# Gauge symmetry enhancing-breaking from a Double Field Theory perspective

## TL;DR

This paper explores how gauge symmetry enhancement and breaking in string theory can be understood through Double Field Theory, emphasizing the role of moduli-dependent fluxes and T-duality invariance in compactifications.

## Contribution

It provides a DFT-based framework to describe gauge symmetry breaking and enhancement, connecting flux dependence on moduli with the generalized tangent frame.

## Key findings

- DFT captures gauge symmetry enhancement and breaking via flux moduli dependence.
- Explicit T-duality invariant formulation aids in understanding symmetry transitions.
- Generalizations to generic torus compactifications are discussed.

## Abstract

Gauge symmetry enhancing, at specific points of the compactification space, is a distinguished feature of string theory. In this work we discuss the breaking of such symmetries with tools provided by Double Field Theory (DFT). As a main guiding example we discuss the bosonic string compactified on a circle where, at the self dual radio the generic $U(1)\times U(1)$ gauge symmetry becomes enhanced to $SU(2)\times SU(2)$. We show that the enhancing-breaking of the gauge symmetry can be understood through a dependence of gauge structure constants (fluxes in DFT) on moduli. This dependence, in DFT description, is encoded in the generalized tangent frame of the double space. Actually, the explicit T-duality invariant formulation provided by DFT proves to be a helpful ingredient. The link with string theory results is discussed and generalizations to generic tori compactifications are addressed.