De Sitter in non-supersymmetric string theories: no-go theorems and brane-worlds

Stefano Lanza,Ivano Basile

doi:10.1007/jhep10(2020)108

Stefano Lanza, Ivano Basile

Open Access

https://doi.org/10.1007/jhep10(2020)108

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Abstract

We study de Sitter configurations in ten-dimensional string models where supersymmetry is either absent or broken at the string scale. To this end, we derive expressions for the cosmological constant in general warped flux compactifications with localized sources, which yield no-go theorems that extend previous works on supersymmetric cases. We frame our results within a dimensional reduction and connect them to a number of Swampland conjectures, corroborating them further in the absence of supersymmetry. Furthermore, we construct a top-down string embedding of de Sitter brane-world cosmologies within unstable anti-de Sitter landscapes, providing a concrete realization of a recently revisited proposal.

Highlights

Despite the numerous successes of string theory, its connection to realistic phenomenology remains a remarkably subtle challenge
We study de Sitter configurations in ten-dimensional string models where supersymmetry is either absent or broken at the string scale
In the following we shall investigate to what extent the de Sitter conjecture and the Transplanckian Censorship conjecture (TCC) are satisfied by the non-supersymmetric string models of section 2, for which we shall provide explicit lower bounds for the parameter c, relating them with the predictions of the TCC

Summary

Introduction

Despite the numerous successes of string theory, its connection to realistic phenomenology remains a remarkably subtle challenge. We shall not attempt to provide a comprehensive account of this extensive subject, since our focus in this paper will be on higher-dimensional approaches [6,7,8,9,10,11,12,13,14] and, in particular, on the search for new solutions This state of affairs provided fertile ground for the development of the ‘Swampland program’ [15],1 whose ultimate aim is to identify a set of criteria that consistent effective field theories (EFTs) coupled to gravity ought to satisfy.

Non-supersymmetric string models

The orientifold models

The heterotic model

The low-energy description

Freund-Rubin compactifications

AdS solutions

The obstructions to de Sitter and Minkowski solutions

A no-go theorem for dS and Minkowski solutions

Including space-time filling sources

Vacua of the lower-dimensional theory and perturbative instabilities

The BSB and type 0 B orientifold models

Swampland conjectures and non-supersymmetric string theories