Strong Coupling Singularities and Non-abelian Gauge Symmetries in $N=2$ String Theory

TL;DR

This paper explores extremal transitions in Calabi-Yau manifolds within type II string theory, revealing how strong coupling effects lead to enhanced non-abelian gauge symmetries and novel massless states.

Contribution

It demonstrates the emergence of non-abelian gauge symmetries from strong coupling effects in string compactifications, linking geometric transitions to gauge symmetry enhancement.

Findings

Identification of extremal transitions with massless states

Evidence of non-abelian gauge symmetry enhancement

Connection between dual heterotic descriptions and strong coupling phenomena

Abstract

We study a class of extremal transitions between topological distinct Calabi--Yau manifolds which have an interpretation in terms of the special massless states of a type II string compactification. In those cases where a dual heterotic description exists the exceptional massless states are due to genuine strong (string-) coupling effects. A new feature is the appearance of enhanced non-abelian gauge symmetries in the exact nonperturbative theory.