Peer Revenue Fully funded

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics General Relativity and Quantum Cosmology

gr-qc Watch General Relativity and Quantum Cosmology

Thursday 13 August

General Relativity and Quantum Cosmology

Cosmological Vacuum Decays from Schwinger-Keldysh Formalism

Zi-Yan Yuwen

In this work, we take a first step to a stochastic real-time description of the vacuum phase transitions in a radiation-dominated FLRW universe from the Schwinger-Keldysh formalism. By splitting the phase transition field $\Phi$ into the long-wavelength mode $\phi$ and the short-wavelength mode $\sigma$ and tracing over the latter as the environment, we obtain a classical Langevin-type equation-of-motion for the long-wavelength field $\phi$, where the quantum effects are encoded in a non-Markov memory kernel and a non-Gaussian noise. As a phenomenological example, we start from a polynomial potential and a thermalized initial state, and study the structure of the memory kernel as well as the correlation functions of the noise term. Further extensions remain possible to describe the whole dynamics of cosmological first-order phase transitions via numerical simulations.
Read the full abstract

General Relativity and Quantum Cosmology · Cross-listed from hep-ph

Scalar induced gravitational waves as probes of dark QCD

Wan-Zhe Feng, Ao Li and Jing-Zhi Zhou

We investigate scalar induced gravitational waves (SIGWs) as probes of a dark QCD crossover. Motivated by twin Higgs and asymmetric twin baryon dark matter scenarios, we consider a dark QCD sector with a confinement scale approximately 5.5 times the Standard Model (SM) QCD scale. We construct the effective energy and entropy degrees of freedom for the SM supplemented by dark QCD sectors containing either three light dark quark flavors or all six dark quark flavors. The resulting equation of state parameter and sound speed are then used to solve the first-order scalar perturbations and the second-order SIGWs through the SM and dark QCD crossover epochs. For a monochromatic primordial curvature power spectrum, we first demonstrate that the realistic SM thermal history modifies the SIGW spectrum relative to the idealized radiation-dominated case. We then show that a dark QCD crossover generates an additional frequency-shifted distortion when the enhanced scalar mode reenters the horizon near the dark confinement scale. This distinctive feature can therefore serve as a characteristic signature of the dark QCD sector. Our results demonstrate that SIGWs provide a complementary cosmological probe of hidden confining sectors, with characteristic spectral features shifted to higher frequencies relative to the SM QCD imprint. The analysis developed in this work can also be extended to other well-motivated theories containing different dark confining sectors.
Read the full abstract

Wednesday 12 August

General Relativity and Quantum Cosmology

Regular Black Holes from Collapsing Dust in a Dark Energy Background

Qazi Abdul Ghafoor

The central singularity in gravitational collapse represents a fundamental breakdown of classical general relativity, yet its resolution remains an open challenge. While conventional regular black hole models invoke exotic matter or nonlinear electrodynamics, the physical origin of such regularization mechanisms remains obscure. In this work, we demonstrate that a radially varying interaction between dust and dark energy can naturally resolve the central singularity. We systematically investigate three cases: no interaction, constant interaction, and radially varying interaction. Only when the interaction grows sufficiently toward the center can the divergent behavior of the density and the central mass contribution simultaneously be eliminated near the center. This yields a mass function scales as $M \sim \chi^3$, a finite Kretschmann scalar ($\lim_{\chi \to 0} K < \infty$), and a de Sitter-like core for the physical regime $w \leq -1$ (with $w=-1$ corresponding to pure de Sitter core). At the center, the resulting configuration satisfies the null, weak, and dominant energy conditions, while the strong energy condition is violated. Unlike charge-based models, our interaction parameter $\alpha(t)$ stabilizes at a non-zero value after the collapse, allowing the regular core to persist in the late-time configuration. This provides a physically motivated alternative to conventional regular black hole models, grounded in the modern cosmological understanding of dark energy rather than exotic fields or charges.
Read the full abstract

General Relativity and Quantum Cosmology · Cross-listed from hep-ph

Massive cold hybrid stars in a modified Polyakov-Nambu-Jona-Lasinio model

Sk Md Adil Imam, Pedro Costa, Mariana Dutra et al. (+3 more)

We propose a modified Polyakov-loop Nambu–Jona-Lasinio (mPNJL) model in which the Polyakov potential is given by an explicit dependence on the quark chemical potential, allowing it to remain finite at zero temperature and thus to describe the confinement-deconfinement transition in cold dense matter. Combining this modified quark sector with hadronic equations of state via a Maxwell construction, we find that, depending on the model parameters, the equation of state can exhibit either two phase transitions, from hadronic matter to confined quark matter and subsequently to deconfined quark matter, or a single transition directly from hadronic to deconfined quark matter or from hadronic to confined quark matter. Stable massive cold hybrid stars with only confined and/or deconfined quark phase are obtained. We systematically examine how the parameters of the modified Polyakov potential and the quark vector interactions control the location of these transitions, and find that repulsive vector interactions are essential to obtain a stable quark core. Hybrid stars with confined and/or a deconfined core can reach maximum masses above $2M_\odot$, provided a sufficiently stiff hadronic equation of state is used at low density. In the core of the maximum-mass configurations, the speed of sound shows variations at finite baryon densities, with c$_s^2(\mu)$ departing from the asymptotic conformal value c$_s^2$ = 1/3 in confined core stars. These variations serve as a diagnostic of the equation-of-state stiffness while remaining fully consistent with causality and thermodynamic stability. This work establishes the qualitative role of each model parameter in shaping hybrid-star structure.
Read the full abstract

