Separators of arithmetically Cohen-Macaulay fat points ${\bf P}^1\times {\bf P}^1$

Let Z be a set of fat points in P^1 x P^1 that is also arithmetically Cohen-Macaulay (ACM). We describe how to compute the degree of a separator of a fat point of multiplicity m for each point in the support of Z using only a numerical description of Z. Our formula extends the case of reduced points which was previously known.

Separators of arithmetically Cohen-Macaulay fat points ${\bf P}^1\times {\bf P}^1$ Journal Articles