High Energy Physics (Phenomenology)
Testing Antimatter Couplings with Spectroscopy
Joerg Jaeckel and Lucas Puetter
We investigate how scalar-mediated potentials with Lorentz-violating couplings to Standard Model
fermions affect spectroscopic observables in atoms and highly charged ions. Suitable combinations of an ordinary scalar and a time-like component of a Lorentz violating vector coupling allow for a split into "matter" and "antimatter" couplings, at least in the non-relativistic limit. By considering hydrogen and antihydrogen spectra, we access both matter and antimatter couplings. While relativistic effects alone lift degeneracies in ordinary hydrogen, providing indirect access to antimatter couplings, comparisons with antihydrogen measurements lead to significantly improved sensitivity to the antimatter couplings. In highly charged ions, enhanced relativistic effects further amplify the sensitivity, compensating for reduced experimental precision and larger theoretical uncertainties. We obtain the strongest bounds to date for scalar masses $m_\phi \gtrsim 400\:\mathrm{keV}$. For comparison, we estimate astrophysical constraints on the same parameter space, providing strong bounds even on antimatter couplings, despite
stars being predominantly composed of matter.
Read the full abstract ▾
Statistical Mechanics
Fuzzy Spectroscopy of Bound States in Massive Quantum Field Theories
Joseph Taylor, Matthew Yusuf and Zlatko Papić
Mesons and glueballs are paradigmatic bound states of confining
quantum field theories (QFTs), but their nonperturbative spectroscopy in the continuum remains challenging beyond one spatial dimension. Here we perform such spectroscopy for the Ising QFT using a recently developed regularization based on noncommutative “fuzzy” geometry. On a thin fuzzy
torus, we reproduce the universal low-lying $\mathbb E_8$
meson masses of the magnetically perturbed $(1{+}1)\mathrm{D}$ Ising QFT. By increasing the
torus aspect ratio, we continuously track the second-lightest $\mathbb E_8$
meson as the system effectively crosses over from 1D to 2D. On the 2D fuzzy
torus and sphere, we find a subthreshold scalar level and above-threshold response features consistent with previous estimates of glueball masses. The same excitations are revealed away from
equilibrium using quench dynamics. Our results establish fuzzy geometries as nonperturbative spectroscopic probes of massive QFTs, including their bound-state
evolution through dimensional crossover.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics
Deus ex $H_0$ – Is evidence for dynamical dark energy conditioned on early cosmology?
Nils Schöneberg, Rodrigo Calderón and Julien Lesgourgues
Some free-form reconstructions of the dark energy equation of state suggest that dynamical dark energy is the only explanation for the observed data. In this letter we argue that early Universe solutions to the Hubble tension (around or before recombination) generically cause the evidence for this claim to strongly reduce, establishing a tight connection between the early and late cosmology. In particular, the level of evidence for dynamical dark energy depends on the parameters $H_0 r_\mathrm{d}$ and $\Omega_\mathrm{m}$ and early universe solutions typically push towards higher values of $H_0 r_\mathrm{d}$ and lower values of $\Omega_\mathrm{m}$, where such evidence is reduced.
Read the full abstract ▾
General Relativity and Quantum Cosmology
Celephais: efficient spectral initial data code for precessing compact binaries
Hao-Jui Kuan
Large numerical-relativity surveys require compact-binary initial data that are both spectrally accurate and inexpensive to construct, including for systems with unequal masses and misaligned
spins. We present \celephais, a compact-object initial-data code built on the Kadath spectral library, that constructs binary-
neutron-
star and black-hole–
neutron-
star initial data without imposing equatorial
symmetry. The method exploits the sparse structure of the globally coupled multi-domain Jacobian and the approximate parity separation of fields. The assembled
matrix is factored with MUMPS and reused as a refreshed right preconditioner in a Jacobian-free Newton–Krylov iteration, thereby avoiding dense storage. An adaptive $hp$–refinement scheme then concentrates resolution where the spectral tails are not yet resolved. For a mass-ratio-$20$ black-hole–
neutron-
star benchmark, the adaptive schemes recover the uniform-grid constraint accuracy with about three times fewer unknowns. We also extend the post-Newtonian force-balance estimate to arbitrary
spin orientations and use it to initialise eccentricity reduction. Validation comprises binding-energy comparisons with post-Newtonian sequences, a precessing binary-
neutron-
star eccentricity-reduction test, and a full
evolution whose waveform-reconstructed precession axis follows a post-Newtonian simple-precession model. These results establish an efficient route to spectrally resolved binary-
neutron-
star and black-hole–
neutron-
star initial data with arbitrary
spin orientations.
Read the full abstract ▾
High Energy Astrophysical Phenomena
Constraints on magnetic monopoles from X-ray observations of neutron stars
Mainak Mukhopadhyay, Daniele Perri and Edward W. Kolb
Magnetic monopoles are captured efficiently by
neutron stars, and if they catalyze nucleon decay, the decay products would thermalize and generate observable X-ray surface emission. We use archival Chandra, XMM-Newton, and Swift-XRT data for old isolated millisecond
pulsars to place conservative limits on the
Galactic monopole flux ($F_M$). For a
benchmark cross-section of $\sigma_{\Delta \rm B} \sim 10^{-27}\ {\rm cm^2}$, our constraint as a function of monopole mass $m_M$ is given by $F_{\rm M}(m_M) \lesssim 6 \times 10^{-19}~\mathrm{cm^{-2}s^{-1}sr^{-1}} \times \max \big(4 \times 10^{-6}, \min (2 \times 10^{11}~\mathrm{(GeV/c^2)}/m_{\rm M} , 1 ) \big)$. These limits improve previous
neutron-
star bounds, provide the strongest constraints to date on $F_M$ for $m_M$ between $10^{11} - 10^{13}\ {\rm GeV/c^2}$, and are competitive to existing constraints for this scenario. We also derive complementary constraints from the measured thermal emission of the Magnificent Seven. Our results demonstrate that
neutron star X-ray observations provide a powerful probe of
magnetic monopoles and motivate dedicated X-ray searches for old
neutron stars as a means to test monopole-induced heating.
