Defect lines, dualities, and generalised orbifolds

TL;DR

This paper explores the role of defect lines in two-dimensional conformal field theories, illustrating their importance in understanding symmetries, dualities, and orbifold constructions, including exceptional cases.

Contribution

It introduces a generalized orbifold framework using defect lines, extending the understanding of symmetries and dualities in conformal field theories.

Findings

Defect lines encode symmetries and dualities in 2D CFTs.

A generalized orbifold construction covers exceptional modular invariants.

Defect junctions provide insight into order-disorder dualities.

Abstract

Defects are a useful tool in the study of quantum field theories. This is illustrated in the example of two-dimensional conformal field theories. We describe how defect lines and their junction points appear in the description of symmetries and order-disorder dualities, as well as in the orbifold construction and a generalisation thereof that covers exceptional modular invariants.