Mathematical Physics
The Hamilton–Jacobi and Symplectic Analysis for Extended Hořava Gravity
Diana Vanessa Castro-Luna and Alberto Escalante
The Hamilton-Jacobi [HJ] analysis and the Faddeev-Jackiw [FJ] quantization for the linearized, non-projectable $\lambda R$ model, extended by the lowest-order term of Blas, Pujolàs, and Sibiryakov and the higher-order term involving the square of the Cotton tensor, were carried out. The cases $\lambda \neq \frac{1}{3}$ and $\lambda = \frac{1}{3}$ are analyzed. Within the Hamilton-Jacobi framework, we obtain the complete set of
Hamiltonians, generalized brackets, fundamental differential, characteristic equations, and gauge transformations of the theory. In the Faddeev-Jackiw framework, a
symplectic tensor is constructed from which the fundamental brackets are identified. The HJ and FJ brackets coincide, and from the
symplectic tensor, the measure for the
quantum path integral is calculated. The differences between the cases $\lambda \neq \frac{1}{3}$ and $\lambda = \frac{1}{3}$ at the
quantum path integral are discussed.
Read the full abstract ▾
High Energy Physics (Theory)
Yutaka Ookouchi
The
chiral soliton lattice (CSL) is conventionally described as a periodic winding configuration of a compact scalar field. In this paper, we formulate the CSL in a higher-form framework based on a Stückelberg coupling between a two-form gauge field $C_2$ and a three-form gauge field $A_3$, in which strings and walls can be treated directly as extended sources. Higher-form gauge invariance requires the string worldsheet to be the boundary of the wall worldvolume. In the quadratic dual effective theory, exchange of the massive higher-form mode generates a repulsive Yukawa interaction between parallel walls. With its coefficient fixed by duality, the resulting CSL
lattice spacing agrees well with the exact Sine–Gordon result without parameter fitting. We then extend the description to a nonlinear, multi-branch higher-form theory. It reproduces the exact dilute wall–wall interaction coefficient, the periodic CSL and its energy-minimization condition, as well as the gapless CSL
phonon. The
phonon is identified as a collective displacement of the periodic higher-form background, while scalar winding is reinterpreted as branch flow of the nonlinear higher-form theory.
Read the full abstract ▾
Plasma Physics · Cross-listed from math.NA
Positivity-preserving semi-Lagrangian discontinuous Galerkin methods for multi-species Vlasov-Ampère models of plasma
Dauda Gambo and James A. Rossmanith
We develop a high-order and positivity-preserving kinetic solver for the multi-species Vlasov-Ampère system that is built within a semi-Lagrangian discontinuous Galerkin (SLDG) framework. The method is designed for efficiency and accuracy across a broad range of conditions, including stiff, multi-scale regimes with strong ion-electron scale separation. Phase space is discretized via high-order discontinuous Galerkin finite elements; time stepping is handled via high-order operator splitting and a series of one-dimensional, unconditionally stable, semi-Lagrangian updates. To improve both accuracy and efficiency, each
plasma species is represented on a different phase-space mesh. On every element and for each species, local positivity-preserving limiters are applied to prevent spurious undershoots and rigorously ensure positivity of the
cell averages at the next time step. The accuracy and robustness of the resulting method are verified on several standard single- and two-species test cases, including manufactured solutions, two-stream instability, weak and strong Landau damping, ion-acoustic wave propagation, ion-acoustic shock formation, and KEEN wave dynamics.
Read the full abstract ▾
Quantum Physics
Inverse-Designed Nanobeam Cavities for High-Cooperativity Spin-Photon Interfaces in Silicon
Nail Letty, Md Sakibul Islam and Wayesh Qarony
Telecom-band
spin defects in silicon offer a compelling platform for integrated
quantum networks by combining scalable silicon photonics with
spin-based
quantum memories and multiqubit registers. The T center and recently demonstrated Al1 center are particularly promising, but their limited coherent zero-
phonon emission requires strong cavity enhancement for efficient
spin-
photon interfaces. Here, we inverse-design silicon nanobeam cavities for both centers using a unified adjoint-optimization framework targeting Purcell enhancement, resonance
alignment, and
photon extraction. For each emitter, symmetric cavities maximize Purcell enhancement, while asymmetric cavities provide directional coupling to an integrated waveguide. Three-dimensional finite-difference time-domain simulations yield loaded quality factors up to 3.25 x 10^6, Purcell factors up to 1.43 x 10^5, and cooperativities of approximately 280-5000, corresponding to cavity-coupled emission fractions exceeding 99.6%. The asymmetric cavities direct approximately 90% of emitted power into a single on-chip waveguide while maintaining cooperativity above 280. Under nanometer-scale fabrication perturbations, all four designs remain within the high-cooperativity regime, and high cooperativity persists when the cavity quality factor is constrained to a realistic absorption-limited value of 10^5. This unified, fabrication-compatible framework establishes a scalable cavity-design route for silicon telecom
spin-
photon interfaces and, to our knowledge, the first cavity designs for the Al1 center.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics
Universality classes of sharp gravitational production of light particles
Kanta Ito, Yusuke Mikura and Shuichiro Yokoyama
We establish a classification of the gravitational production of light particles across sharp transitions connecting different asymptotic forms of the scale factor. A family of smooth scale factors with a transition duration $\Delta\eta$ is characterized by its regularity in the sharp-transition limit $\Delta\eta\to 0$, leading to three qualitatively different universality classes: $C^0$, $C^1$, and $C^2$-or-smoother. We find that the $C^0$ class exhibits a quadratic enhancement in the energy density of produced particles, $\rho\propto\Delta\eta^{-2}$, while the $C^1$ class shows a logarithmic enhancement, $\rho\propto\ln(1/\Delta\eta)$. No sharp-transition enhancement occurs for the $C^2$-or-smoother class. Using a specific $C^\infty$ model of the scale factor, we derive the energy density analytically and confirm both the predicted quadratic scaling and its coefficient by numerically solving the mode equation. These results identify the regularity of the scale factor in the sharp limit as the key property controlling the sharp-transition enhancement.
