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Abstract In this work, we investigate the near horizon and asymptotic symmetries of static and rotating hairy-AdS black hole in the framework of general minimal massive gravity. We obtain energy, angular momentum and entropy of the solutions. Then we show that our results for these quantities are consistent with the first law of black hole thermodynamics. By considering the near horizon geometry of black hole, we find near horizon conserved charges and their algebra. By writing the algebra of conserved charges in terms of Fourier modes we have obtained the conserved charges in terms of zero modes.

Abstract We study some aspects of a class of non-AdS holography where the 3D bulk gravity is given by generalized minimal massive gravity (GMMG). We consider the spacelike warped $$AdS_3$$ A d S 3 ( $$WAdS_3$$ W A d S 3 ) black hole solution of this model where the 2d dual boundary theory is the warped conformal field theory (WFCT). The charge algebra of the isometries in the bulk and the charge algebra of the vacuum symmetries at the boundary are compatible and this is an evidence for the duality conjecture. Further evidence for this duality is the equality of entanglement entropy and modular Hamiltonian on both sides of the duality. So we consider the modular Hamiltonian for the single interval at the boundary in associated to the modular flow generators of the vacuum. We calculate the gravitational charge in associated to the asymptotic Killing vectors that preserve the metric boundary conditions. Assuming the first law of the entanglement entropy to be true, we introduce the matching conditions between the variables in two side of the duality and we find equality of the modular Hamiltonian variations and the gravitational charge variations in two sides of the duality. According to the results of the present paper we can say with more sure that the dual theory of the warped AdS3 black hole solution of GMMG is a Warped CFT.

Abstract Previously we have studied the Generalized Minimal Massive Gravity (GMMG) in asymptotically $$AdS_3$$ A d S 3 background, and have shown that the theory is free of negative-energy bulk modes. Also we have shown GMMG avoids the aforementioned “bulk-boundary unitarity clash”. Here instead of $$AdS_3$$ A d S 3 space we consider asymptotically flat space, and study this model in the flat limit. The dual field theory of GMMG in the flat limit is a $$BMS_3$$ B M S 3 invariant field theory, dubbed (BMSFT) and we have BMS algebra asymptotically instead of Virasoro algebra. In fact here we present an evidence for this claim. Entanglement entropy of GMMG is calculated in the background in the flat null infinity. Our evidence for mentioned claim is the result for entanglement entropy in filed theory side and in the bulk (in the gravity side). At first using Cardy formula and Rindler transformation, we calculate entanglement entropy of BMSFT in three different cases. Zero temperature on the plane and on the cylinder, and non-zero temperature case. Then we obtain the entanglement entropy in the bulk. Our results in gravity side are exactly in agreement with field theory calculations.

Abstract In this paper, we present a method to reconstruct cosmographic parameters, $$\{q,j,s,l\}$$ {q,j,s,l} and their evolution from particular cosmological models. In this method inspired by dynamical system approach, we convert the equation of the cosmological model into an equivalent system of first order differential equations which is much easier to solve numerically. Then, we reproduce the cosmographic parameters in terms of these variables. Instead of best fitting the cosmographic parameters with observation directly, we best fit and estimate the parameters and initial conditions of the model by observational, then the cosmographic parameters will be constrained automatically. The advantage of this method is that, it is free of some of shortcomings reconstructing theories with higher-order derivatives. It also enable us to measure not only the current value of cosmographic parameters $$\{q_{0},j_{0},s_{0},l_{0}\}$$ {q0,j0,s0,l0} the past values, $$\{q_{i},j_{i},s_{i},l_{i}\}$$ {qi,ji,si,li} , future values $$\{q_{f},j_{f},s_{f},l_{f}\}$$ {qf,jf,sf,lf} and their evolution. This can be a useful tool to test, compare and distinguish different cosmological models according to the reconstructed cosmographic parameters at different epoch of the universe.

Abstract Recently, the theory of topologically massive gravity non-minimally coupled to a scalar field has been proposed, which comes from the Lorentz–Chern–Simons theory (JHEP 06, 113, 2015), a torsion-free theory. We extend this theory by adding an extra term which makes the torsion to be non-zero. We show that the BTZ spacetime is a particular solution to this theory in the case where the scalar field is constant. The quasi-local conserved charge is defined by the concept of the generalized off-shell ADT current. Also a general formula is found for the entropy of the stationary black hole solution in context of the considered theory. The obtained formulas are applied to the BTZ black hole solution in order to obtain the energy, the angular momentum and the entropy of this solution. The central extension term, the central charges and the eigenvalues of the Virasoro algebra generators for the BTZ black hole solution are thus obtained. The energy and the angular momentum of the BTZ black hole using the eigenvalues of the Virasoro algebra generators are calculated. Also, using the Cardy formula, the entropy of the BTZ black hole is found. It is found that the results obtained in two different ways exactly match, just as expected.

