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:
“It whispered to the fields of corn,
“Bow down, and hail the coming morn.”
It shouted through the belfry tower,
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—Henry Wadsworth Longfellow (1809–1882)