spectroscopic study of a largely thermonuclear (Type Ia) sample of
supernova remnants (SNRs), aimed at probing the explosion properties and progenitors through a comparison to a suite of nucleosynthesis models available in the literature. Our sample focuses on
Galactic and LMC ejecta-dominated SNRs believed to be, or otherwise assumed to be, of thermonuclear origin. Using archival XMM-Newton observations (and Chandra for G1.9+0.3), we extract spectra from adaptively binned regions across each remnant and model the emission to constrain the
plasma temperature, ionization timescale, and ejecta abundances. We then compare abundance ratios (relative to Si) to a library of 335 individual models spanning 11 commonly-used
supernova nucleosynthesis simulation sets from the literature including seven thermonuclear and four core-collapse sets. Across the sample, we find that individual remnants can be well matched by subsets of models, but no single model reproduces all measured elemental ratios at once. As a result, the best fit model for a given object is typically set by a selection of well-fitted abundance ratios, highlighting both the strength and limitations in yield-based model determination. For some SNRs, the abundance comparisons show better agreement with particular families of Type Ia SN explosions, including near-Chandrasekhar-mass delayed detonations, sub-Chandrasekhar-mass explosions, and dynamically driven double detonations, although these interpretations are not unique. Finally, we outline the need for model improvements, including refined
nuclear reaction rates, higher dimensional treatment of mixing and
turbulence, expanded
metallicity coverage, and the exploration of non-standard
supernova explosion energies.
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Biological Physics
Nuclear mechanics controls the temporal dynamics of cell unjamming
Leon Hillmann, Quirine J. S. Braat, Pablo Gottheil et al. (+9 more)
Cell unjamming in dense tissues is a complex but essential process in embryogenesis and cancer metastasis. Increasing evidence suggests that
nuclear mechanics and density effects play a vital role in collective
cell unjamming. However, state-of-the-art
cell-shape-based theories fail to include
nuclear and density effects, while computer models featuring rigid
nuclei disagree with experimental observations of elongated
nuclei promoting unjamming. Here, we introduce a computational model of confluent
cells with explicitly deformable
nuclei to study the dynamics of
cell unjamming. Our simulations show an unjamming transition controlled by
nuclear size and shape, reconciling conflicting theories of density-driven versus shape-driven mechanisms. We predict general relations connecting cellular and
nuclear shape to collective
cell motion, verified experimentally in distinct monolayers of MCF-10A and MDA-MB-436 breast
cells, with striking accuracy. Our work establishes a rational connection between
nuclear mechanics and tissue-scale
rigidity transitions, highlighting the
nucleus's key role in collective
cell unjamming.
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All authors Leon Hillmann, Quirine J. S. Braat, Pablo Gottheil, Eliane Blauth, Anne Marie Scholz, Kolya M. Lettl, Jürgen Lippoldt, Pieta C. M. Wielstra, Sibylle Hess, Mitko Veta, Josef A. Käs, Liesbeth M. C. Janssen
High Energy Physics (Theory)
Incidence Relations for Self-Dual Black Holes
Joon-Hwi Kim
In Penrose's nonlinear graviton construction, a self-dual spacetime arises as the
moduli space of holomorphic twistor lines in curved twistor space, whose explicit parametrization is concretely given by the incidence relation. We demonstrate a concrete local construction of the incidence relations for self-dual black hole spacetimes in Kerr-Schild coordinates: Eguchi-Hanson, self-dual Taub-NUT, and self-dual Plebański-Demiański. This is facilitated by implementing the Dunajski-Mason recursion in the framework of Plebański's second heavenly equation, for which we explicitly find the Plebański scalar. Our results describe closed-form formulae. Notably, for the self-dual Taub-NUT solution, the exact incidence relation exhibits linear dependence on the gravitational coupling. The construction of zero-rest-mass fields on self-dual black hole backgrounds is briefly sketched as an application.
