Singular Manual: fullSerreRelations

| ##### 7.7.8.0. fullSerreRelations Procedure from library `freegb.lib` (see freegb_lib). Usage: fullSerreRelations(A,N,C,P,d); A an intmat, N,C,P ideals, d an int Return: ring (and ideal) Purpose: compute the inhomogeneous Serre's relations associated to A in given variable names Assume: three ideals in the input are of the same sizes and contain merely variables which are interpreted as follows: N resp. P stand for negative resp. positive roots, C stand for Cartan elements. d is the degree bound for letterplace ring, which will be returned. The matrix A is a generalized Cartan matrix with integer entries The result is the ideal called 'fsRel' in the returned ring. Example:
    LIB "freegb.lib";
    intmat A[2][2] =
    2, -1,
    -1, 2; // A_2 = sl_3 Cartan matrix
    ring r = 0,(f1,f2,h1,h2,e1,e2),dp;
    ideal negroots = f1,f2; ideal cartans = h1,h2; ideal posroots = e1,e2;
    int uptodeg = 5;
    def RS = fullSerreRelations(A,negroots,cartans,posroots,uptodeg);
    setring RS; fsRel;
    ==> fsRel[1]=f1(1)*f2(2)*f2(3)-2*f2(1)*f1(2)*f2(3)+f2(1)*f2(2)*f1(3)
    ==> fsRel[2]=f1(1)*f1(2)*f2(3)-2*f1(1)*f2(2)*f1(3)+f2(1)*f1(2)*f1(3)
    ==> fsRel[3]=e1(1)*e2(2)*e2(3)-2*e2(1)*e1(2)*e2(3)+e2(1)*e2(2)*e1(3)
    ==> fsRel[4]=e1(1)*e1(2)*e2(3)-2*e1(1)*e2(2)*e1(3)+e2(1)*e1(2)*e1(3)
    ==> fsRel[5]=f2(1)*e1(2)-e1(1)*f2(2)
    ==> fsRel[6]=f1(1)*e2(2)-e2(1)*f1(2)
    ==> fsRel[7]=-f1(1)*e1(2)+e1(1)*f1(2)-h1(1)
    ==> fsRel[8]=-f2(1)*e2(2)+e2(1)*f2(2)-h2(1)
    ==> fsRel[9]=h1(1)*h2(2)-h2(1)*h1(2)
    ==> fsRel[10]=h1(1)*e1(2)-e1(1)*h1(2)-2*e1(1)
    ==> fsRel[11]=f1(1)*h1(2)-h1(1)*f1(2)-2*f1(1)
    ==> fsRel[12]=h1(1)*e2(2)-e2(1)*h1(2)+e2(1)
    ==> fsRel[13]=f2(1)*h1(2)-h1(1)*f2(2)+f2(1)
    ==> fsRel[14]=h2(1)*e1(2)-e1(1)*h2(2)+e1(1)
    ==> fsRel[15]=f1(1)*h2(2)-h2(1)*f1(2)+f1(1)
    ==> fsRel[16]=h2(1)*e2(2)-e2(1)*h2(2)-2*e2(1)
    ==> fsRel[17]=f2(1)*h2(2)-h2(1)*f2(2)-2*f2(1)

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