Hello
This is my first question. I hope it's not a stupid one. I have an
finitely presented abelian group and I want to obtain a simple
presentation for the group. The command SimplifedFpGroup is not working
satisfactorily (possibly because it doesn't introduce new generators).
How can I make GAP use the fact that the group is abelian and use an
appropriate method?
I'll give an example:
G;
<fp group on the generators [ f1, f2, f3, f4, f5, f6, f7, f8, f9, f10,
f11,
f12, f13, f14, f15, f16 ]>
(this is my initial group)
Gsimp:=SimplifiedFpGroup(G);
<fp group on the generators [ f1, f2, f5, f6 ]>
(okay, a bit simpler)
RelatorsOfFpGroup(Gsimp);
[ f1*f2*f1^-1*f2^-1, f2^-1*f5^-1*f2*f5, f1^-1*f6^-1*f1*f6,
f5^-1*f6*f5*f6^-1,
f2^-1*f6^-1*f2*f6, f1^-1*f5^-1*f1*f5, f1*f2^3*f1*f2*f1^2 ]
(6 commutators and a relation of length 8)
IsAbelian(Gsimp);
true (so it knows it's abelian)
AbelianInvariants(Gsimp);
[ 0, 0, 0, 4 ]
In this case what I am looking for is a presentation with 4 generators,
three torsion-free and one of order 4, in terms of the original
generators of G.
Thanks in advance,
Martin
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