cov_twist_alex.sa


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class TWIST_ALEX_COV

class TWIST_ALEX_COV is -- twisted Alexander polynomial for the covering. twist_alex(tcode:TCODE, stack:REP_STACK) is rep,repr:ARRAY{MAT_POLYS_INTI}; gens::=tcode.number_gen; rep:=#(gens+1); repr:=#(gens+1); loop g::=1.upto!(gens); s::=stack.st[g]; mat:MAT_POLYS_INTI:=#(stack.Jn,stack.Jn); mat.clear; loop i::=1.upto!(stack.Jn); mat[i-1][s[i]-1]:=POLYS_INTI::one; end; rep[g]:=mat; repr[g]:=mat.trans; end; ALEXMAT_TWIST::AlexMat(tcode,rep,repr); end; end;

class TWIST_ALEX_SL2P

class TWIST_ALEX_SL2P is -- twisted Alexander polynomial for the covering. twist_alex(tcode:TCODE, stack:SL2P_STACK) is rep,repr:ARRAY{MAT_POLYS_FP}; gens::=tcode.number_gen; rep:=#(gens+1); repr:=#(gens+1); loop g:CARD:=1.upto!(gens); s::=stack.st[g]; mat:MAT_POLYS_FP:=#(2,2); mat.clear; mat[0][0]:=#POLYS_FP(s.mat.m[0][0]); mat[0][1]:=#POLYS_FP(s.mat.m[0][1]); mat[1][0]:=#POLYS_FP(s.mat.m[1][0]); mat[1][1]:=#POLYS_FP(s.mat.m[1][1]); rep[g]:=mat; dr::=s.mat.det.inverse; mat:=#(2,2); mat.clear; mat[0][0]:=#POLYS_FP(s.mat.m[1][1]*dr); mat[0][1]:=-#POLYS_FP(s.mat.m[0][1]*dr); mat[1][0]:=-#POLYS_FP(s.mat.m[1][0]*dr); mat[1][1]:=#POLYS_FP(s.mat.m[0][0]*dr); repr[g]:=mat; end; ALEXMAT_TWIST_FP::AlexMat(tcode,rep,repr); end; end;