Abstract
We construct a finitely generated monoid S with a zero element such that for every field K the Jacobson radical of the monoid algebra K[S] is a sum of nilpotent ideals but is not nilpotent. Moreover, the contracted monoid algebra K 0[S] is a monomial algebra.
If K is a field of characteristic p > 0, then we construct a finitely presented group H p such that the Jacobson radical J of the group algebra K[H p ] is a sum of nilpotent ideals, but is not nilpotent. Moreover, K[H p ]/J is a domain.
2000 Mathematics Subject Classification:
Acknowledgments
Work supported by a MNiSW research grant N201 420539 (Poland).
Notes
Communicated by A. Smoktunowicz.