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High Energy Astrophysical Phenomena
Neutrino quantum kinetics for fast flavor conversion in a time-dependent environment
Zewei Xiong and Meng-Ru Wu
Fast
flavor conversions (FFCs) of
neutrinos, driven by the fast
flavor instability (FFI), can reshape the
neutrino flavor content in dense astrophysical environments such as core-collapse
supernovae and
neutron star mergers. Most studies of FFCs adopt a two-step approach, in which a
flavor-unstable state containing deep electron-minus-heavy-
flavor lepton number (E-XLN) angular crossings is first constructed and subsequently evolved. Because realistic crossings should instead develop gradually through
neutrino transport, the validity of such setups has been called into question. We investigate this issue by solving the
neutrino quantum kinetic equations with self-consistent collisional rates in a spherically symmetric
supernova background whose electron fraction evolves in time through a sequence of stages, starting from a configuration free of E-XLN crossings. We find that the
evolution proceeds through three characteristic episodes. In the shallow-crossing episode, FFCs develop from marginally unstable, shallow crossings, carrying small-scale structures consistent with linear stability analysis. In the near-crossing-elimination episode, the balance between collisions and FFCs keeps the system in a near-quasistationary state in which the emerging crossings are continuously eliminated, so that the strongly unstable regime is never reached. In the swapping episodes, the E-XLN reverses sign and a dynamically propagating
flavor-swap E-XLN zero surface forms. We find that the evolved
flavor content at the end of different time stages broadly agrees with the quasistationary solutions obtained in the corresponding two-step models adopting fixed matter backgrounds. In addition, we investigate the robustness of the effective classical transport (ECT) framework that adopts subgrid
flavor redistribution using different parametrized prescriptions. Notably, except during the swapping [abridged]
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Instrumentation and Methods for Astrophysics
On-sky capabilities and performance of the Keck All Sky Precision Adaptive Optics system
Avinash Surendran, Maxwell Service, Jacques R. Delorme et al. (+21 more)
The Keck All Sky Precision Adaptive optics (KAPA) project upgrades the Keck I adaptive optics system to enable
laser tomography using a four
laser guide
star (LGS) asterism. KAPA is now in operation in both narrow field and wide field modes to optimize correction on-axis or over the science field of view of the camera. The use of four LGSs, in conjunction with a tomographic reconstructor and pseudo open-loop control, leads to a significant reduction in wavefront error. We describe the overall architecture, development of the tomographic
algorithm, real-time implementation and preliminary on-sky results here. By comparing the on-sky image quality with that obtained using a single LGS (sLGS) we clearly demonstrate the benefits of
laser tomography, a technology which is crucial to the success of the next generation of extremely large
telescopes.
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All authors Avinash Surendran, Maxwell Service, Jacques R. Delorme, Carlos M. Correia, Marcos A. Van Dam, Eduardo Marin, Antonin Bouchez, Peter Wizinowich, Jason Chin, Sylvain Cetre, Sam Ragland, Uriel Conod, Jacob Taylor, Scott Lilley, Luke Gers, Ed Wetherell, Jessica Lu, Noah Stiegler, Anna Pusack, Zoe Haggard, Will Gauvin, Julien T. Bernard, Dietrich Pescoller, Roberto Biasi
Fluid Dynamics
Set-up and Characterisation of Atmospheric Boundary Layers in the 10'x5' Wind Tunnel
Sita M. Nair and Kevin Gouder
The Atmospheric Boundary Layer (ABL) plays a critical role in influencing objects exposed to atmospheric conditions, making its study crucial. Due to the high cost of real-world testing, this thesis focuses on replicating marine ABLs in a wind tunnel environment. Two profiles were developed: one that served as a framework for establishing commonality among the various international wind engineering standards ('Profile 1'), and a second profile, which is more suitable for modelling the inflow to wind farms in the English Channel and the North Sea ('Profile 2'). The ABLs were generated using Irwin spires without floor roughness elements, and the flow characteristics were measured using
Laser Doppler Anemometry (LDA) and a multi-hole probe (MHP). MHP showed a reasonably high accuracy when compared to LDA, with less than 1% deviation in the streamwise velocity and under 5% standard deviation in the streamwise, spanwise, and wall-normal velocity components. The profiles achieved good agreement with target metrics such as normalised velocity and
turbulence intensity. Spanwise uniformity and spectral analysis confirmed the robustness of the simulation across varying inflow velocities. Overall, Irwin spires proved to be a cost-effective and reliable method for simulating marine ABLs, offering valuable insights for optimising offshore wind energy systems.
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Atmospheric and Oceanic Physics
Models of Wildland Fire and Ember Spread
Kevin Speer, Bryan Quaife and Jie Sun
In this Chapter we explore the nature and theory of ember transport using observations from controlled laboratory settings, prescribed fire, and wildland fire. Specific examples and statistics from fires are used to gain insight and motivate a hierarchy of modeling approaches from simple idealized models to full-physics atmospheric boundary layer models. The emphasis is on the fundamental processes involved in moving embers away from their sources in vegetation and structures on and near the ground or in the atmospheric boundary layer winds and turbulent flows. We describe the problem first in terms of basic theory about the rate of spread of wildland fire, examine the physical principles at work in ember transport for two principle modes of transport near the ground and in the atmosphere well above the surface, and connect these to statistical models for transport.
