Open Descendents of U(2N) Orbifolds at Rational Radii

TL;DR

This paper explicitly constructs open string descendants for specific automorphism invariants of U(2N) orbifolds at rational radii, revealing novel Klein bottle and boundary state configurations.

Contribution

It provides explicit constructions of open descendants for automorphism invariants of U(2N) orbifolds, including new Klein bottle choices and boundary states for the case N=pq with prime p,q.

Findings

Two consistent Klein bottles per automorphism invariant.

Complete set of boundary states for each Klein bottle.

Surprising non-symmetric Klein bottles for charge conjugation automorphisms.

Abstract

We construct explicitly the open descendants of some exceptional automorphism invariants of U(2N) orbifolds. We focus on the case N=pq, p and q prime, and on the automorphisms of the diagonal and charge conjugation invariants that exist for these values of N. These correspond to orbifolds of the circle with radius R^2=2p/q. For each automorphism invariant we find two consistent Klein bottles, and for each Klein bottle we find a complete (and probably unique) set of boundary states. The two Klein bottles are in each case related to each other by simple currents, but surprisingly for the automorphism of the charge conjugation invariant neither of the Klein bottle choices is the canonical (symmetric) one.