local result, l, i; i:= Sqrt(-1); result:= rec(); result.comment:= "2\"A5 as 4 x 4 matrices over Z[i].\n\ Absolutely irreducible representation.\n\ Schur Index 2.\n\ \n\ SEED:\n\ Nonzero v s.t. v.x = i*v and v.x^(yxy) = -i*v where = Q12.\n\ v has 4 x 10 = 40 images under G; has 10 images under G.\n\ BASIS:\n\ v, v.y, v.y^2, v.x^3*y*x*y^2*x.\n\ \n\ Possible matrix entries for any element of the group:\n\ The 9 elements of {0,1,-1,i,-i,1+i,1-i,-1+i,-1-i} only.\n\ The possible norms are in {0,1,2} only.\n\ \n\ Average number of nonzero entries for any element of the group:\n\ 11 + 1/5 (11.2; 70% exactly).\n\ \n\ Entry Av/Mat %Av/Mat\n\ 0 4.8 30\n\ 1 1.6 10\n\ -1 1.6 10\n\ i 1.6 10\n\ -i 1.6 10\n\ 1+i 1.2 7.5\n\ 1-i 1.2 7.5\n\ -1+i 1.2 7.5\n\ -1-i 1.2 7.5\n\ Norm 0 4.8 30\n\ Norm 1 6.4 40\n\ Norm 2 4.8 30\n\ nonzero 11.2 70\n\ "; result.symmetricforms:= []; result.antisymmetricforms:= []; result.hermitianforms:= []; result.centralizeralgebra:= []; result.generators:= List( [ [ i,0,0,0, -1,i,-1+i,-1-i, 1,-1+i,-1-i,-i, -1,-1-i,-i,1-i] ,[ 0,1,0,0, 0,0,1,0, 1,0,0,0, 0,0,0,1] ], l -> List( [ 0 .. 3 ], i -> l{ [ i*4+1 .. (i+1)*4 ] } ) ); l:= [ 0,1,-1,1, -1,0,1,1, 1,-1,0,1, -1,-1,-1,0]; Add( result.antisymmetricforms, List( [ 0 .. 3 ], i -> l{ [ i*4+1 .. (i+1)*4 ] } ) ); l:= [ 2,-i,i,-i, i,2,-i,-i, -i,i,2,-i, i,i,i,2]; Add( result.hermitianforms, List( [ 0 .. 3 ], i -> l{ [ i*4+1 .. (i+1)*4 ] } ) ); Add( result.centralizeralgebra, IdentityMat(4) ); return result;