Difference between revisions of "ApCoCoA-1:VonDyck groups"
From ApCoCoAWiki
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// Parameters of von Dyck group | // Parameters of von Dyck group | ||
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MEMORY.L:=3; | MEMORY.L:=3; | ||
MEMORY.M:=5; | MEMORY.M:=5; | ||
| Line 18: | Line 17: | ||
Use ZZ/(2)[x,y]; | Use ZZ/(2)[x,y]; | ||
NC.SetOrdering("LLEX"); | NC.SetOrdering("LLEX"); | ||
| + | |||
Define CreateRelationsVonDyck() | Define CreateRelationsVonDyck() | ||
Relations:=[]; | Relations:=[]; | ||
// add the relation x^l = 1 | // add the relation x^l = 1 | ||
| − | |||
Append(Relations,[[x^MEMORY.L],[1]]); | Append(Relations,[[x^MEMORY.L],[1]]); | ||
| Line 34: | Line 33: | ||
Append(BufferXY,y); | Append(BufferXY,y); | ||
EndFor; | EndFor; | ||
| − | |||
Append(Relations,[BufferXY,[1]]); | Append(Relations,[BufferXY,[1]]); | ||
| Line 42: | Line 40: | ||
Relations:=CreateRelationsVonDyck(); | Relations:=CreateRelationsVonDyck(); | ||
Relations; | Relations; | ||
| + | |||
GB:=NC.GB(Relations); | GB:=NC.GB(Relations); | ||
GB; | GB; | ||
Revision as of 09:09, 23 August 2013
Description
The von Dyck groups are sometimes referred to as ordinary triangle groups and are subgroups of index 2 in Triangle(l, m, n) generated by words of even length in the generators a, b, c. A specific representation is given for x = ab, y = ca, yx = cb:
D(l,m,n) = <x,y | x^{l} = y^{m} = (xy)^{n} = 1>
(Reference: not found yet)
Computation
/*Use the ApCoCoA package ncpoly.*/
// Parameters of von Dyck group
MEMORY.L:=3;
MEMORY.M:=5;
MEMORY.N:=2;
Use ZZ/(2)[x,y];
NC.SetOrdering("LLEX");
Define CreateRelationsVonDyck()
Relations:=[];
// add the relation x^l = 1
Append(Relations,[[x^MEMORY.L],[1]]);
// add the relation y^m = 1
Append(Relations,[[y^MEMORY.M],[1]]);
// add the relation (xy)^n = 1
BufferXY:=[];
For Index1 := 1 To MEMORY.N Do
Append(BufferXY,x);
Append(BufferXY,y);
EndFor;
Append(Relations,[BufferXY,[1]]);
Return Relations;
EndDefine;
Relations:=CreateRelationsVonDyck();
Relations;
GB:=NC.GB(Relations); GB;
