title: Nonperturbative predictions for cold atom bose gases with tunable interactions.
abstract: We derive a theoretical description for dilute Bose gases as a loop expansion in terms of composite-field propagators by rewriting the Lagrangian in terms of auxiliary fields related to the normal and anomalous densities. We demonstrate that already in leading order this nonperturbative approach describes a large interval of coupling-constant values, satisfies Goldstone's theorem, yields a Bose-Einstein transition that is second order, and is consistent with the critical temperature predicted in the weak-coupling limit by the next-to-leading-order large-N expansion.
authors.affiliation: Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: Fred
authors.initials: F
authors.lastname: Cooper
authors.forename: Chih-Chun
authors.initials: CC
authors.lastname: Chien
authors.forename: Bogdan
authors.initials: B
authors.lastname: Mihaila
authors.forename: John F
authors.initials: JF
authors.lastname: Dawson
authors.forename: Eddy
authors.initials: E
authors.lastname: Timmermans