Wf. Lu et al., Rayleigh-Schrodinger perturbation theory based on Gaussian wave functionalapproach - art. no. 025006, PHYS REV D, 6402(2), 2001, pp. 5006
A Rayleigh-Schrodinger perturbation theory based on the Gaussian wave funct
ional is constructed. The method can be used for calculating the energies o
f both the vacuum and the excited states. A model calculation is carried ou
t for the vacuum state of the lambda phi (4) field theory.