2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/150680We present a nonperturbative field theoretic method based on the Liouville-Neumann (LN) equation. The LN approach provides a unified formulation of nonperturbative quantum fields and also nonequilibrium quantum fields, which makes use of mean-field type equations and whose results at the lowest level are identically the same as those of the Gaussian effective potential approach and the mean-field approach. The great advantageous point of this formulation is its readiness of applicability to time-dependent quantum systems and to finite temperature field theory, and its possibility to go beyond the Gaussian approximation.To appear in the proceedings to be published by World Scientific of APCTP-ICTP Joint International Conference '97 on 'Recent Developments in Nonperturbative Quantum Field Theory', May 26-30, 1997, Seoul, Some typos corrected, ReVTeX, 12 Pages, No FigureHigh Energy Physics - Theorytext