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Higher Effective Actions for Bose Systems
Author(s) -
Kleinert H.
Publication year - 1982
Publication title -
fortschritte der physik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.469
H-Index - 71
eISSN - 1521-3978
pISSN - 0015-8208
DOI - 10.1002/prop.19820300402
Subject(s) - generalization , action (physics) , vertex (graph theory) , effective action , mathematics , variety (cybernetics) , equations of motion , physics , mathematical physics , pure mathematics , statistical physics , classical mechanics , graph , mathematical analysis , quantum mechanics , combinatorics , statistics
We study the generalization of the usual effective action Γ[ϕ] of Bose systems to an explicit functional Γ[ϕ, G , α 2 , α 4 ] of field ϕ, Green's function G , and three‐ and four‐point vertex functions α 3 , α 4 . The equations of motion following by extremization with respect to ϕ, G , α 3 , α 4 provide for non‐linear integral equations whose solution can account for a wide variety of non‐perturbative effects: Condensation of particles, pairs, and three and four‐particle clusters. There can be spontaneous generation of mass as well as of interaction.