Crossed module
= Crossed module
{wiki=Crossed_module}
A crossed module is a concept from the field of algebraic topology and homological algebra, particularly in the study of algebraic structures that relate groups and their actions. A crossed module consists of two groups \\( G \\) and \\( H \\) along with two homomorphisms: 1. A group homomorphism \\( \\partial: H \\to G \\) (called the boundary map).