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:
“Loach: What happened to your nose, Gittes? Somebody slam a bedroom window on it?
J.J. Gittes: Nope, your wife got excited. She crossed her legs a little too quick.”
—Robert Towne (b. 1936)