Accelerator Physics
Feasibility demonstration of a high-momentum, high-purity muon beamline at the J-PARC Hadron Experimental Facility
Kotaro Shirotori, Takaya Akaishi, Kazuya Aoki et al. (+16 more)
We have established and characterized a novel high-purity
muon beam delivery scheme, designated as $\mu$20, at the high-momentum
hadron beamline (B-line) of the J-PARC
Hadron Experimental Facility. This scheme delivers tertiary
muons produced via the in-flight backward decays of secondary pions in the straight section of the beamline, inherently suppressing parent
hadron contamination. In a systematic performance evaluation, the
muon beam achieved a standalone intensity of $1.7\times10{^3}$ particles/spill with a spatial spread (standard deviation, $\sigma$) of approximately 15 mm at the downstream detector position. A systematic attenuation analysis utilizing an iron absorber verified a high
muon purity of 98.0$\pm$0.6% for the 3 GeV/$c$
muon beam mode. Crucially, this work marks the first successful feasibility study of a high-momentum and high-purity
muon beamline operation at an experimental facility in Japan.
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All authors Kotaro Shirotori, Takaya Akaishi, Kazuya Aoki, Wen-Chen Chang, Ryotaro Honda, Yusuke Hori, Takatsugu Ishikawa, Nobuyuki Kobayashi, Ruri Kurasaki, Che-Sheng Lin, Yuhei Morino, Megumi Naruki, Hiroyuki Noumi, Kyoichiro Ozawa, Shinya Sawada, Ken Suzuki, Hitoshi Takahashi, Taiga Toda, Natsuki Tomida
General Relativity and Quantum Cosmology
A Generalized Class of Taub-NUT-Scalar Metrics
Fataneh Bakherad, Behrouz Mirza, Reza Bahani et al. (+2 more)
We consider a class of three-parameter metrics that was introduced in \cite{azizallahi2024three}. The class of metrics contain Zipoy-Voorhees (ZV) and Fisher-Janis-Newman- Winicour (FJNW) spacetimes at certain values of the parameters. We build an axially symmetric and asymptotically flat spacetime with gravitomagnetic effects by introducing a Newman- Unti-Tamburino (NUT) charge into this class of metrics via the Ehlers transformation. We investigate the physical features of this class of Taub-NUT-scalar (TNS) metrics including gravitational
lensing, quasinormal mode (QNM) spectra, and test particle motion. Our results provide fresh insight on how mass, multipole moments, and gravitomagnetic fields behave in the presence of a scalar field and show the effect of the NUT charge on stability of orbits in this class of metrics.
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All authors Fataneh Bakherad, Behrouz Mirza, Reza Bahani, Mahnaz Tavakoli Kachi, Ali Derekeh
Astrophysics of Galaxies
Recovering the effective impact parameters in integral-field absorption-line tomography
J. A. Hernández-Guajardo, L. F. Barrientos, C. Ledoux et al. (+3 more)
Integral-field-unit (IFU) spectroscopy of extended background sources, such as gravitational arcs, delivers many closely spaced absorption sightlines through the circumgalactic medium (CGM) of foreground
galaxies. However, the source extent and smearing through the point spread function (PSF) cause each spaxel to integrate light from a region larger than itself. The usually adopted
geometric spaxel centre is therefore not representative of where the absorbed flux originates. Informed by high-resolution imaging, we introduce a flux-contribution formalism that reconstructs the spatial origin of the flux in each spaxel by defining flux-weighted coordinates and impact parameters. Using a data-driven simulation built on a real gravitational-arc configuration, we show that spaxel centres are displaced from the flux-weighted positions by $|\Delta\mathbf{x}| \propto \theta_{\rm PSF}(1-f)$, with $f$ the spaxel-source overlap fraction, and that the resulting impact-parameter bias scales with the
lensing magnification as $\mu^{-1/2}$. These offsets are largest for off-arc spaxels and flatten the radial column-density profiles. They also inject a coherent geometry-driven scatter that mimics intrinsic CGM structure and that is removed neither by a tighter spaxel selection nor by a finer spatial binning. For identical uncertainties, the spaxel-centre coordinates leave residuals of about twice the noise level ($\chi^2_\nu \sim 4$), whereas the flux-weighted coordinates recover the input profile to within the uncertainties ($\chi^2_\nu \sim 1$) and remain robust to a PSF misspecification of $\pm 10\%$. The method we propose provides a better-motivated and readily adoptable framework for tomographic studies, whether as the primary analysis or as a robustness check on spaxel-centre results.
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All authors J. A. Hernández-Guajardo, L. F. Barrientos, C. Ledoux, N. Tejos, E. J. Johnston, P. Anshul
General Relativity and Quantum Cosmology
A 3D Summation-by-Parts scheme on a Hyperboloidal Foliation of Minkowski
Shalabh Gautam
This paper summarises our previous work on a fully $3$D Summation-by-Parts scheme, derived for a class of linear wave equations on hyperboloidal slices on a fixed Minkowski background. The scheme is derived in spherical polar coordinates, and allows having grid points at the origin and on the $z$-axis, despite coordinate singularities, and at infinity, by introducing compactification followed by rescaling, and is proved to be stable. Reducing it to the standard Cauchy problem, or to finite spacelike slices with an outer boundary, will follow a similarly. Second-order accurate finite-difference methods are used to implement this scheme numerically, but higher-order finite-difference or spectral methods could also be used. Kreiss-Oliger dissipation operators are generalized to curvilinear coordinates and are defined everywhere in the domain, including at the boundary points, such that they satisfy the dissipative property in the energy norms. We also propose new norm convergence tests that include all the grid points at all resolutions and produce more accurate results. Promising results are obtained, giving hope for application to fully nonlinear systems, like the Einstein Field Equations, and extracting the resulting gravitational waves free of systematic errors or gauge ambiguities.
