Modified Brans-Dicke cosmology with matter-scalar field interaction

TL;DR

This paper explores an extended Brans-Dicke cosmological model where matter and scalar fields exchange energy, leading to modified dynamics that can remove initial singularities, produce early entropy, and explain late-time acceleration consistent with observations.

Contribution

It introduces a new matter-scalar field interaction in Brans-Dicke theory, resulting in modified Friedmann equations and novel cosmological solutions with singularity removal and acceleration.

Findings

Complete removal of initial singularity in some solutions

Transient acceleration during radiation era

Late-time acceleration consistent with observations

Abstract

We discuss the cosmological implications of an extended Brans-Dicke theory presented recently, in which there is an energy exchange between the scalar field and ordinary matter, determined by the theory. A new mass scale is generated in the theory which modifies the Friedmann equations with field-dependent corrected kinetic terms. In a radiation universe the general solutions are found and there are branches with complete removal of the initial singularity, while at the same time a transient accelerating period can occur within deceleration. Entropy production is also possible in the early universe. In the dust era, late-times acceleration has been found numerically in agreement with the correct behaviour of the density parameters and the dark energy equation of state, while the gravitational constant has only a slight variation over a large redshift interval in agreement with observational bounds.