Read the full abstract ▾
Disordered Systems and Neural Networks · Cross-listed from stat.ML
Leveraging generative models to assist Monte Carlo sampling
Marylou Gabrié
Sampling high-dimensional probability distributions is a central task in scientific computing, with applications ranging from
Bayesian inference to statistical physics and molecular simulation. Despite decades of methodological developments, two major challenges remain: scaling to high dimensions and efficiently exploring
multimodal distributions characterized by metastable states. Classical approaches such as Markov chain Monte Carlo, tempering methods, or enhanced sampling based on collective variables have achieved major successes, but they also face intrinsic limitations. This tutorial review explores a new paradigm that has recently emerged at the interface of machine learning and computational statistical physics: the use of generative models as tools for sampling. In this context, models such as normalizing flows and
diffusion models are not used in their traditional data-driven setting, but rather as flexible probabilistic models that can assist the sampling of distributions known only up to a normalization constant. This manuscript reviews the early development of this rapidly evolving field and discusses several methodological directions, including exact samplers based on generative models and strategies to train such models in the absence of data. While an exhaustive survey of the literature is not attempted, we present a selection of key ideas and methods, along with a discussion of their strengths and limitations. The review is intended to be an accessible tutorial for both physics and machine learning audiences, and it aims to provide a starting point for researchers interested in exploring this exciting area of research.
Read the full abstract ▾
Fluid Dynamics
Fluid-Structure Interaction and Underwater Hydrostatic Implosion of Thin-Walled Metallic Cylinders in Semi-Confined Conditions
Bolaji Oladipo, Helio Matos, Arun Shukla et al. (+1 more)
This study presents a comprehensive numerical investigation of the dynamic behavior and fluid-structure interactions (FSI) of metallic cylinders undergoing hydrostatic collapse in semi-confined fluid environments using a structured Arbitrary Eulerian-Lagrangian (ALE) formulation in LS-DYNA. The numerical model reproduces the experimentally measured collapse pressure of 3.69 MPa and predicts the first water hammer peak with a 1.01% error, demonstrating high predictive fidelity. Following validation, the effects of material type (aluminum and titanium), cylinder slenderness ratio (L/D), and confinement diameter on collapse behavior, pressure
evolution, and fluid motion are examined. Titanium cylinders exhibited sharper collapses, higher water hammer pressures exceeding 70 MPa, and greater kinetic and strain energy accumulation than aluminum due to their higher stiffness and yield strength. Lower L/D ratios produced more abrupt collapses, whereas higher L/D ratios promoted more gradual, axisymmetric deformation. Larger confinement diameters intensified jet formation and increased fluid velocities. The simulations provide mechanistic insight into the coupling between structural deformation and surrounding fluid, showing that geometry, material stiffness, and confinement govern collapse-induced energy transfer. Full-field FSI analysis captures key phenomena, including radial jetting, peak fluid velocities, and internal cavitation, that are not evident from pressure-time histories alone. These findings provide quantitative guidance for the design and safety assessment of subsea pressure housings, marine pipelines, and other
underwater structures subjected to extreme hydrostatic loading.
Read the full abstract ▾
All authors Bolaji Oladipo, Helio Matos, Arun Shukla, Sumanta Das
Soft Condensed Matter
Reply to Smallenburg: Near-melting nucleation and the exponential growth of hard-sphere nucleation times
Roseanna N. Zia
Smallenburg reports near-melting point simulations and observes a well-predicted spontaneous nucleation with mixed, finite-time morphology, in a Comment on our recent Perspective. The Comment's incorrect broader takeaway — that
equilibrium coexistence is "readily achievable" — rests on an untested generalization from a single state point near the phase envelope, and misses entirely the intriguing role played by Frenkel's underlying mechanism. We reiterate the salient point missed by the Comment: the nucleation time grows astronomically with just tenths of a percent of volume fraction away from 53%. This phenomenology emerges from the
entropy exchange mechanism Frenkel described, which predicts that spontaneous phase separation is dynamically accessible only down to about 53% volume fraction from the melting point, and astronomically long waiting times through most of the remaining phase envelope. We provide here calculations to address the potential misconception created by the Comment.
Read the full abstract ▾
Soft Condensed Matter
A transient nonlinear finite element framework and implementation of coupled electro-chemo-mechanics of polyelectrolyte hydrogels
Bibekananda Datta, Brandon K. Zimmerman and Thao D. Nguyen
Polyelectrolyte (PE) hydrogels exhibit complex behavior characterized by large mechanical deformations, nonlinear stress response, solvent transport, and ion
diffusion. The interplay between these mechanisms can lead to unexpected swelling dynamics, deformation patterns, and stress response. As such, advanced computational tools are needed for the efficient design of PE hydrogel-based devices, such as actuators and sensors for soft robotics, microfluidic valves, and drug delivery systems. In this work, we develop a numerical framework to simulate the coupled electro-chemo-mechanical behavior of PE hydrogels using finite element analysis. Applying this framework, an electro-chemo-mechanical model for PE hydrogels in a dilute ionic solution is implemented as a user element (UEL) subroutine in Abaqus/Standard. The model and UEL implementation are validated by comparing to experiments in the literature for transient free-swelling of a DMAEA gel in a solution of varying ionic strengths, then applied to study the consolidation behavior under confined compression and the transient bending behavior of a hydrogel
bilayer. The simulations show that the ionic strength of the external solution, fixed charge density, and Flory-Huggins parameter play significant roles in the magnitude of the transient swelling and consolidation behavior.
