FOURIER PATH-INTEGRALS, PARTIAL AVERAGING, AND THE POLARON PROBLEM

We evaluate the Fourier path integral for an optical polaron by the method of partial averaging. Higher Fourier coefficients are taken into account by averaging with Feynmans trial action, whereas the first N coefficients are treated explicitly by numerical integration. This method removes the Coulomb singularity in the effective action, yields lower bounds to the partition function, and systematically improves Feynmans variational results. We present numerical results for the exact ground-state energy for small and intermediate values of the coupling constant. © 1990 The American Physical Society.