In mathematics, and especially in homotopy theory, a crossed module consists of groups G and H, where G acts on H (which we will write on the left, ), and a homomorphism of groups
that is equivariant with respect to the conjugation action of G on itself:
and also satisfies the so-called Peiffer identity:
Read more about Crossed Module: Origin, Examples, Classifying Space
Famous quotes containing the word crossed:
“What I have crossed out I didn’t like. What I haven’t crossed out I’m dissatisfied with.”
—Cecil B. De Mille (1881–1959)