Attractor Universe in the Scalar-Tensor Theory of Gravitation

TL;DR

This paper investigates the behavior of solutions in scalar-tensor gravity theories, identifying attractor points and discovering new inflationary solutions influenced by matter coupling.

Contribution

It develops a phase space formulation for scalar-tensor cosmology and uncovers conditions for attractors and novel inflationary regimes.

Findings

Existence of attractor solutions depending on coupling and equation of state.

Identification of new inflationary solutions driven by matter coupling.

Phase space analysis clarifies stability of cosmological solutions.

Abstract

In the scalar-tensor theory of gravitation it seems nontrivial to establish if solutions of the cosmological equations in the presence of a cosmological constant behave as attractors independently of the initial values. We develop a general formulation in terms of two-dimensional phase space. We show that there are two kinds of fixed points, one of which is an attractor depending on the coupling constant and equation of state. In the case with a power-law potential in the Jordan frame, we also find new type of inflation caused by the coupling to the matter fluid.