All authors Sk Md Adil Imam, Pedro Costa, Mariana Dutra, Odilon Lourenço, Renan Pereira, Constança Providência

General Relativity and Quantum Cosmology

Horizon-regular cross-focusing and inner-horizon obstructions in spherical f(R) gravity

Maickol Muñoz-Palma, Francisco S. N. Lobo, Jean Báez Cuevas et al. (+1 more)

We formulate a horizon-regular double-null criterion for regular inner marginal horizons in spherically symmetric metric $f(R)$ gravity. Using normalized outgoing and ingoing radial null vectors $\ell^\mu$ and $n^\mu$, with $n^\mu$ affinely parametrized, we derive an exact evolution law for the area-weighted outgoing expansion $r^2\theta_{(\ell)}$. Its source is controlled by the scalaron $F\equiv f_R>0$ and by a mixed quantity $\mathcal{P}_{\ell n}$ containing matter, scalaron derivatives, and the curvature potential. If $\mathcal{P}_{\ell n}\leq F/r^2$ along a regular ingoing null segment issuing from a nondegenerate future outer marginal sphere, then the outgoing expansion cannot return to zero, and no second regular marginal sphere of the same family can occur on that generator. Conversely, a nondegenerate future inner marginal sphere requires the reverse inequality, so an outer–inner pair necessarily entails a source reversal and an exact integral balance. No trapped-region assumption is required. In the static limit, the criterion reduces to a horizon-regular relation involving the radial derivative of the metric function and remains valid in the degenerate case under the stated regularity conditions. It reproduces the Reissner–Nordström classification and is verified in an exact charged, nonconstant-curvature $f(R)$ black hole with a nonconstant scalaron. The resulting Cauchy-horizon statement is conditional and applies only when the candidate boundary is also a regular nondegenerate future inner marginal horizon.
Read the full abstract

All authors Maickol Muñoz-Palma, Francisco S. N. Lobo, Jean Báez Cuevas, Francisco Tello-Ortiz

General Relativity and Quantum Cosmology

Quasitopological Gravity with Matter: Modified Double-Copy Approach

Valeri P. Frolov

We extend the recently proposed modified double-copy formalism to quasitopological gravity (QTG) coupled to matter. For spherically symmetric configurations, the QTG field equations in $D-$dimensional curved spacetime with a broad class of matter sources are mapped to equations for an auxiliary nonlinear gauge field in a flat $(D+1)$-dimensional spacetime. The nonlinear electrodynamics governing this auxiliary field is determined entirely by the generating function $h(p)$ that specifies the QTG model, while the corresponding current is determined by the matter stress-energy tensor. Restricting the auxiliary solution to a $D$-dimensional hyperplane and applying the modified double-copy prescription yields the Kerr–Schild metric solving the QTG equations. We show that Maxwell and nonlinear electrodynamics, as well as a broad class of spherically symmetric Yang–Mills fields, provide physical matter sources compatible with this construction. In the absence of null-matter fluxes, the corresponding solutions possess an additional Killing vector. This means that they satisfy a generalized Birkhoff theorem, whereas null charged currents naturally generate Vaidya-type solutions. In the Einstein limit, $h(p)=p$, the auxiliary nonlinear electrodynamics reduces to Maxwell theory.
Read the full abstract

General Relativity and Quantum Cosmology

Two-scale magnetically charged regular black holes from nonlinear electrodynamics and a T-duality-inspired zero-point length

Ali Ovgun, Reggie C. Pantig and Joel Saavedra

We construct a two-scale, static, spherically symmetric regular black hole in Einstein gravity sourced by magnetic nonlinear electrodynamics (NED). The zero-point length $\ell$ regularizes the mass and charge profiles, whereas $q$ is the asymptotic magnetic charge. The geometry approaches Reissner-Nordström at large radius, reduces to the neutral zero-point-length solution for $q=0$, and coincides geometrically with the Ayón-Beato-García solution for $\ell=|q|$. For $q\neq0$, inverse reconstruction gives a single-valued magnetic Lagrangian with Maxwell asymptotics and a finite strong-field limit. The center is regular and is de Sitter, locally Minkowski, or anti-de Sitter according to the sign of $2M\ell-q^2$; the weak energy condition holds globally if and only if $3M\ell\geq2q^2$. We derive the extremality curve, the exact heat capacity, and homogeneous horizon-variation and Smarr identities while retaining the Wald area entropy. We also prove that every charged black hole in this family has a nondegenerate extraordinary NED optical metric throughout the domain of outer communication. The associated capture shadow is selected by the global minimum of the optical impact-parameter function and generally differs from the background-geodesic shadow. Weak-field calculations yield the periapsis, bending, time-delay, and redshift corrections; in particular, $\ell$ first appears beyond the standard first-post-Newtonian parameters. Finally, for minimally coupled test radiation in a cold transparent plasma, we obtain exact parametric shadow relations for power-law density profiles and combine Hamiltonian ray tracing with a Novikov-Thorne disk model. A separate extraordinary NED-plasma continuation is displayed only as a phenomenological prescription because a material plasma breaks the conformal ambiguity of the vacuum characteristic metric.
Read the full abstract

General Relativity and Quantum Cosmology

Probing the Distribution and Nature of Dark Matter Around Supermassive Black Holes from EMRI and IMRI Gravitational Waves

