Standard Bases for Fractional Ideals of the Local Ring of an Algebroid Curve

Abstract

In this paper we present an algorithm to compute a Standard Basis for a fractional ideal $\mathcal{I}$ of the local ring $\mathcal{O}$ of an $n$-space algebroid curve with several branches. This allows us to determine the semimodule of values of $\mathcal{I}$. When $\mathcal{I}=\mathcal{O}$, we may obtain a (finite) set of generators of the semiring of values of the curve, which determines its classical semigroup. In the complex context, identifying the Kähler differential module ${\Omega }_{\mathcal{O}/\mathbb{C}}$ of a plane curve with a fractional ideal of $\mathcal{O}$ and applying our algorithm, we can compute the set of values of ${\Omega }_{\mathcal{O}/\mathbb{C}}$, which is an important analytic invariant associated to the curve.

To appear:Journal of Algebra