ON THE CENTRE OF CROSSED MODULES OF GROUPS
摘要
The aim of this paper is twofold. Firstly, it gives an overview of the concept of the centre of a crossed module which was recently introduced by the author both in group theory and the Lie algebra framework. This centre is closely related to the Gottlieb group of the classifying space of a crossed module and also to the Drinfeld centre of a monoidal category introduced independently by Drinfeld and Joyal and Street. Secondly, this paper introduces the homotopy invariance property for the centre of a crossed module, which is a new result.