No accelerating scaling cosmologies at string tree level?

TL;DR

This paper examines string compactifications and argues that potential accelerating cosmologies at string tree level are likely perturbatively unstable, similar to issues found in de Sitter vacua, challenging their viability.

Contribution

It provides a theoretical analysis showing that scaling solutions with acceleration at string tree level are probably perturbatively unstable, extending previous instability arguments.

Findings

Scaling solutions at string tree level are likely unstable.

Accelerating cosmologies at this level face perturbative instabilities.

The results challenge the existence of stable accelerating solutions in this regime.

Abstract

We investigate the scalar potential of string compactifications in the parametric regime where string loops and higher derivative corrections to 10d supergravity can be ignored and where the fields are rolling down exponential slopes leading to powerlaw FLRW cosmologies, aka scaling solutions. We argue that these scaling solutions, if describing an accelerating expansion, are likely to be perturbatively unstable, for reasons identical to the perturbative instabilities in tree-level dS vacua.