Jared Fier, Farah Abdelshahed, Lilly Kowalczyk et al. (+2 more)

The distribution of dark matter in the immediate vicinity of supermassive black holes remains poorly understood despite its importance for galaxy evolution and precision tests of gravity. Future space-based gravitational-wave observatories offer a unique opportunity to probe this relativistic regime through the inspiral of compact objects into supermassive black holes. Building upon our previously constructed exact Einstein-cloud solutions within General Relativity, we develop a fully relativistic framework to investigate the gravitational-wave signatures of collisionless dark-matter halos surrounding supermassive black holes. The framework provides a unified treatment of orbital dynamics, adiabatic inspiral, accumulated gravitational-wave cycles, waveform phase evolution, signal-to-noise ratio, and waveform mismatch for extreme- and intermediate-mass-ratio inspirals (EMRIs/IMRIs). As a representative application, we specialize the formalism to Model I. We show that relativistic dark-matter halos can produce measurable modifications to the accumulated gravitational-wave cycles, waveform phase, signal-to-noise ratio, and waveform mismatch, leading to consistent conclusions regarding detectability. By separating conservative modifications of the spacetime geometry from dissipative effects due to relativistic dynamical friction, we find that the observable signatures are dominated by the former, while the latter remains negligible for the halo models considered. These results demonstrate that future gravitational-wave observations by LISA and similar missions may provide a powerful probe of the relativistic distribution and physical nature of dark matter around supermassive black holes.
Read the full abstract

All authors Jared Fier, Farah Abdelshahed, Lilly Kowalczyk, Zhengfei Lyu, Anzhong Wang

General Relativity and Quantum Cosmology

Dymnikova Black Hole Tidal Forces

M. H. Macêdo, A. A. M. Silva and R. R. Landim

In this work we investigate the tidal properties of the Dymnikova regular black hole and their ef fects on massive particles in radial free-fall. Starting from Dymnikova static, spherically symmetric solution, we derive the equations governing timelike radial geodesics and construct an orthonormal tetrad adapted to a free-falling observer. We then obtain the radial and angular components of the tidal tensor and analyze their dependence on the black hole mass and the characteristic length scale of the de Sitter core. At large radial distances, tidal forces recover Schwarzschild behavior, whereas near the regular center, both components remain finite, reflecting the non-singular nature of the spacetime. We show that the radial and angular tidal forces vanish and change sign at characteris tic radii inside the event horizon, indicating transitions between stretching and compression regimes. A particle released from rest outside the event horizon reaches a turnaround point located inside the Cauchy horizon, rather than reaching the regular center. We also solve the geodesic deviation equations for two sets of initial conditions and examine the evolution of the radial and transverse components of the deviation vector. Although the solutions asymptotically reproduce Schwarzschild behavior, they differ significantly in the inner region: the deviation vector components remain finite up to the turnaround point, whereas the corresponding radial component in the Schwarzschild case diverges at the singularity. These results demonstrate how the de Sitter core regularizes the tidal dynamics of extended falling bodies.
Read the full abstract

General Relativity and Quantum Cosmology

Thermal false vacuum decay near black holes is aspherical

D. S. Gorbunov, D. G. Levkov and V. E. Maslov

We study decay of a scalar field false vacuum near a (3+1)-dimensional Schwarzschild black hole equilibrated at Hawking temperature with the environment. Our scalar field model has negative quartic self-coupling and thereby resembles Higgs sector of the Standard Model in the large-field limit. We demonstrate that if the black hole is not too small, the false vacuum in this model decays aspherically with regard to the black hole center: via formation of expanding true vacuum bubbles emerging on the outer side of the event horizon. More specifically, we identify three regimes of the decay. For the largest and coldest black holes, the main mechanism is quantum tunneling described by an infinitesimally thin bounce sitting at some point of the horizon. In the intermediate-mass regime, the vacuum is destroyed by thermal fluctuations creating aspherical critical bubbles in the horizon vicinity. Finally, near the smallest black holes thermal fluctuations still guide the decay but the dominant critical bubble is spherically symmetric and covers the entire horizon.
Read the full abstract

General Relativity and Quantum Cosmology · Cross-listed from hep-th

A Lapse in the Cosmological Constant Problem with Bulk Dynamics

Justin Khoury, Benjamin Muntz and Antonio Padilla

We have previously proposed a new approach to the cosmological constant problem based on anisotropic scaling in a compact extra dimension. In the ultra-local $z=0$ limit, the interplay between a projectable lapse, foliation-preserving diffeomorphisms, and higher-form fluxes renders the gravitational field equations insensitive to radiative corrections to the matter vacuum energy. Here we extend this framework beyond the ultra-local limit by introducing $z=1$ deformations that restore dynamics along the compact direction. We show that vacuum-energy cancellation persists at the level of the background equations, while generic extrinsic-curvature couplings propagate an additional scalar ghost. A healthy quadratic spectrum selects the Fierz-Pauli relation between these couplings. This motivates a particularly simple realization in terms of five-dimensional Einstein gravity, a top-form flux, and a spacelike khoron scalar field that dynamically defines a preferred projectable foliation. In this covariant formulation, the global constraint arises from an auxiliary einbein on the space of khoron leaves, and constant shifts of the renormalized matter vacuum energy cancel algebraically from the intrinsic Einstein equations. Finally, allowing matter to propagate around the compact dimension generates finite, topology-sensitive Casimir contributions that are not automatically removed by the mechanism. Suppressing these contributions requires additional spectral conditions on the propagating bulk degrees of freedom.
Read the full abstract

