General Relativity and Quantum Cosmology

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New submissions for Fri, 17 May 24

[1]  arXiv:2405.09590 [pdf, ps, other]

Title: Constraining $f({\cal R})$ gravity by Pulsar {\textit SAX J1748.9-2021} observations

Authors: G.G.L. Nashed, Salvatore Capozziello

Comments: 28 pages, 8 figures, Will appear in EPJC

Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th)

We discuss spherically symmetric dynamical systems in the framework of a general model of $f({\cal R})$ gravity, i.e. $f({\cal R})={\cal R}e^{\zeta {\cal R}}$, where $\zeta$ is a dimensional quantity in squared length units [L$^2$]. We initially assume that the internal structure of such systems is governed by the Krori-Barua ansatz, alongside the presence of fluid anisotropy. By employing astrophysical observations obtained from the pulsar {\textit SAX J1748.9-2021}, derived from bursting X-ray binaries located within globular clusters, we determine that $\zeta$ is approximately equal to $\pm 5$ km$^2$. In particular, the model can create a stable configuration for {\textit SAX J1748.9-2021}, encompassing its geometric and physical characteristics. In $f({\cal R})$ gravity, the Krori-Barua approach links $p_r$ and $p_t$, which represent the components of the pressures, to ($\rho$), representing the density, semi-analytically. These relations are described as $p_r\approx v_r^2 (\rho-\rho_{I})$ and $p_t\approx v_t^2 (\rho-\rho_{II})$. Here, the expression $v_r$ and $v_t$ represent the radial and tangential sound speeds, respectively. Meanwhile, $\rho_I$ pertains to the surface density and $\rho_{II}$ is derived using the parameters of the model. Notably, within the frame of $f({\cal R})$ gravity where $\zeta$ is negative, the maximum compactness, denoted as $C$, is inherently limited to values that do not exceed the Buchdahl limit. This contrasts with general relativity or with $f({\cal R})$ with positive $\zeta$, where $C$ has the potential to reach the limit of the black hole asymptotically. The predictions of such model suggest a central energy density which largely exceeds the saturation of nuclear density, which has the value $\rho_{\text{nuc}} = 3\times 10^{14}$ g/cm$^3$. Also, the density at the surface $\rho_I$ surpasses $\rho_{\text{nuc}}$.

[2]  arXiv:2405.09599 [pdf, other]

Title: Gravitational wave spectrum from expanding string loops on domain walls: Implication to nano-hertz pulsar timing array signal

Authors: Yu Hamada, Wakutaka Nakano

Comments: 32 pages, 8 figures

Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)

We analytically calculate the spectrum of stochastic gravitational waves (GWs) emitted by expanding string loops on domain walls in the scenario where domain walls decay by nucleation of string loops. By introducing macroscopic parameters characterizing the nucleation of the loops, the stochastic GW spectrum is derived in a way that is independent of the details of particle physics models. In contrast to GWs emitted from bubble collisions of the false vacuum decay, the string loops do radiate GWs even when they are perfectly circular before their collisions, resulting in that more and more contribution to the spectrum comes from the smaller and smaller loops compared to the typical size of the collided loops. Consequently, the spectrum is linearly proportional to the frequency at the high-frequency region, which is peculiar to this GW source. Furthermore, the results are compared with the recent nano-Hertz pulsar timing array signal, as well as the projected sensitivity curves of future gravitational wave observatories.

[3]  arXiv:2405.09653 [pdf, other]

Title: Fractal signatures of non-Kerr spacetimes in the shadow of light-ring bifurcations

Authors: Konstantinos Kostaros, Padelis Papadopoulos, George Pappas

Comments: 14 pages, 20 figures

Subjects: General Relativity and Quantum Cosmology (gr-qc)

Light-ring bifurcations that can occur for prolate non-Kerr compact objects can leave an indelible signature on SMBH shadows as a fractal sequence of eyebrow-like formations. These fractal features are the result of two properties of these spacetimes. The first is that they allow for multiple escapes for the photons (throats in the effective potential of photon geodesic motion). The second is that photon geodesics can resonate between different generalized light-rings related to the escapes, called fundamental photon orbits, that lead photons to alternate between the different exits either towards the compact object or infinity. The resulting fractal structures of the shadow seem to be a generic feature of prolate non-Kerr objects that may be observable in (accretion-disk)-illuminated compact objects, especially along equatorial lines of sight, but the best orientation depends on the specific parameters. Such fractal features, if observed, would be smoking gun signals of non-Kerr compact objects.

[4]  arXiv:2405.09702 [pdf, other]

Title: Black bounces in conformal Killing gravity

Authors: José Tarciso S. S. Junior, Francisco S. N. Lobo, Manuel E. Rodrigues

Comments: 13 pages, 12 figures. Accepted for publication in EPJC

Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th)

In this work, we analyse black bounce solutions in the recently proposed ``Conformal Killing gravity'' (CKG), by coupling the theory to nonlinear electrodynamics (NLED) and scalar fields. The original motivation of the theory was essentially to fulfil specific criteria that are absent in existing gravitational theories, namely, to obtain the cosmological constant as an integration constant, derive the energy-momentum conservation law as a consequence of the gravitational field equations, rather than assuming it, and not necessarily considering conformally flat metrics as vacuum solutions. In this work, we extend the static and spherically symmetric solutions obtained in the literature, and explore the possibility of black bounces in CKG, coupled to NLED and scalar fields. We find novel NLED Lagrangian densities and scalar potentials, and extend the class of black bounce solutions found in the literature. Furthermore, within black bounce geometries, we find generalizations of the Bardeen-type and Simpson-Visser geometries and explore the regularity conditions of the solutions.

