相关论文: Energy Conditions and Stability in generalized $f(…
In the context of f(G) modified gravity, we address the cosmic application of the most generalized form of holographic dark energy (The European Physical Journal C, 77, (2017): 1-8) in this study, as well as a specific instance of it in the…
Recently Horava proposed a renormalizable gravity theory with higher spatial derivatives in four dimensions which reduces to Einstein gravity with a non-vanishing cosmological constant in IR but with improved UV behaviors. Here, I consider…
The stability criteria for the generalized Brans-Dicke cosmology in a spatially flat, homogeneous and isotropic cosmological model is discussed in the presence of a perfect fluid. The generalization comes through the channel that the…
The present thesis is focused on the study of FLRW cosmology in modified gravities and with scalar fields. The mystery of dark energy has made that the last decade, many efforts in theoretical physics have been focused on the explanation of…
Recently, a generalized gravity theory was proposed by Harko etal where the Lagrangian density is an arbitrary function of the Ricci scalar R and the trace of the stress-energy tensor T, known as F(R,T) gravity. In their derivation of the…
A new method to constrain gravitational theories depending on the Ricci scalar is presented. It is based on the weak energy condition and yields limits on the parameters of a given theory through the current values of the derivatives of the…
The generalized $f(R)$ gravity with curvature-matter coupling in five-dimensional (5D) spacetime can be established by assuming a hypersurface-orthogonal spacelike Killing vector field of 5D spacetime, and it can be reduced to the 4D…
General Relativity (GR) is a phenomenologically successful theory that rests on firm foundations, but has not been tested on cosmological scales. The advent of dark energy (and possibly even the requirement of cold dark matter), has…
The present study is motivated by the study of reference [1], where the generalized second law of thermodynamics has been investigated for a flat FRW universe for two viable models of $f(T)$ gravity. In the present work, we have considered…
We study the evolution of cosmological perturbations in f(G) gravity, where the Lagrangian is the sum of a Ricci scalar R and an arbitrary function f in terms of a Gauss-Bonnet term G. We derive the equations for perturbations assuming…
Via the AdS/CFT correspondence, fundamental constraints on the entanglement structure of quantum systems translate to constraints on spacetime geometries that must be satisfied in any consistent theory of quantum gravity. In this paper, we…
We investigate the radiative stability of Horndeski scalar-tensor theories with luminally propagating gravitational waves (as extensively discussed in the wake of GW170817) and show that in general there is a tension between obtaining…
A modified theory of general relativity is proposed, where the gravitational constant is replaced by a dynamical variable in space-time. The dynamics of the gravitational coupling is described by a family of parametrized null geodesics,…
The Energy Problem (EP) in General Relativity (GR) is analyzed in the context of GR's axiomatic inconsistencies. EP is classified according to its local and global aspects. The local aspects of the EP include noncovariance of the…
We review the status of $f(R,T)$ cosmological models, where $T$ is the trace of the energy momentum tensor $T^{\mu\nu}$. We start focusing on the modified Friedmann equations for the minimally coupled gravitational Lagrangian of the type…
We consider f(R,T) modified theory of gravity in which, in general, the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar and the trace of the energy-momentum tensor. We indicate that in this type of the theory,…
The paper deals with the definition of gravitational energy in conformal teleparallel gravity. The total energy is defined by means of the field equations which allow a local conservation law. Then such an expression is analyzed for a…
Using the corrected entropy-area relation motivated by the loop quantum gravity, we investigate the validity of the generalized second law of thermodynamics in the framework of modified FRW cosmology. We consider a non-flat universe filled…
Late-time cosmic acceleration has motivated the exploration of various extensions of general relativity, among which $f(Q,\mathcal{T})$ gravity, based on the non-metricity scalar $Q$ and the trace of the energy--momentum tensor…
The recently proposed $f(Q, T)$ gravity (Xu et al. Eur. Phys. J. C \textbf{79} (2019) 708) is an extension of the symmetric teleparallel gravity. The gravitational action $L$ is given by an arbitrary function $f$ of the non-metricity $Q$…