73.124 Centre for crossed modules

XModOps.Centre( X )

The kernel of the inner morphism X -> ActX is called the centre of X, generalising the centre of a group G, which is the kernel of G to Aut(G), ; g mapsto (h mapsto h^g). In this example the centre is trivial.

    gap> ZXSC := Centre( XSC );
    Crossed module Centre[c3->s3]  

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