[GAP Forum] Stabilizer problem

[Mathieu Dutour]

Dear Gap Forum,

I am computing with Integral Matrix Groups in GAP.

The set on which those groups act is n-uples
[x_1, ...., x_n] with 0<=x_i<1

The action of the matrix Group on this set is
ActionMod1:=function(eVect, eMat)
  return List(OnPoints(eVect, eMat), x->
(NumeratorRat(x) mod DenominatorRat(x))/Denominator(x) );
end;

Using that action, I want to use function Stabilizer
and RepresentativeAction. Most of the time those functions
works perfectly and I have no complaint. 

However, in some cases, the computation fails by lack of
memory (for example in dimension 15 with the symmetry group
of Lambda15 of order 41287680) Those cases arise when the 
stabilizer groups to be computed are small.

What causes such problems? What possible solutions may be 
available?

  Mathieu

-- 
Mathieu Dutour Sikiric		Researcher in Math
Tel. (+972)2 65 84 103		and Computer Science
Fax. (+972)2 56 30 702		Einstein Institute of Mathematics
E-mail: Mathieu.Dutour at ens.fr	Hebrew University of Jerusalem
http://www.liga.ens.fr/~dutour	Israel