Mixed Segre Numbers and Integral Closure of Ideals

Abstract

We introduce mixed Segre numbers of ideals which generalize the notion of mixed multiplicities of ideals of finite colength and show how many results on mixed multiplicities can be extended to results on mixed Segre numbers. In particular, we give a necessary and sufficient condition in terms of these numbers for two ideals to have the same integral closure. Also, our theory yields a new proof of a generalization of Rees' theorem that links the integral closure of an ideal to its multiplicity. Finally, we give a quick application of our results to Whitney equisingularity.