On the Cosmology of Type IIA Compactifications on SU(3)-structure Manifolds

TL;DR

This paper investigates the cosmological implications of type IIA string theory compactified on SU(3)-structure manifolds with fluxes, revealing constraints on de Sitter vacua and slow-roll inflation, with one promising case showing potential for stable solutions.

Contribution

It refines no-go theorems for de Sitter vacua in type IIA compactifications, identifying the SU(2)xSU(2) manifold as a unique case with potential for stable solutions.

Findings

Refined no-go theorem constrains de Sitter vacua and inflation.

SU(2)xSU(2) manifold admits critical points with zero slow-roll parameter.

All found solutions exhibit tachyonic instability with eta<= -2.4.

Abstract

We study cosmological properties of type IIA compactifications on orientifolds of SU(3)-structure manifolds with non-vanishing geometric flux. These compactifications give rise to effective 4D N=1 supergravity theories that do not fall under some recently-proven no-go theorems against de Sitter vacua and slow-roll inflation. Focusing on a well-understood class of models based on coset spaces, however, we can use a refined no-go theorem that rules out de Sitter vacua and slow-roll inflation in all but one case. The refined no-go theorem uses the dilaton and a specific linear combination of the Kaehler moduli, which is different from the overall volume modulus. It puts a lower bound on the first slow-roll parameter: epsilon>=2. The only case not ruled out is the manifold SU(2)x SU(2), for which we indeed find critical points with epsilon numerically zero. However, all the points we could find have a tachyon corresponding to an eta-parameter eta<= -2.4.