Read the full abstract ▾
General Relativity and Quantum Cosmology
Inhomogeneous dust collapse in five-dimensional AdS-Chern-Simons gravity
Luis Avilés, José Díaz, Cristian Quinzacara et al. (+1 more)
We study the gravitational collapse of a spherically symmetric, inhomogeneous
dust cloud in five-dimensional AdS Chern–Simons
gravity. Working in the torsion-free sector and using comoving Lemaître–Tolman–Bondi coordinates, we derive the reduced field equations and obtain an exact collapsing interior solution. The areal radius evolves periodically in time, but the physical collapsing branch extends only up to shell focusing or an earlier loss of regularity, while the initial density determines a radial function whose square is proportional to the conserved quasilocal mass. This separates the roles of the initial velocity and density profiles in controlling shell focusing and trapping. We derive conditions for central regularity and for avoiding shell crossing, analyze the Kretschmann scalar, and show that shell focusing corresponds to a genuine
curvature singularity, the weak and strong energy conditions are preserved throughout the regular collapsing phase. The homogeneous limit reduces consistently to a five-dimensional FLRW interior. The collapsing cloud is matched smoothly to the black-hole branch of the static AdS Chern–Simons exterior. The null expansions show that a finite-radius apparent horizon forms only when the quasilocal mass exceeds a critical threshold. Initially untrapped shells above this threshold become trapped before shell focusing, whereas below the total-mass threshold no finite-radius future-trapped
symmetry sphere forms in the regular interior.
Read the full abstract ▾
All authors Luis Avilés, José Díaz, Cristian Quinzacara, Patricio Salgado
Solar and Stellar Astrophysics
Successfully Reproducing Solar Orbiter Polar Field Observations with a Surface Flux Transport Model
Ruihui Wang, Jie Jiang, Yukun Luo et al. (+2 more)
The
solar polar field plays a fundamental role in predicting
solar-cycle strength and determines the large-scale structure of the heliospheric
magnetic field. The High Resolution
Telescope of the Polarimetric and Helioseismic Imager aboard
Solar Orbiter (SO/PHI-HRT) provides unprecedented observations of the
solar polar regions, as
Solar Orbiter currently reaches heliographic latitudes of up to $\pm17^\circ$, about $10^\circ$ higher than those accessible from near-ecliptic observations. Using these observations to further test surface flux transport models, we present a successful simulation of the SO/PHI-HRT observations, reproducing the latitudinal profiles of the longitudinally averaged radial
magnetic field in both polar regions. This result is achieved using the meridional-flow profile proposed by \citet{WangRH2026}, which also reproduces the
evolution of the axial dipole strength,
magnetic butterfly diagram, and high-latitude
magnetic fields observed by SDO/HMI during
Solar Cycle 25. We further compare simulations using this profile with simulations employing two representative meridional-flow profiles characterized by different peak latitudes. The latter fail to reproduce the observed high-latitude and polar fields. The comparison demonstrates that the meridional-flow profile strongly regulates poleward flux transport and the resulting polar-field
evolution. Profiles peaking at higher latitudes produce stronger flux surges, and stronger and more concentrated polar fields. These results provide new constraints on the large-scale
solar meridional flow.
Read the full abstract ▾
All authors Ruihui Wang, Jie Jiang, Yukun Luo, D. Calchetti, S. K. Solanki
Mesoscale and Nanoscale Physics
Enhancing magnonic frequency combs via geometric nonlinearity
Yushun Fang and Weichao Yu
Magnonic frequency combs (MFCs) generated via internal
magnetic nonlinearities have exhibited rich physics beyond their optical counterparts. However, existing approaches rely on dynamic nonlinearity, which typically demands high power thresholds and stringent momentum conservation. Here we show that the
geometric nonlinearity intrinsic to
magnetic systems, originating from the unit-norm constraint of the magnetization vector, can serve as an independent nonlinear resource for MFC generation. Through transverse Floquet engineering, this
geometric constraint converts a transverse drive into a longitudinal parametric modulation. In the low-frequency limit, the four-particle process reduces to an effective two-
magnon modulation, enabling low-threshold comb generation in the linear regime, with the modulation amplitude scaling quadratically with the driving field and enhanced flatness arising from
geometric harmonics. These results provide a deeper understanding of frequency combs and
magnon nonlinear interactions, and offer a new theoretical foundation for enhancing MFC performance.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics
Cross-correlation between CMB B-modes and Faraday Rotation as a Novel Probe of Primordial Magnetic Fields
Toshiya Namikawa and Guanming Liang
We investigate the cross-bispectrum between the
cosmic microwave background (CMB) $B$-mode polarization and two Faraday rotation (FR) angles as a new probe of
primordial magnetic fields (PMFs). Assuming Gaussian PMFs with both non-helical and helical components, we derive the $B\alpha\alpha$ bispectrum and decompose it into parity-even and parity-odd contributions. The mixed non-helical–helical contribution appears in the parity-even sector, whereas the purely non-helical and purely helical contributions contribute to the parity-odd sector. This parity dependence provides sensitivity to PMF helicity that is absent in the FR power spectrum alone. We then forecast the detectability of the cross-bispectrum for SO-like and LiteBIRD-like CMB experiments, and find that future observations can probe PMFs with amplitudes at the sub-nG level. The $B\alpha\alpha$ bispectrum is dominated by the helicity-sensitive parity-even sector and provides a promising avenue for constraining both the amplitude and helicity of PMFs.
