F-Theory at Constant Coupling

TL;DR

This paper explores special constant-coupling subspaces in F-theory on K3, revealing new branches with orbifold degenerations, exceptional symmetries, and connections to orientifolds and M-theory orbifolds.

Contribution

It identifies new constant-coupling branches in F-theory on K3 with orbifold degenerations and exceptional symmetries, extending understanding of dualities and non-perturbative structures.

Findings

New branches at special coupling values with orbifold degenerations.

Emergence of exceptional gauge symmetries, including E8 x E8.

Mapping orbifold points to non-perturbative orientifolds and M-theory orbifolds.

Abstract

The subspace of the moduli space of F-theory on K3 over which the coupling remains constant develops new branches at special values of this coupling. These values correspond to fixed points under the SL(2,Z) duality group of the type IIB string. The branches contain points where K3 degenerates to orbifolds of the four-torus by Z_3,Z_4 and Z_6. A singularity analysis shows that exceptional group symmetries appear on these branches, including pure E_8 xE_8, although SO(32) cannot be realised in this way. The orbifold points can be mapped to a kind of non-perturbative generalization of a IIB orientifold, and to M-theory orbifolds with non-trivial action on 2-brane wrapping modes.