Cosmological Exact Solutions in Some Modified Gravitational Theories

Abstract

The Einstein frame representation of scalar-tensor theories introduces an anomalous coupling of the scalar field with matter sector. We have investigated these theories when the coupling strength takes a constant configuration or the coupling functions become exponentials. This introduces a large class of scalar-tensor theories which contains f(R) gravity and the Brans-Dicke theory. In a homogeneous and isotropic cosmology, we introduce general exact solutions for theories in this class for single and double exponential potentials.