Localization for the norm-square of the moment map and the two-dimensional Yang-Mills integral

The first seven sections of the paper contain a version of localization for the norm-square of the moment map in equivariant de Rham theory, similar to that proved by P.-E. Paradan. The last section contains a definition and computation of the Yang-Mills path integral in two dimensions. The idea is to reverse the logic in Witten's paper and take the localization formula as the definition of the path integral. Using a symmetry argument we show that the path integral is given by the Migdal formula.