Berlin 2008 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 2: Statistical physics I (general)
DY 2.1: Vortrag
Montag, 25. Februar 2008, 10:30–10:45, MA 001
Variational Resummation of Effective Potential in Φ4-Theory with Proper Goldstone Modes — •Sonja Overesch1, Axel Pelster2, and Hagen Kleinert1 — 1Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany — 2Fachbereich Physik, Universität Duisburg-Essen, Lotharstraße 1, 47048 Duisburg, Germany
The Hartree-Fock-Bogoliubov approximation, which is very good for electrons, cannot be applied to a Bose gas in the condensed phase since it makes Goldstone modes massive. We investigate this problem within O(N)-symmetric Φ4-Theory by performing a resummation of the renormalized two-loop effective potential in D=3 dimensions by Variational Perturbation Theory (VPT). Using both a longitudinal and a transversal mass as two independent variational parameters, we obtain a resummed effective potential which preserves the Goldstone theorem. Since it takes simultaneously Hartree-, Fock-, and Bogoliubov channels into account, VPT can be regarded as a proper generalization of the Hubbard-Stratonovich transformation to all values of N.