[5]  arXiv:2405.09703 [pdf, other]

Title: Diffeomorphism invariance and general covariance: a pedagogical introduction

Authors: Mateo Casariego

Comments: 6 pages, 3 figures, informal style

Subjects: General Relativity and Quantum Cosmology (gr-qc); History and Philosophy of Physics (physics.hist-ph)

Diffeomorphism invariance is a feature that gets sometimes highlighted as something with profound implications in the physics of spacetime. Moreover, it is often wrongly associated exclusively with General Relativity. The fact that diffeomorphism invariance and general covariance are used interchangeably does not help. Here, we attempt at clarifying these concepts.

[6]  arXiv:2405.09714 [pdf, other]

Title: Cosmological Singularity and Power-Law Solutions in Modified Gravity

Authors: Das Saurya, Haque S.Shajidul, Tema Seturumane

Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)

A bouncing Universe avoids the big-bang singularity. Using the time-like and null Raychaudhhuri equations, we explore whether the bounce near the big-bang, within a broad spectrum of modified theories of gravity, allows for cosmologically relevant power-law solutions under reasonable physical conditions. Our study shows that certain modified theories of gravity, such as Stelle gravity, do not demonstrate singularity resolution under any reasonable conditions, while others including $f(R)$ gravity and Brans-Dicke theory can demonstrate singularity resolution under suitable conditions. For these theories, we show that the accelerating solution is slightly favoured over ekypyrosis.

[7]  arXiv:2405.09732 [pdf, other]

Title: Dynamics of a higher-dimension Einstein-Scalar-Gauss-Bonnet cosmology

Authors: Alfredo D. Millano, Claudio Michea, Genly Leon, Andronikos Paliathanasis

Comments: 25 pages, 5 tables, 13 compound figures

Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th); Mathematical Physics (math-ph)

We study the dynamics of the field equations in a five-dimensional spatially flat Friedmann-Lema\^itre-Robertson-Walker metric in the context of a Gauss-Bonnet-Scalar field theory where the quintessence scalar field is coupled to the Gauss-Bonnet scalar. Contrary to the four-dimensional Gauss-Bonnet theory, where the Gauss-Bonnet term does not contribute to the field equations, in this five-dimensional Einstein-Scalar-Gauss-Bonnet model, the Gauss-Bonnet term contributes to the field equations even when the coupling function is a constant. Additionally, we consider a more general coupling described by a power-law function. For the scalar field potential, we consider the exponential function. For each choice of the coupling function, we define a set of dimensionless variables and write the field equations into a system of ordinary differential equations. We perform a detailed analysis of the dynamics for both systems and classify the stability of the equilibrium points. We determine the presence of scaling and super-collapsing solutions using the cosmological deceleration parameter. This means that our models can explain the Universe's early and late-time acceleration phases. Consequently, this model can be used to study inflation or as a dark energy candidate.

[8]  arXiv:2405.09791 [pdf, ps, other]

Title: Challenging theories of dark energy with levitated force sensor

Authors: Peiran Yin, Rui Li, Chengjiang Yin, Xiangyu Xu, Xiang Bian, Han Xie, Chang-Kui Duan, Pu Huang, Jian-hua He, Jiangfeng Du

Journal-ref: Nature Physics 18, 1181-1185 (2022)

Subjects: General Relativity and Quantum Cosmology (gr-qc); Instrumentation and Methods for Astrophysics (astro-ph.IM); Instrumentation and Detectors (physics.ins-det)

The nature of dark energy is one of the most outstanding problems in physical science, and various theories have been proposed. It is therefore essential to directly verify or rule out these theories experimentally. However, despite substantial efforts in astrophysical observations and laboratory experiments, previous tests have not yet acquired enough accuracy to provide decisive conclusions as to the validity of these theories. Here, using a diamagnetically levitated force sensor, we carry out a test on one of the most compelling explanations for dark energy to date, namely the Chameleon theory, an ultra-light scalar field with screening mechanisms, which couples to normal-matter fields and leaves a detectable fifth force. Our results extend previous results by nearly two orders of magnitude to the entire physical plausible parameter space of cosmologically viable chameleon models. We find no evidence for such a fifth force. Our results decisively rule out the basic chameleon model as a candidate for dark energy. Our work, thus, demonstrates the robustness of laboratory experiments in unveiling the nature of dark energy in the future. The methodology developed here can be further applied to study a broad range of fundamental physics.

[9]  arXiv:2405.09945 [pdf, other]

Title: Near-horizon chaos beyond Einstein gravity

Authors: Surajit Das, Surojit Dalui, Rickmoy Samanta

Comments: 21 pages, 63 figures, 1 table

Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th); Chaotic Dynamics (nlin.CD)

We investigate chaos in the dynamics of outgoing massless particles near the horizon of static spherically symmetric (SSS) black holes in two well-motivated models of $f(R)$ gravity. In both these models, we probe chaos in the particle trajectories (under suitable harmonic confinement) in the vicinity of the black hole horizons, for a set of initial conditions. The particle trajectories, associated Poincar$\acute{e}$ sections, and Lyapunov exponents clearly illustrate the role played by the black hole horizon in the growth of chaos within a specific energy range. We demonstrate how this energy range is controlled by the parameters of the modified gravity theory under consideration. The growth of chaos in such a classical setting is known to respect a surface gravity bound arising from universal aspects of particle dynamics close to the black hole horizon [K. Hashimoto and N. Tanahashi, Phys. Rev. D 95, 024007 (2017)], analogous to the quantum MSS bound [J. Maldacena, S.H. Shenker and D. Stanford, JHEP 08 (2016) 106]. Interestingly, both models studied in our work respect the bound, in contrast to some of the other models of $f(R)$ gravity in the existing literature. The work serves as a motivation to use chaos as an additional tool to probe Einstein gravity in the strong gravity regime in the vicinity of black hole horizons.