General Relativity and Quantum Cosmology

On the Stability of the Euler-Poisson Dark-Fluid Model

Balázs Endre Szigeti, Imre Ferenc Barna and Gergely Gábor Barnaföldi

We present a stability analysis of a dark-fluid model described as a non-relativistic, rotating, non-viscous, self-gravitating fluid. We assume spherical symmetry and model the matter by a polytropic equation of state. The resulting coupled nonlinear partial differential equation system is solved using a self-similar ansatz known from the Guderley-Landau-Stanyukovich problem. We find that three of the four Lyapunov exponents are negative, while only one is positive. This indicates one unstable direction and three contracting directions in phase space. The single positive exponent is relatively small, suggesting that the self-similar solution is only weakly unstable and remains dynamically robust over the investigated interval.
Read the full abstract

General Relativity and Quantum Cosmology

From a Sharp Thin-Shell Obstruction to a Smooth Positive-Density Initial-Data Embedding of a Virialized Halo in Lambda-FLRW Cosmology

Seokcheon Lee

Within classical general relativity, we compare a sharp timelike junction and a smooth finite-width spacelike initial-data embedding of a positive-excess virialized halo in a homogeneous Lambda-FLRW environment. On the ordinary branch, timelike Israel matching at the virial boundary produces a negative surface layer: a distributional representation of the environmental compensation omitted by the sharp construction. We replace this zero-width source by a finite-width, background-relative underdensity whose local rest-frame energy density remains positive. The resulting conformally flat, constant-mean-curvature ADM initial slice satisfies the Hamiltonian and momentum constraints, with the residuals converging under resolution refinement. At finite radius, its geometric and matter variables return to the local-effective FLRW data within the declared tolerances: the constructed slice contains no residual distributional layer and satisfies the reconstructed weak, null, and dominant energy conditions. For radii beyond the numerical endpoint, the exterior is defined by the exact analytic local-effective FLRW solution. The GCT framework supplies the global motivation clock interpretation, while the present calculations are local-effective classical-GR calculations with the bound-sector constants c0 and G0 held fixed: no radial GCT lapse or constant interpolation is constructed.
Read the full abstract

General Relativity and Quantum Cosmology

Phase-plane formulation of weak gravitational deflection in static spherical spacetimes

Reggie C. Pantig and Ali Övgün

This paper develops a phase-plane formulation of gravitational light deflection by static and spherically symmetric black holes, with Schwarzschild spacetime as the principal case. Instead of perturbing the null trajectory and locating the displaced outgoing asymptote, we represent the orbit through an amplitude and an intrinsic phase. The bending angle then follows from the excess physical azimuth accumulated while the intrinsic phase advances between two fixed asymptotic endpoints. For Schwarzschild spacetime, the exact radial first integral reduces the amplitude evolution to a cubic algebraic relation. Its physical branch generates the local phase factor through a single inverse algebraic map. Lagrange inversion then yields an explicit all-order weak-deflection coefficient formula in powers of the invariant ratio \(M/b\). Each coefficient separates into an algebraic phase contribution and a universal trigonometric moment, which explains the alternating rational and \(\pi\)-dependent structure of the Schwarzschild series. Independent comparison with the exact radial scattering integral and conventional orbit perturbation reproduces the standard weak-bending coefficients. The same phase framework extends to general static spherical geometries, while the Schwarzschild cubic represents an especially simple member of a broader algebraic class. The branch singularity of the phase map also coincides with the critical photon orbit and governs the convergence of the weak-deflection expansion.
Read the full abstract

General Relativity and Quantum Cosmology

Rainbow McVittie Horizons in an Expanding Universe

Amani Ashour and Ahmed Farag Ali

We derive the Friedmann dynamics and apparent-horizon thermodynamics of a spatially flat McVittie spacetime in Gravity's Rainbow and construct a consistent non-accreting perfect-fluid sector with an effective rainbow Hubble rate. The Einstein equations, trapping horizon, surface gravity, Misner–Sharp energy, unified first law, and Clausius relation form a closed thermodynamic system reproducing the Friedmann dynamics. We then introduce a low-energy rainbow deformation and constrain it using 32 cosmic-chronometer measurements and 1580 Pantheon+ light curves with the full covariance matrix. Combined with the Planck matter-density prior, the fit gives $H_0=68.75\pm2.63~\mathrm{km\,s^{-1}\,Mpc^{-1}}$, $\Omega_m=0.3157\pm0.0070$, and $\epsilon=0.0106^{+0.0234}_{-0.0231}$. The resulting constraints establish the observational viability of small late-time rainbow corrections and place the general-relativistic limit within the preferred parameter region.
Read the full abstract

General Relativity and Quantum Cosmology · Cross-listed from cond-mat.mes-hall

Wormhole Geometry from a Magnetic Vortex

Dušan \DJ or\dj ević, Fabián Molina and Vladimir Juričić

Strong coupling to a magnetic texture makes an electron propagate through an emergent curved space. We show that an elementary vortex realizes the exterior spatial geometry of an Ellis wormhole: an ultrastatic throat with radius fixed by the topological charge and Hund exchange, cut off at short distances by the microscopic core. Two separable signatures follow directly: the electron deflection collapses onto a single Ellis curve governed by the vortex winding and exchange coupling, while the spin Berry phase produces a half-flux Aharonov–Bohm response switched on and off by winding parity. The same metric can be emulated in a designer honeycomb lattice, where the valley-symmetrized wave-packet response follows the predicted exterior geodesic. These signatures are accessible through real-space electron deflection and scattering, providing experimentally distinct probes of the emergent geometry and Berry flux. The magnetic vortex thus turns a topological defect into a tunable curved-space lens for electrons in quantum materials and designer lattices.
Read the full abstract

