Accelerating Universes in String Theory via Field Redefinition

TL;DR

This paper explores cosmological solutions in heterotic string theory with higher-order corrections, revealing that certain field redefinitions lead to stable, accelerating universe models like de Sitter space.

Contribution

It introduces a class of effective theories with second-order equations of motion derived from string theory, incorporating field redefinition ambiguities, and finds stable accelerating solutions.

Findings

De Sitter solutions found in the effective theory.

Accelerating universes are attractors in the dynamical system.

The theory includes two free coupling constants.

Abstract

We study cosmological solutions in the effective heterotic string theory with $\alpha'$-correction terms in string frame. It is pointed out that the effective theory has an ambiguity via field redefinition and we analyze generalized effective theories due to this ambiguity. We restrict our analysis to the effective theories which give equations of motion of second order in the derivatives, just as "Galileon" field theory. This class of effective actions contains two free coupling constants. We find de Sitter solutions as well as the power-law expanding universes in our four-dimensional Einstein frame. The accelerated expanding universes are always the attractors in the present dynamical system.