43 research outputs found
When are permutation invariants Cohen-Macaulay?
Over a field of characteristic 0, every ring of invariants of any finite
group is Cohen-Macaulay. This is not true for fields of positive
characteristic. We consider permutation representations and their invariant
rings over fields of prime order. We give an efficient algorithm
which for any given permutation representation, determines those primes for
which the invariant ring over is Cohen-Macaulay. Extensions to
subgroups of reflection groups other than the symmetric group are indicated