General Relativity and Quantum Cosmology · Cross-listed from hep-th

A sharp bound on spacetime distance from quantum entanglement

Zhi-Wei Wang, Arshid Shabir, Mir Faizal et al. (+1 more)

Ryu-Takayanagi established how boundary entanglement encodes bulk area. We provide the metric counterpart: boundary mutual information imposes a rigorous lower bound on bulk geodesic separation that diverges logarithmically as correlations vanish. A multiscale iteration promotes this local inequality to a global obstruction to bulk connectivity. For parallel strips in AdS$_5$/CFT$_4$, the bound necessitates a quantum resolution of the classical mutual-information transition and fixes the asymptotic growth of geodesic distance.
Read the full abstract

All authors Zhi-Wei Wang, Arshid Shabir, Mir Faizal, Samuel L. Braunstein

General Relativity and Quantum Cosmology · Cross-listed from hep-th

Aspects of Carrollian field theory from holography

Hare Krishna and Vaishnavi Patil

We study holography for three-dimensional asymptotically flat spacetimes in which the bulk gravitational dynamics is conjectured to be dual to a two-dimensional Carrollian (equivalently BMS) conformal field theory. Such theories are known to arise as ultrarelativistic ($c\rightarrow0$) contractions of relativistic 2d conformal field theories. Under this contraction, the Virasoro algebra becomes the conformal Carrollian algebra and the Brown-Henneaux central charges become $c_L=0$, $c_M=\frac{3}{G}$. In this article, we recover these central charges directly from holography. We first construct the holographic quasilocal stress tensor for asymptotically flat spacetimes carrying Bondi mass and angular momentum. Under BMS$_3$ transformations, the stress tensor acquires an inhomogeneous term, the “BMS Schwarzian", and extracting the central charges from it reproduces the algebraic result exactly. We then obtain the action for the boundary BMS Schwarzian modes. Finally, we show that the holographic stress-tensor correlators satisfy the expected Ward identity, while stress-tensor conservation obeys flux-balance laws.
Read the full abstract

General Relativity and Quantum Cosmology

A Covariant Distributional Approach for Junctions in Torsional Locally Rotationally Symmetric Class II Spacetimes

Ujjwal Agarwal and Sante Carloni

A rigorous framework for consistent study of junctions in a coordinate independent manner is presented. This is achieved by extending a theory of distributions in curved spacetimes with torsion and combining it with covariant formalism. In this way, one can derive general conditions on the differentiability of the joined manifold. Given a specific theory of gravity, in particular the Einstein-Cartan-Sciama-Kibble one, we evaluate the conditions for obtaining a smooth junction. These conditions can be successfully applied independently of the choice of coordinates used to describe the metric, thereby, evading the drawbacks of coordinate dependent Israel-Darmois framework.
Read the full abstract

General Relativity and Quantum Cosmology

Finding black hole spins efficiently during a numerical binary evolution

Himanshu Chaudhary, Rob Owen, Mark A. Scheel et al. (+1 more)

The dynamics of a binary black hole system depend on its masses and spins. For a binary at finite separation, it is not possible to define these quantities in an unambiguous way; however, there are several reasonable definitions that reduce to the expected values in the limit of infinite separation. Approximate Killing vector (AKV) spin is one of the spin definitions used in the numerical relativity code SpEC. AKV spin requires finding approximate Killing vectors on an apparent horizon, which reduces to a generalized eigenvalue problem of size $\mathcal{O}(L^2)$, and a direct solve has time complexity $\mathcal{O}(L^6)$, where $L$ is the highest spherical harmonic mode used to represent the apparent horizon. This scaling means that the cost of computing AKV spins increases rapidly as we simulate systems at higher resolutions, especially those with high spin or mass ratios. We describe a new algorithm for computing AKV spins that is much faster than the current algorithm.
Read the full abstract

All authors Himanshu Chaudhary, Rob Owen, Mark A. Scheel, Saul A. Teukolsky

General Relativity and Quantum Cosmology · Cross-listed from hep-th

On divergences in a four-derivative scalar field theory

Maegan Anderson, Sam Bateman, Franz Herzog et al. (+1 more)

We perform a detailed diagrammatic analysis of the renormalisation of a family of asymptotically free, shift-symmetric four-derivative scalar field theories introduced by Holdom in arXiv:2303.06723 and arXiv:2402.09223. We extend the renormalisation of the theory from one to three loops using both an $R^*$ method and an asymptotic expansion in momenta. We prove that the Euclidean correlators (or off-shell amplitudes) are IR finite, to all orders in perturbation theory, and derive a non-renormalisation theorem describing the all-order structure of the renormalisation constants. In particular, a purely cubic interaction is RG invariant and a perfect square Lagrangian density is preserved under renormalisation. The latter result is due to a Ward identity in a related $\textit{ gravitational}$ theory $-$ the conformally flat limit of quadratic gravity (CFQG). We show that the beta function for the perfect square theory maps exactly to that of an $O(2)$-symmetric, two-derivative, massless $\phi^4$ theory at negative coupling. We verify this relationship explicitly up to three loops and thus determine the beta function and anomalous dimension for both the perfect square theory and CFQG to six loops.
Read the full abstract