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Astrophysics of Galaxies
Laplace surface of eccentric orbits around Kerr black hole and black-hole effects on Lidov-Kozai cycles
Haonan Quan and Xing Wei
We study the Laplace surface of eccentric orbits around a Kerr black hole with a companion
star. The two relativistic effects (periapsis apsidal precession and Lense-Thirring precession) balance companion's
tidal effect. By solving the secular equations, we find that the two branches of
equilibrium solutions exist only in a narrow range of orbital inclinations of test particle, and that the stability exists when companion's obliquity approaches 90 degree. We then study the black-hole effects on Lidov-Kozai cycles. In addition to the black-hole suppression on cycle amplitude, we find that the cycle frequency is non-monotonic about distance from black hole and reaches its minimum in the transition between GR apsidal precession and companions's
tidal precession. Finally we use this mechanism to well interpret the nearly isotropic orientation of S-cluster in the
Galactic center.
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Mesoscale and Nanoscale Physics
Quantum geometric signatures of Link-Unlink transitions and nonlinear Hall response in Hopf-link semimetals
Kamalesh Bera, Arijit Saha and Debashree Chowdhury
Quantum geometry, comprising of
quantum metric and Berry
curvature, plays a significant role in the electronic transport properties of solids. In this work, we theoretically investigate the
quantum geometric properties of a
Hopf-link semimetal, a distinct topological class that is charecterized by a nodal link-unlink transition. We compute the interband optical conductivity of the
Hopf link, which effectively distinguishes between linked and trivial phases. While recent studies establish
quantum metric dipole-mediated scattering-free nonlinear
Hall effect, this effect becomes even more fascinating in systems where the Berry-
curvature-dipole contribution to nonlinear
Hall conductivity vanishes. Owing to the underlying $PT$
symmetry of the
Hopf-link semimetal, the Berry
curvature and its corresponding contribution to the nonlinear
Hall effect are entirely suppressed. Consequently, by introducing an appropriate perturbation, a finite nonlinear
Hall conductivity emerges solely due to the
quantum metric in the
Hopf semimetal. Notably, this purely intrinsic,
symmetry-driven nonlinear response remains entirely unmixed with extrinsic components.
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Astrophysics of Galaxies
A systematic study of AGN feedback in a disk galaxy using MACER. III. High Gas Fractions in AGN Hosts
Yuxuan Zou, Feng Yuan, Suoqing Ji et al. (+4 more)
We use high-resolution hydrodynamic simulations in the MACER framework to explain why low-
redshift PG
quasar hosts can retain substantial cold-gas reservoirs, with gas fractions and gas-to-
stellar mass ratios showing little dependence on instantaneous AGN luminosity. This paper is the third in a series systematically studying AGN feedback in a disk
galaxy subject to cosmological gas inflow. The simulations include multiphase gas,
star formation,
stellar feedback, and self-consistent radiative and mechanical AGN feedback. We reproduce the observed weak connection between host-
galaxy gas content and AGN luminosity over L_AGN/L_Edd ~ 10^{-5}-10, while the
galaxy nevertheless undergoes pronounced gas depletion and
star-formation quenching. During the quenching phase, the cold-gas mass declines by nearly three orders of magnitude, and the
evolution of the gas distribution shows that AGN feedback progressively removes both cold and hot gas from the
galaxy. The
star formation rate is more closely linked to the cold-gas mass than to AGN luminosity. This behavior arises from a timescale mismatch: AGN luminosity varies on ~ 10^5-10^6 yr timescales, whereas repeated AGN-driven
outflows cumulatively deplete the
galaxy-scale gas reservoir over ~ 1 Gyr. Our simulations therefore provide a physical explanation for the gas-rich PG
quasar hosts and show that their observed gas properties are fully consistent with effective, long-term ejective AGN feedback.
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All authors Yuxuan Zou, Feng Yuan, Suoqing Ji, Jinyi Shangguan, Hassen M. Yesuf, Lu Shen, Luis C. Ho
High Energy Physics (Phenomenology)
Multi-messenger signal from QCD-Axion Ultracompact Minihalos
Dorian W. P. Amaral, Enrico D. Schiappacasse and Karla Tapia-Rebolledo
We explore the multimessenger signatures from ultracompact minihalos (UCMHs) seeded by
stellar-mass
primordial black holes (PBHs) and composed of QCD-
axion dark matter. Using the secondary-infall framework, with relic-abundance and isocurvature conditions from a pre-inflationary Peccei-Quinn scenario, we numerically recover the characteristic
halo profile and adopt a conservative constant-density core for the innermost region. We study the gravitational wave and electromagnetic signatures from
neutron-
star-PBH inspirals inside these dense structures. Dynamical friction produces a gravitational-wave dephasing relative to the
vacuum binary, observable with LISA for
primordial black holes with masses $\lesssim\! 10M_\odot$. Simultaneously, gravitationally focused
axions can resonantly convert into
photons in the
neutron-
star magnetosphere, producing a narrow-band
radio signature. For nearby
galactic neutron stars, the projected sensitivity of the Green Bank
radio telescope GBT captures the QCD-
axion band in the $\mu{\rm eV}$ mass range. Gravitational waves therefore probe the presence and structure of the UCMH, while the
radio signal probes the particle nature of its dark matter, making their joint observation a distinctive test of a mixed dark sector.
