Christophe Eyral

## Title:

Introduction to Lê numbers

## Abstract:

Certainly the most important numerical invariant of an isolated hypersurface singularity is its Milnor number. This number contains a crucial information about the singularity. For non-isolated singularities, the Milnor number (which is always infinite) is no longer relevant. However, for such singularities, D. Massey introduced a series of numerical invariants which generalize the data given by the Milnor number for an isolated singularity. These numerical invariants are called the Lê numbers. The purpose of this talk is to introduce Massey's theory of Lê numbers.