The European Physical Journal C最新文献

Exploring the universal structure of the gravitational path integral beyond semi-classical saddles and uncovering a compelling statistical interpretation of black hole thermodynamics have long been significant challenges. We investigate the statistical interpretation of the Kerr-AdS black hole thermodynamics through an ensemble-averaged theory. By extending the phase space to include all possible states with conical singularities in their Euclidean counterparts, we derive the probability distribution of different states inherited from the Euclidean gravitational path integral. Moreover, we can define a density matrix of all states in the phase space. By ensemble-averaging over all states, we show that the black hole phase transition naturally arises in the semi-classical limit. Away from the semi-classical regime, the ensemble-averaged theory exhibits a notable deviation from the conventional phase transition. Expanding around the classical saddles yields the subleading-order correction to the Gibbs free energy, which is half of the Hawking temperature. We demonstrate that the half Hawking temperature correction is a universal feature inherent to black holes in asymptotically AdS spacetime. With the subleading-order correction to Gibbs free energy, we also suggest that the whole black hole thermodynamic should be corrected accordingly.

The detection of gravitational waves with ground-based laser interferometers has opened a new window to test and constrain General Relativity (GR) in the strong, dynamical, and non-linear regime. In this paper, we follow an agnostic approach and we study the quasi-normal modes of gravitational perturbations of Johannsen black holes under the assumptions of the validity of the Einstein Equations and of low values of the black hole spin parameter and deformation parameters. We find that the deformation parameter (alpha _{13}) has a stronger impact on the quasi-normal modes than the other leading order deformation parameters ((alpha _{22}), (alpha _{52}), and (epsilon _{3})). We derive a fitting formula for the fundamental modes with (l=2) and (l=3) for the deformation parameter (alpha _{13}) valid in the slow rotation approximation ((a_* < 0.4)). Finally, we constrain (alpha _{13}) from the event GW170104; within our analysis, we find that the data of GW170104 are consistent with the predictions of GR.

This manuscript gathers and reviews part of our work focusing on the exploration of modified theories of gravity known as degenerate higher order scalar-tensor (DHOST) theories. It focuses on the construction of exact solutions describing both black holes and radiative spacetimes. After motivating the need for alternatives theories of gravity beyond general relativity, we discuss in more details the long terms objectives of this research program. The first one is to characterize both the theory and some sectors of the solution space of DHOST gravity. The second one is to provide concrete and exact solutions of the DHOST field equations describing compact objects, in particular black holes, that can be used to confront DHOST theories to current and future observations in the strong field regime. A key tool towards these two objectives is the concept of disformal field redefinition (DFR) which plays a central role in this exploration. We start be reviewing the structure of the DHOST theory space, the notion of degeneracy conditions and the stability of these degeneracy classes under DFR. Then we review several key notions related to stationary and axi-symmetric black holes, and in particular the no-hair theorems derived in GR and in its scalar-tensor extensions. The rest of the sections are devoted to a review of the disformal solution generating map, the subtle role of matter coupling and how it can be used to construct new hairy black holes solutions. The case of spherically symmetric solutions, axi-symmetric but non-rotating solutions, and finally rotating solutions are discussed, underlining the advantages and the limitations of this approach. A brief review of the rotating black holes solutions found so far in this context is followed by the detailed description of the disformed Kerr black hole. We further comment on on-going efforts to construct rotating black hole solutions mimicking the closest the Kerr geometry. Then, we discuss how DFR affects the algebraic properties of a gravitational field and in particular its Petrov type. This provides a first systematic characterization of this effect, paving the road for constructing new solutions with a fixed Petrov type. Finally, we review more recent works aiming at characterizing the effect of a DFR on non-linear radiative geometries. We derive the general conditions for the generation of disformal tensorial gravitational wave and we study in detail a concrete example in DHOST gravity. While most of the material presented here is a re-organized and augmented version of our published works, we have included new results and also new proposals to construct phenomenologically interesting solutions.

We provide an improved definition of new conserved quantities derived from the energy–momentum tensor in curved spacetime by introducing an additional scalar function. We find that the conserved current and the associated conserved charge become geometric under a certain initial condition of the scalar function, and show that such a conserved geometric current generally exists in curved spacetime. Furthermore, we demonstrate that the geometric conserved current agrees with the entropy current in an effective theory of a perfect fluid, thus the conserved charge is the total entropy of the system. While the geometric charge can be regarded as the entropy for a nondissipative fluid, its physical meaning should be investigated for more general cases.