Tachyon inflationary universe model on the brane in the context of warm inflation is studied. In slow-roll approximation and in longitudinal gauge, we find the primordial perturbation spectrums for this scenario. We also present the general expressions of the tensor-scalar ratio, scalar spectral index, and its running. We develop our model by using exponential potential; the characteristics of this model are calculated in great detail. We also study our model in the context of intermediate (where scale factor expands as a=a0exp⁡Atf) and logamediate (where the scale factor expands as a=a0exp⁡Aln⁡tν) models of inflation. In these two sectors, dissipative parameter is considered as a constant parameter and a function of tachyon field. Our model is compatible with observational data. The parameters of the model are restricted by Planck data.

In a series of papers, Quesne and Tkachuk (2006) presented a D + 1-dimensional (β, β′)-two-parameter Lorentz-covariant deformed algebra which leads to a nonzero minimal measurable length. In this paper, the Lagrangian formulation of electrodynamics in a 3 + 1-dimensional spacetime described by Quesne-Tkachuk algebra is studied in the special case of β′ = 2β up to the first order over the deformation parameter β. It is demonstrated that at the classical level there is a similarity between electrodynamics in the presence of a minimal measurable length (generalized electrodynamics) and Lee-Wick electrodynamics. We obtain the free space solutions of the inhomogeneous Maxwell’s equations in the presence of a minimal length. These solutions describe two vector particles (a massless vector particle and a massive vector particle). We estimate two different upper bounds on the isotropic minimal length. The first upper bound is near to the electroweak length scale ( ℓ electroweak ~ 10−18 m), while the second one is near to the length scale for the strong interactions ( ℓ strong ~ 10−15 m). The relationship between the Gaete-Spallucci nonlocal electrodynamics (2012) and electrodynamics with a minimal length is investigated.

We consider the realization of 2-dimensional Galilean conformal algebra (GCA2) on the boundary of cosmological new massive gravity. At first, we consider the contracted BTZ black hole solution. We obtain entropy formula for the GCA2 in terms of contracted scaling dimension Δ and central charge C1. This entropy formula exactly matches with the nonrelativistic limit of Bekenstein-Hawking entropy of BTZ black hole. Then, we extend our study to the contracted warped AdS3 black hole solution of CNMG. We obtain the entropy of dual GCA2 in terms of central charges and finite temperatures, T1, T2. Again, this expression coincides with the nonrelativistic limit of Bekenstein-Hawking entropy formula of warped AdS3 black hole.

Abstract Using the quasi-normal modes frequency of near extremal Schwar-zschild-de Sitter black holes, we obtain area and entropy spectrum for the black hole horizon. By using Bohr-Sommerfeld quantization for an adiabatic invariant I = ∫dEω(E), where E is the energy of the system and ω(E) is the vibrational frequency, we arrive at an equally spaced mass spectrum. In the other terms, we extend directly the Kunstatter’s approach kun [6] to determine mass and entropy spectrum of near extremal Schwarzschild-de Sitter black holes which are asymptotically de Sitter rather than asymptotically flat. We show the mass and area spectrum is equally spaced only for a fixed l. For different l there are multiplets with different values of spacing. [ABSTRACT FROM AUTHOR]

The Casimir stress on a cylindrical shell in the de Sitter background for a massless scalar field satisfying Dirichlet boundary conditions on the cylinder is calculated. The metric is written in conformally flat form to make maximal use of the Minkowski space calculations. In the framework of a toy model, we have considered the quantum vacuum effect in the evolution of a domain wall between a cylindrical or in fact circle region around the z axis in which vacuum is Λin and the remaining part of space where vacuum is Λout. [ABSTRACT FROM AUTHOR]

In this paper we show that warped AdS3 black hole spacetime is a solution of the generalized minimal massive gravity (GMMG) and introduce suitable boundary conditions for asymptotically warped AdS3 spacetimes. Then we find the Killing vector fields such that transformations generated by them preserve the considered boundary conditions. We calculate the conserved charges which correspond to the obtained Killing vector fields and show that the algebra of the asymptotic conserved charges is given as the semi direct product of the Virasoro algebra with U(1) current algebra. We use a particular Sugawara construction to reconstruct the conformal algebra. Thus, we are allowed to use the Cardy formula to calculate the entropy of the warped black hole. We demonstrate that the gravitational entropy of the warped black hole exactly coincides with what we obtain via Cardy’s formula. As we expect, the warped Cardy formula also gives us exactly the same result as we obtain from the usual Cardy’s formula. We calculate mass and angular momentum of the warped black hole and then check that obtained mass, angular momentum and entropy to satisfy the first law of the black hole mechanics. According to the results of this paper we believe that the dual theory of the warped AdS3 black hole solution of GMMG is a warped CFT. [ABSTRACT FROM AUTHOR]

