# SmallGroup(81,8)

(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
View a complete list of particular groups (this is a very huge list!)[SHOW MORE]

## Definition

This is a group of order 81 given by the following presentation (with $e$ denoting the identity element): $G := \langle a,b,c \mid a^9 = b^3 = c^3 = e, ab = ba, cac^{-1} = ab, cbc^{-1} = a^3b \rangle$

## GAP implementation

### Group ID

This finite group has order 81 and has ID 8 among the groups of order 81 in GAP's SmallGroup library. For context, there are 15 groups of order 81. It can thus be defined using GAP's SmallGroup function as:

SmallGroup(81,8)

For instance, we can use the following assignment in GAP to create the group and name it $G$:

gap> G := SmallGroup(81,8);

Conversely, to check whether a given group $G$ is in fact the group we want, we can use GAP's IdGroup function:

IdGroup(G) = [81,8]

or just do:

IdGroup(G)

to have GAP output the group ID, that we can then compare to what we want.

### Description by presentation

The group can be described using a presentation by means of the following GAP command/code:

gap> F := FreeGroup(3);
<free group on the generators [ f1, f2, f3 ]>
gap> G := F/[F.1^9,F.2^3,F.3^3,F.1*F.2*F.1^(-1)*F.2^(-1),F.3*F.1*F.3^(-1)*F.1^(-1)*F.2^(-1),F.3*F.2*F.3^(-1)*F.1^(-3)*F.2^(-1)];
<fp group on the generators [ f1, f2, f3 ]>
gap> IdGroup(G);
[ 81, 8 ]