Let G be a finite group and F a field. If e is an idempotent in the group algebra FG, the map M -> Me is an exact functor from the category of right FG-modules to the category of right eFGe-modules, called "condensation".
If K is a subgroup with char F prime to |K|,
e = |K|^(-1) \sum_{k\in K} k
is an idempotent in the group algebra FG. For the case of such an e
and M being a permutation module for G, the "condensed module" can be
calculated combinatorically.
This package contains programs that do this.
Click here for further explanations.
May 2000,
Frank Lübeck and Max Neunhöffer
Download Direct Condense 2.00 (.tar.gz)