Exotic Branes and Symmetries of String Theory

TL;DR

This paper explores how duality transformations in string theory manifest as spontaneously broken discrete gauge symmetries in flat space-time, contrasting with their explicit breaking in AdS space, and discusses the observability of various exotic branes.

Contribution

It demonstrates that duality transformations are spontaneously broken discrete gauge symmetries in flat space-time through monodromies around exotic branes, differing from their explicit breaking in AdS space.

Findings

Duality transformations are spontaneously broken in flat space-time.

Monodromies around exotic branes reveal observable consequences.

Differences between flat space and AdS space in duality symmetry behavior.

Abstract

Are duality transformations symmetries of string theory? For AdS space-time the answer is no for generic asymptotic values of the moduli, since the duality symmetry is broken explicitly in the dual conformal field theory. In contrast, in string theory in flat space-time, monodromies around codimension two exotic branes show that duality transformations are spontaneously broken discrete gauge symmetries with observable consequences, provided macroscopic loops of these branes are not hidden behind an event horizon. We discuss how this can be achieved and how the situation in flat space-time differs from that in AdS space-time. We also discuss observability of codimension two non-BPS branes, codimension one BPS and non-BPS branes and higher codimension branes of infinite tension.