Read the full abstract ▾
High Energy Astrophysical Phenomena
Spin wandering of an accreting neutron star near torque balance: implications for gravitational wave searches
Andrew Melatos
Torque balance between gravitational radiation reaction and magnetocentrifugal
accretion is one reason why accreting
neutron stars rotate slower than centrifugal break-up. Random processes in the
accretion disk, such as Rayleigh-Taylor instabilities and flicker noise, drive the
spin frequency $f_\ast$ and gravitational wave frequency $f_{\rm gw}\propto f_\ast$ to wander stochastically around their torque balance values. Here it is shown theoretically, in terms of an idealized Ornstein-Uhlenbeck model, that the standard deviation of $f_{\rm gw}$ is given by $\sigma_{f_{\rm gw}}(h_0) \propto f_{\rm gw} h_0 D \beta T^{1/2}$, or equivalently $\sigma_{f_{\rm gw}}(F_{\rm X}) \propto f_{\rm gw}^{1/2} F_{\rm X}^{1/2} D \beta T^{1/2}$, where $h_0$ is the characteristic wave strain, $F_{\rm X}$ is the X-ray flux, $D$ is the source distance, and $\beta$ and $T$ are the fractional amplitude and autocorrelation time-scale of the
stochastic torque. One can use $\sigma_{f_{\rm gw}}(h_0)$ and $\sigma_{f_{\rm gw}}(F_{\rm X})$ to check the physical consistency of a detection candidate in a gravitational wave search by comparing with $\sigma_{f_{\rm gw}}$ observed.
Spin wandering impacts search design, because it sets the maximum time interval $\max(T_{\rm coh})$, during which the signal may be treated as coherent. The Ornstein-Uhlenbeck calculation predicts $10^{-1} \lesssim \max(T_{\rm coh}) / (1\, {\rm day}) \lesssim 10^3$, with $3\times 10^{-2} \lesssim \beta T^{1/2} / (1 \, {\rm s^{1/2}} ) \lesssim 4$, for Rayleigh-Taylor instabilities and flicker noise. The predicted $\max(T_{\rm coh})$ is shorter typically than the year-long observation runs of audio-band interferometers operating today, emphasizing the utility of semi-coherent search
algorithms, which divide the data into multiple coherent segments of duration $\max(T_{\rm coh})$.
Read the full abstract ▾
Astrophysics of Galaxies
H-alpha Star Formation Rates of the SHIELD Dwarf Galaxies
Madeline Shepley, David G. Gormanous, John J. Salzer et al. (+9 more)
The Survey of HI in Extremely Low-mass
Dwarfs (SHIELD)
galaxy sample is an HI-selected catalog of
galaxies that occupy the extreme low-mass end of the HI mass function. Our team is carrying out a comprehensive multi-wavelength observational program targeting these gas-rich,
star-forming
dwarf galaxies. The current paper presents H-alpha narrowband observations of the full SHIELD sample. We detect 55 of the 82
galaxies (67%) with nebular H-alpha emission, and infer sensitive upper limits to the H-alpha fluxes for the 27 non-detections. We derive H-alpha luminosities and
star formation rates (SFRs), or upper limits, for all 82 SHIELD
galaxies. We also present, for the first time, deep broadband and continuum-subtracted H-alpha images plus a summary of the properties for the entire sample. Our analysis of the H-alpha data re-affirms previous results which show that at low levels of
star formation (log(SFR_{H-alpha}) < -2.5), H-alpha becomes an increasingly poor tracer of the recent average SFR as measured by far-UV (FUV) luminosities. However, we show that this effect is not strictly correlated with the mass of the
galaxy. Some very low-mass SHIELD
galaxies with higher H-alpha-based SFRs show good agreement with SFR_{FUV}. The SHIELD
galaxies show no correlation between H-alpha SFR and gas mass fraction, but reveal a modest correlation between H-alpha specific SFR and gas mass fraction. Overall, the
star formation efficiency exhibited by the SHIELD
dwarfs is rather low, despite the gas-rich nature of the sample (68% have M_{gas} > M_{
stellar}).
