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Strange dimension for trivial extensions #57

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Nakayamaalgebra opened this issue May 19, 2021 · 0 comments
Open

Strange dimension for trivial extensions #57

Nakayamaalgebra opened this issue May 19, 2021 · 0 comments

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@Nakayamaalgebra
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Nakayamaalgebra commented May 19, 2021

Here is something strange happening in QPA:
first we obtain the trivial extension of a quiver algebra as follows:

Q:=Quiver( ["v1"], [["v1","v1","a"],["v1","v1","b"],["v1","v1","te_a1_1_1"]] );kQ:=PathAlgebra(Rationals,Q);AssignGeneratorVariables(kQ); rel:=[ (1)*a^2, (1)*te_a1_1_1^2, (-1)*a*b+(-1)*b^2+(1)*a*b*a, (1)*a*b^2, (-1)*te_a1_1_1*a+(-1)*te_a1_1_1*b+a*te_a1_1_1*a, (1)*te_a1_1_1*a+(1)*te_a1_1_1*b+(1)*a*te_a1_1_1*b, (1)*b*a*b, (-1)*b*te_a1_1_1+(1)*te_a1_1_1*a+(1)*te_a1_1_1*b+(1)*b*a*te_a1_1_1, -a*b+(1)*b^2+(1)*b^2*a, (1)*b^3, (1)*b^2*te_a1_1_1, (-1)*a*b*te_a1_1_1+(1)*b*te_a1_1_1*a, (1)*b*te_a1_1_1*b, (-1)*b*te_a1_1_1+(-1)*a*b*te_a1_1_1+(1)*te_a1_1_1*a*b, (1)*te_a1_1_1*a*te_a1_1_1, (1)*te_a1_1_1*b*a, (1)*b*te_a1_1_1+(1)*te_a1_1_1*b^2, (1)*te_a1_1_1*b*te_a1_1_1 ];A:=kQ/rel;Dimension(A);B:=TrivialExtensionOfQuiverAlgebra(A);Dimension(B); A:=B;Q:=QuiverOfPathAlgebra(A);Display(Q);RelatorsOfFpAlgebra(A);

the algebra has dimension 16.

Now we copy and paste the obtained quiver and relations of the trivial extension to define the quiver algebra directly in QPA:

Q:=Quiver( ["v1"], [["v1","v1","a"],["v1","v1","b"],["v1","v1","te_a1_1_1"],["v1","v1","te_a1_1_1"]] );kQ:=PathAlgebra(Rationals,Q);AssignGeneratorVariables(kQ); rel:=[ (1)*a^2, (1)*a*b, (1)*b^2, (1)*b*te_a1_1_1, (1)*te_a1_1_1^2, (-1)*b*te_a1_1_1+(1)*te_a1_1_1*b, (1)*te_a1_1_1^2, (-1)*te_a1_1_1*a+(-1)*te_a1_1_1*b+(1)*a*te_a1_1_1*a, (1)*te_a1_1_1*a+(1)*te_a1_1_1*b+(1)*a*te_a1_1_1*b, (-1)*a*te_a1_1_1+(-1)*b*te_a1_1_1+(1)*a*te_a1_1_1*a, (1)*te_a1_1_1*a+(1)*te_a1_1_1*b+(1)*b*a*te_a1_1_1, (1)*b*a*te_a1_1_1, (1)*a*te_a1_1_1+(1)*b*te_a1_1_1+(1)*b*te_a1_1_1*a, (1)*b*te_a1_1_1*te_a1_1_1, (1)*te_a1_1_1*a*te_a1_1_1, (-1)*te_a1_1_1*te_a1_1_1+(-1)*a*te_a1_1_1*te_a1_1_1+(1)*te_a1_1_1*a*te_a1_1_1, (1)*te_a1_1_1*b*a, (1)*te_a1_1_1*te_a1_1_1+(1)*te_a1_1_1*b*te_a1_1_1, (1)*te_a1_1_1*te_a1_1_1*a, (1)*te_a1_1_1*te_a1_1_1*te_a1_1_1, (-1)*te_a1_1_1*te_a1_1_1+(-1)*a*te_a1_1_1*te_a1_1_1+(1)*te_a1_1_1*a*te_a1_1_1, (1)*te_a1_1_1*a*te_a1_1_1, (-1)*a*te_a1_1_1*te_a1_1_1+(1)*te_a1_1_1*te_a1_1_1*a, (1)*te_a1_1_1*te_a1_1_1*b, (1)*te_a1_1_1*te_a1_1_1*te_a1_1_1 ];A:=kQ/rel;Dimension(A);

But this time the vector space dimension of the quiver algebra is infinite instead of 16.

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