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Materials Science
Realization of Air-Stable Two-Dimensional Superconductor Nb2Pd3Te5 With Quasi-One-Dimensional Pair Density Modulation
Jiayi Wang, Hui Guo, Hao Zhang et al. (+12 more)
Two-dimensional (2D)
superconductors provide a fertile platform for exploring reduced-dimensional superconductivity and emergent
quantum phenomena. Incorporating quasi-one-dimensional (quasi-1D) structural motifs into 2D
superconductors offers a powerful route to engineer strong electronic anisotropy, enabling unconventional superconducting states and anisotropic superconducting transport functionalities. However, such systems remain rarely realized. Here we report the realization of a 2D
superconductor Nb2Pd3Te5, exhibiting an intrinsic quasi-1D pair density modulation. Monolayer and
bilayer Nb2Pd3Te5 is synthesized via van-der-Waals epitaxy. Using ultralow-temperature scanning tunneling microscopy/spectroscopy, we observe the quasi-1D
crystal structure and superconductivity below ~0.6 K with a pronounced quasi-1D pair density modulation. Remarkably, both monolayer and
bilayer Nb2Pd3Te5 show strong air stability. Our findings establish atomically 2D Nb2Pd3Te5 as a robust and promising platform for exploring novel low-dimensional
quantum phenomena and anisotropy-enabled superconducting devices.
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All authors Jiayi Wang, Hui Guo, Hao Zhang, Haowei Chen, Peixuan Li, Xianghe Han, Ziang Wang, Siyu Xu, Qian Fang, Haohao Xu, Shixuan Du, Chengmin Shen, Hui Chen, Wang Yao, Hong-Jun Gao
High Energy Physics (Experiment)
Operation of Unshielded Kinetic-Inductance Traveling-Wave Parametric Amplifiers in Multi-Tesla Fields
Christian Boutan, Erik Lentz, Corwin Shiu et al. (+12 more)
Cryogenic parametric amplifiers are used to amplify
radio-frequency signals for a range of applications in basic and applied science. Both Josephson Parametric Amplifiers and Josephson Traveling-Wave Parametric Amplifiers have been used as first-stage amplifiers enabling readout chains operating within a few quanta of the
quantum limit. However, these devices are highly sensitive to
magnetic fields, having critical current suppressed by the Fraunhofer effect, requiring substantial field-free zones. In a dark matter
axion search experiment,
axions convert to detectable microwave
photons in the presence of a strong
magnetic field, necessitating amplifiers that can reliably operate close to these environments. Kinetic-inductance Traveling-Wave Parametric Amplifiers (KTWPAs) may be the ideal candidate for this type of application having high critical
magnetic field of the materials used throughout their construction. In this letter we demonstrate that KTWPAs can provide high gain (>20dB) over a multi-GHz bandwidth in spite of from multiple exposures to multi-Tesla fields. Further, we explore operational characteristics of these devices under harsh conditions as a function of overall field strength, device orientation within the field, applied bias current, and pump power & frequency. In so doing, we find KTWPA gain vanishes in devices oriented perpendicularly to a field of 0.02T, but gain values >10dB are achievable in fields over 1T when oriented near~parallel to the device plane, with peak gain achieved with an applied 0.25T to 0.5T field. It is our expectation that KTWPAs will expand the accessibility of
quantum-limited RF measurements in the presence of Tesla-scale fields.
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All authors Christian Boutan, Erik Lentz, Corwin Shiu, Deniz Erdag, Stephen Jones, Joseph Van Vlack, Logan Howe, Andrea Giachero, Paul Szypryt, Michael Vissers, Jason Austermann, Johannes Hubmayr, Stefan Knirck, Douglas Bennett, Joel Ullom
Soft Condensed Matter
Multiple pattern formation in quorum sensing of density enhanced motility
Itay Azizi
Using Langevin dynamics simulations, I investigate nonequilibrium systems of particles following a density-enhanced motility (DEM) rule: particles are passive below a critical local density and active above it. This mechanism represents an inverse of the conventional quorum-sensing rule. I explore specifically quorums much larger than particle size and at two levels of activity. Above critical values of the density, quorum size, and activity, the system undergoes phase separation into low- and high-energy regions. The passive particles organize into distinct spatial patterns, including holes, stripes, and labyrinthine structures, while the active particles form a gas. I characterize the resulting steady states and identify the qualitative mechanisms governing the selection of different morphological regimes. I further discuss the relevance of these results to biological systems governed by analogous quorum-sensing mechanisms and to biological systems exhibiting related forms of spatial organization. Finally, I present directions for future investigation.
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General Relativity and Quantum Cosmology
The relationship between spacetime singularities and regions at infinity
Junbang Liu, Ben Andrews and Susan M Scott
Ideal attached points are a core concept in general relativity for pseudo-Riemannian
manifolds, and whether the spacetime can be extended with certain properties is a central consideration in their choice. This paper establishes a sufficient condition for the separability between singularities and points at infinity for any maximally extended pseudo-Riemannian
manifold. We focus on the incomplete geodesics of $(\mathcal{M},g)$, and produce an envelopment $(\mathcal{M},g,\hat{\mathcal{M}})$ of the spacetime such that an incomplete geodesic $\gamma:[0,1) \rightarrow \mathcal{M}$ has an endpoint $q$ in $\hat{\mathcal{M}}$. If there is no pair of geodesics approaching $q$ which is intertwined, then $q$ is a singularity. Additionally, $q$ will not be approached by any geodesic with infinite affine parameter, and therefore cannot cover a point at infinity, thereby rendering it a pure singularity in the abstract boundary framework. We apply the Endpoint
Theorem to the maximal g-boundary introduced by Graf and Beld-Serrano in arXiv:2307.11034, and also provide a result on the separability between directional singularities and pure singularities. This analysis is then applied to the Schwarzschild spacetime.