Motivated by the recent progress on the holographic dual of the extended thermodynamics for black holes in anti-de Sitter (AdS) space, we investigate the holographic thermodynamics for the five-dimensional neutral Gauss–Bonnet AdS black hole in the context of the anti-de Sitter/conformal field theory (AdS/CFT) correspondence. Through the extended bulk thermodynamics for the five-dimensional Gauss–Bonnet AdS black hole, we derive the first law of the CFT thermodynamics which is obtained by directly translating the arbitrary conformal factors in the dual CFT. In addition to the newly defined chemical potential (mu ) conjugating to the central charge C, we obtain other pairs of thermodynamics for the CFT, such as the temperature ({tilde{T}}) and the entropy S, the Gauss–Bonnet coupling constant ({tilde{alpha }}) and its conjugate variable (tilde{mathcal {A}}), the pressure (mathcal {P}) and its conjugate volume (mathcal {V}). In the fixed C, (mathcal {V}) and ({tilde{alpha }}) canonical ensemble, we obtain the canonical description of the CFT thermodynamics and observe the standard swallowtail behavior in the Helmholtz free energy vs the temperature plot. The self-intersection point of the Helmholtz free energy indicates the phase transition between the high and low entropy states of the CFT. By using Maxwell’s equal area law, we get the critical point and coexistence curve for the high and low entropy phases of the CFT. Besides, we get the critical exponents for the CFT, and find that the critical point and critical exponents associated with the ({tilde{T}}-S) criticality of the CFT are the same as those of the five-dimensional Gauss–Bonnet AdS black hole.

Non-relativistic conformal field theory describes many-body physics at unitarity. The correlation functions of the system are fixed by the requirement of the conformal invariance. In this article, we discuss the correlation functions of scalar operators in non-relativistic conformal field theories in momentum space. We discuss the solution of conformal Ward identities and express 2,3, and 4-point functions as a function of energy and momentum. We also express the 3- and 4-point functions as the one-loop and three-loop Feynman diagram computations in the momentum space. Lastly, we generalize the discussion to the momentum space correlation functions in the presence of a boundary.

We study the role of the equilibrium equation in bootstrapped Newtonian gravity (BNG) by including terms inspired by the post-Newtonian expansion of the Tolman–Oppenheimer–Volkov (TOV) equation. We then compare (approximate) BNG solutions for homogenous stars with their Newtonian and General Relativistic exact solutions. Regardless of the additional terms from the conservation equation, BNG stars do not exhibit a Buchdahl limit. However, specific extra terms added to this equation can cause the pressure to become negative inside stars with compactness smaller than the critical values for BNG black hole formation.

We study genuine N-partite entanglement of massless Dirac fields new a black hole event horizon (BEH) and a cosmological event horizon (CEH) in the Schwarzschild–de Sitter (SdS) spacetime, respectively. We obtain the general analytical expression of genuine N-partite entanglement shared by N observers, each located near the BEH and CEH, respectively. It is shown that genuine N-partite entanglement situated near the BEH can decrease to zero with the decrease of the mass of the black hole, suggesting that the Hawking effect of the black hole destroys quantum entanglement. Because the Hawking effect of the black hole located near the CEH is very weak, its impact on quantum entanglement is negligible. In addition, choosing appropriate initial parameters is beneficial to protecting quantum entanglement in multi-event horizon spacetime.

The cosmic growth rate, which is related to peculiar velocity and is a primary scientific objective of galaxy spectroscopic surveys, can be inferred from the Redshift Space Distortion effect and the kinetic Sunyaev–Zel’dovich (kSZ) effect. However, the reconstruction noise power spectrum of the radial velocity field in kSZ is significantly dependent on the measurement of the small-scale galaxy-electron power spectrum (P_{text {ge}}.) In this study, we thoroughly discuss the enhancement of cosmic growth rate measurements facilitated by Fast Radio Bursts (FRBs), which probe the electron density of the universe along their propagation paths to provide crucial additional information on (P_{text {ge}}.) Subsequently, we utilize future spectroscopic surveys from the Chinese Space Station Telescope and the CMB-S4 experiment, combined with FRB dispersion measures, to achieve precise measurements of the cosmic growth rate at redshifts (z_{text {g}} = 0.15,,0.45,,0.75.) Employing Fisher matrix forecasting analysis, we anticipate that constraints on (fsigma _8) will reach a precision of 0.1% with a sample size of (10^6) FRBs. Furthermore, we perform a global analysis using Markov Chain Monte Carlo methods to constrain key parameters of three distinct dark energy models and a modified gravity model based on cosmic growth rate measurements. The results demonstrate that these refined (fsigma _8) measurements considerably enhance the constraints on relevant cosmological parameters compared to those obtained from Planck CMB data. As the number of observed FRBs increases, alongside more precise galaxy surveys and next-generation CMB observations, new opportunities will arise for constraining cosmological models using the kSZ effect and for developing novel cosmological applications of FRBs.

Recent pulsar timing array collaborations have reported evidence of the stochastic gravitational wave background. The gravitational waves induced by primordial curvature perturbations, referred to as scalar-induced gravitational waves (SIGWs), could potentially be the physical origins of the gravitational wave background. Due to nonlinearity of Einstein’s gravity, there is non-Gaussianity of SIGWs even when the sourced primordial curvature perturbation is Gaussian. This paper investigates the intrinsic non-Gaussianity of SIGWs influenced by formation of primordial black holes. Specifically, we examine whether spectral width of Gaussian primordial curvature perturbations can affect non-Gaussianity of SIGWs. In order to ensure us to correctly quantify the degree of non-Gaussianity, we introduce an oscillation average scheme that can conserve the exact results of skewness of SIGWs. In this framework, the oscillation of SIGWs not only suppresses the bispectrum amplitude but also leads to a flattened-type bispectrum. Based on our results of skewness, it is found that the primordial curvature power spectrum with a narrower width can enhance the intrinsic non-Gaussianity.