ApCoCoA-1:Picard group
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Description
The Picard Group is PSL_{2}(O_{1}) where O_{1} is the ring of integers in the quadratic imaginary number field Q sqrt(-1).
Reference
L. Greenberg - "Discontinuous Groups and Riemann Surfaces: Proceedings" - Princeton University Press (1974) 151; B. Fine - "THE EUCLIDEAN BIANCHI GROUPS" - COMMUNICATIONS IN ALGEBRA, 18(8), 2461-2484 (1990) 2461
Computation
/*Use the ApCoCoA package ncpoly.*/ Use ZZ/(2)[a,l,t,u]; NC.SetOrdering("LLEX"); Define CreateRelationsPicard() Relations:=[]; // add the relation a^2 = 1 Append(Relations,[[a,a],[1]]); // add the relation l^2 = 1 Append(Relations,[[l,l],[1]]); // add the relation (al)^2 = 1 Append(Relations,[[a,l,a,l],[1]]); // add the relation (tl)^2 = 1 Append(Relations,[[t,l,t,l],[1]]); // add the relation (ul)^2 = 1 Append(Relations,[[u,l,u,l],[1]]); // add the relation (at)^3 = 1 Append(Relations,[[a,t,a,t,a,t],[1]]); // add the relation (ual)^3 = 1 Append(Relations,[[u,a,l,u,a,l,u,a,l],[1]]); //add the relation tu = ut Append(Relations,[[t,u],[u,t]]); Return Relations; EndDefine; Relations:=CreateRelationsPicard(); Relations; Gb:=NC.GB(Relations,31,1,100,1000); Gb;
Example in Symbolic Data Format
<FREEALGEBRA createdAt="2014-03-26" createdBy="strohmeier"> <vars>a,l,t,u</vars> <uptoDeg>9</uptoDeg> <basis> <ncpoly>a*a-1</ncpoly> <ncpoly>l*l-1</ncpoly> <ncpoly>a*l*a*l-1</ncpoly> <ncpoly>t*l*t*l-1</ncpoly> <ncpoly>u*l*u*l-1</ncpoly> <ncpoly>a*t*a*t*a*t-1</ncpoly> <ncpoly>u*a*l*u*a*l*u*a*l-1</ncpoly> <ncpoly>t*u-u*t</ncpoly> </basis> <Comment>The partial LLex Gb has 104 elements</Comment> <Comment>Picard_group</Comment> </FREEALGEBRA>