F-Theory on Spin(7) Manifolds: Weak-Coupling Limit

TL;DR

This paper explores F-theory on Spin(7) manifolds, analyzing its weak-coupling limit and dualities, revealing specific brane configurations and supersymmetry properties in various limits.

Contribution

It provides a detailed analysis of the weak-coupling limit of F-theory on Spin(7) manifolds, identifying the resulting brane objects and supersymmetry enhancements.

Findings

Identification of O7-, O5-, and X5-planes in the weak-coupling limit.

Presence of exotic O3- and X3-planes on orbifold singularities.

Restoration of four-dimensional N=1 supersymmetry in the infinite-interval limit.

Abstract

F-theory on appropriately fibered Spin(7) holonomy manifolds is defined to arise as the dual of M-theory on the same space in the limit of a shrinking fiber. A class of Spin(7) orbifolds can be constructed as quotients of elliptically fibered Calabi-Yau fourfolds by an anti-holomorphic involution. The F-theory dual then exhibits one macroscopic dimension that has the topology of an interval. In this work we study the weak-coupling limit of a subclass of such constructions and identify the objects that arise in this limit. On the Type IIB side we find space-time filling O7-planes as well as O5-planes and orbifold five-planes with a (-1)^{F_L} factor localised on the interval boundaries. These orbifold planes are referred to as X5-planes and are S-dual to a D5-O5 system. For other involutions exotic O3-planes and X3-planes on top of a six-dimensional orbifold singularity can appear. We show that the objects present preserve a mutual supersymmetry of four supercharges in the bulk of the interval and two supercharges on the boundary. It follows that in the infinite-interval and weak-coupling limit full four-dimensional N=1 supersymmetry is restored, which on the Type IIA side corresponds to an enhancement of supersymmetry by winding modes in the vanishing interval limit.