New instabilities for non-supersymmetric AdS$_4$ orientifold vacua

TL;DR

This paper investigates non-supersymmetric AdS4 orientifold vacua in massive type IIA string theory, analyzing their stability, localised sources, and compatibility with the Weak Gravity Conjecture, revealing new instabilities and open questions.

Contribution

It provides a detailed 10d analysis of non-supersymmetric AdS4 vacua, including stability considerations and membrane constructions related to the Weak Gravity Conjecture.

Findings

All vacua exhibit localised sources and scale separation.

Most vacua satisfy the Weak Gravity Conjecture with superextremal membranes.

Some vacua's non-perturbative stability remains unresolved.

Abstract

We consider massive type IIA orientifold compactifications of the form AdS$_4 \times X_6$, where $X_6$ admits a Calabi-Yau metric and is threaded by background fluxes. From a 4d viewpoint, fluxes generate a potential whose vacua have been classified, including one $\mathcal{N}=1$ and three perturbatively stable $\mathcal{N}=0$ branches. We reproduce this result from a 10d viewpoint, by solving the type IIA equations at the same level of detail as previously done for the $\mathcal{N}=1$ branch. All solutions exhibit localised sources and parametric scale separation. We then analyse the non-perturbative stability of the $\mathcal{N}=0$ branches. We consider new 4d membranes, obtained from wrapping D8-branes on $X_6$ or D6-branes on its divisors, threaded by non-diluted worldvolume fluxes. Using them we show that all branches are compatible with the Weak Gravity Conjecture for membranes. In fact, most vacua satisfy the sharpened conjecture that predicts superextremal membranes in $\mathcal{N}=0$ settings, except for a subset whose non-perturbative stability remains an open problem.