Crossed Module

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:

    I married a miner myself. I had ten children. I’ve got seven now; thirty-one grandchildren and eight great-grandchildren. And I’m happy to say not a one’s ever crossed a picket line.
    Florence Reese (c. 1900–?)