Read the full abstract ▾
All authors Madeline Shepley, David G. Gormanous, John J. Salzer, Nathalie Haurberg, Steven Janowiecki, John M. Cannon, Elizabeth A. K. Adams, Martha P. Haynes, Alec S. Hirschauer, Kristen B. W. McQuinn, Katherine L. Rhode, Evan D. Skillman
Fluid Dynamics
A deterministic Fokker–Planck/lattice-Boltzmann micro–macro solver for dilute Hookean polymer solutions
Xueqin Liu, Shi Shu, Yaolong Yu et al. (+3 more)
Deterministic micro–macro simulation of
polymer solutions requires the coupled
evolution and spatial transport of a configuration distribution, together with the conversion of its moments into macroscopic stress and feedback to the flow. We develop a Fokker–Planck/
lattice-Boltzmann solver for this coupling in two-dimensional dilute Hookean
polymer solutions. The solver represents the distribution on the unbounded configuration space by Hermite coefficient fields, advances local configuration dynamics and physical-space transport in separate steps, and recovers Kramers stress from the second moment to achieve two-way coupling with a purified two-relaxation-time
lattice-Boltzmann flow solver. To assess whether this configuration description recovers the corresponding macroscopic response, we use the exact second-moment closure of the continuous Hookean model as a macroscopic reference for comparison with analytical and independently discretized macroscopic solutions. The calculations reproduce velocity overshoot and damped oscillations in start-up Poiseuille flow, with velocity profiles approaching the analytical start-up transient under grid refinement; in four-roll flow with spatially nonuniform extension and stress feedback, the maximum full-domain relative differences in velocity and
polymer stress are approximately $0.0309\%$ and $3.84\%$, respectively, over the tested Weissenberg numbers at corresponding sampling times. These comparisons support the solver's ability to recover the Hookean macroscopic response from configuration-distribution
evolution. Further calculations of wall-bounded recirculation and open cross-slot flow exhibit the corresponding conformation responses and symmetric and asymmetric flow states, extending this deterministic micro–macro method to viscoelastic flows under different boundary constraints.
Read the full abstract ▾
All authors Xueqin Liu, Shi Shu, Yaolong Yu, Yuan Yu, Hao Zhang, Yuting Zhou
Solar and Stellar Astrophysics
Self-constrained Magnetic Reconnection of a Solar Flare Co-spatial with a Non-ejected Filament
Ye Qiu, Changxue Chen, Anqin Chen et al. (+11 more)
For
flares associated with eruptive filaments, the filament normally rises above the post-
flare loops. Here, we report an unusual event in which the post-
flare loops instead overlie a filament that remains non-ejected throughout the
flare. This event was simultaneously captured by the Chinese H$\alpha$
Solar Explorer (CHASE), the
Solar Extreme-UltraViolet Imager (SUVI) onboard Fengyun-4C, the Hard X-ray Imager (HXI) onboard the Advanced Space-based
Solar Observatory (ASO-S) and the
Solar Dynamics Observatory (SDO). Extreme Ultraviolet (EUV) observations provided by FY4C/SUVI and SDO show that two hot loop systems form at the
flare onset. The western end of the northern loop system undergoes a southwestward drifting motion with gradually increasing shear, whereas the southern loop system progressively converges toward and eventually overlies the northern one. Meanwhile, three-dimensional
magnetic field extrapolations reveal an increase in both the twist of the filament-supporting
magnetic structure and its poloidal
magnetic field after the
flare. Taken together, these observations suggest that the
flare is driven by a self-constraining zipper-type
magnetic reconnection, in which highly sheared arcades reconnect to form a series of overlying
flare arcades and an underlying flux rope. This reconnection continuously strengthens the
magnetic confinement of the filament, preventing its outward eruption, while facilitating substantial
plasma drainage along the reconnected
magnetic field revealed by the CHASE H$\alpha$ spectroscopic observations.
Read the full abstract ▾
All authors Ye Qiu, Changxue Chen, Anqin Chen, Chuan Li, Yang Guo, Linggao Kong, Feng Lu, Xiaohu Zhang, Weiguo Zong, Jinsong Wang, Xinkai Li, Peng Wang, Kefei Song, Bo Chen
Geophysics
Efficient One-Step Surface-Wave Tomography through Implicit Differentiation and Jacobian Factorization
Yiran Jiang, Ping Tong and Jianwei Ma
Surface-wave
tomography provides important constraints on the crust and upper mantle, but directly inverting millions of measurements for three-dimensional structure remains computationally demanding. We develop an efficient Gauss–Newton framework for one-step surface-wave
tomography that jointly inverts multiperiod interstation traveltimes for shear-wave velocity, accounting for both lateral wave propagation and depth sensitivity. Implicit differentiation of the converged discrete Eikonal equations provides individual traveltime sensitivity kernels, which are constructed efficiently by reusing the Eikonal dependency structure across receivers. A factorized Jacobian retains these kernels separately from shared model and dispersion mappings, reducing storage and repeated-product costs within each linearized solve. Synthetic experiments show that the framework recovers three-dimensional velocity anomalies with fewer model updates and lower model errors than the tested comparison workflows at similar data fits. Computational
benchmarks demonstrate substantial savings in operator storage and the cost of linearized model updates compared with using explicitly assembled Jacobians. We apply the framework to 6.34 million Rayleigh-wave phase traveltimes across the contiguous United States. The recovered model captures major crustal and uppermost mantle velocity variations, including the broad contrast between the tectonically active western United States and the continental interior, consistent with previous surface-wave studies. These results demonstrate a practical Gauss–Newton approach to imaging the crust and upper mantle using large surface-wave data sets.
Read the full abstract ▾
High Energy Physics (Theory)
Hairy Taub-NUT solution in gauged supergravity
Masato Nozawa
We present and study a family of exact Taub-NUT-AdS solutions with scalar hair in four-dimensional ${\cal N}=2$ gauged supergravity. The solutions are supported solely by a nontrivial scalar field and its self-interaction potential, with all gauge fields switched off. We determine the conditions under which Killing horizons exist and demonstrate that the spacetime admits at most one Killing horizon, and whenever it exists it is necessarily nondegenerate. In particular, the NUT deformation can give rise to a horizon in a branch whose static limit is horizonless. We also establish that the solutions with nontrivial scalar hair admit no Killing spinors. As in ordinary Taub-NUT-AdS spacetime, the global structure is afflicted by closed timelike curves. We compute the conserved mass using the covariant phase space method and formulate a restricted first law with the NUT parameter held fixed. Finally, we study the Euclidean sector, including an exceptional family specific to Euclidean signature, and determine the regularity conditions for bolts and nuts.