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High Energy Astrophysical Phenomena
Do Accretion Disks Get Bent Out of Shape? Investigating the Origin of Rapid Fluctuations in the Tails of Long Thermonuclear X-ray Bursts
D.R. Ballantyne and N. Degenaar
Thermonuclear X-ray bursts from the surfaces of
neutron stars affect the surrounding
accretion flow, revealing details of the underlying physical processes influencing
accretion physics. In this context, we perform a spectral analysis of 5 long X-ray bursts that exhibit temporary rapid flux variations during the tails of their light curves. In all cases, spectra extracted from before, during and after the time of fluctuations show evidence for relativistic, ionized reflection with the blackbody from the
neutron star often hidden from view. Both the properties of the reflecting region and the observed fraction of the blackbody vary as the fluctuations start and stop. These results are compared to a sample of 5 similar bursts without fluctuations in their light curves, and we find that spectra from 4 of the bursts in the control sample are best described by a simple absorbed blackbody. The bursts with fluctuations are longer and more energetic than those without fluctuations, in agreement with the prediction that radiatively-driven warps are impacting the
accretion disks of the bursts with fluctuations. This result would also imply that these
accretion disks must have large viscosity parameters. The lack of reflection in bursts from the control sample may result from lower
accretion rates, as these disks would have smaller surface densities and would expand and become Compton-thin due to heating from the burst. High-throughput, time-resolved spectral analysis of X-ray bursts that undergo warping would give insight into the strength of
accretion disk viscosity.
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General Relativity and Quantum Cosmology
Innermost stable circular orbit (ISCO) of arbitrary-mass compact binaries with spins at the fourth post-Newtonian order
Luc Blanchet, David Langlois and Etienne Ligout
We compute, up to 4th post-Newtonian (4PN) order, the gauge-invariant stability criterion determining the innermost stable circular orbit (ISCO) for arbitrary-mass compact binaries with
spins aligned with the orbital angular momentum. Our calculation, a perturbation analysis, incorporates
spin-orbit and
spin-
spin contributions, both up to next-to-next-to-leading order, as well as leading-order cubic and quartic
spin contributions, all calculated in prior works within the effective-field-theory (EFT)
Hamiltonian formalism. In the test-mass limit, we recover the Kerr ISCO truncated at 4PN order. Estimating the ISCO shift at first order in the mass ratio and comparing our results with numerical gravitational self-force (GSF) calculations, we find good agreement for retrograde
spin (the smallest discrepancy being obtained for maximal retrograde
spin) and moderate prograde
spin. For nearly maximal prograde
spin, the PN approach fails to determine the ISCO, for it is close to the black hole (BH) horizon. We also estimate the ISCO shift due to the test-particle
spin and compare our result with the exact prediction from the Mathisson-Papapetrou-Dixon (MPD) equations for a spinning particle orbiting a Kerr black hole. Finally, we discuss the stability and the ISCO of corotating black-hole binaries.
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Quantum Physics
A Quantum-Enhanced Feedback Oscillator
Hudson A. Loughlin, Daniel M. DeSantis, Nergis Mavalvala et al. (+1 more)
Feedback oscillators, such as
lasers and masers, serve as time references in modern computing, communication, and measurement.
Quantum fluctuations ultimately limit their phase stability and ability to keep time precisely; in the absence of
quantum engineering, their phase stability is bounded by a standard
quantum limit (SQL). Techniques to improve the frequency stability of feedback oscillators beyond the SQL have been theorized, but have not yet been demonstrated. We demonstrate an opto-electronic oscillator (OEO), a type of feedback oscillator, with phase stability approaching the SQL. We then engineer the OEO's
quantum state to improve its phase stability, thereby demonstrating the essential principle
quantum-enhancement of feedback oscillators. Similar techniques may be employed to evade the SQL in other feedback oscillators such as masers and
lasers.
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All authors Hudson A. Loughlin, Daniel M. DeSantis, Nergis Mavalvala, Vivishek Sudhir
Astrophysics of Galaxies
Circumgalactic CIV Absorption Found Only Within 30 Degrees of the Minor Axis of Present-Epoch Galaxies
Mark A. Croom, Christopher W. Churchill, Bart Wakker et al. (+2 more)
We studied CIV 1548,1550 absorption in the circumgalactic medium (CGM) of 88 isolated, bright (L_B > 0.2L*_B)
galaxies at z < 0.03 selected without prior knowledge of CGM absorption. The
galaxies have observationally-unbiased distributions of inclination and
galaxy-
quasar sightline azimuthal angle. Above a 5-sigma rest-frame equivalent width detection threshold of W_r > 0.1 angstroms, we found absorption in the CGM of 9/88 of the
galaxies within projected separation R_perp < 350 kpc. All nine absorbers arise within 30 deg of the projected minor axes and R_perp < 1.2R_vir of
star-forming
galaxies [log(sSFR/yr^-1) > -10.75]. To a confidence level of 99.998% (4.3-sigma), we can rule out that these absorbers are drawn from a random distribution of
galaxy-
quasar azimuthal angles. These findings suggest strong evidence for biconical polar winds related to the moderately elevated
star formation in these present-epoch
galaxies and we describe simple spatial-kinematic models that support this hypothesis. High specific
star-formation rates may not be a sufficient condition for predicting minor-axis CIV absorption because the covering fraction of the subsample of
star-forming
galaxies within 30 deg of their minor axes is f_cov ~ 0.5; this may imply transient and/or patchy
outflows. Incorporating studies of MgII and OVI CGM absorption, we favor a scenario in which CIV-bearing CGM gas interfaces between these low- and high-ionization regimes, comprising enriched intermediate-ionization clouds entrained and collimated in biconical
stellar winds while mixing and cooling via non-
equilibrium photoionization.