[10]  arXiv:2405.09968 [pdf, ps, other]

Title: New insights on null and timelike warped symmetric spacetime splittings

Authors: Alan Maciel, Morgan Le Delliou, José P. Mimoso

Comments: 27pp

Subjects: General Relativity and Quantum Cosmology (gr-qc)

We explore in detail the 2+2 and 1+1+2 formalism in spherically symmetric spacetimes, spanning from deducing the dynamical equations to relating them to the well-known generalised Painlev\'e-Gullstrand (GPG) coordinate system. The evolution equations are the Raychaudhuri equations for null rays, including those also known as cross-focusing equations whose derivation, to the best of our knowledge, we present for the first time. We physically interpret the scalars that arise in this scenario, namely the flow 2-expansion $\Theta_{n}$, the flow acceleration $\mathcal{A}$, and the radial extrinsic curvature $\mathcal{B}$. We derive a coordinate independent formula for the redshift which shows that $\mathcal{B}$ is the sole source for the redshift in spherically symmetric spacetimes. We also establish the correspondence between the 1+1+2 scalars and the 1+3 splitting scalars, expansion and shear. We further make a comparison with the Newman-Penrose formalism, in order to clarify the context where each formalism is more useful, and finally, we extend our results to planar and hyperbolic symmetric warped spacetimes as well, in particular, the relationship between $\mathcal{B}$ and the redshift.

[11]  arXiv:2405.10013 [pdf, ps, other]

Title: Charged rotating wormholes: charge without charge

Authors: Hyeong-Chan Kim, Sung-Won Kim, Bum-Hoon Lee, Wonwoo Lee

Comments: 24 pages, 3 figures

Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)

We present a family of charged rotating wormhole solutions to the Einstein-Maxwell equations, supported by anisotropic matter fields. We first revisit the charged static cases and analyze the conditions for the solution to represent a wormhole geometry. The rotating geometry is obtained by applying the Newman-Janis algorithm to the static geometry. We show the solutions to Maxwell equations in detail. We believe that our wormhole geometry offers a geometric realization corresponding to the concept of 'charge without charge'.

[12]  arXiv:2405.10127 [pdf, other]

Title: Mergers of hairy black holes: Constraining topological couplings from entropy

Authors: Kabir Chakravarti, Amit Reza, Leonardo G. Trombetta

Comments: 10 pages, 5 figures

Subjects: General Relativity and Quantum Cosmology (gr-qc)

Hairy black-holes are a unique prediction of certain theories that extend General Relativity (GR) with a scalar field. The presence of scalar hair is reflected non-trivially in the entropy of the black hole along with any topological coupling that may be present in the action. Demanding that a system of two merging black holes obeys the global second law of thermodynamics imposes a bound on this topological coupling coefficient. In this work we study how this bound is pushed from its GR value by the presence of scalar hair by considering estimates of binary black-hole merger parameters through inference studies of mock gravitational-wave (GW) events. We find that the scalar charge may produce a statistically significant deviation of the change in entropy over the GR prediction. However, we also find the latter is susceptible to biases arising out of GW inferences which ends up being two orders of magnitude larger, therefore overwhelming any change induced by the scalar hair.

[13]  arXiv:2405.10169 [pdf, other]

Title: Most likely configurations for fermion localization in a Braneworld-$f(Q,B_Q)$

Authors: A. R. P. Moreira, Shi-Hai Dong, M. E. Rodrigues

Subjects: General Relativity and Quantum Cosmology (gr-qc)

This study delves deeply into braneworld scenarios within modified gravity models, investigating their impact on particle localization and the structure of branes. Through a comprehensive blend of numerical analyses and theoretical inquiries, we unravel a nuanced correlation between deviations from standard General Relativity (GR) and the emergence of split branes. By employing probabilistic measurements, we pinpoint stable configurations that align with brane division intervals, thus challenging prevailing assumptions regarding the gravitational framework of our universe. Furthermore, our investigation extends to the localization of fermions within the brane, exposing intricate dynamics shaped by scalar field characteristics and modifications to gravitational models. By harnessing quantum information measurements, notably Shannon entropy, we discern heightened probabilities of fermion localization within the brane as gravitational models diverge from standard paradigms. This underscores the limitations of General Relativity in comprehensively describing the complexities inherent in our universe. Lastly, our exploration of massive fermions unveils their potential to breach the confines of the brane, hinting at promising avenues for future experimental endeavors aimed at probing the nature of extra dimensions and gravitational interactions. This suggests exciting prospects for advancing our understanding of fundamental physics beyond conventional boundaries.

[14]  arXiv:2405.10201 [pdf, other]

Title: Investigating cosmic histories with a stiff era through Gravitational Waves

Authors: Hannah Duval, Sachiko Kuroyanagi, Alberto Mariotti, Alba Romero-Rodríguez, Mairi Sakellariadou

Comments: 18 pages, 9 figures

Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Phenomenology (hep-ph)

We investigate the potential of gravitational-wave background searches to constrain cosmic histories characterised by a stiff equation of state, preceded by a period of matter domination. Such a scenario leads to a characteristic peak in the primordial gravitational-wave spectrum originating from cosmological inflation. Assuming instant transitions between distinct epochs, which allows an analytical treatment of the gravitational-wave spectrum, we perform a Bayesian inference analysis to derive constraints from the first three observing runs of the LIGO-Virgo-KAGRA Collaboration. Additionally, we consider a smooth transition, employing an axion-like particle physics model, and highlight the difference with the instant transition approximation. We then forecast detection prospects for such a cosmic history through future gravitational-wave experiments.

