The Barriola-Vilenkin global monopoles are topological defects predicted by certain grand unified theories and have been extensively studied for their astrophysical and cosmological implications, including their distinctive spacetime geometry and characteristic gravitational lensing effects. Despite this interest, an exact solution for a global monopole remains elusive, with research largely confined to approximations of the static, spherically symmetric case. This paper addresses the fundamental question of whether a rotating global monopole can exist as a solution to the coupled Einstein-scalar field equations. We first prove that metrics generated by applying the Newman-Janis algorithm to the static monopole are inconsistent with the scalar field’s equation of motion. Furthermore, we perform an asymptotic analysis for general static, axially symmetric spacetimes and establish that the only such solution that is regular at large distances is the spherically symmetric one. These results lead to the conclusion that the Barriola-Vilenkin global monopoles are incompatible with rotating spacetime within the framework of Einstein’s general relativity.

We analyze the spherical harmonic mode amplitudes of quasicircular, nonprecessing binary black hole mergers using 275 numerical relativity simulations from the SXS, RIT, and MAYA catalogs. We construct fits using the leading-order post-Newtonian (PN) dependence on intrinsic parameters, replacing the PN velocity with fit coefficients. We compare these to polynomial fits in symmetric mass ratio and spin. We analyze $(\ell ,m)$ modes with $\ell \le 4$ from late inspiral [$t=-500M$ relative to the (2, 2) peak] to postmerger ($t=40M$). For nonspinning systems, the (2, 2), (2, 1), and (3, 3) modes retain the leading-order PN dependence on mass ratio throughout the merger. Higher-order modes deviate from the PN dependence only near and after the merger, where polynomial fits of degree $N\le 3$ can capture the amplitude behavior up to $40M$. For aligned-spin systems at fixed mass ratio, the (2, 1) mode retains its PN spin dependence, while the (3, 2) and (4, 3) modes exhibit a quadratic spin dependence near merger. The PN-inspired fits lose accuracy with increasing mass ratio, particularly near merger. Results broadly agree across catalogs, though discrepancies appear in the (3, 1), (4, 2), and (4, 1) modes, likely from resolution differences. Our results clarify the extent to which PN structure persists in mode amplitudes. Although the fits cannot be fully interpreted within the PN formalism near merger, low-degree polynomial corrections to the PN amplitude Ansätze can capture strong-field behavior, enabling closed-form and efficient modeling of waveform amplitudes in this regime.

We perform a Bayesian comparison between thawing quintessence and a cosmological constant, incorporating theoretically motivated priors on the phenomenological Padé-w parameters used to model thawing dynamics. We find that thawing quintessence is consistently preferred over a cosmological constant when combining baryon acoustic oscillation data from DESI DR2 and CMB data from $\mathrm{Planck}+\mathrm{ACT}$ with any of the major supernova compilations, including the recently updated DES-Dovekie sample. This preference is not sensitive to our choice of prior, but it is contingent on the inclusion of supernovae in the analysis. We comment on the consistency between various information criteria and Bayesian evidence ratios, finding that the deviance information criterion tracks the Bayesian evidence more reliably than either the Akaike information criterion or the Bayesian information criterion. Finally, we use observational likelihoods to identify which thawing trajectories are compatible with the available data, independently of theoretical priors.

Generalized parton distribution functions (GPDs) are off-diagonal light-cone matrix elements that encode the internal structure of hadrons in terms of quark and gluon degrees of freedom. In this work, we present the first nonperturbative study of quasi-GPDs in the massive Schwinger model, quantum electrodynamics in $1+1$ dimensions (${\mathrm{QED}}_2$), within the Hamiltonian formulation of lattice field theory. Quasidistributions are spatial correlation functions of boosted states, which approach the relevant light-cone distributions in the luminal limit. Using tensor networks, we prepare the first excited state in the strongly coupled regime and boost it to close to the light-cone on lattices of up to 400 lattice sites. We compute both quasiparton distribution functions and, for the first time, quasi-GPDs, and study their convergence for increasingly boosted states. In addition, we perform analytic calculations of GPDs in the two-particle Fock-space approximation and in the Reggeized limit, providing qualitative benchmarks for the tensor network results. Our analysis establishes computational benchmarks for accessing partonic observables in low-dimensional gauge theories, offering a starting point for future extensions to higher dimensions, non-Abelian theories, and quantum simulations.

