Cosmological evolution of two-scalar fields cosmology in the Jordan frame

Abstract

In the present article we study the cosmological evolution of a two-scalar field gravitational theory defined in the Jordan frame. Specifically, we assume one of the scalar fields to be minimally coupled to gravity, while the second field which is the Brans-Dicke scalar field is nonminimally coupled to gravity and also coupled to the other scalar field. In the Einstein frame this theory reduces to a two-scalar field theory where the two fields can interact only in the potential term, which means that the quintom theory is recovered. The cosmological evolution is studied by analyzing the equilibrium points of the field equations in the Jordan frame. We find that the theory can describe the cosmological evolution in large scales, while inflationary solutions are also provided.

A Kaluza-Klein Inspired Brans-Dicke Gravity with Dark Matter and Dark Energy Model

“…It is evident that the complications of the autonomous system in Eqs. (40)(41)(42)(43)(44)(45)(46)(47) in the case of M (5) = 0 lead to the very complicated solutions of the fixed points which can not generically be represented in terms of λ and µ parameters analytically. To demonstrate DM and DE profiles of the KK inspired BD model in this work, we simply analyze the dynamical system in our model by assuming that there are decoupled fields in various settings.…”

“…Having use of the dynamical system analysis, a good candidate of the cosmological models needs to consequently evolve following the series of standard cosmological epochs, i.e., inflation → radiation → dust (matter) → DE phase [8]. A huge number of the studies in the BD cosmological models are extensively analyzed using dynamical system in various classes of the potentials with additional matter fields [28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44]. Interestingly, the BD gravity with the quadratic potential gives the de-Sitter (dS) attractor critical point in the phase space of this model and provides an explanation of the accelerated expansion of the Universe without introducing any form of the exotic matter fields [34].…”

New Conservation Laws and Exact Cosmological Solutions in Brans–Dicke Cosmology with an Extra Scalar Field

“…In the present study, we consider a cosmological model in which the gravitational Action Integral is that of Brans-Dicke theory with an additional scalar field minimally coupled to gravity [43,44]. This two-scalar-field model belongs to the family of multi-scalar field models which have been used as unified dark energy models [45][46][47] or as alternative models for the description of the acceleration phases of the universe [48][49][50][51].…”

Time-averaging axion-like interacting scalar fields models

“…The detailed analysis of inflation driven by two massive scalar fields was presented in [38]. The case of exponential potential and interaction is well studied in [39,40]. In the pioneering paper [41], it was shown Einstein equations, with quantum one-loop contributions of conformally covariant matter fields, do admit a class of nonsingular isotropic homogeneous solutions, which corresponds to an early time de Sitter (inflationary) state.…”