[15]  arXiv:2405.10228 [pdf, other]

Title: The fermionic double smeared null energy condition

Authors: Duarte Fragoso, Lihan Guo

Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)

Energy conditions are crucial for understanding why exotic phenomena such as traversable wormholes and closed timelike curves remain elusive. In this paper, we prove the Double Smeared Null Energy Condition (DSNEC) for the fermionic free theory in 4-dimensional flat Minkowski space-time, extending previous work on the same energy condition for the bosonic case [1][2] by adapting Fewster and Mistry's method [3] to the energy-momentum tensor $T_{++}$. A notable difference from previous works lies in the presence of the $\gamma_0 \gamma_+$ matrix in $T_{++}$, causing a loss of symmetry. This challenge is addressed by making use of its square-root matrix. We provide explicit analytic results for the massless case as well as numerical insights for the mass-dependence of the bound in the case of Gaussian smearing.

[16]  arXiv:2405.10270 [pdf, other]

Title: Quadratic quasi-normal mode dependence on linear mode parity

Authors: Patrick Bourg, Rodrigo Panosso Macedo, Andrew Spiers, Benjamin Leather, Béatrice Bonga, Adam Pound

Comments: 4 pages, 1 figure

Subjects: General Relativity and Quantum Cosmology (gr-qc)

Quasi-normal modes (QNMs) uniquely describe the gravitational-wave ringdown of post-merger black holes. While the linear QNM regime has been extensively studied, recent work has highlighted the importance of second-perturbative-order, quadratic QNMs (QQNMs) arising from the nonlinear coupling of linear QNMs. Previous attempts to quantify the magnitude of these QQNMs have shown discrepant results. Using a new hyperboloidal framework, we resolve the discrepancy by showing that the QQNM/QNM ratio is a function not only of the black hole parameters but also of the ratio between even- and odd-parity linear QNMs: the ratio QQNM/QNM depends on what created the ringing black hole, but only through this ratio of even- to odd-parity linear perturbations.

[17]  arXiv:2405.10287 [pdf, ps, other]

Title: Exotic compact objects and light bosonic fields

Authors: Farid Thaalba, Giulia Ventagli, Thomas P. Sotiriou

Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th)

In this note, we discuss the effect of light, non-gauge, bosonic degrees of freedom on the exterior spacetime of an exotic compact object. We show that such fields generically introduce large deviations from spacetimes of vacuum General Relativity near and outside the surfaces of ultra-compact exotic objects unless one assumes they totally decouple from the standard model or new heavy fields. Hence, using solutions of vacuum General Relativity to model ultra-compact exotic objects and their perturbations relies implicitly on this assumption or on the absence of such fields.

[18]  arXiv:2405.10293 [pdf, ps, other]

Title: Charged Black Holes from Interacting Vacuum

Authors: Rodrigo Maier, Manuella Corrêa e Silva

Subjects: General Relativity and Quantum Cosmology (gr-qc)

In this paper charged black holes are obtained assuming that a Born-Infeld electrodynamics may arise from an interaction between the electromagnetic field and a vacuum component. In this context Cauchy horizons do not appear in the maximal analytical extension once an event horizon is formed so that the interior spacetime does not suffer from any sort of instabilities which are well known in the literature. On the contrary, the causal structure exhibits an event horizon -- encapsulating a spacelike singularity -- and a cosmological horizon. We show that the strong cosmic censorship is then restored for a wide range of the parameters including configurations in which the black hole charge is much larger than its mass. We also show that the black hole thus formed described by our solution exhibits an unstable photon sphere analogous to that of the Schwarzschild metric.

[19]  arXiv:2405.10321 [pdf, ps, other]

Title: Probing Hidden Dimensions via Muon Lifetime Measurements

Authors: Jorge G. Russo

Comments: Honorable Mention in the Gravity Research Foundation 2024 Awards for Essays on Gravitation. 11 pages

Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)

In the context of Kaluza-Klein theories, the time dilation of charged particles in an external field depends on the charge in a specific way. Experimental tests are proposed to search for extra dimensions using this distinctive feature.

Cross-lists for Fri, 17 May 24

[20]  arXiv:2405.09607 (cross-list from astro-ph.CO) [pdf, other]

Title: Probing Dark Matter Isocurvature with Primordial Non-Gaussianity

Authors: Michael Geller, Soubhik Kumar, Lian-Tao Wang

Comments: 17 pages, 4 figures

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)

Multiple fields can become dynamical during the inflationary epoch. We consider an example where a light field acquires isocurvature fluctuations during inflation and contributes to the dark matter abundance at late times. Interactions between the light field and the adiabatic sector contribute to mixed adiabatic-isocurvature non-Gaussianity (NG). We show the resulting form of NG has a different kinematic dependence than the 'local shape' commonly considered, and highlight the parameter space where a dedicated search is expected to significantly improve the current $\textit{Planck}$ sensitivity. We interpret our results in the context of the QCD axion and illustrate how the proposed NG searches can improve upon the existing searches for isocurvature power spectrum and bispectrum.