We use numerical Monte Carlo simulations to determine the mass spectrum of the bosonic sector of the electroweak model in an external magnetic field of the electroweak-scale strength (${10}^{20}\mathrm{T}$) at zero temperature. It is known that as the magnetic field gets stronger, the electroweak vacuum undergoes two consecutive crossover-type transitions, passing from (i) the conventional symmetry-broken homogeneous phase to (ii) an intermediate inhomogeneous vortex phase characterized by a (superconducting) condensate of electrically charged $W$ bosons and then to (iii) a homogeneous phase with a restored electroweak symmetry. We show that the spin component of the $W$ boson aligned with the direction of the magnetic field is the lightest excitation in all three phases. Its mass continuously decreases in the low-field broken phase and becomes very small in the intermediate phase. We argue that this nearly massless excitation corresponds to a Goldstone acoustic phonon mode associated with vibrations of the lattice of electroweak vortices. In the high-field symmetry-restored phase, where the vortices disappear, the lightest $W$ mass rises again. Neither Higgs nor $Z$ boson masses vanish across all studied phases and crossover transitions.

We apply the strategy proposed in the companion paper [Phys. Rev. D 113, 074017 (2026).] for dealing with multiple dispersive bounds, to the case of subthreshold branch cuts, which is a topic addressed extensively in the literature [J. Phys. A 14, 1271 (1980); Phys. Lett. B 380, 376 (1996); Nucl. Phys. B461, 493 (1996); Phys. Rev. D 58, 056001 (1998); Phys. Rev. D 84, 073006 (2011); Phys. Rev. D 90, 074027 (2014); Phys. Rev. D 111, L031501 (2025)]. We consider the simultaneous application of a double dispersive bound as a proper way to take into account unitarity constraints within phenomenological analyses of hadronic form factors in the presence of subthreshold branch cuts. Accordingly, the standard $z$-expansion of hadronic form factors, commonly referred to as the Boyd-Grinstein-Lebed approach [Nucl. Phys. B461, 493 (1996); Phys. Rev. Lett. 74, 4603 (1995); Phys. Lett. B 353, 306 (1995); Phys. Rev. D 56, 6895 (1997)], is modified by including simultaneously the dispersive bounds related to the pair-production and to the subthreshold regions. For the latter one the effects of above-threshold poles are described through a simple resonance model and the possible choices of the outer function outside the pair-production region are discussed. A detailed numerical analysis of the experimental data or lattice QCD results in the spacelike region for the charged kaon form factor is presented as a direct application of the procedure of double dispersive bound. The comparison with other methodologies present in literature and with the $z$-expansion based on the single, total dispersive bound clearly shows that the $z$-expansion including the double dispersive bound provides the most precise extrapolation at large momentum transfer as well as the most stable results with respect to the choice of the outer function outside the pair-production region.

We propose the implementation of two ingredients in the phenomenological applications of the unitary approach based on the $z$-expansion of hadronic form factors, commonly referred to as the Boyd-Grinstein-Lebed (BGL) $z$-expansion [Phys. Rev. Lett. 74, 4603 (1995).; Phys. Lett. B 353, 306 (1995).; Nucl. Phys. B461, 493 (1996).; [Phys. Rev. D 56, 6895 (1997).] . The first ingredient is the explicit addition of a unitarity filter applied to a given set of input data for the hadronic form factors. This further constraint is not usually taken into account in the phenomenological applications of the BGL $z$-expansion. We show that it follows from the equivalence between the BGL approach and the dispersion matrix (DM) method [Phys. Rev. D 104, 054502 (2021).], which also describes hadronic form factors in a completely model-independent and nonperturbative way. The second ingredient is represented by the introduction of suitable kernel functions in the evaluation of unitarity bounds, leading to the application of multiple dispersive bounds to hadronic form factors, whenever data and/or (non)perturbative techniques allow to do so. This idea may be useful for the investigation of many physical processes, from the analysis of the electromagnetic form factors of mesons and baryons to the study of weak semileptonic decays of hadrons. An explicit numerical application will be presented in the companion paper [Phys. Rev. D 113, 074018 (2026).], where the effects of subthreshold branch-cuts are analyzed.