Read the full abstract ▾
Materials Science · Cross-listed from cs.AI
Agent-MD: Selective LLM Intervention with Event-Driven Escalation for Stateful GCMC–MD Campaigns
Yijie Wang, Zhen-Yu Yin, Zhenheng Tang et al. (+1 more)
Long-running molecular simulation campaigns require repeated continuation from saved states, provenance-aware progression, adaptive assessment, and occasional interpretation of workflow conditions that cannot be resolved safely by fixed rules. Here, we present
Agent-MD, a framework that places large
language model (LLM)
reasoning selectively at campaign construction and event-triggered review, while routine simulation, analysis, continuation, archiving, and state progression are handled by a persistent rule-based campaign
agent using approved policies and explicit state records.
Agent-MD was demonstrated in a grand canonical Monte Carlo-molecular dynamics (GCMC-MD) water-vapor desorption campaign comprising five montmorillonite systems and three sequential relative-humidity states (RH = 0.9-0.3-0.1). Across 15 system-RH states, the workflow completed 120 segmented simulation cycles with state-specific sampling lengths and provenance-aware restart inheritance. Routine production required no live
reasoning-
agent invocation, while one state reached a review boundary; two preserved incidents were subsequently evaluated through blinded
reasoning-
agent replay, which identified the underlying workflow problems and recommended appropriate follow-up actions. The simulations also revealed distinct composition-dependent low-RH responses, with Ca-bearing montmorillonite retaining more interlayer water and maintaining a larger basal spacing than the Na- and K-bearing systems, while the highest-charge Na system retained more residual water under dry conditions. These results demonstrate that long-running scientific workflows need not place every operation inside an LLM
reasoning loop: selective
reasoning can instead be combined with deterministic execution, structured evidence, and validated control handoffs to provide reproducible and auditable
agent-assisted molecular simulation.
Read the full abstract ▾
All authors Yijie Wang, Zhen-Yu Yin, Zhenheng Tang, Xiaowen Chu
High Energy Physics (Theory)
Three-loop onset of the wormhole length in DSSYK
Eleonora Alfinito and Matteo Beccaria
The length of the Einstein-Rosen bridge in sine-dilaton
gravity at disk level equals the Krylov spread complexity of the dual double-scaled SYK (DSSYK) model, with the double-scaling parameter $\lambda$ controlling the semiclassical expansion. We compute the onset value, $L_{0}$, in the thermofield double state at $t=0$ and arbitrary inverse temperature $\beta$, through three loops and in closed form, extending the known one-loop result. The quantity $L_{0}$ represents the preparation complexity of the initial thermal Hartle-Hawking state. In DSSYK, $L_{0}$ is $\lambda$ times the average chord number of the thermal state, providing a microscopic, unambiguous determination of an additive constant otherwise fixed only by a choice of
holographic renormalization scheme. The two-loop contribution follows from a saddle point evaluation of the DSSYK two-point function at coincident insertion points, where individually divergent contributions cancel only in their sum. At three loops, we bypass the saddle point analysis using an exact recursion relation that generates long high-temperature expansions at low cost, fixing and testing a proposed Ansatz against many independent data points. Finally, in the low-temperature regime each loop order contributes one further power of $\beta$, reorganizing the semiclassical series into an expansion in the Schwarzian coupling $\lambda\beta$, whose leading coefficient we check against an independent one-loop Schwarzian computation. The same methods, applied to the length variance and third-order cumulant at $t=0$, give their semiclassical expansion through two loops.
Read the full abstract ▾
Instrumentation and Methods for Astrophysics
Environmental Noise Challenges for the Einstein Telescope - A Review
Matteo Di Giovanni
Einstein
Telescope (ET) will be a next-generation ground based interferometric gravitational-wave detector designed to explore the Universe to an unprecedented depth and detail. With its 10-15 km long arms, underground infrastructure, and advanced cryogenic technologies to suppress thermal noise, ET aims at achieving a sensitivity up to eight orders of magnitude better than current detectors such as Virgo, LIGO, and KAGRA. The coverage of the low-frequency band, starting at 2 Hz, will enable the observation of earlier inspiral phases of compact binary coalescences, enhancing early-warning capabilities and improving multi-messenger follow-up. However, this increased sensitivity also implies a higher susceptibility to environmental disturbances, particularly in the 2-10 Hz range where anthropogenic, seismic and infrastructural noise noise are most relevant. Therefore, understanding and mitigating environmental contributions are essential to fully exploit the scientific potential of ET. This chapter reviews the ongoing studies on environmental noise for ET, summarizes the main challenges related to site characterization and infrastructure design and outlines the strategies currently under development to ensure optimal detector performance.