[21]  arXiv:2405.09678 (cross-list from astro-ph.GA) [pdf, other]

Title: How Stellar Stream Torsion may reveal aspherical Dark Matter Haloes

Authors: Adriana Bariego-Quintana

Comments: 4 pages, 1 figure, proceedings for ICWIP 2023

Subjects: Astrophysics of Galaxies (astro-ph.GA); General Relativity and Quantum Cosmology (gr-qc)

Flat rotation curves follow from elongated Dark Matter distributions, as shown by our earlier competitive fits to the SPARC database. Intending to probe that distortion of the DM halo one needs observables not contained by the galactic plane. Stellar streams are caused by tidal stretching of massive substructures such as satellite dwarf galaxies, and would lie on a plane should the DM-halo gravitational field be spherically symmetric. But if the field does not display such spherical symmetry, stellar trajectories, as well as stellar streams, should torsion out of the plane. This is where the torsion of the stream can be of use: it is a local observable that measures the deviation from planarity of a curve; thus, it quantifies how noncentral the gravitational potential is. We have performed small simulations to confirm that indeed a galactic central force produces negligible torsion, and quantified the torsion for prolate haloes instead. Examining observational data, we select several streams at large distance from the galactic center, as most promising for the study, and by means of helicoidal fits extract their differential torsion. We see that their torsion is much larger than expected for a central spherical bulb alone, pointing to an elongated Milky Way halo.

[22]  arXiv:2405.09687 (cross-list from hep-th) [pdf, other]

Title: Scattering and bound observables for spinning particles in Kerr spacetime with generic spin orientations

Authors: Riccardo Gonzo, Canxin Shi

Comments: 6 pages + appendices, 1 ancillary file

Subjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)

We derive the radial action of a spinning probe particle in Kerr spacetime from the worldline formalism in the first-order form, focusing on linear in spin effects. We then develop a novel covariant Dirac bracket formalism to compute the impulse and the spin kick directly from the radial action, generalizing some conjectural results in the literature and providing ready-to-use expressions for amplitude calculations with generic spin orientations. This allows, for the first time, to find new covariant expressions for scattering observables in the probe limit up to $\mathcal{O}(G^6 s_1 s_2^4)$. Finally, we use the action-angle representation to compute the fundamental frequencies for generic bound orbits, including the intrinsic spin precession, the periastron advance and the precession of the orbital plane.

[23]  arXiv:2405.09723 (cross-list from hep-ph) [pdf, other]

Title: Gravitational Wave-Induced Freeze-In of Fermionic Dark Matter

Authors: Azadeh Maleknejad, Joachim Kopp

Comments: 6 pages, 2 figures

Subjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)

The minimal coupling of massless fermions to gravity does not allow for their gravitational production solely based on the expansion of the Universe. We argue that this changes in presence of realistic and potentially detectable stochastic gravitational wave backgrounds. We compute the resulting energy density of Weyl fermions at 1-loop using in--in formalism. If the initially massless fermions eventually acquire mass, this mechanism can explain the dark matter abundance in the Universe. Remarkably, it may be more efficient than conventional gravitational production of superheavy fermions.

[24]  arXiv:2405.09729 (cross-list from astro-ph.HE) [pdf, other]

Title: The proper way to spatially decompose the gravitational-wave origin in stellar collapse simulations

Authors: Shuai Zha

Comments: 13 pages, 11 figures, submitted to PRD

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

Gravitational waves (GWs) hold great potential for an unobscured view of protoneutron stars (PNSs) formed as a result of stellar collapses. While waiting for discovery, deepening the understanding of GW emission in theory is beneficial for both optimizing searching strategies and deciphering the eventual data. One significant aspect is the spatially dependent contribution to the overall GW signal extracted from sophisticated hydrodynamic simulations. I present the proper way to perform the spatial decomposition of GW strain with the quadrupole formula in the slow-motion and weak-field approximation. Then I demonstrate the approach using the results of a 2D axisymmetric pseudo-Newtonian hydrodynamic simulation of core-collapse supernova. I discuss the possible misleading interpretation based on the incorrect method in the literature that favors the dominant contribution by the PNS convective layer. Moreover, with the correct approach, the GW spatial profiles agree well with those calculated from a consistent perturbative method. This work re-emphasizes the global emission picture of GWs from PNS and motivates future prudent analyses with 3D simulations.

[25]  arXiv:2405.09739 (cross-list from astro-ph.HE) [pdf, other]

Title: Are all models wrong? Falsifying binary formation models in gravitational-wave astronomy

Authors: Lachlan Passenger, Eric Thrane, Paul D. Lasky, Ethan Payne, Simon Stevenson, Ben Farr

Comments: 8 pages, 3 figures, 1 table

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

As the catalogue of gravitational-wave transients grows, several entries appear "exceptional" within the population. Tipping the scales with a total mass of $\approx 150 M_\odot$, GW190521 likely contained black holes in the pair-instability mass gap. The event GW190814, meanwhile, is unusual for its extreme mass ratio and the mass of its secondary component. A growing model-building industry has emerged to provide explanations for such exceptional events, and Bayesian model selection is frequently used to determine the most informative model. However, Bayesian methods can only take us so far. They provide no answer to the question: does our model provide an adequate explanation for the data? If none of the models we are testing provide an adequate explanation, then it is not enough to simply rank our existing models - we need new ones. In this paper, we introduce a method to answer this question with a frequentist $p$-value. We apply the method to different models that have been suggested to explain GW190521: hierarchical mergers in active galactic nuclei and globular clusters. We show that some (but not all) of these models provide adequate explanations for exceptionally massive events like GW190521.

[26]  arXiv:2405.09833 (cross-list from hep-th) [pdf, other]

Title: Quantum cosmology as automorphic dynamics

Authors: Victor Godet

Comments: 40 pages

Subjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)

We revisit pure quantum cosmology in three dimensions. The Wheeler-DeWitt equation can be solved perturbatively and the dynamics reduces to a particle on moduli space. Its time evolution is equivalent to the $T\overline{T}$ deformation. Focusing on spacetimes with torus slices, we show that inflationary cosmologies correspond to particle trajectories in Artin's billiard. The resulting automorphic dynamics is developed both from a first and second quantized perspectives. Our main application is to give an interpretation for the Hartle-Hawking state which is here the analytic continuation of the Maloney-Witten partition function. We obtain its spectral decomposition and an exact representation as an average involving the M\"obius function.

