# Difference between revisions of "ApCoCoA-1:Higman groups"

### Higman group

#### Description

The Higman group is an infinite finitely presented group with no non-trivial finite quotients and is generated by the elements a,b,c and d with the following relations:

``` H = <a,b,c,d | a^{-1}ba = b^{2}, b^{-1}cb = c^{2}, c^{-1}dc = d^{2}, d^{-1}ad = a^{2}>
```

(Reference: Higman, Graham (1951), "A finitely generated infinite simple group", Journal of the London Mathematical Society. Second Series 26 (1): 61–64)

#### Computation

``` /*Use the ApCoCoA package ncpoly.*/

// a is invers to e, b is invers to f, c is invers to g and d is invers to h
Use ZZ/(2)[a,b,c,d,e,f,g,h];
NC.SetOrdering("LLEX");
Define CreateRelationsHigman()
Relations:=[];

// add the relation of the invers element
Append(Relations,[[a,e],[1]]);
Append(Relations,[[e,a],[1]]);
Append(Relations,[[b,f],[1]]);
Append(Relations,[[f,b],[1]]);
Append(Relations,[[c,g],[1]]);
Append(Relations,[[g,c],[1]]);
Append(Relations,[[d,h],[1]]);
Append(Relations,[[h,d],[1]]);

// add the relation a^{-1}ba = b^2
Append(Relations,[[e,b,a],[b^2]]);

// add the relation b^{-1}cb = c^2
Append(Relations,[[f,c,b],[c^2]]);

// add the relation c^{-1}dc = d^2
Append(Relations, [[g,d,c],[d^2]]);