All authors Maegan Anderson, Sam Bateman, Franz Herzog, Neil Turok

General Relativity and Quantum Cosmology · Cross-listed from astro-ph.IM

LIGO Detector Characterization in the Second and Third Parts of the Fourth Observing Run

J. Glanzer, A. F. Helmling-Cornell, A. Calafat et al. (+244 more)

LIGO detector characterization efforts enabled the confident detection of gravitational waves from hundreds of compact binary coalescences during the fourth observing run. Reliable production of high quality detector data and rapid noise mitigation efforts allow the extraction of the most in-depth knowledge of gravitational wave sources and their progenitors. In this paper we describe LIGO detector characterization activities during the second and third parts of O4-O4b and O4c. We summarize changes in detector configuration and performance at the LIGO Hanford and LIGO Livingston Observatories between the end of the first part of O4a and the end of O4c, including upgrades made during the commissioning break preceding O4b and during repairs performed in O4c. We describe instrumental investigations carried out at both sites designed to understand and subsequently mitigate the effect on detector sensitivity of transient glitches, narrowband spectral lines, and vibration-driven noise, among other data quality concerns. We then review the tools and procedures used to validate gravitational wave candidates and the data quality products thus supplied to searches for gravitational waves from compact binary coalescences and unmodeled transients, continuous gravitational waves, and the stochastic gravitational wave background. The efforts of the detector characterization group are essential for maintaining and improving the sensitivity and reliability of the LIGO detectors especially as observing runs lengthen and more events are detected. We conclude with prospects for LIGO detector characterization activities in future observing runs.
Read the full abstract

All authors J. Glanzer, A. F. Helmling-Cornell, A. Calafat, S. R. Callos, E. Capote, A. Effler, T. A. Ferreira, E. Goetz, A. M. Knee, J. R. Mérou, D. Malakar, B. Mannix, D. Nandi, K. Pham, R. M. S. Schofield, P. Sharma, Z. Yarbrough, N. Arnaud, B. K. Berger, K. Burtnyk, C. M. Compton, G. Connolly, D. Davis, F. Di Renzo, G. Grant, J. C. Martins, G. Mo, A. Neunzert, L. K. Nuttall, J. Oberling, J. R. Olson, S. Soni, M. Trevor, R. Abbott, I. Abouelfettouh, R. X. Adhikari, A. Ahuja, S. Álvarez-López, A. Ananyeva, S. Appert, S. K. Apple, K. Arai, J. Areeda, N. Aritomi, S. M. Aston, M. Ball, S. W. Ballmer, D. Barker, L. Barsotti, J. Betzwieser, Z. S. Bhalla, D. Bhattacharjee, G. Billingsley, S. Biscans, C. D. Blair, N. Bode, E. Bonilla, V. Bossilkov, A. Branch, A. F. Brooks, D. D. Brown, R. Bruntz, J. Bryant, C. Cahillane, H. Cao, C. Chatterjee, N. Christensen, F. Clara, J. Collins, R. Cottingham, D. C. Coyne, R. Crouch, J. Csizmazia, A. Cumming, L. P. Dartez, N. Demos, E. Dohmen, K. L. Dooley, J. C. Driggers, S. E. Dwyer, A. Ejlli, T. Etzel, M. Evans, J. Feicht, R. Frey, W. Frischhertz, P. Fritschel, V. V. Frolov, M. Fuentes-Garcia, P. Fulda, M. Fyffe, D. Ganapathy, B. Gateley, T. Gayer, J. A. Giaime, K. D. Giardina, R. Goetz, G. Gonzalez, A. W. Goodwin-Jones, S. Gras, C. Gray, D. Griffith, H. Grote, T. Guidry, J. Gurs, E. D. Hall, J. Hanks, J. Hanson, M. C. Heintze, N. A. Holland, N.-T. Howard, D. Hoyland, H. Y. Huang, B. Hughey, Y. Inoue, A. L. James, A. Jamies, K. Jani, R. Jaume, A. Jennings, W. Jia, D. H. Jones, H. B. Kabagoz, S. Kandhasamy, S. Karat, S. Karki, M. Kasprzack, K. Kawabe, N. Kijbunchoo, P. J. King, J. S. Kissel, K. Komori, A. Kontos, R. Kumar, K. Kuns, M. Landry, B. Lantz, M. Laxen, K. Lee, M. Lesovsky, F. Llamas Villarreal, E. Lofquist-Fabris, M. Lormand, B. R. Lott, H. A. Loughlin, R. Macas, M. MacInnis, C. N. Makarem, G. L. Mansell, R. M. Martin, K. Mason, F. Matichard, N. Mavalvala, N. Maxwell, G. McCarrol, R. McCarthy, D. E. McClelland, S. McCormick, J. McIver, R. McNeil, T. McRae, F. Mera, E. L. Merilh, F. Meylahn, R. Mittleman, S. Mohan S, D. Moraru, G. Moreno, A. Mullavey, M. Nakano, T. J. N. Nelson, S. A. Nichols, J. Notte, T. O'Hanlon, R. Oram, C. Osthelder, D. J. Ottaway, H. Overmier, W. Parker, O. Patane, A. Pele, S. Perry, H. Pham, M. Pirello, J. Pullin, V. Quetschke, K. E. Ramirez, K. Ransom, J. Reyes, J. W. Richardson, K. Riles, M. Robinson, J. G. Rollins, C. L. Romel, J. H. Romie, M. P. Ross, B. I. Rotimi, K. Ryan, T. Sadecki, A. Sanchez, E. J. Sanchez, L. E. Sanchez, R. L. Savage, D. Schaetzl, M. G. Schiworski, R. Schnabel, E. Schwartz, D. Sellers, T. Shaffer, R. W. Short, D. Sigg, B. J. J. Slagmolen, J. R. Smith, C. Soike, V. Srivastava, T. Starkman, L. Sun, D. B. Tanner, J. Tasson, M. Thomas, P. Thomas, K. A. Thorne, E. M. Todd, M. R. Todd, C. I. Torrie, G. Traylor, A. S. Ubhi, R. P. Udall, G. Vajente, J. Vanosky, A. Vecchio, P. J. Veitch, A. M. Vibhute, E. R. G. von Reis, J. Warner, B. Weaver, R. Weiss, C. Whittle, P. Wilcox, B. Willke, C. C. Wipf, J. L. Wright, V. A. Xu, H. Yamamoto, L. Zhang, Z. Zhang, M. E. Zucker