[27]  arXiv:2405.10031 (cross-list from astro-ph.CO) [pdf, other]

Title: Constraining the nonstandard propagating gravitational waves in the cosmological background with GWTC-3

Authors: Zu-Cheng Chen, Lang Liu

Comments: 7 pages, 1 figure;

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

The detection of gravitational waves (GWs) has opened a new window to test the fundamental nature of gravity. We present constraints on the nonstandard propagation of GWs using the spectral siren method applied to binary black hole (BBH) mergers from the third Gravitational-Wave Transient Catalog (GWTC-3). The spectral siren method exploits the redshift distribution of BBHs to probe the cosmic expansion history and break degeneracies between cosmology and modified gravity effects. We focus on the friction term $\nu$ in the nonstandard GW propagation equation, which characterizes the running of the Planck mass. Assuming the standard $\Lambda$CDM cosmology, we find $\nu = 0.5^{+3.5}_{-2.6}$ (median and $90\%$ credible interval), improving upon previous constraints from the bright siren event GW170817 by an order of magnitude. This improvement is due to the higher redshifts of BBHs in GWTC-3, reaching up to $z \sim 1$. Our result suggests that the propagation of GWs is consistent with the predictions of general relativity, placing limits on modified gravity theories that predict a time-varying Planck mass. As the sensitivity of GW detectors improves, the spectral siren method will provide a powerful tool for testing gravity on cosmological scales and probing the physics of the early Universe.

[28]  arXiv:2405.10061 (cross-list from hep-th) [pdf, other]

Title: Warped CFT duals of the Plebański-Demiański family of solutions

Authors: Xuhao Jiang, Jianfei Xu

Comments: 26 pages

Subjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)

In this paper, we analyze the symmetry properties of the complete family of type D spacetimes generalized form the Pleba\'{n}ski-Demia\'{n}ski solution in four dimensions holographically in terms of a warped CFT. The generalized Pleba\'{n}ski-Demia\'{n}ski solutions are black hole-like spacetimes characterized by seven physical parameters. Most of the black holes in four dimensions are included within this family. Generically consider a solution with horizon in this family, we figure out the possible warped conformal symmetry attached to the horizon. The horizon can be either extremal or non-extremal. In the extremal case, the near horizon region can be mapped to an infinite spacetime with geometry given by a warped and twist product of AdS$_2$ and S$^2$. The new boundary conditions for AdS$_2$ as well as their higher dimensional uplifts are applied here to manifest the asymptotic symmetry as the warped conformal symmetry. In the non-extremal case, the global warped conformal symmetry is singled out by analyzing the scalar wave equation with constant frequency. The local warped conformal symmetries are represented by the charge algebra associated to the vector fields which preserve the scalar wave equation as well as its frequency. In defining the variation of the covariant charges, a proper counterterm is introduced for consistency conditions which is supposed to be suitable for all the solutions within the family. As a consistency check, the horizon entropy is reproduced by the entropy formula of the warped CFT by using its modular covariance and the central terms derived in the bulk spacetimes.

[29]  arXiv:2405.10081 (cross-list from astro-ph.HE) [pdf, other]

Title: General relativistic magnetohydodynamics simulations for binary neutron star mergers

Authors: Kenta Kiuchi

Comments: Invited chapter for the edited book {\it New Frontiers in GRMHD Simulations} (Eds. C. Bambi, Y. Mizuno, S. Shashank and F. Yuan, Springer Singapore, expected in 2024)

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

Binary neutron star mergers used to be the most promising candidate for gravitational waves for ground-based gravitational wave detectors, such as advanced LIGO and advanced VIRGO. This was proved by the detection of gravitational waves from a binary neutron star merger in 2017. Numerical modeling is pivotal in predicting and interpreting binary neutron star mergers. This chapter reviews the progress of fully general relativistic magnetized binary neutron star merger simulations. From 2008 to 2024, about forty numerical relativity simulations of magnetized binary neutron star mergers were conducted with a different level of sophistication. This chapter aims to comprehensively view the magnetohydrodynamics effect in binary neutron star mergers by reviewing all the related works.

[30]  arXiv:2405.10100 (cross-list from hep-th) [pdf, other]

Title: Dimensionally reducing the Classical Regge Growth (CRG) conjecture

Authors: Joan Quirant

Comments: 6 pages + appendices, 2 figures

Subjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)

We explore the Classical Regge Growth conjecture (CRG) in the 4d effective field theory that results from compactifying $D$-dimensional General Relativity on a compact, Ricci-flat manifold. While the higher dimensional description is given in terms of pure Einstein gravity and the conjecture is automatically satisfied, it imposes several non-trivial constraints in the 4d spectrum. Namely, there must be either none or an infinite number of massive spin-2 modes, and the mass ratio between consecutive KK spin-2 replicas is bounded by the 4d coupling constants.

[31]  arXiv:2405.10108 (cross-list from hep-th) [pdf, other]

Title: Quantum Field Theory in Curved Spacetime Approach to the Backreaction of Dynamical Casimir Effect

Authors: Yu-Cun Xie

Comments: Undergraduate thesis

Subjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); Quantum Physics (quant-ph)

In this thesis, we investigate the dynamical Casimir effect, the creation of particles from vacuum by dynamical boundary conditions or dynamical background, and its backreaction to the motion of the boundary. The backreaction of particle creation to the boundary motion is studied using quantum field theory in curved spacetime technique, in 1+1 dimension and 3+1 dimension. The relevant quantities in these quantum field processes are carefully analyzed, including regularization of the UV and IR divergent of vacuum energy, and estimation of classical backreaction effects like radiation pressure. We recovered the qualitative result of backreaction in 1+1 dimensions. In the 3+1 dimension, we find that the backreaction tends to slow down the system to suppress the further particle creation, similar to the case of cosmological particle creation.