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All authors Mark A. Croom, Christopher W. Churchill, Bart Wakker, Glenn G. Kacprzak, Nikole M. Nielsen
Mesoscale and Nanoscale Physics
Probing intermittent polariton vortex dynamics with two-point correlations
R. Cherbunin, A. Liubomirov, P. Kozhevin et al. (+5 more)
Superconducting single-
photon detectors with time resolution of 80 ps have been used to study the spatiotemporal dynamics of a trapped bosonic condensate of
exciton-polaritons. Both second- and first-order correlation functions are found to exhibit pronounced oscillations in time governed by the dynamics of the polariton condensate in the trap. We have identified the intermittent regime of
stochastic transitions between stationary and limit-cycle regimes near the Andronov-
Hopf bifurcation manifested in asymmetric distortions of the correlation function. This rich interplay of deterministic and
stochastic condensate dynamics is explained theoretically as a manifestation of mutually compensating self-repulsion and reservoir-mediated attraction.
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All authors R. Cherbunin, A. Liubomirov, P. Kozhevin, M. Chukeev, M. Petrov, S. Kavokina, A. Nalitov, A. Kavokin
Mesoscale and Nanoscale Physics
Dynamical quantum phase transitions in a hybrid quantum dot system with superconducting and ferromagnetic leads
Antoni Jankiewicz, Kacper Wrześniewski and Ireneusz Weymann
We theoretically explore the non-
equilibrium dynamics of a single
quantum dot system coupled to both
ferromagnetic and superconducting electrodes. To investigate its time
evolution, we utilize the time-dependent numerical renormalization group technique, which captures the system's response to abrupt parameter changes in a fully non-perturbative manner. Our analysis focuses on dynamics following a sudden modification in the couplings to the leads or a shift of the orbital level. In particular, we calculate the time
evolution of the induced local superconducting pairing correlations and magnetization. In this context, the relevant energy spectra are examined. Moreover, we study the behavior of the Loschmidt echo and the return function to shed light on the signatures of dynamical
quantum phase transitions. The determined dependencies reveal non-trivial competition between relevant correlations, involving superconducting pairing and
ferromagnetic-contacted induced exchange field, and deepen our understanding of nanoscale hybrid systems' dynamical behavior.
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Instrumentation and Methods for Astrophysics
Spectrally dispersed non-redundant aperture-masking interferometry in the thermal infrared with LBTI/ALES
T. A. Stuber, J. M. Stone, J. W. Isbell et al. (+5 more)
Non-redundant aperture-masking interferometry maximizes the angular resolution of a
telescope by turning it into an interferometric array using pupil plane masks. If the interference pattern on the detector is spectrally dispersed, deeper contrasts of the astrophysical scenery and an improved coverage of its spatial
Fourier modes is achieved. We combined a non-redundant aperture mask with the integral field spectrograph ALES of LMIRcam at the Large Binocular
Telescope Interferometer (LBTI). With this setup, we recorded spectrally dispersed non-redundant aperture-masking observations in the $L$ band ($\sim$3-4$\,\mu$m). We present commissioning data with which we recovered a known binary
star and derived contrast detection limits for further point-source components of ${\sim} 5 \times 10^{-3}$ for separations of ${\gtrsim} 80\,$mas. This is the first time that an integral field spectrograph was combined with a non-redundant aperture mask in the $L$ band. Opening up the thermal infrared for this technique, this new capability enables the LBTI to efficiently survey nearby, bright
stars for faint companions, which is of great importance for studies on hot exozodiacal
dust and target vetting for future exo-Earth imaging missions such as NASA's Habitable Worlds Observatory. A further application is aperture synthesis of extended sources such as active
galactic nuclei or evolved
stars.
