Reconstructing the universe history, from inflation to acceleration, with phantom and canonical scalar fields

TL;DR

This paper demonstrates how scalar-tensor theories with various scalar fields can be used to reconstruct a universe history that includes both early inflation and late-time acceleration, aligning with observational constraints.

Contribution

It introduces a reconstruction method for scalar-tensor gravity theories with multiple scalar fields, unifying inflation and cosmic acceleration in a consistent framework.

Findings

Universe expansion history can be realized with scalar fields.

Different scalar field combinations can unify inflation and acceleration.

Reconstruction is consistent with observational bounds.

Abstract

We consider the reconstruction technique in theories with a single or multiple (phantom and/or canonical) scalar fields. With the help of several examples, it is demonstrated explicitly that the universe expansion history, unifying early-time inflation and late-time acceleration, can be realized in scalar-tensor gravity. This is generalized to the theory of a scalar field coupled non-minimally to the curvature and to a Brans-Dicke-like theory. Different examples of unification of inflation with cosmic acceleration, in which de Sitter, phantom, and quintessence type fields play the fundamental role--in different combinations--are worked out. Specifically, the frame dependence and stability properties of de Sitter space scalar field theory are studied. Finally, for two-scalar theories, the late-time acceleration and early-time inflation epochs are successfully reconstructed, in realistic situations in which the more and more stringent observational bounds are satisfied, using the freedom of choice of the scalar field potential, and of the kinetic factor.