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Dear gap-forum,

In a letter to gap-trouble, Leonard Soicher writes:

There appears to be an inconsistency with the AbelianInvariants function:

gap> AbelianInvariants(CyclicGroup(6)); [ 2, 3 ] gap> F:=FreeGroup(1);; gap> AbelianInvariants(F/[(F.1)^6]); [ 6 ] gap> quit;(The result of the second application of the function contradicts the

GAP manual.) Please explain.

We are grateful to Leonard for alerting us to this problem. There is, in

fact, an inconsistency. The abelian invariants should always be provided

in form of prime powers as stated in the manual, but for certain groups

the function simply calls the function ElementaryDivisorsMat and hence

returns them in form of elementary divisors. We will of course fix this

in the next patch or release.

However, as it is a simple task to transform the elementary divisors into

the corresponding prime powers and vice versa, we hope that we can live

with the current state until then.

Volkmar Felsch

(volkmar.felsch@math.rwth-aachen.de)

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