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All authors T. A. Stuber, J. M. Stone, J. W. Isbell, T. De Prins, J. P. Scott, J. A. Eisner, J. Carlson, S. Ertel
High Energy Physics (Theory)
Bumpy horizons from non-linear sigma models
Fabrizio Canfora, Nicolás Grandi, Carla Henríquez-Báez et al. (+1 more)
We show that black hole horizons with non-constant
curvature can be constructed in any even dimension, when the source of the Einstein equations is given by the stress-energy tensor of a non-linear sigma model of a particular class
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All authors Fabrizio Canfora, Nicolás Grandi, Carla Henríquez-Báez, Julio Oliva
Astrophysics of Galaxies
Mapping Gas Accretion and Stellar Kinematics to Sub-kiloparsec Scales in NGC 4696 with JWST/NIRSpec
Mathieu Marquis, Julie Hlavacek-Larrondo, Olivia Pereira et al. (+35 more)
We present JWST/NIRSpec IFU spectroscopy of the central $618\times618$ pc$^2$ ($\sim3''\times3''$) of NGC 4696, the BCG in the Centaurus cluster. Leveraging the $\sim0.1''$ ($20.6$ pc) pixel size of JWST, we resolve a compact circumnuclear rotating disk (radius of $\sim120$ pc) traced by Pa$\alpha$ and H$_2$ 1$-$0 S(1) emission, which allows a reassessment of the AGN position based on the kinematic centre of this disk. A central Pa$\alpha$ velocity dispersion reaching $\sigma\sim449$ km s$^{-1}$ implies a SMBH mass of $\sim10^9$ M$_\odot$, corresponding to a sphere of influence of $r_\mathrm{inf}\sim60$ pc, resolved by our observations. Position-velocity diagrams reveal an increase from $\sim-200$ to $\sim600$ km s$^{-1}$ on scales of $\sim150$ pc (a gradient of $4.7$ km s$^{-1}$ pc$^{-1}$) and an
accretion rate of $\sim18$ M$_\odot$ yr$^{-1}$ feeding the CND. The Pa$\alpha$ emission shows a double-component in the core, with a high-dispersion redshifted component reaching $\sigma\sim600$ km s$^{-1}$. In contrast, MUSE H$\alpha$ observations covering the $\sim10$ kpc-scale filamentary structure recover only weak velocity gradients ($\lesssim150$ km s$^{-1}$) within $\sim300\times300$ pc$^2$ and do not resolve the disk due to larger PSFs and pixel sizes. ALMA CO(2-1) data reveal only compact molecular clumps within a $\sim410\times410$ pc$^2$ region, with no extended counterpart to the structures traced by Pa$\alpha$ and H$_2$ 1$-$0 S(1).
Stellar kinematics show a smooth velocity field and broad dispersion profile, clearly decoupled from both the multiphase gas and the hot ICM probed by XRISM. These results provide a direct, spatially resolved view of gas dynamics within the inner few hundred parsecs, demonstrating the power of JWST/NIRSpec to probe SMBH feeding.
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All authors Mathieu Marquis, Julie Hlavacek-Larrondo, Olivia Pereira, Michael Reefe, Hyunseop Choi, Jorge Barrera-Ballesteros, Benjamin Vigneron, Ming Sun, Rebecca E. A. Canning, Gregory Taylor, Loïc Albert, Francesco D'Eugenio, Megan Donahue, Andrew C. Fabian, Gary J. Ferland, John S. Gallagher, Marie-Lou Gendron-Marsolais, Pierre Guillard, Minghao Guo, Nina Hatch, Ralf Kotulla, Yuan Li, Roberto Maiolino, Allison Man, Michael A. McDonald, Brian R. McNamara, Valeria Olivares, Marine Prunier, Christopher S. Reynolds, Carter Rhea, Annabelle Richard-Laferrière, Helen R. Russell, Philippe Salomé, Prathamesh Tamhane, Auriane Thilloy, Grant R. Tremblay, G. Mark Voit, Stephen A. Walker
Mesoscale and Nanoscale Physics
Ferroelectric-controllable spin-orbit torque in two-dimensional multiferroic heterostructure
Weiyi Pan, Gusthavo M.S. Brizolla and Jaroslav Fabian
Spin-orbit torque (SOT), which enables electrical control of magnetization, plays a crucial role in the development of next-generation spintronic devices. Realizing SOT in two-dimensional van der Waals systems, together with achieving efficient nonvolatile manipulation via ferroelectricity, would be highly beneficial for the implementation of tunable logic devices with enhanced storage density. In this work, based on first-principles calculation and using a multiferroic Fe$_{3}$GeTe$_{2}$/In$_{2}$Se$_{3}$
heterostructure as a representative example, we demonstrate that switching the ferroelectric polarization of the In$_{2}$Se$_{3}$ layer induces a pronounced modification in the magnetization-dependent distribution of torkance within the
heterostructure. Specifically, when the magnetization is in the plane, where the torque is maximal, reversing the polarization of In$_{2}$Se$_{3}$ from upward to downward enhances the total torkance to more than 150% of its original value. This substantial variation primarily originates from the polarization-induced modulation of the $z$ component of the time-reversal-odd torkance, which is mainly associated with an approximately 233% change in the atomic-resolved torque contributed from the middle Fe layer in Fe$_{3}$GeTe$_{2}$ layer. Further analysis reveals that the electronic states near $\Gamma$ on the
Fermi surface undergo significant reconstruction upon polarization switching, which is responsible for the observed variation in the time-reversal-odd torque. Our results not only provide new insights into the functional potential of van der Waals multiferroic
heterostructures, but also offer a viable strategy for achieving electrically tunable SOT, paving the way for future programmable spintronic devices.