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Materials Science
Beyond linear stability: Heterogeneity-induced fingering of crack fronts
Manish Vasoya, Laurent Ponson and Veronique Lazarus
We investigate the stability of elastic interfaces beyond the linear regime by considering penny-shaped crack fronts propagating through toughness heterogeneities. Using fracture mechanics simulations, we drive crack fronts through arrays of obstacles with tunable toughness contrast. At low contrast, the crack front stiffness remains finite and stabilizes front perturbations. Above a critical threshold, however, the stiffness vanishes and the front destabilizes into long fingers that evolve into daughter cracks propagating between obstacles while the original crack remains pinned. Near threshold, the crack front response displays the characteristic square-root scaling behavior of classical saddle-node bifurcations. Yet, our analysis reveals a fundamentally different mechanism: the stable energy-minimizing crack-front configuration disappears without colliding with an unstable counterpart. Instead, the instability originates from a global loss of Griffith-compatible
equilibria governed by the nonlocal interactions along the crack front. Beyond fracture mechanics, these findings point toward a broader class of collective global bifurcations in nonlocal elastic interfaces and may help rationalize the brittle-to-quasibrittle transition in heterogeneous solids.
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High Energy Astrophysical Phenomena
Constraining gamma-ray burst viewing angles with Swift/XRT afterglow light curves
Cheng-Jie Sun, Shuang-Xi Yi, Lin Zhou et al. (+6 more)
Gamma-ray bursts (GRBs) are among the most energetic phenomena in the universe, and their afterglow light curves encode information about jet geometry and viewing angle. To constrain GRB viewing angles, we analyzed jet break features in Swift X-Ray
Telescope afterglow light curves using two top-hat jet models: a simplified
geometric model without high-latitude emission (model 1) and a comprehensive model including it (model 2). Both models were applied to a sample of 20 GRBs in an interstellar medium (ISM) and 20 in a wind medium, selected so that jet breaks are attributed to the edge effect with sufficient data coverage, and fitted with Markov Chain Monte Carlo methods. We examined viewing angles and off-axis ratios q = $\theta_{\rm obs}/\theta_{\rm jet}$ under both density profiles, evaluating the impact of high-latitude emission. Based on reduced chi-squared and
Bayesian information criterion comparisons, model 1 fits all GRBs better. Most GRBs have small off-axis ratios (mean q = 0.1851 for model 1), indicating viewing angles generally close to the jet axis; the log-space viewing-angle distribution is approximately Gaussian. A Kolmogorov-Smirnov test shows no significant difference in off-axis ratios between ISM and wind media, nor between bursts with and without an X-ray plateau. While viewing angles decrease significantly with
redshift, the off-axis ratio shows no significant
evolution, consistent with off-axis
alignment being independent of
cosmic epoch.
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All authors Cheng-Jie Sun, Shuang-Xi Yi, Lin Zhou, Yuan-Chuan Zou, Yu-Peng Yang, Si-Ji Xin, Yan-Kun Qu, Wen-Long Zhang, Fa-Yin Wang
Earth and Planetary Astrophysics
Centimeter-wave OH observations of comets 12P/Pons-Brooks and C/2023 A3 (Tsuchinshan-ATLAS) with FAST
Long-Fei Chen, Juncen Li, Zhen Wang et al. (+5 more)
We present centimeter-wave spectroscopic observations of the OH 18-cm lines in two bright comets, 12P/Pons-Brooks and C/2023 A3 (Tsuchinshan-ATLAS), conducted with the Five-hundred-meter Aperture Spherical
radio Telescope (FAST) during their 2024 apparitions. For the Halley-type comet 12P/Pons-Brooks, five epochs of OH observations were obtained. The main OH lines at 1665 and 1667 MHz were robustly detected in absorption during one pre-perihelion epoch, while upper limits were derived for two post-perihelion epochs. For the dynamically new Oort Cloud comet C/2023 A3 (Tsuchinshan-ATLAS), six epochs of OH observations were obtained. The 1665 and 1667 MHz lines were robustly detected in absorption during two epochs immediately following the comet's closest approach to Earth. We also reported a tentative detection of the 1721 MHz satellite line in one of these two epochs. The low OH detection rates for these two bright comets are primarily attributable to their unfavorable heliocentric radial velocity during the observations, which resulted in the anti-maser negative inversion mode of the OH excitation. We calculated the OH production rates for both comets and found that, after considering the small beam size of FAST and the collisional quenching effect, production rates are consistent with the data from literature. Specifically, this matches the power-law fit of the OH production rates for comet 12P/Pons-Brooks, as well as the production rates at comparable heliocentric distances among comet C/2023 A3 (Tsuchinshan-ATLAS) and four other dynamically new Oort Cloud comets.
