Refining the boundaries of the classical de Sitter landscape

TL;DR

This paper establishes strict no-go theorems that restrict the existence of classical de Sitter solutions in string theory with certain brane configurations, significantly narrowing the landscape of viable models.

Contribution

It derives new, highly constraining no-go theorems for classical de Sitter vacua in type II supergravity with parallel sources, clarifying which configurations are impossible.

Findings

Vacua for p=3, 7, 8 are excluded.

Tight constraints for p=4, 5, 6.

Derived an expression for the four-dimensional Ricci scalar.

Abstract

We derive highly constraining no-go theorems for classical de Sitter backgrounds of string theory, with parallel sources; this should impact the embedding of cosmological models. We study ten-dimensional vacua of type II supergravities with parallel and backreacted orientifold Op-planes and Dp-branes, on four-dimensional de Sitter space-time times a compact manifold. Vacua for p=3, 7 or 8 are completely excluded, and we obtain tight constraints for p=4, 5, 6. This is achieved through the derivation of an enlightening expression for the four-dimensional Ricci scalar. Further interesting expressions and no-go theorems are obtained. The paper is self-contained so technical aspects, including conventions, might be of more general interest.