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High Energy Astrophysical Phenomena
Capture Driven Evolution of Asymmetric Dark Matter in Non-rotating Neutron Stars
Peiran Liu and Wenrong Sun
We develop a self-consistent framework that connects dark matter capture to the long term accumulation and structural
evolution of
neutron stars, allowing us to quantify the impact of capture driven asymmetric dark matter on gravitational wave observables over astrophysical timescales. We model cold, non-rotating
neutron stars using a three layer polytropic EoS coupled to a dark matter component through the two fluid Tolman Oppenheimer Volkoff equations, and reconstruct the long term
evolution using a time dependent dark matter capture formalism. By exploring a wide range of astrophysical conditions, including extreme environments designed to maximize the capture efficiency, we derive conservative upper bounds on the effects of dark matter accumulation over a Hubble time. Even under these deliberately optimistic assumptions, the accumulated dark matter component remains subdominant and induces limited structural modifications. In particular, dark matter accumulation increases the
stellar compactness while suppressing the Love number and
tidal deformability. Significant
evolution occurs only in extreme
Galactic center like environments over Hubble time scales, whereas for realistic
Galactic or cluster dark matter densities the corresponding deviations remain negligible. We therefore conclude that capture driven dark matter accumulation is unlikely to produce detectable signatures in current or near future gravitational wave observations of
neutron stars.
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Quantum Physics
Emergent Non-Markovian Nonlinear Qubit From Collective Spin Interactions
Gregory T. Carroll, Michael R. Geller and Andre Erpenbeck
Open-system descriptions are typically introduced by coupling a
quantum system to an external environment. Here we show that a closed interacting many-body system can itself generate a controlled non-Markovian
quantum channel acting on a reduced nonlinear
qubit through finite-size corrections to a nonlinear mean-field limit. We demonstrate this using the Kitagawa-Ueda one-axis twisting model, $H=\chi J_z^2$, a paradigmatic model of collective
spin dynamics,
spin squeezing, and two-component Bose-Einstein condensates. Although the large-$N$ regime of this model has been extensively studied, the conventional fixed-$\chi$ scaling does not yield a nontrivial dynamical large-$N$ limit. In this paper, we investigate a complementary large-$N$ formulation obtained from the double limit $N\rightarrow\infty$ and $\chi\rightarrow O(g/N)$, where $g$ is a coupling constant. We derive the leading finite-$N$ corrections to this limit and show that they correspond to an emergent non-Markovian dephasing process, producing a Gaussian decay of the Bloch-vector coherence with characteristic timescale $t_\varphi\geq\sqrt{N}/(2g)$. Exact finite-$N$ calculations demonstrate that this effective open-system description becomes quantitatively accurate for systems containing on the order of one hundred
qubits. The resulting framework provides a microscopic realization of non-Markovian dephasing generated intrinsically by a closed many-body system and enables efficient simulation of collective
quantum dynamics beyond
unitary mean-field theory. These results link the long-studied phenomenon of phase
diffusion in atomic ensembles and Bose-Einstein condensates to the growing effort to characterize non-Markovian, beyond-Lindblad noise in
quantum computing hardware, providing a rare case in which such a noise channel is derived from microscopic dynamics rather than fit phenomenologically.
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Fluid Dynamics · Cross-listed from cs.LG
Neural Operators for Immersed-Boundary Soft Swimmers Locomotion
Mohammad Sadegh Eshaghi, Yizheng Wang, Navid Valizadeh et al. (+2 more)
High-fidelity immersed-boundary simulation resolves the coupled motion of a deforming swimmer and its surrounding flow, but the resulting cost limits repeated evaluations for engineering design, parameter studies, and control. We develop neural-operator surrogates for temporal prediction of the hydrodynamic fields generated by planar and volumetric eel swimmers. The surrogates are trained on regular-grid fields exported from adaptive fluid–structure simulations and are conditioned on swimmer geometry and Reynolds number. The planar model jointly predicts two velocity components, scalar vorticity, and pressure. On five held-out high-Reynolds-number trajectories, its full-domain global relative L^2 error is 3.51 %. The volumetric formulation uses three target-specific models with a common multichannel input: one model predicts three-dimensional velocity, one predicts vorticity, and one predicts pressure. Their full-domain global relative L^2 errors on five held-out within-range trajectories are 3.44 %, 5.58 %, and 19.2 %. Together, the results demonstrate the feasibility of field-resolved neural surrogates for moving-boundary swimmer flows while identifying pressure accuracy and physical consistency as priorities for further development.
