2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/82642Starting from full quantum field theory, various mean field approaches are derived systematically. With a full consideration of external source dependence, the stationary phase approximation of an action gives a nuclear mean field theory which includes quantum correlation effects (such as particle-hole or ladder diagram) in a simpler way than the Brueckner-Hartree-Fock approach. Implementing further approximation, the result can be reduced to Hartree-Fock or Hartree approximation. The role of the source dependence in a mean field theory is examined.8 pages in REVTEX. No figureNuclear TheoryHigh Energy Physics - Phenomenologytext