BIMSA > BIMSA TQFT and Higher Symmetries Seminar BIMSA TQFT and Higher Symmetries Seminar Extensions of topological symmetries
Extensions of topological symmetries
Organizers
Ansi Bai , Hank Chen , Liang Kong , Yilong Wang , Zhihao Zhang , Hao Zheng
Speaker
Ingo Runkel
Time
Tuesday, April 21, 2026 4:00 PM - 5:30 PM
Venue
A6-101
Online
Zoom 361 038 6975 (BIMSA)
Abstract
Topological defects play a key role in understanding properties of quantum field theories, such as dualities or renormalisation group flows. One can ask if there is a larger class of defects which share some of the good properties of topological defects, and which can be thought of as an extension of topological symmetries. Two-dimensional conformal field theory is a natural laboratory for such questions, and indeed one finds that translation invariant defects form such a larger class. These contain topological line defects and they still allow for a non-singular fusion operation. They still form a tensor category, which, however, is no longer fusion, as it is non-semisimple and possesses infinitely many simple objects. In this talk I want to present some properties of this larger class of defects and give an applications defect renormalisation group flows. This is joint work with Federico Ambrosino, Anatoly Konechny, and Gérard Watts.