Read the full abstract ▾
Quantum Physics
Readout-Rank Laws for Isotropic Quantum Tangents
Marwan Ait Haddou
Deep parameterized
quantum circuits may remain sensitive to a parameter change while the observables retained by a learning model barely respond. We study this separation for a fixed computational-basis measurement. For a pure-state tangent, we compare the
quantum Fisher information $F_Q$, the Fisher information $F_{\rm full}$ in the complete bitstring distribution, and the largest variance-normalized response $\mathcal I_{\mathcal A}$ available to a diagonal readout space $\mathcal A$. If the joint state–tangent frame is Haar random, we prove that the two successive information fractions are independent Beta variables whose means are $1/2$ and $r/(2^n-1)$, where $r$ is the centered dimension of the readout. Consequently, even the joint span of all computational-basis Pauli strings through any fixed weight $k$ retain only $O(n^k2^{-n})$ of the full-record information. Exact-statevector experiments across six
circuit families show increasing finite-size agreement with this hierarchy in five nonconserving ensembles as the
circuit depth grows. A number-conserving family departs strongly from the isotropic prediction even after correcting the support and readout rank, showing that rank alone is insufficient without tangent isotropy.
Read the full abstract ▾
Quantum Physics
Beyond the Quantum Promise: A Security Analysis of Classical Control in Quantum Key Distribution
Ali Hamza Malik, Raja Hasnain Anwar and Muhammad Taqi Raza
Quantum Key Distribution (QKD) protocols provide information-theoretic security by using
quantum mechanical principles. Yet QKD is fundamentally a hybrid protocol: its security depends on the correct integration of the
quantum phase with classical post-processing. While ETSI and ITUT specifications standardize QKD architectures and interfaces, they evaluate protocol security in isolation, leaving cross-layer interactions as an underexplored attack surface. This paper introduces a formal verification framework that holistically models QKD protocols based on ETSI and ITUT QKD specifications. Our model is the first hybrid QKD protocol model that supports automated analysis of protocollevel security focusing on how classical operations influence the security guarantees provided by the
quantum phase of the QKD protocol. We formalize a comprehensive symbolic model of QKD protocols, based on ETSI and ITU-T QKD specifications, in Tamarin, an automated protocol verifier. Applying this framework, we obtain formal evidence of three specification-level vulnerabilities in ETSI- and ITU-T-grounded protocol models under adversary Eve+: subverted
entanglement injection, basis-deferred measurement, and message reflection. Each arises from a classical control-plane omission in the procedure text and is established under a symbolic abstraction rather than as a claim about all practical deployments. We introduce two protocol improvements: measurement commitment and identitybound message authentication codes (MACs). Tamarin verification confirms that these countermeasures eliminate the identified vulnerabilities under Eve+. We have communicated our results and recommendations to relevant standardization organizations.
Read the full abstract ▾
High Energy Physics (Phenomenology)
A $\Gamma_{3}$ modular symmetric approach for two-zero textures in left-right symmetric model
Ankita Kakoti and Happy Borgohain
The observed pattern for
neutrino masses and mixing provides compelling evidence for Beyond Standard Model physics which further motivates the search for predictive frameworks that can simultaneously address
flavor structure and its phenomenological consequences. This work particularly investigates the realization of all possible seven two-zero
neutrino mass textures within the generic left-right symmetric model with $A_{4}$ modular
symmetry. By considering modular weights 4,8 and 10, we systematically construct all the possible classes of 2-0 textures without the introduction of any flavon fields which enhances the predictive power of the framework. In this work, we also identify the texture classes capable of simultaneously accommodating current
neutrino data, reproducing the observed
baryon asymmetry and also yielding experimentally testable results for the effective Majorana
neutrino mass for new physics contributions of neutrinoless double beta decay.
Read the full abstract ▾
High Energy Physics (Phenomenology)
Probing Dark Matter and Phantom Field Effects on Neutrino Oscillations around Black Holes
Ikrom Ergashov, Bakhtiyor Narzilloev, Ibrar Hussain et al. (+1 more)
This study investigates how dark matter in the background of the phantom field (DMPF) near a black hole influences
neutrino flavor oscillations using a two-
flavor model. It is found that gravitational effects are cancelled for radially moving
neutrinos, causing the oscillation phase to increase with distance and mass-splitting, similar to flat spacetime. However, deflected
neutrinos experience additional phase shifts due to dark matter, which slightly alters the mass-difference term and the total phase. Numerical analysis supports these findings and reveals a degeneracy between lens mass and dark matter parameters, affecting the transition probability curves based on source angle changes.
Neutrinos modeled as Gaussian wave packets show that decoherence in a gravitational field is minimally influenced by dark matter, with the absolute
neutrino mass determining the oscillation duration. Our findings imply that curved spacetime and dark matter significantly impact
neutrino oscillations, offering potential insights into dark matter through
neutrino astronomy in extreme environments.
Read the full abstract ▾
All authors Ikrom Ergashov, Bakhtiyor Narzilloev, Ibrar Hussain, Bobomurat Ahmedov
Cosmology and Nongalactic Astrophysics
HST imaging, pipeline modeling, and time-delay predictions of 2 triply-imaged and 15 quadruply-imaged lensed quasars
William Sheu, Tommaso Treu, Adriano Agnello et al. (+10 more)
The Hubble tension remains a significant challenge in modern cosmology, exhibiting a discrepancy between early-Universe
cosmic microwave background measurements and local distance ladder observations. Strong
lensing time-delay cosmography provides an independent,
geometric probe of $H_0$ that can help resolve this discrepancy. Although hundreds of lensed
quasars have been discovered, only a handful have been analyzed due to the resource-intensive follow-up required to measure precise time delays and break degeneracies. We present uniform gravitational lens modeling of 17 recently discovered lensed
quasar systems (2 triply-imaged and 15 quadruply-imaged) to identify and prioritize the most promising candidates for future cosmological study. Using high-resolution near-infrared Hubble Space
Telescope WFC3/IR F160W imaging (PID: 17916, PI: T. Treu), we perform uniform pipeline modeling with Lenstronomy. We constrain the mass and light profiles of the deflector
galaxies, and assuming a fiducial cosmology, we predict their Fermat potential differences and expected time delays. Our pipeline successfully yields models and time-delay predictions for all 17 systems. Assuming ideal monitoring conditions, we estimate the total contribution from time-delay and Fermat potential modeling errors to the time-delay distance. From this, we classify the systems by estimated time-delay distance uncertainties: six "excellent" ($\leq 3\%$), five "good" ($3\%$-$7\%$), three "suitable" ($7\%$-$12\%$), and three "impractical" ($>12\%$). We recommend prioritizing follow-up campaigns on the 11 "excellent" and "good" systems, which have the potential to deliver high-precision, independent constraints on $H_0$ to help resolve the Hubble tension.