Understanding physical phenomena at the intersection of quantum mechanics and general relativity remains a major challenge in modern physics. While various experimental approaches have been proposed to probe quantum systems in curved spacetime, most focus on the Newtonian regime, leaving post-Newtonian effects such as frame dragging largely unexplored. In this study, we propose and theoretically analyze an experimental scheme to investigate how post-Newtonian gravity affects quantum systems. We consider two setups: (i) a quantum clock interferometry setup designed to detect the gravitational field of a rotating mass, and (ii) a scheme exploring whether such effects could be used to generate gravity-induced entanglement. Due to the symmetry of the configuration, the proposed setup is insensitive to Newtonian gravitational contributions but remains sensitive to the frame-dragging effect. Furthermore, our scheme allows for testing whether the observed gravity-induced entanglement is consistent with the quantum equivalence principle. While the predicted effects appear too small to detect with current technology, our scheme offers a starting point for future experiments probing post-Newtonian quantum gravitational effects.

We investigate the relation between the one–dimensional free particle and the harmonic oscillator from a unified viewpoint based on projective geometry, Cayley transformations, and the Schwarzian derivative. Treating time as a projective coordinate on ${\mathbb{RP}}^1$ clarifies the $SL(2,\mathbb{R})\cong Sp(2,\mathbb{R})$ conformal sector of the Schrödinger-Jacobi symmetry and provides a common framework for two seemingly different correspondences: the Cayley-Niederer (lens) map between the time-dependent Schrödinger equations and the conformal bridge transformation relating the stationary problems. We formulate these relations as canonical transformations on the extended phase space and as their metaplectic lifts, identifying the quantum Cayley map with the Bargmann transform. General time reparametrizations induce oscillator–type terms governed universally by the Schwarzian cocycle, connecting the present construction to broader appearances of Schwarzian dynamics.

We show that, for any $d\ge 3$, the one-loop graviton path integral on $S^2\times S^{d-1}$ factorizes into bulk and edge parts. The bulk equals the thermal partition function of an ideal graviton gas in the Lorentzian Nariai geometry. The edge factor is the inverse of the path integral over two identical copies, each containing one shift-symmetric vector and three shift-symmetric scalars on $S^{d-1}$. Unlike the round $S^{d+1}$ case, all scalars are massless, indicating that graviton edge partition functions probe beyond the horizon’s intrinsic geometry—in contrast to $p$-form gauge theories. In the course of this work, we obtain a compact formula for the one-loop Euclidean graviton path integral on any $\mathrm{\Lambda }>0$ Einstein manifold.

One-loop $S^{d+1}$ path integrals were shown to factorize into two parts: a bulk thermal ideal gas partition function in a $d{S}_{d+1}$ static patch and an edge partition function associated with degrees of freedom living on $S^{d-1}$. Here, we analyze the $\mathfrak{so}(d)$ structure of the edge partition functions for massive and massless totally symmetric tensors of arbitrary rank in any $d\ge 3$. For linearized Einstein gravity on $S^{d+1}$, we find that the edge partition function receives contributions from shift-symmetric vector and scalar fields on $S^{d-1}$, suggesting a possible interpretation in terms of an embedded $S^{d-1}$ brane.

