Computing the Castelnuovo-Mumford regularity of some subschemes of P-K(n) using quotients of monomial ideals

Given a homogeneous ideal I subset of K[x(0), ..., x(n)] defining a subsche me X of projective n-space P-K(n), we provide an effective method to comput e the Castelnuovo-Mumford regularity of X in the following two cases: when X is arithmetically Cohen-Macaulay, and when X is a not necessarily reduced projective curve. In both cases, we compute the Castelnuovo-Mumford regula rity of X by means of quotients of zero-dimensional monomial ideals. (C) 20 01 Elsevier Science B.V. All rights reserved.