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All authors Long-Fei Chen, Juncen Li, Zhen Wang, Jian-Yang Li, Wing-Huen Ip, Zhong-Yi Lin, Bin Yang, Chao-Wei Tsai
Optics
Nanophotonic control of spatial information in scintillation detectors
Joshua Chen, Simo Pajovic, Seou Choi et al. (+9 more)
X-rays enable non-invasive imaging across medicine, security, materials science, and beyond, yet modern systems remain constrained by the need to resolve finer structures at lower radiation dose. Scintillators are the dominant materials for detecting X-rays, but face a longstanding compromise: thick scintillators absorb X-rays effectively, whereas optical
photons generated throughout their volume spread before detection, degrading spatial information. Existing scintillator architectures largely try to preserve resolution by physically confining light using pixels, columnar
crystals, or microstructured channels. Here, we show that high-resolution detection does not require the volumetric confinement of scintillation light. A metalens integrated directly with a bulk scintillator uses nanophotonic wavefront control to preferentially transfer high-spatial-frequency information from volumetrically generated scintillation light to the detector, while retaining the X-ray absorption of a thick scintillator. We experimentally recover fine spatial detail in X-ray images of inorganic and biological specimens. In a detector geometry relevant to computed
tomography (CT), the experimentally validated model predicts a fivefold reduction in required X-ray dose and a 25-fold increase in resolution bandwidth relative to a state-of-the-art pixelated scintillator. These results establish wavefront engineering as a route to separating efficient X-ray absorption from optical image formation, with the potential for substantially higher-resolution, lower-dose CT.
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All authors Joshua Chen, Simo Pajovic, Seou Choi, Sachin Vaidya, William Michaels, Louis Martin-Monier, Christina M. Spägele, Steven E. Kooi, Juejun Hu, Rajiv Gupta, Charles Roques-Carmes, Marin Soljačić
Soft Condensed Matter
Splay-induced charging of ferroelectric droplets in highly non-uniform electric fields
Lorenzo Fiorentini, Elia Rocchetti, Raouf Barboza et al. (+2 more)
Ferroelectric sessile droplets on a superhydrophobic surface can be put into motion by highly non-uniform electric fields, in a direction that depends on the field sign. This indicates that droplets carry a non-vanishing electrostatic charge, which we interpret as acquired through contact electrification at the interface with the superhydrophobic substrate. This phenomenon is not observed in the presence of a uniform or quasi-uniform electric field, suggesting that droplets charging is favored in highly nonuniform fields able to induce localized distortions of the ferroelectric polarization, in turn producing localized charge accumulation sites. Electrostatic charging is thus understood as a splay-induced contact electrification and interpreted as a strategy to minimize the accumulated charge. Electrophoretic-like motion is observed in about 30% of the experiments, meaning that splay-induced charging requires the proper combination of conditions such as droplets size, distance from the field source, freshness of the substrate coating and other experimental details that are not easily quantified. When charging does not occur, effects related to droplet polarization such as dielectrophoresis, ejection of polarized fluid jets and electrostriction-like deformations are observed.
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All authors Lorenzo Fiorentini, Elia Rocchetti, Raouf Barboza, Roberta Galeazzi, Liana Lucchetti
High Energy Physics (Theory)
Beyond Strong Subadditivity: Holographic Entropy Inequalities Along Renormalization Group Flows
Ning Bao and Christian Ferko
Strong subadditivity (SSA) on a common light cone gives the Casini-Huerta entropic proof of the three-dimensional $F$-
theorem. We ask whether
holographic entropy inequalities beyond SSA similarly constrain renormalization group flows for which every intermediate theory admits a semiclassical
holographic description. For small, disjoint deformations of a common light-cone region, we show that the second-order response of a broad class of balanced
holographic inequalities depends only on pairwise correlations already controlled by SSA. A six-party example shows that the full finite inequality nevertheless contains genuinely multipartite information, so its disappearance is a limitation of the second-order expansion rather than of the inequality itself. Two natural finite constructions do not recover the missing information. We nevertheless find two ways in which information beyond SSA survives. A five-party inequality bounds the rate at which a conditional correlation grows as one region is enlarged. Separately, a continuum limit of the odd-cyclic inequalities gives a constraint on the angular shape dependence of
entanglement entropy, and Lorentz
symmetry relates this constraint to radial
evolution. Thus
holographic entropy inequalities beyond SSA do constrain
entanglement along RG flows, although we do not obtain a second universal analogue of the $F$-function.
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Mathematical Physics · Cross-listed from math.OC
Schrödinger Bridges over Kinetic Swarming Models
Asmaa Eldesoukey, Md Zulfiqur Haider, Italo Napolitano et al. (+2 more)
Paradigmatic interaction models explain how collective behaviors can emerge in complex systems from interactions among the constituent
agents. In bio-inspired swarms, however, interactions alone may not suffice to bring the population to a desired aggregate configuration within a prescribed time horizon, as needed in applications ranging from targeted therapy to collective transport and emergency evacuation. In the present work, we consider finite-horizon minimum-energy collective steering for inertial swarms that are subject to
stochastic disturbances. We focus on the mean-field representations of these multi-
agent systems driven by Cucker–Smale
alignment or Morse attraction–repulsion interactions. Our objective is to steer the swarm between prescribed endpoint distributions using a state-feedback control, where the endpoint specifications can be full phase-space distributions (positions and velocities) or position marginals alone. Our formalism is rooted in the theory of Schrödinger bridges, which has inspired contemporary developments spanning statistical inference, biological modeling,
stochastic control, and generative learning. Within the bridges framework, the uncontrolled interacting
stochastic dynamics are viewed as a prior model, and the optimal control as the minimum-energy corrective drift needed to realize the prescribed distributions. We derive nonlinear, coupled necessary optimality systems with a time-symmetric structure reminiscent of classical Schrödinger bridges, and propose nested fixed-point schemes to numerically solve them. Numerical examples show that the obtained optimal control (corrective drift) can dynamically exploit or counteract the interaction forces, depending on whether the latter are favorable or
adversarial to the steering task.