This article investigates the possibility that Hawking-like quanta emitted by a moving mirror can be purified by late-time vacuum fluctuations, as proposed in Hotta, Schützhold and Unruh [Phys. Rev. D 91, 124060 (2015)]. Our motivation originates from recent discussions in Wald [Phys. Rev. D 100, 065019 (2019)] and Osawa et al. [Phys. Rev. D 110, 025023 (2024)] on whether vacuum purification necessarily entails a prohibitively large (indirect) energy cost, and our goal is to help clarify this issue. We identify the aspects of the mirror trajectory that determine the partners of Hawking quanta, as well as those that govern the energy carried to future null infinity. This allows us to highlight a fundamental disconnection within quantum field theory between the fluxes of quantum information (or purification) and energy. Throughout, we focus on quantities such as local correlation functions and energy fluxes, thereby avoiding reliance on a particle-based interpretation. Finally, we introduce an analytic mirror trajectory that produces Hawking radiation with an adiabatically varying temperature, mimicking the emission from an evaporating black hole. Our analysis identifies constraints on the mirror trajectory under which vacuum purification remains compatible with a prescribed energy budget, and we discuss the lessons that may be drawn from this model for realistic evaporating black holes.

Out-of-time ordered correlators have been extensively studied in recent years in a wide variety of systems. In this paper, the formalism for calculating out-of-time ordered correlators is presented for $\eta$-pseudo Hermitian systems, incorporating the modified inner product structure. Two varieties of $\eta$-pseudo Hermitian models, namely Hatano-Nelson-type models and generalized Swanson models, have been considered. A number of polynomial potentials are analyzed by analytical and numerical methods. Similarities and differences with the relevant literature for Hermitian systems are pointed out along with the constraints the non-Hermitian nature of the system imposes on the results.

We study the absorption and scattering of massless scalar waves by Frolov black holes, a regular deformation of the Reissner-Nordström geometry. A null-geodesic analysis provides the photon-sphere radius and the critical impact parameters governing capture and glory scattering. Using a partial-wave approach, we compute total/partial absorption cross sections and differential scattering cross sections over a broad frequency range. When the absorption spectrum is rescaled by photon-sphere scales, the high-frequency oscillations exhibit a pronounced data collapse in the variables $\widehat{\sigma }={\sigma }_{\mathrm{abs}}/{\sigma }_{\mathrm{geo}}$ and $x=\omega /{\mathrm{\Omega }}_c$, highlighting photon-sphere control of the absorption fine structure. We clarify the parameter dependence under the horizon-radius normalization and relate the apparent trends to the variation of the dimensionless mass across parameter space. Finally, comparing Frolov, Reissner-Nordström, and Hayward black holes with matched critical or glory impact parameters, we find that their absorption and scattering patterns can become remarkably close, indicating that in the intermediate-to-high frequency regime the dominant signatures are largely governed by the unstable photon orbit, while core effects enter as subleading corrections.

We study the structural and dynamical consequences of introducing a distributional density profile inside a neutron star, representing a massless, topological shell located at an arbitrary radius. We incorporate this effect into the structure of neutron stars and construct an equilibrium sequence for several realistic equations of state. Radial stability is examined through the Sturm-Liouville formulation of the $\ell =0$ perturbation equation, supplemented with a jump condition and imprinting distinct features on the fundamental $f$-mode spectrum. We find strong, nonmonotonic variations in the mode frequency relative to standard no-shell models. Using first-principles scaling relations, we estimate various gravitational-wave observables such as the damping time, quality factor, luminosity, and characteristic strain. These observables are then compared with the sensitivity of Advanced LIGO and third-generation detectors such as the Einstein Telescope and Cosmic Explorer. Our results demonstrate that internal topological shells can leave potentially observable signatures in the oscillation and gravitational-wave properties of neutron stars.

The recently proposed first-order viscous relativistic hydrodynamics formulation by Bemfica, Disconzi, Noronha, and Kovtun (commonly known as the BDNK formulation) has been shown to be causal, stable, strongly hyperbolic, and thus locally well posed. It is now a viable new option for modeling out-of-equilibrium effects in fluids, and has attracted wide attention in its potential applications to astrophysical systems. In this work, we present the first nonlinear numerical simulation of spherically symmetric neutron stars using the BDNK formulation under the Cowling approximation. Using a simplified equation of state, we show that stable evolutions can be constructed within a restricted parameter space up to the simulation time we explored. From these simulations, we analyze the frequency content of the quasinormal modes and the decay rate of the fundamental mode. This analysis serves as a first step toward constructing a fully consistent model of neutron stars using the BDNK formulation.