Read the full abstract ▾
All authors William Sheu, Tommaso Treu, Adriano Agnello, Timo Anguita, Simon Birrer, Daniel Gilman, Xiaosheng Huang, Richard G. McMahon, Nicholas D. Morgan, Veronica Motta, Anna Nierenberg, Kenneth C. Wong, Ioana Zelko
Fluid Dynamics
Efficient three-dimensional variational data assimilation of multi-plane PIV data
Uttam Cadambi Padmanaban, Samaresh Midya, Ping He et al. (+2 more)
We perform three-dimensional variational data assimilation (3DVar) using a discrete adjoint approach to optimise the time-averaged momentum equations. The experimental data consist of sparse stereoscopic particle image velocimetry (PIV) measurements collected along $12$ cross-stream planes in the wake of a vehicle-like bluff body at a Reynolds number $Re_L = 5.64 \times 10^5$ based on the streamwise body length. Adjoint localisation is proposed and implemented to reduce the
memory footprint of the discrete adjoint method for spatially-varying control variables in 3DVar by confining the control variable space to a user-defined subdomain. Restricting the control variable to $12$ % of the full control space yields a maximum reduction in peak
memory of $64$ %, while producing assimilated fields of comparable fidelity with respect to mean velocity and the optimised momentum forcing field. The localised adjoint case improves upon the baseline Spalart–Allmaras
turbulence model and recovers the correct asymmetric
topology of the complex three-dimensional (3D) recirculation bubble. The assimilated Reynolds shear stress agrees well with the experiment, and the assimilated mean pressure is shown to be physically consistent when correlated with the in-plane vorticity fields. A data efficiency study is also performed, in which the number of planes provided for assimilation is progressively reduced, demonstrating that the data coverage must extend at least to the end of the primary recirculation bubble to adequately constrain the near-wake dynamics. The efficiency that adjoint localisation affords is crucial for assimilating sparse, experimental data for 3D separated flows on fine meshes that can tackle industrial problems of interest.
Read the full abstract ▾
All authors Uttam Cadambi Padmanaban, Samaresh Midya, Ping He, Bharathram Ganapathisubramani, Sean Symon
High Energy Physics (Theory)
Quantum de Sitter and Analytically Continued Chern Simons Theory
Stephon Alexander and Kenneth Blakey
We give a Lefschetz thimble definition of the Chern–Simons–Kodama wavefunctional in Lorentzian self-dual
gravity with positive cosmological constant. By complexifying the connection and choosing the Lefschetz thimble attached to the self-dual de~Sitter saddle, Witten's analytic continuation of Chern–Simons theory replaces the real contour, on which the defining integral is at best conditionally convergent, by an absolutely convergent integration cycle and yields a controlled semiclassical expansion. The relevant integrand is the full holomorphic exponential $e^{I}$, with $I=\kappa Y_{\rm CS}+(\text{source})$, and the steepest descent flow is governed by the Morse function $h=\operatorname{Re} I$. In the homogeneous isotropic de Sitter reduction, the construction reproduces the Hartle–Hawking Airy wavefunction. In the Bianchi~IX truncation, we take the Lefschetz thimble attached to the expanding de~Sitter saddle (the contracting branch defines a conjugate Lefschetz thimble); within this sector, the symmetric configuration is the only critical point for $\Lambda>0$. The corresponding Lefschetz thimble contains one trace direction with the FRW Airy structure and two anisotropic shear directions that are real-Gaussian damped at leading quadratic order. This gives a finite Bianchi~IX wavefunction which, to leading order, is the FRW Airy factor multiplied by a real anisotropy Gaussian. Thus, the Airy behavior is not an artifact of the one-dimensional minisuperspace reduction, but the leading form of the wavefunction on the Lefschetz thimble. We also discuss how the Lefschetz thimble prescription interfaces with Lorentzian reality conditions.
Read the full abstract ▾
Plasma Physics
Characterization of a prototype parallel-plate $^{238}$U fission chamber with DD and DT fusion neutron sources
V. Hagenlocker, R.A. Tinguely, X. Wang et al. (+5 more)
The SPARC tokamak will employ $^{238}$U-based fission chambers (FCs) to monitor high-performance deuterium-tritium (DT)
plasma operations, spanning
neutron yield rates from ${\sim}10^{15}$ to ${>}10^{19}$ n/s. This work validates the $^{238}$U FC design, which utilizes a parallel-plate detector geometry and borated polyethylene collimation to prioritize unscattered DD and DT fusion
neutrons. Experimental testing with both DD and DT
neutron generators corroborates vendor-specified efficiencies and demonstrates excellent detector linearity, with measured count rates showing good agreement with OpenMC neutronics simulations. Further characterization confirms the $^{238}$U FC's robustness against SPARC-relevant environmental challenges, including stray
magnetic fields up to 14 mT and possible signal degradation risks associated with $\sim$30 m long cable runs. These results confirm that the $^{238}$U FC, supported by indirect
neutron shielding as well as appropriate pulse height thresholds, provides a reliable solution for fusion power measurements as part of the SPARC
neutron diagnostics suite.