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All authors Asmaa Eldesoukey, Md Zulfiqur Haider, Italo Napolitano, Yongxin Chen, Abhishek Halder
Cosmology and Nongalactic Astrophysics
The optimal redshift for dark energy II: application to cosmological data and the evidence for the phantom crossing of the CPL equation of state
Travis Seth Rippentrop, Mustapha Ishak and Kristian Gonzalez
Recent results from DESI and other cosmological
datasets have indicated a preference for dynamical dark energy, with a time-evolving equation of state (EOS), $w(z)$. Furthermore, analyses using the CPL parameterization give an EOS with a phantom crossing of the $w(z)=-1$ line. In a companion paper-I, we assumed the CPL parameterization and its generalization, and introduced the formalism of the optimal scale factor (or
redshift), a quantity designed to simultaneously maximize the distance from the cosmological constant value of $-1$ and to minimize the uncertainty on the EOS, thereby maximizing the tension with the cosmological constant at that specific
redshift for a given
dataset combination. In this paper-II, we apply the optimal-
redshift formalism to available
baryon acoustic oscillation,
Cosmic Microwave Background, and
supernova dataset combinations, with a particular focus on the phantom-line crossing within CPL. Motivated by the relatively low significance of previous constraints on the EOS in the region below the phantom line, we calculate the optimal
redshift for a variety of
dataset combinations to identify those that best constrain departures from $w(z)=-1$ before and after the crossing. We find combinations and corresponding optimal
redshifts for which $w(z)$ lies below the “$-1$” line with new significance levels reaching $3.01$–$3.22\sigma$ before the crossing point, and $3.30$–$3.55\sigma$ above “$-1$" after the crossing. Our focus in this work is the application of a new framework that maximizes the significance of the phantom-crossing signal within CPL using currently available
datasets. Determining whether this crossing is effective or intrinsic, and identifying the underlying microphysical models, constitute separate questions from the aim of the present work and remain important directions for future investigation, further motivated by our findings. Abridged.
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Superconductivity
Distinct Surface and Bulk Superconductivity in the Kagome Superconductor SrSn$_3$
Qun Zhu, Yong-Wei Wang, Ji-Hai Zhang et al. (+6 more)
Surface and bulk superconductivity may possess fundamentally different superconducting properties in
quantum materials with nontrivial electronic structures, yet their superimposed spectroscopic signatures often prevent direct experimental access to each superconducting channel. Here we reveal, in epitaxial films of the kagome
superconductor SrSn$_3$, distinct surface and bulk superconducting channels with markedly different superconducting gaps, upper critical fields, and
vortex-core electronic states by tuning the tunneling junction resistance in scanning tunneling spectroscopy. The surface superconductivity is characterized by a thickness-independent superconducting gap and an enhanced upper critical field, whereas the bulk superconducting channel exhibits a larger superconducting gap that decreases with reducing film thickness and a much lower upper critical field. Within
magnetic vortex cores, robust non-split zero-bias conductance peaks are observed exclusively in the surface superconducting channel, while pronounced zero-bias suppression is consistently associated with the bulk superconducting channel. These findings demonstrate that the
vortex-core electronic structure depends sensitively on the underlying superconducting channel, providing new insight into
vortex-bound states in topological
quantum materials.
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All authors Qun Zhu, Yong-Wei Wang, Ji-Hai Zhang, Qiang-Jun Cheng, Chen-Yu Hu, Jun-Zhong Wang, Qi-Kun Xue, Xu-Cun Ma, Can-Li Song
Materials Science
High-throughput Discovery of Magnetic Rare Earth Transition Metal Alloys
Shuo Tao, Osman Goni Ridwan, Liqin Ke et al. (+1 more)
We present an accelerated materials discovery framework that combines
diffusion-based
crystal structure generation with hierarchical screening to identify new rare-earth–transition-metal magnets simultaneously achieving high magnetization and thermodynamic stability. Using this workflow, we systematically explored over 3000 binary (R-T) and ternary (R-T-T$'$) compositions spanning R~$\in \{\text{Y, Sm}\}$, T~$\in \{\text{Fe, Co, Ni}\}$, and T$' \in \{\text{Ti, V, Cr, Mn, Cu, Zn}\}$, and filtered approximately 240{,}000 generated
crystal structures through machine-learning interatomic potential prescreening and
spin-polarized density functional theory validation. We identify 300+ low-energy
magnetic candidates within 0.1~eV/atom above the convex hull at the DFT level, including 5 thermodynamically stable phases. The highest saturation magnetization reaches ${\sim}1.8$~T in Fe-rich binary and ternary phases (SmFe$_{12}$, YFe$_{12}$, YFe$_{18}$Ti and Sm$_2$Fe$_{16}$Mn).
Symmetry analysis reveals that the majority of ternary candidates are subgroup derivatives of known binary prototypes through Wyckoff site splitting that accommodates T$'$ substitution. Site-resolved
magnetic moment analysis further shows that Mn aligns ferromagnetically with the Fe sublattice with minimal magnetization loss, whereas Cr couples antiferromagnetically, providing systematic guidance for dopant selection. These findings demonstrate a generalizable strategy for targeted
magnetic materials discovery and suggest that extending generative searches to larger unit
cells ($>$20 atoms) with higher Fe fractions is a promising route toward stable phases with saturation magnetization exceeding 1.8~T.
