Exact results on the two-particle Green's function of a Bose-Einstein condensate

Abstract

Starting from the Dyson-Beliaev and generalized Gross-Pitaevskii equations with an extra nonlocal potential, we derive an exact expression of the two-particle Green's function K for an interacting Bose-Einstein condensate in terms of unambiguously defined self-energies and vertices. The formula can be a convenient basis for approximate calculations of K. It also tells us that poles of K are not shared with (i.e. shifted from) those of the single-particle Green's function, contrary to the conclusion of previous studies.

5 pages, 2 figures, to appear in Phys. Rev. B

References in corpus (2)

• Introduction to Nonequilibrium Statistical Mechanics with Quantum Field
• Self-consistent perturbation expansion for Bose-Einstein condensates satisfying Goldstone's theorem and conservation laws

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