  A path-integral approach for the computation of quantum-mechanical
propagators and energy Green's functions is presented. Its effectiveness is
demonstrated through its application to singular interactions, with particular
emphasis on the inverse square potential--possibly combined with a
delta-function interaction. The emergence of these singular potentials as
low-energy nonrelativistic limits of quantum field theory is highlighted. Not
surprisingly, the analogue of ultraviolet regularization is required for the
interpretation of these singular problems.