General Relativity and Quantum Cosmology

Robustness of the primordial power spectrum in hybrid loop quantum cosmology to approximations near the bounce

Kristina Giesel, Almudena Guillén, Guillermo A. Mena Marugán et al. (+1 more)

We prove the robustness of the analytic approximation used in (hybrid) loop quantum cosmology to compute the primordial power spectrum of the cosmological perturbations for a recently proposed vacuum state (the non-oscillatory state with asymptotic Hamiltonian diagonalization). To investigate this, we study different approximations to the effective mass of these perturbations near the bounce, showing that the Pöschl-Teller potential employed in previous works leads to indistinguishable power spectra compared to other estimations of the mass, provided that they successfully capture the characteristic scale of the bounce, which translates into a scale of power suppression.
Read the full abstract

All authors Kristina Giesel, Almudena Guillén, Guillermo A. Mena Marugán, Leonardo Ricci

General Relativity and Quantum Cosmology

Models of a point particle in a three-dimensional AdS universe

Petr Lukeš and Pavel Krtouš

In 2+1-dimensional gravity, a conical deficit is commonly interpreted as a point-like particle. A distributional description of such a source is problematic since the Einstein equations are non- linear. Moreover, the total mass of the spacetime with nontrivial asymptotics is obfuscated by the infinite amount of background energy in the distant regions. In this work, we support the standard claim that the mass of a point particle is given by the angular deficit of the asymptotic geometry. We approximate the singular matter source by a sufficiently regular energy distribution, and we study the limit of negligible size for such a distribution while keeping the asymptotic geometry intact. Comparing spacetimes with equal asymptotics ensures that we correctly identify and remove the cosmological matter. We find that the angular deficit of the resulting conical spacetime is given by a limit of the local mass of the object, where the local mass is a natural concept of additive mass in 2+1 gravity. Surprisingly, the limiting mass is different from the BTZ mass parameter, although both masses are closely related.
Read the full abstract

General Relativity and Quantum Cosmology

Coherent quantum geometry: de Sitter spacetime in different foliations

Tommaso Bambagiotti, Roberto Casadio, Andrea Giusti et al. (+1 more)

In any theory of quantum gravity, an interesting question to address is to what extent known solutions of the Einstein field equations can be obtained as expectation values of metric operators on suitable quantum states. In this work, we consider coherent states (to ensure minimum uncertainty) for different foliations of the de~Sitter spacetime and study temporal evolution and coordinate invariance. A general framework will first be introduced for metrics that can be diagonalised globally. We will then find that the normalisability of coherent states in this framework requires using reference frames without coordinate singularities.
Read the full abstract

All authors Tommaso Bambagiotti, Roberto Casadio, Andrea Giusti, Pedro Meert

General Relativity and Quantum Cosmology · Cross-listed from hep-th

Why There is No Memory Burden in Holographic Space-time Models of Black Hole Formation and Evaporation

T. Banks

Recent papers\cite{dvali} have claimed that general quantum information considerations put macroscopic constraints on the properties of large black holes, which can affect their lifetimes in cosmologically and astrophysically interesting ways. We examine black hole evaporation in Holographic Space Time (HST) models\cite{hstbh}, which appear to have the memory burden effect responsible for these deviations from semi-classical expectations, and explain why, in those models, no such effect exists. It is basically a consequence of Fermi's Golden Rule/The Principle of Detailed Balance, but depends crucially on both the definition of energy in HST models and the way in which causality is implemented.
Read the full abstract

General Relativity and Quantum Cosmology

Lorentz Symmetry Breaking Traversable Wormhole Models Supported by Einasto Dark Matter

Rana Muhammad Zulqarnain, M. Yousaf, Allah Ditta et al. (+3 more)

