A note on obstinate tachyons in classical dS solutions

TL;DR

This paper investigates the stability of de Sitter solutions in string theory compactifications, revealing that tachyons are confined to specific scalar subspaces and identifying a novel supersymmetric Minkowski limit with implications for tachyon behavior.

Contribution

It demonstrates that tachyons in known dS solutions are restricted to certain scalar directions and uncovers a new supersymmetric Minkowski limit where tachyons align with the sgoldstino.

Findings

Tachyons are within the subspace spanned by the dilaton, volume, and orientifold cycle volumes.

In the O6 compactification example, a supersymmetric Minkowski limit with a tachyon-sgoldstino alignment is found.

The size of orientifold-wrapped cycles imposes strong stability constraints on dS solutions.

Abstract

The stabilisation of the dilaton and volume in tree-level flux compactifications leads to model independent and thus very powerful existence and stability criteria for dS solutions. In this paper we show that the sizes of cycles wrapped by orientifold planes are scalars whose scalings in the potential are not entirely model independent, but enough to entail strong stability constraints. For all known dS solutions arising from massive IIA supergravity flux compactifications on SU(3)-structure manifolds the tachyons are exactly within the subspace spanned by the dilaton, the total volume and the volumes of the orientifold cycles. We illustrate this in detail for the well-studied case of the O6 plane compactification on SU(2)xSU(2)/Z_2xZ_2. For that example we uncover another novel structure in the tachyon spectrum: the dS solutions have a singular, but supersymmetric, Minkowski limit, in which the tachyon exactly aligns with the sgoldstino.