In this paper we consider the Einstein–Maxwell theory and define a combined transformation composed of diffeomorphism and U(1) gauge transformation. For generality, we assume that the generator χ of such transformation is field-dependent. We define the extended off-shell ADT current and then off-shell ADT charge such that they are conserved off-shell for the asymptotically field-dependent symmetry generator χ. Then, we define the conserved charge corresponding to the asymptotically field-dependent symmetry generator χ. We apply the presented method to find the conserved charges of the asymptotically AdS3 spacetimes in the context of the Einstein–Maxwell theory in three dimensions. Although the usual proposal for the quasi local charges provides divergent global charges for the Einstein–Maxwell theory with negative cosmological constant in three dimensions, here we avoid this problem by introducing proposed combined transformation χ [ABSTRACT FROM AUTHOR]

In the present work, a warm inflationary Universe model with viscous pressure on the brane in a high-dissipation regime is studied. We derive a condition that is required for this model to be realized in a slow-roll approximation. We also present analytic expressions for the density perturbation and the amplitude of the tensor perturbation in a longitudinal gauge. General expressions of the tensor-to-scalar ratio and the scalar spectral index and its running are obtained. We develop our model using chaotic potential. The characteristics of the model are calculated for two specific cases: (1) when the dissipative parameter Γ and the bulk viscous parameter ζ are constant parameters and (2) with the dissipative parameter as a function of scalar field ϕ and the bulk viscous parameter as a function of radiation-matter mixture energy density ρ. The parameters of the model are restricted by WMAP9 and Planck observational data. [ABSTRACT FROM AUTHOR]

We show that a BTZ black hole solution of cosmological topological massive gravity has a hidden conformal symmetry. In this regard, we consider the wave equation of a massless scalar field propagating in BTZ spacetime and find that the wave equation could be written in terms of the SL(2, R) quadratic Casimir. From the conformal coordinates, the temperatures of the dual conformal field theories (CFTs) could be read directly. Moreover, we compute the microscopic entropy of the dual CFT by the Cardy formula and find a perfect match to the Bekenstein-Hawking entropy of a BTZ black hole. Then, we consider Galilean conformal algebras (GCA), which arises as a contraction of relativistic conformal algebras (x - [?]x, t - t, [?] - 0). We show that there is a correspondence between GCA2 on the boundary and contracted BTZ in the bulk. For this purpose we obtain the central charges and temperatures of GCA2. Then, we compute the microscopic entropy of the GCA2 by the Cardy formula and find a perfect match to the Bekenstein-Hawking entropy of a BTZ black hole in a non-relativistic limit. The absorption cross section of a near-region scalar field also matches the microscopic absorption cross section of the dual GCA2. So we find further evidence that shows correspondence between a contracted BTZ black hole and two-dimensional GCA. [ABSTRACT FROM AUTHOR]

We show that the extremal Einstein-Maxwell-Dilaton-Axion (EMDA) black hole and the extremal Kaluza-Klein black hole have a hidden conformal symmetry. In this regard, we consider the wave equations of a massless scalar field propagating in EMDA and Kaluza-Klein spacetimes and find in the 'near region', the wave equations in the extremal limit can be written in terms of SL(2, R) Casimir invariants. Moreover, we obtain the microscopic entropy of the extremal EMDA black hole and extremal Kaluza-Klein black hole and find that the correlation function of a near-region scalar field matches the microscopic graybody factor of the dual 2D CFT. [ABSTRACT FROM AUTHOR]

Vacuum expectation values of the energy-momentum tensor and the Casimir forces are evaluated for scalar and electromagnetic fields in the geometry of two curved boundaries on the background of the Robertson-Walker spacetime with negative spatial curvature. The boundaries under consideration are conformal images of the flat boundaries in Rindler spacetime. Robin boundary conditions are imposed in the case of the scalar field and perfect conductor boundary conditions are assumed for the electromagnetic field. We use the conformal relation between the Robertson-Walker and Rindler spacetimes and the corresponding results for two parallel plates moving with uniform proper acceleration through the Fulling-Rindler vacuum. For the general scale factor the vacuum energy-momentum tensor is decomposed into the boundary-free and boundary-induced parts. The latter is non-diagonal. The Casimir forces are directed along the normals to the boundaries. For the Dirichlet and Neumann scalars and for the electromagnetic field these forces are attractive for all separations. [ABSTRACT FROM AUTHOR]

Warm inflationary model in the context of loop quantum cosmology is investigated. To this aim we consider two cases intermediate inflation and logamediate inflation. In both the cases, assuming a constant dissipation coefficient, we study the model under consideration in weak dissipation regime and also in strong dissipation regime. In each of these cases, we obtain various parameters such as potential function of inflationary scalar field and slow-roll parameters. Perturbation theory and also finding relations between perturbative parameters is studied.