73.98 DerivationSection

DerivationSection( C, xi )

This function converts a section of C to a derivation of the associated crossed module X. This function is inverse to SectionDerivation.

    gap> xi4 := Cat1SectionByImages( SC, allSC.genimageList[4] );
    Cat1SectionByImages( s3, c3^2

Xc2, [ (4,5,6), (2,3)(5,6) ], 
       [ (1,3,2)(4,6,5), (2,3)(5,6) ] )
    gap> chi4 := DerivationSection( xi4 );
    XModDerivationByImages( s3, c3, [ (4,5,6), (2,3)(5,6) ],
       [ (1,3,2)(4,5,6), () ] )  

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