Read the full abstract ▾
All authors V. Hagenlocker, R.A. Tinguely, X. Wang, J.L. Ball, B. Buschmann, M. Gatu-Johnson, R. Gocht, P. Raj
Statistical Mechanics
Ruicheng Bao and Yue Liu
Generating
entanglement rapidly and reliably is essential for
quantum information processing, communication, and metrology. Dissipative preparation is attractive because engineered reservoirs robustly drive a system toward an entangled target, yet relaxation can carry a substantial time cost. Here we formulate the
entanglement Mpemba effect, whereby an initially less entangled state overtakes a more entangled state under the same open-system dynamics. This effect turns initial-state engineering into a route for faster preparation without altering the dissipative protocol. We derive a general criterion for the reversal from the relaxation spectrum, applicable even when
entanglement evolves nonmonotonically. A reversal of deterministic local operations and classical communication (LOCC)-reachability preorder provides a measure-independent certificate of reversed
entanglement order. Exactly solvable models show that initial-state selection can substantially shorten the time required to reach high
entanglement. We further propose an experimentally relevant trapped-ion protocol that can realize the
entanglement Mpemba effect.
Read the full abstract ▾
Astrophysics of Galaxies
A clear detection of proper motion confirms that the claimed $\mathbf{z\simeq32}$ galaxy candidate, "Capotauro”, is a Y-type brown dwarf
F.-Y. F. Liu, D. J. McLeod, B. J. Sutlieff et al. (+13 more)
The compact red source “Capotauro”, discovered in deep JWST imaging in 2025, has been suggested as a possible
galaxy candidate at
redshift $z\simeq32$ on account of its extreme NIRCam colours. However, given the lack of evidence that this source is spatially resolved, a very cool brown
dwarf, at a distance consistent with the scale-height of the Milky Way
stellar disc ($\simeq 500$ pc), provides an alternative explanation of the observed photometry. Here we exploit new medium-band NIRCam imaging obtained $\simeq 3.5$ years after the discovery data to test this hypothesis. Using filter-dependent point-spread-function fitting, a robust local relative astrometric frame defined by 68 compact reference sources, and a joint four-image injection-recovery analysis, we show that Capotauro has moved by $132 \pm 20$ mas over the 3.5-yr interval span of the observations, ruling out the possibility that it is an extragalactic source (
galaxy, AGN, or
supernova) at $> 6 \sigma$. The observed apparent proper motion is $(\mu_\xi,\mu_\eta)=(+9.4^{+6.4}_{-4.8},-35.6^{+5.1}_{-5.9})$ mas yr$^{-1}$, or $37.6^{+5.5}_{-5.6}$ mas yr$^{-1}$ in total. Through comparison of its photometric spectral energy distribution with empirical templates, we find that Capotauro is best described as a brown
dwarf of spectral type Y$1.0\pm0.5$ ($T_{\rm eff}\approx350$ K) at a distance of $730\pm110$ pc (although the existing data and spectral templates are insufficient to rule out an even colder, later-type brown
dwarf). Capotauro is thus one of the most distant Y
dwarfs found to date, as expected given its discovery in a deep JWST extragalactic survey field. This result demonstrates the value of multi-epoch imaging for identifying substellar contaminants among the most extreme photometric-
redshift candidates.
Read the full abstract ▾
All authors F.-Y. F. Liu, D. J. McLeod, B. J. Sutlieff, T. J. Dupuy, J. S. Dunlop, X. Chen, R. J. McLure, H.-H. Leung, S. Antonogiannaki, C. Bondestam, E. Laplace, R. Begley, A. C. Carnall, F. Cullen, C. T. Donnan, R. S. Ellis
Disordered Systems and Neural Networks · Cross-listed from cs.AI
Interaction Creates Dynamical AI Behavior Absent in Isolation
Bella Xinrui Li, Frank Yingjie Huo and Neil F Johnson
What will happen when AI
agents interact in daily life, e.g. when one AI starts bossing another around? We find a counterintuitive answer that opens new avenues for out-of-
equilibrium Physics. When a boss AI directs a stream of messages at the subordinate AI while ignoring its replies, it drives the subordinate into an alien behavioral state that it would never have exhibited alone. Although the two AIs share the same well-defined (decoding) temperature, the subordinate neither copies its boss nor returns to how it behaves on its own; instead, it adopts an entirely different behavior. The boss's added value is similar to a pre-recorded tape. When the boss listens, they both adopt a similar alien dynamical state. A simple kinetic theory captures the principal effects, such as why the way in which the same messages are delivered will matter in future AI-AI interactions.
