On deformations of maps and curve singularities

Abstract

We study several deformation functors associated to the normalization of a reduced curve singularity $(X,0) \subset (\c^n,0)$. The main new results are explicit formulas, in terms of classical invariants of (X,0), for the cotangent cohomology groups $T^i, i = 0,1,2,$ of these functors. Thus we obtain precise statements about smoothness and dimension of the corresponding local moduli spaces. We apply the results to obtain explicit formulas resp. estimates for the $\hoa{A}_e$-codimension of a parametrized curve singularity, where $\hoa{A}_e$ denotes the Mather-Wall group of left-right equivalence.