Magnetized Einstein–Maxwell-dilaton model under an external electric field

We employ an analytic solution of a magnetized Einstein–Maxwell-dilaton gravity model whose parameters have been determined so that its holographic dual has the most similarity to the confining QCD-like theories. Analyzing the total potential of a quark–antiquark pair, we are able to investigate the effect of an electric field on different phases of the background which are the thermal AdS and black hole phases. This is helpful for better understanding of the confining character and the phases of the system. We find out that the field theory dual to the black hole solution is always deconfined, as expected. However, although the thermal AdS phase generally describes the confining phase, for quark pairs parallel to B (longitudinal case) with $$B>B_{\mathrm {critical}}$$ B > B critical the response of the system mimics the deconfinement, since there is no IR wall in the bulk and the critical field $$E_s=0$$ E s = 0 , as is the case for the deconfined phase. We moreover observe that in the black hole phase with sufficiently small values of $$\mu $$ μ and in the thermal AdS phase, for both longitudinal and transverse cases, the magnetic field enhances the Schwinger effect, which can be termed as the inverse magnetic catalysis (IMC). This is deduced both from the decrease of critical electric fields and decreasing the height and width of the total potential barrier the quarks are facing with. However, by increasing $$\mu $$ μ to higher values, IMC turns into magnetic catalysis, as also observed from the diagram of the Hawking–Page phase transition temperature versus B for the background geometry.

Islands in multiverse models

We consider multiverse models in two-dimensional linear dilaton-gravity theories as toy models of false vacuum eternal inflation. Coupling conformal matter we calculate the Von Neumann entropy of subregions. When these are sufficiently large we find that an island develops covering most of the rest of the multiverse, leading to a Page-like transition. This resonates with a description of multiverse models in semiclassical quantum cosmology, where a measure for local predictions is given by saddle point geometries which coarse-grain over any structure associated with eternal inflation beyond one’s patch.

Replica wormholes and capacity of entanglement

We consider the capacity of entanglement as a probe of the Hawking radiation in a two-dimensional dilaton gravity coupled with conformal matter of large degrees of freedom. A formula calculating the capacity is derived using the gravitational path integral, from which we speculate that the capacity has a discontinuity at the Page time in contrast to the continuous behavior of the generalized entropy. We apply the formula to a replica wormhole solution in an eternal AdS black hole coupled to a flat non-gravitating bath and show that the capacity of entanglement is saturated by the thermal capacity of the black hole in the high temperature limit.

2D holography beyond the Jackiw-Teitelboim model

Having in mind extensions of 2D holography beyond the Jackiw-Teitelboim model we propose holographic counterterms and asymptotic conditions for a family of asymptotically AdS2 dilaton gravity models leading to a consistent variational problem and a finite on-shell action. We show the presence of asymptotic Virasoro symmetries in all these models. The Schwarzian action generates (a part) of the equations of motion governing the asymptotic degrees of freedom. We also analyse the applicability of various entropy formulae. By a dilaton-dependent conformal transformation our results are extended to an even larger class of models having exotic asymptotic behavior. We also analyse asymptotic symmetries for some other classes of dilaton gravities without, however, constructing holographic counterterms.

Quasinormal Frequencies of a Two-Dimensional Asymptotically Anti-de Sitter Black Hole of the Dilaton Gravity Theory

We numerically calculate the quasinormal frequencies of the Klein-Gordon and Dirac fields propagating in a two-dimensional asymptotically anti-de Sitter black hole of the dilaton gravity theory. For the Klein-Gordon field we use the Horowitz-Hubeny method and the asymptotic iteration method for second order differential equations. For the Dirac field we first exploit the Horowitz-Hubeny method. As a second method, instead of using the asymptotic iteration method for second order differential equations, we propose to take as a basis its formulation for coupled systems of first order differential equations. For the two fields we find that the results that produce the two numerical methods are consistent. Furthermore for both fields we obtain that their quasinormal modes are stable and we compare their quasinormal frequencies to analyze whether their spectra are isospectral. Finally we discuss the main results.

Two-dimensional black holes in the limiting curvature theory of gravity

In this paper we discuss modified gravity models in which growth of the curvature is dynamically restricted. To illustrate interesting features of such models we consider a modification of two-dimensional dilaton gravity theory which satisfies the limiting curvature condition. We show that such a model describes two-dimensional black holes which contain the de Sitter-like core instead of the singularity of the original non-modified theory. In the second part of the paper we study Vaidya type solutions of the model of the limiting curvature theory of gravity and used them to analyse properties of black holes which are created by the collapse of null fluid. We also apply these solutions to study interesting features of a black hole evaporation.

Komar integral and Smarr formula for axion-dilaton black holes versus S duality

We construct the Komar integral for axion-dilaton gravity using Wald’s formalism and momentum maps and we use it to derive a Smarr relation for stationary axion-dilaton black holes. While the Wald-Noether 2-form charge is not invariant under SL(2, ℝ) electric-magnetic duality transformations because Wald’s formalism does not account for magnetic charges and potentials, the Komar integral constructed with it turns out to be invariant and, in more general theories, it will be fully symplectic invariant. We check the Smarr formula obtained with the most general family of static axion-dilaton black holes.