Emergent universe supported by chiral cosmological fields in 5D Einstein-Gauss-Bonnet gravity

Abstract

We propose the application of the chiral cosmological model (CCM) for the Einstein-Gauss-Bonnet (EGB) theory of gravitation with the aim of finding new models of the Emergent Universe (EmU) scenario. We analysed the EmU supported by two chiral cosmological fields for a spatially flat universe, while we have used three chiral fields when we investigated open and closed universes. To prove the validity of the EmU scenario we fixed the scale factor and found the exact solution by decomposition of EGB equations and solving the chiral field dynamics equation. To this end, we suggested the decomposition of the EGB equations in such a way that the first chiral field is responsible for the Einstein part of the model, while the second field, together with kinetic interaction term, is connected with the Gauss-Bonnet part of the theory. We proved that both fields are phantom ones under this decomposition, and that the model has a solution if the kinetic interaction between the fields equals a constant. We have presented the exact solution in terms of cosmic time. This was done for a spatially flat universe. In the case of open and closed universes we introduced the third chiral field (canonical for closed and phantom for open universe) which is responsible for the EGB and curvature parts. The solution of the third field equation is obtained in quadratures. Thus we have proved that the CCM is able to support EmU scenario in EGB gravity for spatially flat, open and closed universes.

Cosmological solutions in multiscalar field theory

“…Multi-scalar field models where interaction exists in the kinetic term of the Lagrangian is where this work focuses. A specific family of these models, where the two scalar fields defined into a two-dimensional space of constant nonvanishing curvature, are the Chiral cosmological models [33,40,41] which are directly related with the non-linear sigma cosmological model [42][43][44]. In this work we consider two-scalar field cosmological model where the one field is quintessence and the second field interact with the quintessence only in the kinetic term.…”

Emergent universe with interacting fluids and the generalized second law of thermodynamics

“…A spatially flat universe is most likely as predicted from recent cosmological and astronomical observations. Such an emergent universe scenario can be realized also in a modified theory of gravitation [22] by including a Gauss-Bonnet term in the presence of dilaton coupling [23], Brane world gravity [29,30,26], Brans-Dicke theory [27], the non-linear sigma model [28], Chiral cosmological fields in Einstein Gauss-Bonnet gravity [29], dark sector fields in a chiral cosmological model [30] and exact global phantonical solution [31]. Emergent universe accommodates a late time de-Sitter phase and thus it naturally leads to the late time acceleration of the universe, as well.…”

Cosmic evolution in f(T) gravity theory

“…In cosmic evolution to have an emergent scenario, the evolution of Hubble parameter have the well known differential equation [52,53,34]…”