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All authors Mohammad Sadegh Eshaghi, Yizheng Wang, Navid Valizadeh, Xiaoying Zhuang, Timon Rabczuk
Plasma Physics
PASCHEN-1D: A one-dimensional fluid plasma solver with multi-mechanism surface emission and flexible external circuit coupling
Asif Iqbal, Yves Heri, Bingqing Wang et al. (+3 more)
We present PASCHEN-1D (
Plasma Advanced Solver with Coupled High-fidelity Emission and external Network), a one-dimensional time-dependent fluid
plasma solver developed for self-consistent simulation of gas discharges and
plasma breakdown with coupled electrode surface emission and flexible external
circuit networks. The code solves drift-
diffusion continuity equations for electrons and ions together with Poisson's equation. It is dynamically coupled to lumped RLC
circuits, which self-consistently treat
plasma transport,
plasma-surface interaction, dielectric effects, and
circuit response within a single framework. The electrode emission module includes ion-induced secondary electron emission, Fowler-Nordheim and Murphy-Good field emission, Richardson-Dushman thermionic emission, and photoemission based on a general, exact
quantum mechanical emission theory. A finite-volume formulation with Kurganov-Tadmor fluxes, explicit
diffusion, and fourth-order Runge-Kutta time integration is employed to ensure stable transient (sometimes ultrafast)
evolution across breakdown and glow regimes. The solver is validated against multiple
benchmark cases, including nanosecond pulsed dielectric-barrier discharges, DC breakdown and glow transitions, and Paschen curve construction for argon and nitrogen, with results consistent with published studies. With high-fidelity emission physics and a flexible
circuit-coupling framework, PASCHEN-1D provides a versatile and efficient tool for modeling breakdown and transient discharge phenomena.
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All authors Asif Iqbal, Yves Heri, Bingqing Wang, Lan Jin, Md Arifuzzaman Faisal, Peng Zhang
Quantum Physics
Randomized product formulas beyond optimal deterministic scaling
Leeseok Kim and Luis Pedro García-Pintos
Product formulas, also known as Trotter formulas, are among the most widely used and practical methods for simulating
quantum systems on
quantum computers. Here we introduce two new classes of randomized product formulas for simulating
Hamiltonians with separated energy scales, $H=A+\alpha B$, where $\alpha$ is small. In the standard access model, where one can implement exponentials of $A$ and $B$ separately, our randomized formulas achieve $\mathcal O(\alpha^2)$ error scaling at the cost of only doubling the gate depth of the corresponding deterministic formula. We further prove an $\Omega(\alpha)$ lower bound for deterministic product formulas. In a stronger access model, allowing exponentials of $A+\alpha B_\ell$ for $B = \sum_{\ell}B_\ell$, our randomized formula, based on Trotter Heuristic Resource Improved Formulas for Time-dynamics (THRIFT)~[J. L. Bosse et al., Nat. Commun. 16, 2673 (2025)], achieves $\mathcal O(\alpha^3)$ error scaling with only constant-factor expected gate overhead. We also establish an $\Omega(\alpha^2)$ lower bound for deterministic product formulas in this access model. Numerical simulations confirm gate-count reductions for simulating physically motivated systems.
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Cosmology and Nongalactic Astrophysics
Axion dark matter search with a photonic bandgap cavity haloscope and dielectric tuning rod over 10.25-10.45 GHz
Morgan Lynn, Ankur Agrawal, Arjun Ghosh et al. (+4 more)
We report the development of a new widely tunable cavity and demonstrate its use in a search for dark matter
axions. We achieve unloaded quality factors above $10^{5}$, roughly $25\times$ larger than a bare copper cavity at the same frequency, using concentric sapphire shells to reduce Ohmic losses on the cavity barrel. A rotating sapphire rod tunes our cavity mode over the $10.1-11.7$ GHz range, approximately $16\%$ of its resonant frequency. Using an amplified receiver chain, we demonstrate sensitivity to new
axion parameter space by tuning the cavity over the $200$ MHz range between $10.25-10.45$ GHz (42.4 - 43.2, $\mu$eV) to constrain the
axion-to-
photon coupling to $|g_{a\gamma\gamma}|$ $\leq$ 1 $\times$ $10^{-12}$ ${GeV}^{-1}$. This cavity can scan its tuning range about $9$ times faster compared to a bare copper cavity when paired with a
photon counting device, laying the groundwork for a definitive search for the QCD
axion over $10.1-11.7$ GHz.