Read the full abstract ▾
Astrophysics of Galaxies
Tracing Winds through the Fog: A Comprehensive Survey of LMC's Galactic Outflows with ULLYSES
Suraj Poudel, April Horton, Kathleen A. Barger et al. (+21 more)
We investigate nearside
stellar-driven
outflows from the Large Magellanic Cloud (LMC) using UV absorption-line spectroscopy of 170 OB
stars, complemented by HI 21-cm emission and H$_{\alpha}$ emission. Using Voigt-profile fitting and AOD analysis of SiII, OI, and SII transitions, we map the velocity-dependent structure of foreground gas. The SiII column densities for the Voigt-fitted components decline smoothly from the LMC disk and reach a minimum at $v_{\rm LMCSR} \approx -100$ to $-200~{km~s^{-1}}$, marking the transition from a denser, slower wind to more diffuse high-velocity material. Comparisons with local
star-formation rate surface densities reveal a modest positive correlation for the slower wind component, linking it to recent massive-
stellar feedback. Photoionization modeling of 13 absorbers in the $+100\lesssim v_{\rm LSR} \lesssim +150~{km~s^{-1}}$ range reveals wide diversity in
metallicity,
dust depletion, and ionization conditions, consistent with multiple possible origins. While a substantial fraction of this predominately ionized gas is consistent with the high-velocity extension of the LMC wind, part of it may arise from contamination by Milky Way (MW) high-velocity clouds (HVCs) and Magellanic circumgalactic medium (CGM). We estimate a nearside cool-gas
outflow mass of ${\sim}1.8\times10^{7}\,M_{\odot}$, implying $\dot{M}_{\rm out}\approx0.15$-$0.33\,M_{\odot}\,\mathrm{yr^{-1}}$ and a mass-loading factor of $\eta\approx0.6$-1.3. On regional scales, 30 Doradus contributes $\sim10\%$ and N11 contributes $\sim3\%$ of the total
outflow mass, while the trailing side contains more wind material than the leading side, consistent with ram-pressure stripping. These results provide the comprehensive kinematic and physical characterization of how
stellar feedback,
galactic environment, and foreground contamination shape the multiphase wind emerging from the LMC.
Read the full abstract ▾
All authors Suraj Poudel, April Horton, Kathleen A. Barger, Frances H. Cashman, Jo Vazquez, Andrew J. Fox, Nicolas Lehner, J. Christopher Howk, Scott Lucchini, Dhanesh Krishnarao, Sabra Catalano, Anders Ripley, Wanyan Yuan, Natalie Van Tol, Citlali Alcala, Jordan Elliott, N. M. McClure Griffiths, Elena D'Onghia, Jason Tumlinson, Ananya Goon Tuli, Jacco Th. van Loon, Julia Roman-Duval, Yik Ki Ma, Callum Lynn
Optics
Geometry-Controlled Polarization Photocurrents in Scalable PtSe2 Infrared Pixels
Eunice Y. Paik, Owen A. Vail, Madaline R. Marland et al. (+11 more)
Polarization-sensitive photodetectors provide multi-dimensional optical information beyond the capabilities of traditional intensity-based detectors. The noble metal dichalcogenide PtSe2 presents unique opportunities for tunable polarization detection due to its strong
spin-orbit coupling, material stability, customizable broadband polarization responses, and direct compatibility with a wide range of substrates for back-end-of-line silicon integration. In this work, we demonstrate room-temperature near-infrared to mid-wavelength infrared polarization photoresponses using scalable, as-grown, wide-area PtSe2 films, and we show that the measured polarization response is reshaped by device geometry. Finite-element current-flow simulations reproduce the observed spatial redistribution of the polarization-sensitive response and localize the transverse polarization response near the pixel center. This geometry-enabled separation allows wavelength-dependent
laser spot scans to distinguish
symmetry-allowed photocurrents from contact-proximate, dichroism-mediated photothermal contributions. At near-infrared wavelengths, we observe spatial response that is consistent with linear-dichroic photothermoelectric currents, whereas mid-wavelength infrared measurements reveal a helicity-dependent photothermal contribution under oblique illumination. These results identify pixel boundary engineering as both a design lever and a diagnostic tool for scalable PtSe2 polarization-sensitive infrared pixels.
Read the full abstract ▾
All authors Eunice Y. Paik, Owen A. Vail, Madaline R. Marland, William A. Beck, Antonio Llopis-Jepsen, Wendy L. Sarney, Jeffery H. Leach, Stefan Heiserer, Nikolas Dominik, Cormac Ó Coileáin, Paul B. Seifert, Georg S. Duesberg, Blair C. Connelly, George J. de Coster
High Energy Astrophysical Phenomena
Polarization Signatures of Sgr A* with Tilted Hybrid Magnetic Fields
Yushu Feng, Hao Yin, Songbai Chen et al. (+1 more)
The
magnetic field geometry in the near-horizon region is very important in shaping polarimetric signatures of black hole images. With a hybrid
magnetic field consisting of an axisymmetric split-monopole field and a tilted uniform external field, we investigate the effects of external
magnetic field inclination on the polarimetric signatures of Sgr A* by employing a stationary semi-analytical radiatively inefficient
accretion flow (RIAF) model and general relativistic polarized radiative transfer simulations. Our results show that the external
magnetic field tilt significantly modifies the electric vector position angle (EVPA) pattern and brightness distribution. The induced non-axisymmetry from the tilted
magnetic filed component renders polarization morphology dependent on the observer's azimuthal angle, which is a novel behavior absent in purely axisymmetric
magnetic field configurations. In combination with Event Horizon
Telescope (EHT) data, we analyse the possibility of such hybrid
magnetic fields around Sgr A*.
