Orbifolds of M-theory

TL;DR

This paper explores Z2-orbifolds of M-theory on various tori, revealing connections to type IIB string theory on K3 and discussing anomaly cancellation and supersymmetry breaking.

Contribution

It identifies a new orbifold model T5/Z2 that corresponds to type IIB on K3 and analyzes the role of anomaly cancellation in twisted sector state emergence.

Findings

T5/Z2 orbifold corresponds to type IIB on K3

Most models break spacetime supersymmetry

M-theory tends to produce chiral orbifold compactifications

Abstract

We study Z2-orbifolds of 11-dimensional M-theory on tori of various dimensions. The most interesting model (besides the known S1/Z2 case) corresponds to T5/Z2, for which we argue that the resulting six-dimensional theory is equivalent to the type IIB string compactified on K3. Gravitational anomaly cancellation plays a crucial role in determining what states appear in the twisted sector. Most of the other models appear to break spacetime supersymmetry. We observe that M-theory tends to produce chiral compactifications on orbifolds, and that our results may provide an insight into the mechanism by which twisted-sector states arise in this hypothetical theory.