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All authors Morgan Lynn, Ankur Agrawal, Arjun Ghosh, Sara Sussman, Steven G. Johnson, David I. Schuster, Aaron S. Chou
Quantum Physics
Implicit Differentiation for Measurement-Efficient Bilevel Quantum-Classical Optimization
Tobias Rohe, Markus Baumann, Federico Harjes Ruiloba et al. (+3 more)
Quantum optimization has shown promising results for quadratic unconstrained binary optimization (QUBO) problems. Real-world applications, however, often involve
polynomial coefficients that depend on tunable external factors - such as demand forecasts or risk preferences - giving rise to bilevel optimization structures. We show how variational
quantum algorithms (VQAs) can efficiently handle such parametric problems, making three contributions. First, we propose a bilevel optimization model for diagonal cost
Hamiltonians where coefficients depend on a tunable outer parameter: an outer loop adjusts this parameter - reshaping the cost landscape - while an inner VQA optimizes
circuit variables. Second, since derivative-free probing methods incur a multiplicative overhead when each outer evaluation requires a complete inner solve, we develop correlator-reuse implicit differentiation (CR-ID), which obtains outer gradients by reusing
quantum measurements already collected during inner energy estimation, requiring essentially no additional
circuit executions. Experiments across three coefficient families show that CR-ID consistently improves budget-normalized efficiency by ~4% in 1D and over 14% in multi-dimensional settings, showing a significant performance advantage compared to finite-difference methods. Third, we show that this property is architecture-dependent: VQE admits exact reuse gradients, whereas QAOA introduces a state-dependent term that creates a cost-bias trade-off.
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All authors Tobias Rohe, Markus Baumann, Federico Harjes Ruiloba, Maximilian Zorn, Jonas Stein, Claudia Linnhoff-Popien
Strongly Correlated Electrons
Engineering correlated phases through manipulation of Van Hove singularities
Thomas P. Sheerin, Maria Ramirez, Chris A. Hooley et al. (+1 more)
Controlling the ordered phases of correlated electron systems remains a central challenge in
quantum materials design. Divergences in the electronic density of states, known as Van Hove singularities (VHSs), are one obvious route to such control. It is clear from recent work that the exact functional form of these divergences can profoundly affect which phases are realized; a full picture, however, remains elusive. In this work, we use both the hot-spot parquet renormalization group and the truncated-unity functional renormalization group to theoretically study the emergent correlated states of a two-dimensional square-
lattice Hubbard model with VHSs at or near the
Fermi level. By varying a single hopping parameter, $t_3$, we are able to change the strength of the VHS divergence in the density of states from logarithmic (for $t_3 < t_{3c}$) to power-law (for $t_3 = t_{3c}$). Further increase of $t_3$ ($t_3 > t_{3c}$) causes each original Van Hove point to split into two, both of the conventional logarithmic type. We show that which of these regimes we are in strongly influences the predicted ordered states. We also study the dependence on doping, and find that the
ferromagnetic state that occurs at Van Hove filling in these models is unstable to very small shifts in the
Fermi level, often giving way to distinct ordered states depending on whether the model is electron- or hole-doped. These results highlight the importance of tuning VHS properties to control ordered states in correlated materials, and offer design rules to engineer these phases in novel systems.
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All authors Thomas P. Sheerin, Maria Ramirez, Chris A. Hooley, Luke C. Rhodes
Quantum Physics
The Case for the Everett Multiverse
David Wallace
I give a non-technical presentation of the argument that
quantum mechanics, in the form in which it is currently used, needs to be understood in many-worlds (Everettian) terms; the alternatives that have been discussed are at present not able to reproduce the full empirical content of the theory. This is a draft of a chapter for the forthcoming Blackwell Companion to Philosophy and the Multiverse (Klaas Kraay and Daniel Rubio, eds.)
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High Energy Physics (Theory)
Supertranslations are Soft Dressings
Asaad Elkhidir, Donal O'Connell and Radu Roiban
Asymptotic states of massive particles in electrodynamics and
gravity are not uniquely defined because of the absence of a mass gap. Working in the KMOC formalism, we study the classical implications of this freedom in the dressing of massive particle states. We show that coherent-state dressings modify observables by a large gauge/BMS transformation. The associated coherent-state displacement operator can be completed into a conserved charge, the BMS charge in the gravitational case, which implements large gauge transformations on scattering data. The parameter of our dressing is directly the large gauge/BMS transformation parameter, and we explain that observables do not depend on monopolar and dipolar parts of the transformation parameter to all orders. Our construction is driven by soft factorization rather than by an underlying local
symmetry, and we illustrate this by exhibiting the same structure in a scalar theory with no gauge
symmetry. We explore the action of large gauge transformations on two-particle states for scalar, abelian gauge and graviton mediators, obtaining a universal shift of the impact parameter and clarifying the frame dependence of the radiated angular momentum vis à vis the frame-independence of the total angular momentum. The transformation connecting the canonical BMS frame, in which the Schwarzschild metric takes the Kerr-Schild form, to the intrinsic frame, in which it takes the De Donder form, illustrates these effects concretely.
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