On de Sitter vacua in O(d,d) invariant cosmology

TL;DR

This paper investigates the existence and stability of de Sitter vacua within O(d,d) invariant cosmological models, revealing their non-eternal nature in Einstein frames and extending analysis to anisotropic universes.

Contribution

It provides a comprehensive analysis of de Sitter vacua in O(d,d) invariant cosmologies, including stability, non-perturbative effects, and extension to anisotropic Bianchi I universes.

Findings

De Sitter vacua are unstable in the string frame.

De Sitter vacua cannot be eternal in the Einstein frame.

O(d,d) symmetry enables de Sitter vacua in anisotropic universes.

Abstract

We perform a thorough analysis of de Sitter vacua in O(d,d) invariant cosmologies. Starting with a homogeneous and isotropic framework we examine conditions for the existence of such vacua, non-perturbative in \alpha' in both the string frame and the Einstein frame. We elucidate the nature of the instability in the string frame vacuum. For the Einstein frame, we demonstrate that the de Sitter vacuum cannot be eternal. We then extend our analysis to include Bianchi I universes where the O(d,d) symmetry includes scale factor exchange as well as scale factor duality. We show how the theory can be extended to the anisotropic case so that it admits de Sitter vacua, noting the crucial role played by the O(d,d) symmetry in satisfying any additional constraints.