Read the full abstract ▾
All authors Yushu Feng, Hao Yin, Songbai Chen, Jiliang Jing
Fluid Dynamics
Reconstruction of Molten Pool Flow Fields from High-Speed Video Using Physics-Informed Neural Networks
Yue Cao, Qin Su, Dung Hoang Tien et al. (+1 more)
Molten pool flow significantly influences bead geometry, defect formation, and solidification microstructure in wire-arc directed energy deposition (DED). However, direct flow sensing remains an open challenge due to extreme temperatures, intense arc illumination, and complex flow patterns. Traditional research has relied either on computationally intensive fluid dynamics simulations, which require assumed boundary conditions and lack empirical anchoring, or on
vision-based tracer particle tracking, which yields sparse, noisy, and physically unconstrained velocity estimates. This work bridges these two paradigms by reconstructing physics-constrained 2D surface flow fields from high-speed imaging of a GTAW-based wire-arc DED process under distinct flow regimes: quasi-steady convection and periodic droplet impact. The pipeline begins with homography correction to calibrate the oblique camera view, followed by dense optical flow extraction to provide raw velocity observations. For quasi-steady pools, a physics-informed neural network (PINN) reconstructs the surface velocity field by jointly enforcing data fidelity, incompressible Navier-Stokes momentum equations, no-penetration boundary conditions, and an arc-forcing prior through composite loss minimization. For pools subject to periodic droplet impact, a phase-conditioned time-dependent PINN is further developed to resolve the cyclic flow
evolution throughout the impact period. This work provides a unified framework that bridges high-speed visual sensing and fluid mechanics, enabling physics-grounded flow diagnostics for wire-arc DED processes.
Read the full abstract ▾
All authors Yue Cao, Qin Su, Dung Hoang Tien, Van Anh Nguyen
Quantum Physics
Counterdiabatic quasi-Floquet control for the generation of entangled BICs using giant atoms
Alexis R. Legón, Pedro Orellana and Ariel Norambuena
Bound states in the continuum (BICs) provide a mechanism for preserving
entanglement in waveguide
quantum electrodynamics. Here, using
quantum control techniques in a configuration of two braided
giant atoms, we propose a robust approach to create high-fidelity entangled BICs. The protocol combines quasi-Floquet modulation of the effective atom–waveguide couplings with an independent phase-controlled atomic exchange, which provides restricted counterdiabatic assistance for preparing the complete dressed BIC. In the lossless effective model, we obtain a full-state BIC fidelity of $0.99992$ and an unconditional atomic Bell fidelity of $0.99588$ using a fast control protocol. Microscopic finite-mode simulations validate the central-sideband description during the passage, while static calibration-error scans quantify its control tolerances. A separate microscopic study with relaxation and dephasing, using experimentally motivated component scales, identifies a finite useful
entanglement window and a benefit from shaping the coupling envelopes. These results support controlled preparation, retention, and
retrieval of dressed
entanglement within the stated control and noise assumptions.
Read the full abstract ▾
Mesoscale and Nanoscale Physics
In-Memory AM Demodulation Using an All-Silicon Independent-Dual-Gate Gain-Cell Memory with $<10^{-22}$ A Leakage Determined by Single-Electron Counting
Katsuhiko Nishiguchi, Toshiaki Hayashi, Kensaku Chida et al. (+3 more)
Ultra-low-leakage
memories are attracting increasing
attention for in-
memory sensing and computing. However, achieving sufficiently long retention in silicon
memories for analog signal processing remains challenging because of leakage through the access transistor. In this work, we demonstrate an all-silicon independent-dual-gate
memory whose leakage current, inferred from single-electron counting statistics, is below $10^{-22}$ A, giving a measured retention time exceeding 1000 s. Owing to the extremely low leakage, the subthreshold nonlinearity of the access transistor can be exploited without disturbing the stored charge, enabling in-
memory amplitude-modulation (AM) demodulation. The proposed
memory provides a CMOS-compatible platform for ultra-low-power signal processing and in-
memory sensing.
Read the full abstract ▾
All authors Katsuhiko Nishiguchi, Toshiaki Hayashi, Kensaku Chida, Takase Shimizu, Gento Yamahata, Seiya Kasai
Materials Science
Temperature Dependent Evolution of the Electronic Structure in EuZn2As2 across the Neel Transition
Milo Sprague, Anup Pradhan Sakhya, Barun Ghosh et al. (+8 more)
Magnetoresistive materials have been tremendously important for the development of
magnetic memory storage and spintronic devices. Recently, the
antiferromagnetic EuX2Pn2 compounds, with X being a transition metal and Pn being a pnictogen, have seen intensive research interest due to their unusual anomalous
Hall effect behavior and pronounced resistive anomaly near the Neel temperature (TN). These magnetotransport phenomena have been interpreted in the context of shortranged
ferromagnetic Structuations,
magnetic polaron formation, canted
spin configurations, and temperature dependent metal
insulator transitions in the electronic structure. Here, we report the observation of such a pronounced resistivity anomaly in EuZn2As2 near TN = 19 K. We demonstrate the suppression of this anomaly using applied
magnetic fields, both in plane and out of plane. To further interpret the origin of the observed transport behavior, we studied the temperature dependent electronic structure using combined angle resolved photoemission spectroscopy (ARPES) and first principles density functional theory (DFT) calculations, which exhibits limited modifications to the bands across TN away from the
Fermi energy. This lack of involvement of the electronic structure indicates a
spin-scattering origin of the aforementioned transport properties, rather than a reconstruction of the
Fermi surface.
