Variational approximations for correlation functions in quantum field theories

Abstract

Applying the time-dependent variational principle of Balian and Vénéroni, we derive variational approximations for multi-time correlation functions in ${\Phi }^4$ field theory. We assume first that the initial state is given and characterized by a density operator equal to a Gaussian density matrix. Then, we study the more realistic situation where only a few expectation values are given at the initial time and we perform an optimization with respect to the initial state. We calculate explicitly the two-time correlation functions with two and four field operators at equilibrium in the symmetric phase.

60 pages, Latex, to be published in Annals of Physics

References in corpus (2)

• Real-time Relaxation and Kinetics in Hot Scalar QED: Landau Damping
• The Poisson structure of the mean-field equations in the Phi^4 theory

Cited by in corpus (4)

• Nuclear Quantum Many-Body Dynamics: From Collective Vibrations to Heavy-Ion Collisions
• Self-consistent theory of Bose-Einstein condensate with impurity at finite temperature
• Quantum correlations in dipolar droplets: Time-dependent Hartree-Fock-Bogoliubov theory
• Nuclear Quantum Many-Body Dynamics: From Collective Vibrations to Heavy-Ion Collisions (2nd edition)