[32]  arXiv:2405.10307 (cross-list from hep-th) [pdf, other]

Title: On the lapse contour

Authors: Batoul Banihashemi, Ted Jacobson

Comments: 7 pages

Subjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)

The gravitational path integral is usually implemented with a covariant action by analogy with other gauge field theories, but the gravitational case is different in important ways. A key difference is that the integrand has an essential singularity, which occurs at zero lapse where the spacetime metric degenerates. The lapse integration contour required to impose the local time reparametrization constraints must run from $-\infty$ to $+\infty$, yet must not pass through zero. This raises the question: what is the correct integration contour, and why? We study that question by starting with the reduced phase space path integral, which involves no essential singularity. We observe that if the momenta are to be integrated before the lapse, to obtain a configuration space path integral, the lapse contour should pass below the origin in the complex lapse plane. This contour is also consistent with the requirement that quantum field fluctuation amplitudes have the usual short distance vacuum form, and with obtaining the Bekenstein-Hawking horizon entropy from a Lorentzian path integral. We close with a discussion of related issues, including potential obstacles to deriving a nonperturbative covariant gravitational path integral.

Replacements for Fri, 17 May 24

[33]  arXiv:2201.13211 (replaced) [pdf, ps, other]

Title: Three-dimensional AdS black holes in massive-power-Maxwell theor

Authors: B. Eslam Panah, K. Jafarzade, A. Rincón

Comments: 20 pages, 5 figures, 2 tables

Journal-ref: Gen. Relativ. Gravit. 56, 46 (2024)

Subjects: General Physics (physics.gen-ph); General Relativity and Quantum Cosmology (gr-qc)

[34]  arXiv:2304.13304 (replaced) [pdf, ps, other]

Title: The integrated perturbation theory for cosmological tensor fields III: Projection effects

Authors: Takahiko Matsubara

Comments: 30 pages, no figure, this paper is the third of a series, the first one is arXiv:2210.10435, the second one is arXiv:2210.11085 and the fourth one is arXiv:2405.09038

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

[35]  arXiv:2306.12914 (replaced) [pdf, other]

Title: The Dilaton Improves Goldstones

Authors: Roman Zwicky

Comments: 19 pages + refs, 1 figure, major revision. Includes discussion on Weyl-gauging and more general soft theorem discussion

Subjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Lattice (hep-lat); High Energy Physics - Phenomenology (hep-ph)

[36]  arXiv:2306.16227 (replaced) [pdf, other]

Title: The second data release from the European Pulsar Timing Array: IV. Implications for massive black holes, dark matter and the early Universe

Authors: J. Antoniadis, P. Arumugam, S. Arumugam, P. Auclair, S. Babak, M. Bagchi, A.-S. Bak Nielsen, E. Barausse, C. G. Bassa, A. Bathula, A. Berthereau, M. Bonetti, E. Bortolas, P. R. Brook, M. Burgay, R. N. Caballero, C. Caprini, A. Chalumeau, D. J. Champion, S. Chanlaridis, S. Chen, I. Cognard, M. Crisostomi, S. Dandapat, D. Deb, S. Desai, G. Desvignes, N. Dhanda-Batra, C. Dwivedi, M. Falxa, F. Fastidio, R. D. Ferdman, A. Franchini, J. R. Gair, B. Goncharov, A. Gopakumar, E. Graikou, J.-M. Grießmeier, A. Gualandris, L. Guillemot, Y. J. Guo, Y. Gupta, S. Hisano, H. Hu, F. Iraci, D. Izquierdo-Villalba, J. Jang, J. Jawor, G. H. Janssen, A. Jessner, B. C. Joshi, F. Kareem, R. Karuppusamy, E. F. Keane, M. J. Keith, D. Kharbanda, T. Khizriev, T. Kikunaga, N. Kolhe, M. Kramer, M. A. Krishnakumar, et al. (53 additional authors not shown)

Comments: 30 pages, 23 figures, replaced to match the version published in Astronomy & Astrophysics, note the change in the numbering order in the series (now paper IV)

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA); General Relativity and Quantum Cosmology (gr-qc)

[37]  arXiv:2307.12222 (replaced) [pdf, other]

Title: Atom-field dynamics in curved spacetime

Authors: Syed Masood A. S. Bukhari, Li-Gang Wang

Comments: 34 pages, 5 figures

Journal-ref: Front. Phys. 19, 54203 (2024)

Subjects: General Relativity and Quantum Cosmology (gr-qc)

[38]  arXiv:2311.04977 (replaced) [pdf, other]

Title: A visual tool for assessing tension-resolving models in the $H_0$-$σ_8$ plane

Authors: Igor de O. C. Pedreira, Micol Benetti, Elisa G. M. Ferreira, Leila L. Graef, Laura Herold

Comments: 15 pages, 3 figures, 5 tables. Replaced to match PRD accepted version (May 2024)

Journal-ref: Phys. Rev. D 109, 103525 (2024)

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)

[39]  arXiv:2312.02270 (replaced) [pdf, other]

Title: Study of a cubic cavity resonator for gravitational waves detection in the microwave frequency range

Authors: Pablo Navarro, Benito Gimeno, Juan Monzó-Cabrera, Alejandro Díaz-Morcillo, Diego Blas