Read the full abstract ▾
All authors Milo Sprague, Anup Pradhan Sakhya, Barun Ghosh, Mazharul Islam Mondal, Arun K. Kumay, Himanshu Sheokand, Kapil Gope, Tetiana Romanova, Dariusz Kaczorowski, Arun Bansil, Madhab Neupane
Statistical Mechanics · Cross-listed from cs.AI
Escaping Alignment: A Physical Trap Model of Best-of-N Jailbreaking
Marco Biroli
Best-of-$N$ jailbreaking (BoN) bypasses safeguards of aligned models by drawing $N$ independent augmentations of an unsafe
prompt and sampling $M$ completions of each. Previous works have shown that the attack success rate (ASR) seems to follow a power-law in $N$, which we challenge. The exponent drifts with $N$, with an exponential crossover which is a finite-size artifact of the
adversarial dataset. Little work has been done to explore the entire two-budget ($N, M$) attack surface as well as its dependence on the generation temperature $T$. We introduce a simple barrier model where each
prompt has a baseline safety level and each augmentation a random thermally activated barrier. Then four numbers, each backed by an interpretable safety mechanism, determine the entire ($N, M$) attack surface. They extrapolate predictions from $N \leq 100$ to $N = 10^4$, collapse five distinct models on the same scaling function and predict ASR at different temperatures from the one they were fitted at.
Read the full abstract ▾
Mathematical Physics · Cross-listed from math.SP
Discrete Mixed Quantization for Cat Maps
Elena Kim and Qiaochu Ma
In this paper, we develop a mixed quantization technique for graph vector bundles that combines semiclassical analysis and
quantum cat maps. We apply it to study the Kesten–McKay law and
quantum ergodicity.
Instrumentation and Detectors
Enhancing Conversion Gain in HEB Mixers using Negative Differential Resistance
Boris S. Karasik and Changyun Yoo
This work investigates how negative differential resistance (NDR) can be utilized to enhance conversion gain in superconducting niobium nitride (NbN) hot-electron bolometer (HEB) mixers. Conventional HEB operation avoids NDR regions due to parasitic oscillations caused by interactions between thermal inertia and bias-line reactance. Recent experimental results show that reducing the bias-T inductance suppresses these oscillations and enables stable biasing within the NDR regime, thereby increasing the mixer conversion gain beyond levels achievable under positive differential resistance (PDR) bias. Using a lumped thermal-electrical model, we interpret these experimental findings, derive stability conditions for NDR-biased operation, and predict the future performance limits achievable through optimized bias
circuit designs. Our results indicate that further reductions in bias inductance, combined with appropriate load-line conditions, could yield several decibels of additional gain while maintaining practical IF bandwidths.
Read the full abstract ▾
Earth and Planetary Astrophysics
COSINE (Cometary Object Study Investigating their Nature and Evolution) II: Colors and Sizes of Comet Nuclei
Yuna G. Kwon, Dar W. Dahlen, Joseph R. Masiero et al. (+6 more)
Comet
nuclei preserve a record of planetesimal formation, but their sizes are difficult to measure because the
nucleus is usually blended with its coma. We present a catalog of
nucleus sizes for 523 comets (235 long-period and 288 short-period comets; LPCs and SPCs) from the 14.5-year WISE/NEOWISE archive, supplemented by Spitzer photometry. A coma-
nucleus decomposition of the radial profiles yields conservative upper limits for all 523 comets and diameters with uncertainties for 301 (107 LPCs and 194 SPCs), with median diameters of 5.3 and 2.5 km, respectively.
Nucleus colors across the four WISE bands follow the heliocentric trend expected from the transition between reflected and thermal emission, with no measurable difference between the two dynamical classes. The cumulative size-frequency distribution of the SPCs has a slope of $\gamma = 1.45_{-0.13}^{+0.15}$ (68% confidence interval) over $D = 2$–15 km, steepening to $2.05_{-0.38}^{+0.47}$ for the perihelion $q < 2$ au subset. The LPC distribution is smoothly concave down: a broken power law places a break near 35 km, with slopes of $0.92_{-0.12}^{+0.13}$ below and $3.68_{-1.24}^{+1.96}$ above, while the $q < 2$ au subset gives $1.39_{-0.28}^{+0.35}$ over $D = 4$–20 km. All distributions flatten below the fitted ranges and level off near 1 km. We discuss the implications of our results and their connection with models of the destabilized trans-Neptunian population.
