On the A-D-E classification of the simple singularities of functions

Abstract

We show how the classification of simple singularities of functions can be reduced directly, not using the normal forms, to the classification of irreducible Weyl groups. We also prove that the class of a singularity in its local algebra always belongs to the tangent cone to the stratum $μ=const$ of the singularity. An interesting characterization of Coxeter elements among quasi-Coxeter elements of a Weyl group (of one of the types A-D-E) is found.