Non-BPS path to the string lamppost

TL;DR

This paper explores the non-BPS pathways in 9-dimensional supergravities, providing new insights into the string lamppost principle through Swampland conjectures, black hole entropy, and SCFT classification, without relying solely on string theory.

Contribution

It offers a bottom-up explanation for UV features and a Swampland argument for the countability of string limits, advancing understanding of the string lamppost principle in 9d supergravities.

Findings

Infinite distance limits with heavy BPS states decompactify to type IIA on an interval

Provides UV explanations near orientifold branes and 8-brane worldvolume theories

Establishes countability of inequivalent string limits up to dualities

Abstract

We provide further motivation for the string lamppost principle in 9d supergravities. Using a blend of ideas which includes Swampland conjectures, finiteness of black hole entropy, and classification of SCFTs, we show that infinite distance limits that keep BPS states heavy must decompactify to type IIA supergravity on an interval. Without relying on string theory, we provide bottom-up explanations for various UV features of the theory, such as the physics near the orientifold branes and the worldvolume theories of different stacks of non-perturbative 8-branes. We also provide a Swampland argument for the countability of the number of inequivalent string limits up to dualities which is a strong result with applications beyond this work.