L\^e Modules and Traces

Abstract

We show how some of our recent results clarify the relationship between the L\^e numbers and the cohomology of the Milnor fiber of a non-isolated hypersurface singularity. The L\^e numbers are actually the ranks of the free Abelian groups -- the L\^e modules -- appearing in a complex whose cohomology is that of the Milnor fiber. Moreover, the Milnor monodromy acts on the L\^e module complex, and we describe the traces of these monodromy actions in terms of the topology of the critical locus.