Over-extremal brane shells from string theory?

TL;DR

This paper proposes the existence of overcharged spherical brane shells in 4D derived from IIB string theory compactifications, which are classical, stable, and larger than the string scale, without naked singularities.

Contribution

It introduces a new class of over-extremal, stable spherical brane shells in 4D from string theory compactifications, expanding understanding of possible classical objects.

Findings

Existence of stable, overcharged spherical brane shells in 4D.

Shell sizes can exceed the string scale depending on compactification details.

These shells are classical objects without naked singularities.

Abstract

We demonstrate that, if the usual phenomenological compactifications of IIB string theory with warped throats and anti-branes make sense, there must exist spherical brane shells in 4d that are overcharged. They correspond to classical over-extremal objects but without the usual naked singularities. The objects are made from D3-particles that puff into spherical 5-branes that stabilise at finite radii in 4d and whose inside corresponds to the supersymmetric AdS vacuum. One can think of these shells as stabilised Brown-Teitelboim bubbles. We find that these objects can be significantly larger than the string scale depending on the details of the warped compactification.