Multiple Field Scalar-Tensor Theories of Gravity and Cosmology

TL;DR

This paper explores multi-scalar field theories of gravity, analyzing their compatibility with solar system tests and cosmological evolution, including potential inflation, while highlighting stability issues of solutions.

Contribution

It provides conditions for two-field scalar-tensor theories to satisfy solar system tests and examines their cosmological dynamics across different epochs.

Findings

Power law solutions can meet solar system constraints but are unstable.

Cosmological solutions are found for dust, radiation, and cosmological constant epochs.

Inflationary possibilities are discussed within these theories.

Abstract

We consider multiple scalar fields coupled to gravity, with special attention given to two-field theories. First, the conditions necessary for these theories to meet solar system tests are given. Next, we investigate the cosmological evolution of the fields to see if these conditions can be met. Solutions are found in the dust era, as well as radiation and cosmological constant dominated epochs. The possibility of inflation in these theories is discussed. While power law growth of the scalar fields can yield the appropriate conditions to meet solar system constraints, these solutions are unstable.