SMEARING FORMULA FOR HIGHER-ORDER EFFECTIVE CLASSICAL POTENTIALS

In the variational approach to quantum statistics, a smearing formula efficiently describes the consequences of quantum fluctuations upon an interaction potential. The result is an effective classical potential from which the partition function can be obtained by a simple integra l. In this work, the smearing formula is extended to higher orders in the variational perturbation theory. An application to the singular Co ulomb potential exhibits the same fast convergence with increasing ord ers that has been observed in previous variational perturbation expans ions of the anharmonic oscillator with quartic potential.