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All authors Shuo Tao, Osman Goni Ridwan, Liqin Ke, Qiang Zhu
Superconductivity
Grain Boundary Engineering Effect on Vortex Matter in Superconducting Films
Qun Wang, Ting Chen, Ya-Xun He et al. (+6 more)
Grain boundaries (GBs) in polycrystalline superconducting films act as a double-edged sword: they can pin
vortices or degrade superconductivity through Josephson-like weak-link coupling. Here, we demonstrate that sputtering pressure tunes GB coupling in NbTiN films and visualize its consequences for
vortex matter. The 5 mTorr film exhibits dispersed grain orientations and a two-step resistive transition under field, signaling intergranular weak-link behavior. In contrast, the 7 mTorr film develops a (111) texture, a single-step transition, higher critical current density, a second magnetization peak, and a {\delta}l-type pinning response consistent with improved GB coupling. Cryogenic
magnetic force microscopy reveals a spatially heterogeneous, cluster-like
vortex configuration in the 5 mTorr film, whereas the 7 mTorr film hosts a more uniform distribution with enhanced local order. These results establish a connection between deposition-controlled GB connectivity, macroscopic weak-link transport, and microscopic
vortex organization, providing a practical route to tailor
vortex pinning in polycrystalline superconducting films.
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All authors Qun Wang, Ting Chen, Ya-Xun He, Xing-Jian Liu, Jian-Wen Sun, Kang-Hong Yin, Fang-Ting Lin, Shi-Xun Cao, Jun-Yi Ge
Strongly Correlated Electrons
Electric excitation of spin resonance in altermagnetic and antiferromagnetic conductors
R. Ramazashvili, V. Shablenko and Ya. B. Bazaliy
We predict electric-dipole
spin resonance (EDSR) in altermagnetic conductors: in a
magnetic field ${\mathbf H}_\perp$, perpendicular to the magnetization axis, an AC electric field will induce a
spin resonance peak above the lower threshold frequency $\omega_- = 2H_\perp$. In sufficiently clean samples, this peak shall be clearly visible on the background of ohmic absorption. EDSR can thus serve as a diagnostic of altermagnetism in conducting materials and as a means to distinguish it from higher-
symmetry antiferromagnetic order.
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Mesoscale and Nanoscale Physics
Metastable magnetic domains and the anomalous $B_\parallel=0$ resistance peak in twisted double bilayer graphene
Zhenxiang Gao, Christopher Coleman, Silvia Lüscher et al. (+7 more)
In
graphene moirés, valley polarization gives rise to orbital magnetism, manifested as an anomalous
Hall effect and resulting in Barkhausen jumps in longitudinal resistance when changing domain configurations modify quasiparticle scattering. Beyond a simple picture of polarized domains, however,
spin and valley textures within and between the domains are less well understood, as is the effect of these textures on transport. In the valley-polarized quarter-metal state of twisted double
bilayer graphene, a sharp and metastable peak in longitudinal resistance often appears at zero in-plane
magnetic field, whose microscopic origin has yet to be identified. Here, we show that this peak depends on the configuration of domains of orbital magnetism, which is itself set by the gate-voltage trajectory used to enter the ordered state and by the
magnetic field — particularly the in-plane component — present during that trajectory. The sensitivity of the effect to in-plane
magnetic field components points to
spin, linked to valley polarization through
spin-orbit coupling, as the key degree of freedom in both the domain formation and the resistance peak.
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All authors Zhenxiang Gao, Christopher Coleman, Silvia Lüscher, Ruiheng Su, Manabendra Kuiri, Kenji Watanabe, Takashi Taniguchi, Nemin Wei, Chunli Huang, Joshua Folk
Optics
Intrinsic Radial Landau Rainbow in Triaxial Strained Photonic Crystal
Guangti Lu and Satoshi Iwamoto
Localized resonances are essential for enhancing light matter interaction, controlling emission, and realizing compact optical resonators and
lasers. Landau levels offer a distinct route to organizing photonic states through synthetic
magnetic fields, but their high degeneracy does not define spectrally separated localized resonances. Here, we report the intrinsic lifting of degeneracy in photonic Landau levels in a triaxially strained photonic
crystal, leading to the emergence of an intrinsic radial Landau rainbow. The triaxial deformation generates photonic Landau levels through a strain induced pseudomagnetic field, while an accompanying pseudoelectric field lifts the degeneracy of the Landau levels. As a result, each Landau level splits into an equally spaced frequency ladder of localized resonances. In zeroth Landau level, these modes exhibit intensity maxima that move progressively outward from the device center, establishing a radial frequency position mapping and Landau rainbow. Our results reveal an intrinsic fine structure of photonic Landau levels in a triaxial strained photonic
crystal and provide a route to spatially ordered Landau level resonances.