We compute relativistic Lindblad torques for circular, equatorial extreme-mass-ratio inspirals (EMRIs) embedded in relativistic thin accretion discs, including spinning black hole configurations. We find that relativistic effects can amplify the magnitude of these torques by orders of magnitude in the strong-field regime, and that the torque can even reverse direction as the EMRI approaches the innermost stable circular orbit (ISCO). However, we show that the location of this reversal is highly spin-dependent, shifting progressively closer to the ISCO, where gravitational-wave emission completely dominates the inspiral, as the spin of the central black hole increases. Spin also modifies the radial dependence of the Lindblad torques. We investigate whether Lindblad torques can be approximated by parametrized power laws of the form $T_{\mathrm{LR}}=A{(r_s/10M)}^{n_r}$ (or combinations thereof), and find significant spin- and disc-dependent variations in the slope parameter $n_r$. For instance, for spin $a/M=0.9$, we find $n_r=3.6$ in the strong-field regime, compared to the Newtonian value of $n_r=4.5$. Given current forecasts of parameter recovery for “golden,” loud EMRIs in accretion discs ($\mathrm{\Delta }{n}_r\sim 0.5$), we predict LISA could distinguish between different disc configurations through their relativistic Lindblad torque signatures, providing the first direct probe of the midplane structure of the inner region of accretion discs, which is inaccessible to electromagnetic observations.

We study Weyl-invariant purely gravitational theories formulated within the Einstein-Cartan framework. In the Einstein-frame description, these models are dynamically equivalent to standard general relativity coupled to an axionlike pseudoscalar degree of freedom, which naturally drives a period of cosmic inflation. Without committing to a specific microscopic mechanism for reheating, we demonstrate that the postinflationary reheating dynamics play a crucial role in shaping the inflationary predictions. In particular, we show that assumptions about the reheating temperature and the equation-of-state parameter can significantly affect the predicted values of inflationary observables, highlighting the necessity of consistently incorporating reheating effects into the phenomenological analysis of inflationary models.

We introduce the first-order noncommutative (NC) corrections to the general nonlinear electrodynamics (NLE) Lagrangian depending on two electromagnetic invariants. The NC deformation of Einstein-NLE theory is implemented using the ${\partial }_t\wedge {\partial }_{\phi }$ Drinfel’d twist and the NC effects are encoded in the matter sector through the Seiberg-Witten map. The resulting equations of motion reflect two distinct sources of nonlinearity in this framework; one arising from replacing Maxwell’s electrodynamics with its nonlinear modifications and another from the NC deformations. Assuming a general form of static, spherically symmetric dyonic black hole as a seed solution in the commutative limit, we solve the equations of motion perturbatively to the first order in the NC parameter $a$. Finally, we evaluate the obtained corrections to the metric tensor and gauge potential for several prominent NLE theories.

This paper proposes a new avenue for understanding the cosmological singularity. The standard cosmological model contains a generic initial singularity usually referred to as the big bang. Herein, we present a novel idea to extend the description of our Universe beyond this limit. The proposal relies on rewriting physics in a purely Riemannian, i.e., locally Euclidean, four-dimensional space and the emergence of Lorentzian patches owing to the interaction of all matter fields to a clock field that is responsible for a signature change. If our Universe is contained within one of these patches, the initial singularity is replaced by a smooth boundary on which the signature of the physical metric flips. In this paper, we first define the model and draw the necessary conditions on its arbitrary functions for solutions to exist. Next, we prove the existence of solutions that lead to an emergent universe with a primordial (almost) de Sitter phase. To finish, we discuss the consequences of this construction for the universe on scales much larger than our observable Universe: a large “Euclidean sea” in which Lorentzian islands locally emerge and host an expanding universe potentially similar to ours. While speculative, this scenario has specific features that can be tested, and the present paper sets the basis for further phenomenological investigations.