Read the full abstract ▾
High Energy Physics (Phenomenology)
Optimal Calibration-Free Observable for the Nucleon-Coupling Ratio in a Dual-Alkali Comagnetometer for Dark Matter Searches
Yossi Rosenzweig, Yevgeny Kats, Eli Sarid et al. (+3 more)
A dual-alkali single-
cell $^{87}$Rb-$^{39}$K-$^{3}$He comagnetometer can read an
axion-like dark matter signal through two optical rotation channels, encoding the ratio $\mathcal{R}=\xi_n/\xi_p$ of the field's
neutron and
proton spin couplings in their relative response. The inter-species phase difference $\Delta\varphi$ has been proposed as a calibration-free readout that is sensitive to $\mathcal{R}$. Treating the extraction of $\mathcal{R}$ as a statistical estimation problem, we show that the estimate of $\mathcal{R}$ depends on the two channels only through their complex ratio, which splits into $\Delta\varphi$ and an amplitude ratio, of which only $\Delta\varphi$ is insensitive to the relative gain and hence calibration free. For our choice of comagnetometer parameters, above $\sim\!100$ Hz the phase difference alone captures most of the coupling-ratio information. At lower frequencies $\Delta\varphi$ is no longer near-sufficient. Below $\sim\!40$ Hz, the amplitude ratio would improve the precision on $\mathcal{R}$ by a factor of $\gtrsim2$. Recovering that information, however, requires the relative gain to be known sufficiently accurately, so $\Delta\varphi$ remains the robust observable even where it is not the most informative one.
Read the full abstract ▾
All authors Yossi Rosenzweig, Yevgeny Kats, Eli Sarid, Menachem Givon, Yonathan Japha, Ron Folman
Solar and Stellar Astrophysics
White Dwarf Kicks via Episodic Mass Ejection from Red Giant Stars
Jim Fuller
Recent observations have found evidence that white
dwarf (WD)
stars receive a kick of $\sim$1 km/s as the envelopes of their red
giant progenitors are expelled. We show that these kicks can arise from asymmetric and episodic mass loss of red
giant stars. Based on simple hydrodynamic models of red
giant mass loss, each mass ejection event likely expels of order $\sim \! 10^{-4} \, M_\odot$, imparting a small and randomly oriented kick to the
star, with the net kick to the WD arising from a combination of many $(N \sim 10^4)$ events. Each kick is of order $v_k \sim 5 \, {\rm m/s}$, with a total kick of order $v_{\rm k,tot} \approx \sqrt{N} v_k \sim 0.5 \, {\rm km/s}$. We predict substantially larger net kicks for higher mass WDs. We also model the orbital
evolution of binary
stars experiencing a
stochastic series of kicks, developing analytic models to explain numerical integrations. For nominal mass ejection parameters, widely separated binaries $(a \gtrsim 10^3 \, {\rm AU})$ can become unbound, with larger fractions of unbound systems at larger separations and for higher WD masses. The orbital eccentricities can also approach unity, causing
stellar collisions that may result in luminous transients and eccentric common envelope events.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics
Sensitivity of Next-Generation CMB Surveys to Neutrinos and Other Light Relics
Cynthia Trendafilova, Srinivasan Raghunathan, Benjamin Wallisch et al. (+33 more)
Neutrinos and other light relics leave characteristic imprints in the
cosmic microwave background anisotropies, making their observation a sensitive probe of the particle content and thermal history of the early universe. The energy density in these relativistic species is parameterized by their effective number $N_\mathrm{eff}$. Measuring this parameter at the percent level, which is a long-standing science goal of CMB-S4 and other experiments, would test a wide range of well-motivated physics within and beyond the Standard Model of particle physics. In this paper, we present Fisher-
matrix forecasts of the projected sensitivity to $N_\mathrm{eff}$ of several CMB-S4 survey configurations considered during its extensive design phase. The conceptual design reaches $\sigma(N_\mathrm{eff}) < 0.03$ over its seven-year observing period, while the revised configuration achieves the same precision over a longer timescale. We complement these results with a
cosmic-variance-limited survey over the same multipole range to quantify the room for improvement accessible with additional instrumental, observational, and theoretical efforts. Finally, we discuss the broad implications of precise $N_\mathrm{eff}$ measurements for the radiation sector, big bang nucleosynthesis, light thermal relics, and other early-universe physics. The forecasts presented in this work are performed with the publicly released DRAFT (Dark Radiation Anisotropy Flowdown Team) tool. It provides an end-to-end pipeline from simulated foreground maps and component separation to delensing and projected sensitivities for any cosmological parameter, and it can be directly applied to other
cosmic microwave background survey designs.
Read the full abstract ▾
All authors Cynthia Trendafilova, Srinivasan Raghunathan, Benjamin Wallisch, Joel Meyers, Kevork N. Abazajian, Edoardo Altamura, Carlo Baccigalupi, Kimberly K. Boddy, Thejs Brinckmann, Yuji Chinone, Gabriele Coppi, Francis-Yan Cyr-Racine, Jacques Delabrouille, Katherine Freese, Helena García Escudero, Martina Gerbino, Shamik Ghosh, Vera Gluscevic, Daniel Green, Daniel Grin, Kevin M. Huffenberger, Mudit Jain, Lloyd Knox, Anto I. Lonappan, Marilena Loverde, Philip Lubin, Gabriele Montefalcone, Valentine Novosad, Marco Raveri, Christian L. Reichardt, Sayan Saha, Murali M. Saravanan, Emmanuel Schaan, Sara M. Simon, Julien Tang, Scott Watson
Statistical Mechanics
Active movement of foraging sea turtles generates anomalous looping
Vijay Kumar, Vladimir V. Palyulin, Perla Roman-Torres et al. (+2 more)
Animals inhabiting diverse environments by moving across different spatial scales, from insects to birds, marine predators, mammals and even humans, often display apparently random movement paths. Over the past decade, novel biologging technologies have recorded these patterns in increasing detail, generating a wealth of experimental data. A central challenge is to understand such complex patterns by constructing data-driven mathematical models. Many animal movements depart from Brownian motion, as described by correlated random walks, Lévy walks, or active particle dynamics. Yet, these movement models do not incorporate long-term non-Markovian
memory extracted from experimental trajectories. Here, we construct a
stochastic generalised Langevin equation from satellite tracking data for loggerhead sea turtles (Caretta caretta) foraging off the coast of West Africa. We find that these turtles exhibit active movement characterised by large-scale loops that are not explained by ocean currents or chirality. These loops maintain movement within a specific foraging region and, over intermediate timescales, generate superdiffusion similar to Lévy walks. We thus identify a loop-based form of active anomalous search related to foraging patterns observed across a wide range of animal species, which may inspire robotic search strategies and AI-based metaheuristic optimisation
algorithms.
