Testing Some f(R,T) Gravity Models from Energy Conditions

Abstract

 , f We consider R T theory of gravity, where is the curvature scalar and T is the trace of the energy momentum tensor. Attention is attached to the special case,and two expressions are assumed for the func-parameters. We observe that by adjusting suitably these input parameters, energy conditions can be satisfied. Moreover, an analysis of the perturbations and stabilities of de Sitter solutions and power-law solutions is performed with the use of the two models. The results show that for some values of the input parameters, for which energy conditions are satisfied, de Sitter solutions and power-law solutions may be stables.

Regular black holes inf(T) Gravity through a nonlinear electrodynamics source

“…1) 2) where g µν is the metric of the space-time, η ab the Minkowski metric, e a the tetrads ( that belongs to the co-tangent space) and e a µ and their inverses e µ a , the tetrads matrices satisfying the relations e a µ e ν a = δ ν µ and e a µ e µ b = δ a b . In terms of these matrix, the root of the determinant of the metric is given by √ −g = det[e a µ ] = e. Then, one can define a geometry where the curvature should be set equal to zero.…”

Searching for a cosmological preferred axis in complicated class of cosmological models: case study f (R, T ) model

“…[33] introduced this type of the Modified Gravity, f (R, T ), which obtained significant outcomes: the reconstruction of cosmological solutions, where late-time acceleration was accomplished by [34] and the energy conditions was analyzed by [3]. [52] studied the thermodynamics of FriedmannLemaître-Robertson-Walker (FLRW) spacetimes.…”

Spotting deviations fromR2inflation

“…Let us now consider a similar K-essence model, whose gravitational Lagrangian is given by, 14) i.e., the gravitational Lagrangian is split into two different contributions: the first function γ(R) corresponds to a standard scalar-tensor f (R) theory, whose physical motivation as next-order terms in the low-energy correction to GR was thoroughly explained in the Introdduction. The second function α(ξ) , i.e., a K-essence Lagrangian, may for instance represent the first approximation to either a dark fluid driving a late-time acceleration or, as is the interest of the present manuscript, to a slow-roll inflaton field.…”

“…A recent line of research has also considered Lagrangians which depend both on the Ricci curvature and on the trace of the energy-momentum tensor T = T µ µ . Originally introduced in [10] and later in [11], some cosmological aspects have been already explored for these kinds of theories, such as the reconstruction of cosmological solutions [12,13] and other issues on energy conditions, thermodynamics and singularities [14][15][16]. However, theories with non standard couplings between the geometry and the matter Lagrangian usually fail to conserve the energy-momentum tensor, which implies a stringent shortcoming for their viability [17].…”