Cosmological Inflation in f(Q, T) Gravity

Abstract

We study the cosmological inflation within the context of f (Q, T ) gravity, wherein Q is the nonmetricity scalar and T is the trace of the matter energy-momentum tensor. By choosing a linear combination of Q and T , we first analyze the realization of an inflationary scenario driven via the geometrical effects of f (Q, T ) gravity and then, we obtain the modified slow-roll parameters, the scalar and the tensor spectral indices, and the tensor-to-scalar ratio for the proposed model. In addition, by choosing a few appropriate inflationary potentials and by applying the slow-roll approximations, we calculate these inflationary observables in the presence of an inflaton scalar field. The results indicate that by properly restricting the free parameters, the proposed model provides appropriate predictions that are consistent with the observational data obtained from the Planck 2018.

FLRW solutions in $f(Q)$ theory: the effect of using different connections

“…In the time gauge that we are, where Q = −t, and since (20) holds, the Hubble function is just given by H = t 6 . In order to obtain its functional behaviour in the cosmic time gauge, where N = 1, we need to first calculate τ as a function of t from (31). If we choose the minus sign expression from (38a) (this is done, as we are going to see immediately afterwards, so as to map the function τ to the positive half-line) and consider that α is positive, then we obtain…”

“…Both of the above solutions can be easily transformed into the cosmic time gauge. We just need to use (31) to derive the t(τ ) relation, then the scalars a(t) and Q(t) can be easily calculated by a straightforward substitution. For the γ(t) however, we need to remind ourselves that this is not a scalar, so we cannot simply substitute in it the t(τ ).…”

“…Wormhole solutions in the context of f (Q) gravity are given in [28]. Non-minimal couplings to matter have been considered in [29], generalizations including the trace of the energy momentum tensor are found in [30,31] and studies on observational constraints are given in [32,33].…”

Evolution of gravitational waves in non-minimal coupling between geometry and matter theories of gravity

“…The cosmological parameters were obtained in some functional forms of f (Q, T ), which favored an accelerated universe expansion using geometrical modification instead of a cosmological constant. Observational constraints of f (Q, T ) gravity [59], cosmological implications of its Weyl-type gravity [60][61][62], the various energy conditions [63][64][65], transit cosmological models of f (Q, T ) gravity [66], dynamical aspects and cosmic acceleration in f (Q, T ) gravity [67][68][69][70] and cosmological inflation in f (Q, T ) gravity [71] shows that f (Q, T ) gravity can provide a consistent solution to the dark energy problem. Moreover, in a recent paper, a covariant formulation of the theory is obtained that is equivalent and provides a direct comparison with GR [72].…”