Read the full abstract ▾
All authors Yuna G. Kwon, Dar W. Dahlen, Joseph R. Masiero, Yanga R. Fernández, Adeline Gicquel, James M. Bauer, Yoonyoung Kim, Frank Masci, Amy K. Mainzer
Quantum Physics
Particles, Localization and "Collapse"
Anthony Rizzi
Hegerfeldt's
theorem shows that the localization of a particle (or field) is not possible under very general assumptions of
quantum mechanics and special relativity. This
theorem, and further developments and associated
theorems force penetrating questions on the proper understanding of the theory and its use. In particular, the use of the collapse postulate is called into question. The existence of particles and even localized fields are called into question. And, this in turn challenges local measurements. It generally forces one to consider the profound problems and even wrong results that arise from the collapse postulate. We give a qualitatively new example of such a wrong result. Researchers and students alike are bothered by these fundamental issues. Students' ability to learn the material, and even their interest in physics, can be compromised by such disturbing conundra that seem to make physics, or at least QFT and its QM limit, seem incomprehensible and even inconsistent. This article resolves these issues in a way accessible to undergraduates, by applying the natural (minimal) interpretation of
quantum mechanics (QM) (the ensemble interpretation) and explicating and clarifying the basic principles and premises used in QM and the Hegerfeldt
theorem and its application to measurements.
Read the full abstract ▾
Materials Science · Cross-listed from cs.RO
Active 3D weaves for load-bearing and damage-resilient locomotion
Guowei Wayne Tu and Evgueni T. Filipov
The craft of weaving, where different materials are interlaced, has tremendous potential for creating active and functional systems for use in soft
robots, prosthetics, wearables, exoskeletons, and more. These textile-like systems are flexible and safe for human-machine interaction; however, this inherent flexibility limits their ability to carry loads, which is essential for many robotic functions. In this work, we introduce a general framework for integrating active materials into three-dimensional (3D) woven shells to create robotic structures that combine high axial stiffness for load bearing, low bending stiffness for efficient actuation, and system-level resilience for damage tolerance. These woven
robots can be modularly assembled from 'woven corners', a fundamental unit of 3D woven structures. We use
eigenvalue calculations to identify load bearing and actuation mechanisms of the 3D woven structures, and use that information to make five different
robots capable of locomotion. We demonstrate that these 3D woven
robots can locomote carrying loads 70 times their self-weight, and can maintain repeatable performance even after being subjected to extreme compression. This work is a pathway toward the design, manufacturing, and simulation of future 3D woven robotic systems where load bearing, high stiffness, active functional deformation, locomotion, and system-level resilience are all needed.
Read the full abstract ▾
Earth and Planetary Astrophysics
The NEID Earth Twin Survey. VI. Discovery of a Low-Mass Planet Orbiting HD 126053 and RV Signals Near the Rotation Periods of HD 168009 and HD 10780
Arvind F. Gupta, Sarah E. Logsdon, Jacob K. Luhn et al. (+19 more)
Extreme precision radial velocity (EPRV) spectrographs are making strides in extending the limits of radial velocity
exoplanet detection. Perhaps the best evidence for this is how readily EPRV instruments are facilitating the discovery and detailed characterization of small-amplitude planetary signals around
stars that have already been intensively monitored for decades with less stable instruments. In this paper, we use data from the ongoing NEID Earth Twin Survey (NETS) to detect and confirm the
planet HD 126053 b (P=10.91 d), which is among the least massive
planets (m sin i = 3.60 m M_\oplus) around
solar-type
stars within 25 pc. We then jointly characterize the known
planet HD 168009 b (P=15.14 d; m sin i = 8.64 M_\oplus) orbiting a
solar analog along with a previously unreported signal at 27.8 d which we tentatively attribute to rotational modulation of
stellar activity (P_rot = 30.1 d). We also analyze and discuss periodic RV variations in HD 10780 arising from a combination of rotationally-modulated activity and a long-term activity cycle. We discuss HD 126053 b and HD 168009 b in the context of the broader small
planet population and our sensitivity to long-period
planets in these systems, and we comment on our capacity to disambiguate
planet-induced and activity-induced radial velocity signals. HD 126053 is exceptionally RV-quiet, making it a promising target for continued RV monitoring in search of low-mass
exoplanets in the habitable zone.
Read the full abstract ▾
All authors Arvind F. Gupta, Sarah E. Logsdon, Jacob K. Luhn, Evan Fitzmaurice, Suvrath Mahadevan, Paul Robertson, Eric B. Ford, Chad F. Bender, Mark R. Giovinazzi, Samuel Halverson, Te Han, Daniel M. Krolikowski, Andrea S.J. Lin, Joe P. Ninan, Michael L. Palumbo III, Leonardo A. Paredes, Jayadev Rajagopal, Arpita Roy, Christian Schwab, Gudmundur Stefansson, Ryan C. Terrien, Jason T. Wright
High Energy Physics (Theory)
Learning Scattering Amplitudes with Transformer Reinforcement Learning
Philip Velie, Tianji Cai, Piyush Jha et al. (+2 more)
We introduce a
transformer reinforcement learning
algorithm that learns to solve high loop-level scattering amplitudes in planar N = 4 Super Yang-Mills theory. Our
algorithm improves on previous
transformer-only results by incorporating previously derived
symmetries and relationships into the learning
algorithm. This results in a greatly decreased fraction of the solution that needs to be known a priori to solve the entire problem. An additional benefit is that our
algorithm also ensures that every output obeys the set of known relationships. Rather than predicting all coefficients independently, the model proposes assignments that are propagated through exact linear relations, while MCTS searches over assignments when propagation alone is insufficient. This is crucial to the generalization of machine learning approaches to higher loops, as without this, there is no way to overcome the factorially scaling of state sizes and compare to results derived via other methods. Using the symbology representation of the form factor, we frame the problem as learning a mapping between discrete sequences and integer coefficients.
Read the full abstract ▾
All authors Philip Velie, Tianji Cai, Piyush Jha, Vijay Ganesh, Aishik Ghosh