Multiple Realisations of N=1 Vacua in Six Dimensions

TL;DR

This paper explores various string theory frameworks—Type IIB, heterotic, M-theory, and F-theory—to realize and relate six-dimensional N=1 vacua, revealing their non-perturbative features and dualities.

Contribution

It demonstrates how six-dimensional N=1 vacua can be constructed and connected across different string theories, including M-theory and F-theory, highlighting their non-perturbative aspects.

Findings

Identification of M-theory models matching orientifold spectra

Relation of heterotic and F-theory compactifications to Type IIB models

Explicit F-theory limit connecting to orientifold models

Abstract

A while ago, examples of N=1 vacua in D=6 were constructed as orientifolds of Type IIB string theory compactified on the K3 surface. Among the interesting features of those models was the presence of D5-branes behaving like small instantons, and the appearance of extra tensor multiplets. These are both non-perturbative phenomena from the point of view of heterotic string theory. Although the orientifold models are a natural setting in which to study these non-perturbative Heterotic string phenomena, it is interesting and instructive to explore how such vacua are realised in Heterotic string theory, M-theory and F-theory, and consider the relations between them. In particular, we consider models of M-theory compactified on K3 x S^1/Z_2 with fivebranes present on the interval. There is a family of such models which yields the same spectra as a subfamily of the orientifold models. By further compactifying on T^2 to four dimensions we relate them to Heterotic string spectra. We then use Heterotic/Type IIA duality to deduce the existence of Calabi-Yau 3-folds which should yield the original six dimensional orientifold spectra if we use them to compactify F-theory. Finally, we show in detail how to take a limit of such an F-theory compactification which returns us to the Type IIB orientifold models.