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Mesoscale and Nanoscale Physics
Signatures of a ferro-Josephson effect in twisted graphene
Ruiheng Su, Zhenxiang Gao, Christopher Coleman et al. (+9 more)
When a
spin-polarized current is driven across a
magnetic domain wall, the resulting
spin-transfer torque may, beyond a critical threshold, set the wall's moments into precession. This precession modulates the Berry
curvature experienced by electrons traversing the wall, producing an electromotive force that is topological in nature and proportional to the precession frequency, mapping precisely onto the DC Josephson effect and leading to the name ferro-Josephson effect. We report signatures consistent with this effect in a twisted
graphene van der Waals
heterostructure, where
spin and valley textures are linked by exchange, Hund's coupling, and
spin-orbit interactions. Tuned to fillings where the isospin degeneracy is spontaneously broken, the samples develop a sharp peak in the longitudinal resistance within a fraction of a millitesla of $B_\parallel=0$—a peak that disappears as the current is reduced toward zero. In differential resistance the feature resolves into sharp resonances that disperse with $B_\parallel$ on microtesla and picoampere scales. We argue that these arise from the current-driven precession of
spin-domain-wall moments, in competition with the in-plane anisotropy set by a minuscule applied field, and that they establish nonlinear transport as a sensitive probe of isospin domain-wall dynamics at energy scales far below $k_BT$.
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All authors Ruiheng Su, Zhenxiang Gao, Christopher Coleman, Manabendra Kuiri, Dacen Waters, Kenji Watanabe, Takashi Taniguchi, Matthew Yankowitz, Nemin Wei, Chunli Huang, Allan H. MacDonald, Joshua Folk
Quantum Physics · Cross-listed from cs.MS
The Pauli Lightcone: Information-Theoretic Error Mitigation Beyond the Autocorrelation
Paolo D'Alberto
We introduce the wavemap: a spatial portrait of noise effects that assigns each site a per-noise-level arrival delay l_\gamma (v) and cross-
entropy loss L_\gamma(v). These observables are exact at the lightcone frontier, where bond dimension \chi is small and the simulation is most faithful.
Eigenvalue analysis of the composed gate-plus-noise Pauli transfer
matrices confirms that the studied noise is pure amplitude damping: the spatial propagation pattern is entirely determined by the gate, making the wavemap a model-free noise diagnostic. We apply the multi-product formula (MPF) to recover the noiseless Pauli weight field from the noisy samples, subject to the Lieb-Robinson causal constraint nMPF <= nnl . Fitting time-adaptive coefficients \alpha(t) over the frontier recovers up to 55% of the information loss relative to the best noisy sample, exploiting the fact that the frontier is where truncation error is smallest. On an IBM heavy-hex
lattice with heterogeneous hardware noise the method identifies an information-starved regime, pointing to calibrated synthetic noise as the next required experiment.
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High Energy Astrophysical Phenomena
What is the reason for the lack of cool evolved stars near the center of the Galaxy?
Petr Kurfürst, Michal Zajaček, Norbert Werner et al. (+2 more)
The observed deficit of bright late-type
giants in the central parsec of the Milky Way remains an open problem. We investigate whether repeated passages of red
giants (RGs) through a past jet from Sgr$~$A$^*$ can modify their envelopes and apparent spectral types. Three-dimensional hydrodynamical simulations follow a $1\,M_\odot$, $100\,R_\odot$ RG through up to ten jet crossings at $10^{-3}\,\text{pc}$, using jet kinetic luminosities of $10^{42}$, $10^{44}$, and $10^{48}\,\text{erg}\,\text{s}^{-1}$. Each passage produces shocks, envelope ablation, and an asymmetric downstream tail. For jet luminosities up to $10^{44}\,\text{erg}\,\text{s}^{-1}$, the cumulative ablated mass evolves approximately as $\Delta M\propto t^{1/2}$ and reaches about $10^{-4}\,M_\odot$ over a $10^5\,\text{yr}$ active phase. Repeated heating also raises the surface temperature from about $3600$ to $8500\,\text{K}$ during the first ten passages, potentially making an M-type
giant appear as an A-type source. Jet feedback may therefore contribute to the apparent depletion of cool
giants and the excess of hot
stars in
galactic nuclei (GN).
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All authors Petr Kurfürst, Michal Zajaček, Norbert Werner, Jiří Krtička, Matúš Labaj
Nuclear Theory
Joint cluster-EFT analysis of $^{16}$N $\beta$-delayed $\alpha$ spectra and $\alpha$-$^{12}$C scattering
Jubin Park, Myeong-Hwan Mun and Shung-Ichi Ando
The $\beta$-delayed $\alpha$ decay (BDAD) of $^{16}$N probes the $p$-wave $\alpha$-$^{12}$C continuum relevant to the low-energy $E1$ transition of $^{12}$C$(\alpha,\gamma)^{16}$O. We analyze the spectra of Azuma et al. and Tang et al. within cluster effective field theory, fitting each independently together with the same elastic-scattering data. The baseline eight-parameter fits yield $\chi^2_{\rm A}/N_{\rm A} = 1.732$ for the Azuma spectrum and $\chi^2_{\rm T}/N_{\rm T} = 2.028$ for the Tang spectrum, substantially improving upon the corresponding fixed-propagator values of 4.06 and 3.56, respectively. The raw simultaneous fit yields $\chi^2_{\rm A}/N_{\rm A} = 4.319$, $\chi^2_{\rm T}/N_{\rm T} = 10.901$, and $\chi^2_{\rm el}/N_{\rm el}= 6.366$ for the Azuma, Tang, and elastic-scattering data, respectively. With sector-balanced weighting, the corresponding values are 3.308, 8.993, and 6.466, respectively. Thus, reducing the relative elastic weight improves the BDAD sectors but does not recover the quality of the independent fits. The common strong parameters and normalization ratio remain stable, whereas the fitted weak-current coefficients depend on the objective. The two spectra are separately compatible with a common strong continuum, but the minimal common weak-current amplitude does not reproduce them simultaneously; its fitted coefficients also depend on the objective. These results define the experimental and model sensitivities that must be propagated in a future unified analysis including radiative capture.
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