F Theory Orientifolds, M Theory Orientifolds, and Twisted Strings

TL;DR

This paper investigates orientifolds derived from F theory and M theory, revealing the necessity of twisted open strings in these models and exploring their interpretation through torsion and S-duality.

Contribution

It provides evidence that twisted open strings are essential in F and M theory orientifold models, offering new insights into their structure and dualities.

Findings

Twisted open strings are required in certain orientifold models.

A reinterpretation of torsion in F theory models can avoid twisted strings.

S-duality supports the existence of these twisted strings.

Abstract

Orientifolds of the type IIB superstring that descend from F theory and M theory orbifolds are studied perturbatively. One finds strong evidence that a previously ignored twisted open string is required in these models. An attempt is made to interpret the $J$ type torsion in F theory where one finds a realization of Gimon and Johnson's models which does not require these twisted strings. S-duality also provides evidence for these strings.