Comments: 26 pages, 12 figures; v2 matches published version

Subjects: High Energy Physics - Phenomenology (hep-ph); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Experiment (hep-ex); Instrumentation and Detectors (physics.ins-det)

[40]  arXiv:2312.11622 (replaced) [pdf, other]

Title: Mixmaster chaos in an AdS black hole interior

Authors: Marine De Clerck, Sean A. Hartnoll, Jorge E. Santos

Comments: 74 pages including references and appendices. 18 figures. v2: added reference and a minor clarification. v3: added reference, details on numerics and comment on unitarity bound. v4: minor clarifications and references added

Subjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)

[41]  arXiv:2312.16147 (replaced) [pdf, other]

Title: Causal bounds on cosmological angular correlation

Authors: Craig Hogan, Ohkyung Kwon, Stephan S. Meyer, Nathaniel Selub, Frederick Wehlen

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)

[42]  arXiv:2401.06018 (replaced) [pdf, other]

Title: Implications of comprehensive nuclear and astrophysics data on the equations of state of neutron star matter

Authors: Sk Md Adil Imam, Tuhin Malik, Constança Providência, B. K. Agrawal

Subjects: Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)

[43]  arXiv:2401.09846 (replaced) [pdf, other]

Title: Phase structure of holographic superconductors in an Einstein-scalar-Gauss-Bonnet theory with spontaneous scalarization

Authors: Hong Guo, Wei-Liang Qian, Bean Wang

Comments: 24 pages and 10 figures

Subjects: General Relativity and Quantum Cosmology (gr-qc)

[44]  arXiv:2401.13746 (replaced) [pdf, other]

Title: Torsional four-fermion interaction and the Raychaudhuri equation

Authors: Shibendu Gupta Choudhury, Sagar Kumar Maity, Amitabha Lahiri

Comments: 30 pages, 1 figure; comments and suggestions are welcome

Subjects: General Relativity and Quantum Cosmology (gr-qc)

[45]  arXiv:2401.14331 (replaced) [pdf, other]

Title: Collapsing Domain Wall Networks: Impact on Pulsar Timing Arrays and Primordial Black Holes

Authors: Ricardo Z. Ferreira, Alessio Notari, Oriol Pujolàs, Fabrizio Rompineve

Comments: 15 pages, 13 figures, minor additions, version to appear on JCAP

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)

[46]  arXiv:2401.15574 (replaced) [pdf, other]

Title: Classical Observables using Exponentiated Spin factors: Electromagnetic Scattering

Authors: Samim Akhtar, Arkajyoti Manna, Akavoor Manu

Comments: v3: 36 pages, 4 figures, references updated, derivation of orbital angular impulse expression in the KMOC Formalism added (Appendix B), matched with the published version

Journal-ref: JHEP 05(2024) 148

Subjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)

[47]  arXiv:2402.03472 (replaced) [pdf, other]

Title: Efficient prescription to search for linear gravitational wave memory from hyperbolic black hole encounters and its application to the NANOGrav 12.5-year dataset

Authors: Subhajit Dandapat, Abhimanyu Susobhanan, Lankeswar Dey, A. Gopakumar, Paul T. Baker, Philippe Jetzer

Comments: 20 pages, 11 figures

Journal-ref: Phys. Rev. D 109, 103018, 2024

Subjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA); General Relativity and Quantum Cosmology (gr-qc)

[48]  arXiv:2403.01910 (replaced) [pdf, other]

Title: Status of Birkhoff's theorem in polymerized semiclassical regime of Loop Quantum Gravity

Authors: Luca Cafaro, Jerzy Lewandowski

Comments: 13 pages, 3 figures

Subjects: General Relativity and Quantum Cosmology (gr-qc)

[49]  arXiv:2403.07056 (replaced) [pdf, other]

Title: Gravitational back-reaction is magical

Authors: ChunJun Cao, Gong Cheng, Alioscia Hamma, Lorenzo Leone, William Munizzi, Savatore F.E. Oliviero

Comments: 62 pages, 20 figures; title changed, Theorem 1 and 2 refined, references added

Subjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); Quantum Physics (quant-ph)

[50]  arXiv:2403.18333 (replaced) [pdf, other]

Title: Quantum gravity of the Heisenberg algebra

Authors: Ahmed Almheiri, Akash Goel, Xu-Yao Hu

Comments: 30 pages + appendices; v2: typos corrected, references added

Subjects: High Energy Physics - Theory (hep-th); Strongly Correlated Electrons (cond-mat.str-el); General Relativity and Quantum Cosmology (gr-qc)

[51]  arXiv:2404.00181 (replaced) [pdf, other]

Title: Oscillations in the Dark?

Authors: Luis A. Escamilla, Supriya Pan, Eleonora Di Valentino, Andronikos Paliathanasis, J. Alberto Vázquez, Weiqiang Yang

Comments: 12 pages, 5 figures, 4 tables

Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)

[52]  arXiv:2405.08080 (replaced) [pdf, other]

Title: Plato Meets de Sitter, or de Sitter's Allegory of the Cave

Authors: Willy Fischler, Sarah Racz

Comments: 21 pages, 7 figures. v2; reference added, fixed typo in eqns 5.2,5.3, & 5.4 results unchanged

Subjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)

[53]  arXiv:2405.09257 (replaced) [pdf, other]

Title: Static spherically symmetric perfect fluid solutions in teleparallel F(T) gravity

Authors: Alexandre Landry

Comments: 47 pages, no figure. Will appear in Axioms

Subjects: General Relativity and Quantum Cosmology (gr-qc); Mathematical Physics (math-ph)

• New submissions
• Cross-lists
• Replacements