Cosmic Evolution in a Modified Brans-Dicke Theory

TL;DR

This paper explores a modified Brans-Dicke theory with a self-interacting potential, demonstrating solutions that allow for accelerated expansion in a flat universe and a constant matter-scalar field energy density ratio.

Contribution

It introduces a class of solutions in Einstein frame where accelerated expansion occurs with large Brans-Dicke parameter values, aligning with local gravity tests.

Findings

Accelerated expansion possible for large Brans-Dicke parameter

Constant ratio of matter and scalar field energy densities achieved

Theory behaves as an interacting quintessence model

Abstract

We consider Brans-Dicke theory with a self-interacting potential in Einstein conformal frame. We introduce a class of solutions in which an accelerating expansion is possible in a spatially flat universe for positive and large values of the Brans-Dicke parameter consistent with local gravity experiments. In this Einstein frame formulation, the theory appears as an interacting quintessence model in which the interaction term is given by the conformal transformation. In such an interacting model, we shall show that the solutions lead simultaneously to a constant ratio of energy densities of matter and the scalar field.