M-Theory on (K3 X S^1)/Z_2

TL;DR

This paper studies M-theory compactified on a specific orbifold of K3 and S^1, revealing a rich structure of gauge symmetry enhancements, tensionless strings, and low-energy supergravity limits in six dimensions.

Contribution

It provides a detailed analysis of the moduli space of M-theory on (K3 x S^1)/Z_2, including gauge symmetry enhancements and the emergence of tensionless strings.

Findings

Low energy limit is N=1 supergravity in six dimensions.

Gauge symmetry can be enhanced to E8 at special points.

Tensionless strings appear at certain moduli space points.

Abstract

We analyze $M$-theory compactified on $(K3\times S^1)/Z_2$ where the $Z_2$ changes the sign of the three form gauge field, acts on $S^1$ as a parity transformation and on K3 as an involution with eight fixed points preserving SU(2) holonomy. At a generic point in the moduli space the resulting theory has as its low energy limit N=1 supergravity theory in six dimensions with eight vector, nine tensor and twenty hypermultiplets. The gauge symmetry can be enhanced (e.g. to $E_8$) at special points in the moduli space. At other special points in the moduli space tensionless strings appear in the theory.