Dear Peter, dear all, Is not so hard to implement the classical formulae for homogeneous components (i.e. the components that are direct sums of isomorphic copies of a particular irreducible), etc. The projectors are appropriate linear combinations of conjugacy class sums.
In fact I am working at the moment on a GAP package that constructs the coherent configuration of a not necessarily transitive permutation group and computes its irreducible representations --- as a by-product one would get a decomposition of the permutation module into irreducibles... I have (re)invented an efficient way to compute the conjugacy class sums, along the way. HTH, Dima 2008/9/26 Peter Cameron <[EMAIL PROTECTED]>: > Dear Forum, > > Is there a simple way to decompose rational permutation modules? A quick > browse of the manual suggests that one can decompose modules over finite > fields (I suppose this uses the MeatAxe) but not over the rationals > (which I naively thought would be easier). > > In particular cases one can spot a vector in each submodule and then take > the sumbodule spanned by its images, but it would be nice to have something > more general... > > Peter Cameron. > > _______________________________________________ > Forum mailing list > [email protected] > http://mail.gap-system.org/mailman/listinfo/forum > _______________________________________________ Forum mailing list [email protected] http://mail.gap-system.org/mailman/listinfo/forum
