Generalized Global Symmetries and the Swampland

Abstract

The recent discovery of a large class of generalized global symmetries has significantly impacted our understanding of many phenomena in quantum field theory, ranging from anomalies to confinement with applications to both low- and high-energy physics. It is widely believed however, that exact global symmetries are forbidden in consistent theories of quantum gravity. By studying how generalized global symmetries are avoided in string theory, we may discover mechanisms which turn out to be general features of quantum gravity. In this thesis we will follow this approach and apply it to a large class of effective field theories obtained from Calabi-Yau compactification of type IIB string theory. After a review of these effective theories, we give an accessible introduction to generalized global symmetries with a focus on their role in the swampland program. Using asymptotic Hodge theory we then extract the most general limiting form of the action near boundaries in the complex structure moduli space. With these in hand, we enumerate the global symmetries that may emerge in these limits and explore how they are broken by stringy effects.