2008/12/02 by Thomas Gasenzer
Physics and Astronomy · #Cold Atom Physics and Bose-Einstein Condensates #Quantum many-body systems #Quantum, superfluid, helium dynamics #cond-mat.other
paper · pdf · doi:10.1140/epjst/e2009-00960-5
59 pages, 26 figures; Compiled from notes for lectures held at 46. Internationale Universitaetswochen fuer Theoretische Physik 2008 in Schladming, Austria. To be published in Eur. Phys. J. Special Topics
arxiv created 2008/12/02 · openalex publication_date 2009/02/01 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/29
Ultracold atomic quantum gases belong to the most exciting challenges of modern physics. Their theoretical description has drawn much from classical field equations. These mean-field approximations are in general reliable for dilute gases in which the atoms collide only rarely with each other, and for situations where the gas is not too far from thermal equilibrium. With present-day technology it is, however, possible to drive and observe a system far away from equilibrium. Functional quantum field theory provides powerful tools to achieve both, analytical understanding and numerical computability, also in higher dimensions, of far-from-equilibrium quantum many-body dynamics. In the article, an outline of these approaches is given, including methods based on the two-particle irreducible effective action as well as on renormalisation-group theory. Their relation to near-equilibrium kinetic theory is discussed, and the distinction between quantum and classical statistical fluctuations is shown to naturally emerge from the functional-integral description. Example applications to the evolution of an ultracold atomic Bose gas in one spatial dimension underline the power of the methods. The article is compiled from the notes for lectures held at 46. Internationale Universitaetswochen fuer Theoretische Physik 2008 in Schladming, Austria.