63.36 CollapsedAdjacencyMat

CollapsedAdjacencyMat( G, gamma )

This function returns the collapsed adjacency matrix for gamma, where the collapsing group is G. It is assumed that G is a subgroup of Aut(<gamma>).

The (i,j)-entry of the collapsed adjacency matrix equals the number of edges in { [x,y] | y in j-th G-orbit }, where x is a fixed vertex in the i-th G-orbit.

See also OrbitalGraphIntersectionMatrices.

    gap> gamma := JohnsonGraph(4,2);;
    gap> G := Stabilizer( gamma.group, 1 );;
    gap> CollapsedAdjacencyMat( G, gamma );
    [ [ 0, 4, 0 ], [ 1, 2, 1 ], [ 0, 4, 0 ] ] 

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