We investigate static, spherically symmetric traversable wormholes in Kalb Ramond gravity, where spontaneous Lorentz symmetry breaking arises from a non-vanishing vacuum expectation value of the antisymmetric Kalb Ramond field. The matter sector is modeled by the Einasto dark matter density profile, yielding an analytical shape function expressed via the incomplete Gamma function. The resulting geometry satisfies the throat, flare-out, and asymptotic-flatness requirements, with embedding diagrams providing a geometric visualization of the wormhole structure. The energy density stays positive throughout the considered domain, while the radial null energy condition is violated near the throat, showing that the exotic matter required for traversability can be localized to a restricted region. The internal structure is further characterized through the complexity factor, which is most pronounced near the throat and gradually decays to zero at larger radii. We also examine the total gravitational energy, active gravitational mass, average pressure, and equilibrium behavior via the generalized TOV equation and pressure anisotropy; for the constant-redshift configuration, equilibrium is maintained by a balance between the hydrostatic and anisotropic forces. The optical properties of the spacetime are further explored through the photon sphere, critical impact parameter, light deflection angle, and echo time. Finally, the volume integral quantifier is used to estimate the total amount of null-energy-condition-violating matter, showing that the exotic contribution remains concentrated near the wormhole throat. The analysis highlights the combined role of the Kalb Ramond gravitational parameter and the Einasto matter distribution in shaping the geometric, energetic, and observational characteristics of the resulting wormhole configurations.
Read the full abstract

All authors Rana Muhammad Zulqarnain, M. Yousaf, Allah Ditta, Asifa Ashraf, Ahmadjon Abdujabbarov, Farruh Atamurotov

General Relativity and Quantum Cosmology

Emergent scalar field dynamics in a cosmological spacetime from GFT quantum gravity

Roukaya Dekhil, Federico Greco, Stefano Liberati et al. (+1 more)

We derive an effective scalar field theory for matter in group field theory condensate cosmology, starting from the fundamental quantum-gravity dynamics in a fully relational framework and encompassing both early- and late-universe regimes. The collective hydrodynamics of the underlying quantum geometry allows us to reconstruct both the homogeneous cosmological dynamics of matter and geometry and an inhomogeneous local field-theory description. Localization in space and time is defined relationally with respect to a material reference frame. At the homogeneous level, we obtain a modified scalar field theory on the emergent FLRW spacetime selected by the condensate. It recovers the standard dynamics of a massless scalar field in the late-time general-relativistic regime while retaining quantum-gravity corrections near the cosmological bounce. At the perturbative level, scalar inhomogeneities obey an effective wave equation that carries signatures of the underlying quantum-gravity microstructure. In the early-universe regime, this equation exhibits a modified dispersion relation with both dispersive and dissipative contributions. These corrections provide a concrete avenue for identifying phenomenological signatures of quantum gravity directly from a fundamental quantum-gravity framework.
Read the full abstract

All authors Roukaya Dekhil, Federico Greco, Stefano Liberati, Daniele Oriti

General Relativity and Quantum Cosmology

Blandford-Znajek Scaling in a Power-Law Rotating Kalb-Ramond Geometry: Magnetic-Flux Systematics and Bayesian Identifiability

Sardor Murodov, Olimjon Kholturayev, Bekzod Rahmatov et al. (+3 more)

Relativistic jets from spinning black holes offer a possible strong-field probe of gravity through the Blandford-Znajek mechanism. We study the leading jet-power scaling in the four-dimensional power-law rotating Kalb-Ramond geometry introduced by Kumar, Ghosh, and Wang. The metric is used here as a stationary background, without assuming that it constitutes a newly established exact rotating solution. We first examine the deformation at the metric level. For $s=2$ it is absorbed completely by a mass redefinition, whereas for $s>2$ the correction decays more slowly than the usual mass term. Our main benchmark is therefore the nondegenerate $s=3/2$ case, whose correction falls faster than the Kerr mass term; $s=3$ is kept as a secondary comparison. We evaluate the BZ scaling under three magnetic assumptions: fixed total horizon flux, fixed local normal field with the proper horizon area, and a reduced radius-based flux proxy. The resulting trends differ appreciably, showing that the magnetic prescription is itself a leading systematic. For GRO J1655-40 and GRS 1915+105, the marginalized deformation posterior remains close to the horizon-conditioned effective prior for both a uniform prior and a truncated-Gaussian alternative. The jet-only profile likelihood is also nearly flat over the allowed deformation range, with the same qualitative behavior in the $s=3$ test. Thus, within the present setup, the jet-power proxies do not independently determine the Kalb-Ramond deformation. A stronger inference will require better control of the rotating background, source-dependent magnetic flux, non-Kerr spin estimates, and a larger sample.
Read the full abstract

All authors Sardor Murodov, Olimjon Kholturayev, Bekzod Rahmatov, Javlon Rayimbaev, Islom Egamberdiev, Shavkat Karshiboev

General Relativity and Quantum Cosmology

Squeezed quantum states and partner modes in the moving mirror model of black hole evaporation

Kuan-Nan Lin, Pisin Chen, Michael R.R. Good et al. (+1 more)

The standard moving mirror model in (1+1)-dimensional spacetime is known to reproduce several quantum aspects of black hole evaporation. A perfectly reflecting, accelerating mirror can emit radiation whose frequency spectrum resembles that of Hawking radiation, although this correspondence holds only under certain approximations. Moreover, the standard in-out formulation does not provide a natural notion of the partner modes associated with the Hawking radiation. In this paper, we reformulate the moving mirror model in terms of Rindler/Milne modes. This formulation not only attributes the origin of the required approximations to mode squeezing effects but also naturally incorporates the notion of partner modes. Furthermore, as a consequence of these mode squeezing effects, the radiation received by an inertial observer at future null infinity exhibits additional nontrivial quantum correlations, even though its frequency spectrum approximately follows a Bose–Einstein or Fermi–Dirac distribution.
Read the full abstract

All authors Kuan-Nan Lin, Pisin Chen, Michael R.R. Good, Yasusada Nambu