Read the full abstract ▾
All authors Vijay Kumar, Vladimir V. Palyulin, Perla Roman-Torres, Christophe Eizaguirre, Rainer Klages
Atomic Physics
Observation of $\Pi$-symmetry ultralong-range Rydberg molecules
Matthew T. Eiles, Aleksandr Zaitsev, Dominik Dorer et al. (+5 more)
We observe weakly-bound $\Pi$-
symmetry electronic states in the spectroscopy of $^{87}$Rb$(nP_{3/2})$+$^{87}$Rb($5S_{1/2}$) ultralong-range Rydberg molecules. We detect these molecules in Rydberg states having principal
quantum number $13\le n \le 16$. Their $\Pi$-state character is unambiguously identified via their observed multiplet structure: the $2F+1$
magnetic sublevels of the ground-state rubidium atom separate, as in the Zeeman effect, because of the
spin-
spin coupling between the Rydberg and valence electrons. We find a rapid decrease in the molecular binding energy $\propto (n-\mu_{P_{3/2}})^{-11}$, where $\mu_{P_{3/2}}$ is the
quantum defect, indicating that the low-$n$ regime of Rydberg states is ideally suited for studies of $\Pi$-
symmetry molecules. Our observations are in good agreement with Green's function-based calculations for $14\le n\le 16$, with poorer agreement for $n=13$ hinting at the beginning of a breakdown of the
Fermi pseudopotential approach at low $n$.
Read the full abstract ▾
All authors Matthew T. Eiles, Aleksandr Zaitsev, Dominik Dorer, Shinsuke Haze, Markus Deiß, S. Efe Gürleyen, Chris H. Greene, Johannes Hecker Denschlag
Materials Science
Permutation invariant neural network prediction of vacancy formation under deformation and varying chemical environment in FCC high entropy alloys
Tanvir Sohail and Swarnava Ghosh
Vacancy formation energies govern
diffusion, irradiation damage, phase stability, and dynamic failure in high-
entropy alloys (HEAs), yet their strong dependence on local chemical environments and mechanical deformation makes atomistic calculations prohibitively expensive for large-scale studies. Here, we develop an atomistically informed permutation invariant machine learning framework for predicting strain dependent vacancy formation energies in FCC HEAs from local atomic environments. The model employs a vacancy-centered representation constructed from objective
geometric descriptors together with invariants of the local deformation gradient, enabling the coupled effects of chemical disorder and finite deformation to be learned within a unified framework. Atomistic simulations reveal that volumetric deformation is the dominant factor controlling the average variation in vacancy formation energy, whereas shear deformation has a comparatively minor influence. At the same time, substantial site to site variability persists under identical macroscopic loading, demonstrating that local chemical environments govern the statistical distribution of vacancy energetics beyond species-averaged trends. The proposed framework accurately predicts vacancy formation energies across diverse deformation states while providing orders-of-magnitude faster evaluation than direct atomistic simulations. These results establish an efficient route for incorporating stress-dependent defect energetics into multiscale models of
diffusion, irradiation damage, and dynamic failure in chemically complex
alloys.
Read the full abstract ▾
Strongly Correlated Electrons
A quantum geometric mechanism for chiral domain wall metastability: Application to twisted transition-metal dichalcogenides
Nisarg Chadha, Qiang Gao, Eslam Khalaf et al. (+1 more)
Band
topology can have an imprint on the excitations of a ferromagnet. A known example is
quantum Hall ferromagnets and their
lattice analogs; when both
flavors have the same Chern number $C$, a smooth skyrmion texture binds charge $-eC$ per unit winding. Here, we consider instead the case of conjugate Chern bands related by time-reversal. We show that, despite the vanishing net charge response, a smooth texture can be associated with a dipole response—a domain wall (DW) with an in-plane winding along its length can bind a nonzero dipole density transverse to the wall. The strength of this dipole density is controlled by a dimensionless coefficient $c_G$. Although not quantized, the
geometric dipole coefficient $c_G$ is a moment of the second Chern form of the occupied projector in mixed (momentum and order-parameter) space and is generally nonzero. The dipole-decorated DW can thus become metastable at a finite radius due to the competition between dipolar repulsion and the usual surface tension, even at a finite Zeeman field. In a realistic model of twisted MoTe$_2$, we find that $c_G$ drops sharply across a transition within the valley-polarized (VP) phase from a $C=1$ to a $C=0$ ferromagnet. This naturally explains recent pump-probe experiments~\cite{exp} at hole filling $\nu=1$, in which a long-lived excitation survives reverse fields far exceeding the saturation field but disappears at an intermediate displacement field despite only weak changes in conventional
magnetic diagnostics. Metastable
spin textures thus serve as a sensitive probe of band
quantum geometry, and as an intrinsic bottleneck for fast optical control of moiré ferromagnets in Chern-conjugate bands.
Read the full abstract ▾
All authors Nisarg Chadha, Qiang Gao, Eslam Khalaf, Zhaoyu Han