Theory of Many-Particle Systems. I

摘要: This is the first of a series papers dealing with many-particle systems from unified, nonperturbative point view. It contains derivations and discussions various field-theoretical techniques which will be applied in subsequent papers. In short introduction general method approach summarized, its relationship to other field-theoretic problems indicated. second section macroscopic properties spectra are described. Asymptotic evaluations performed characterize these features terms intensive parameters, parameters thermodynamics discussed. The special characteristics ground state shown follow as limiting case asymptotic evaluations. third devoted time-dependent field correlation functions, or Green's describe microscopic behavior multiparticle system. These functions defined, related variables when energy number particles large. Spectral representations one-particle derived. fourth treatment non-equilibrium processes considered. As particular example, electromagnetic system expressed two-particle function describes current correlation. discussion yields specifically fluctuation-dissipation theorem, sum rule for conductivity, certain dispersion relations. fifth deals differential equations determine functions. boundary conditions that exhibited without reference adiabatic decoupling. A solving approximately, by treating correlations among successively larger numbers particles, approximation this sequence yield generalized Hartree-like equation. related, but rigorous, identity single-particle then approximation, takes into account, produce additional effects: interaction between altered manner characterized modification spread energy-momentum relation come play. final compact formal expressions physical quantities Alternative systematic approximations obtained.