Twisted Open Strings from Closed Strings: The WZW Orientation Orbifolds

TL;DR

This paper develops a framework for constructing twisted open strings from closed WZW strings using world-sheet orientation-reversing automorphisms, revealing new properties of orientation orbifolds distinct from traditional open-string sectors.

Contribution

It introduces a novel approach to orientation orbifolds incorporating automorphisms, and constructs their operator algebras and twisted KZ systems, expanding understanding of open-string sectors.

Findings

Orientation-orbifold sectors are twisted open WZW strings with unique properties.

Constructed operator algebras and twisted KZ systems for these sectors.

Illustrated classical limits and free-boson examples on abelian g.

Abstract

Including {\it world-sheet orientation-reversing automorphisms} $\hat{h}_{\sigma} \in H_-$ in the orbifold program, we construct the operator algebras and twisted KZ systems of the general WZW {\it orientation orbifold} $A_g (H_-) /H_-$. We find that the orientation-orbifold sectors corresponding to each $\hat{h}_{\sigma} \in H_-$ are {\it twisted open} WZW strings, whose properties are quite distinct from conventional open-string orientifold sectors. As simple illustrations, we also discuss the classical (high-level) limit of our construction and free-boson examples on abelian $g$.