Berlin 2005 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
MP: Theoretische und Mathematische Grundlagen der Physik
MP 5: Condensed Matter
MP 5.4: Fachvortrag
Dienstag, 8. März 2005, 15:00–15:20, TU MA141
Renormalization group flows into phases with broken symmetry — •Oliver Lauscher1, Manfred Salmhofer1, Carsten Honerkamp2, and Walter Metzner2 — 1Institut für Theoretische Physik, Universität Leipzig, Augustusplatz 10, 04109 Leipzig, Germany — 2Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, 70569 Stuttgart, Germany
We describe a way to continue the fermionic renormalization group flow into phases with broken global symmetry. The method does not require a Hubbard-Stratonovich decoupling of the interaction. Instead an infinitesimally small symmetry-breaking component is inserted in the initial action, as an initial condition for the flow of the selfenergy. Its flow is driven by the interaction and at low scales it saturates at a nonzero value if there is a tendency for spontaneous symmetry breaking in the corresponding channel. For the reduced BCS model we show how a small initial gap amplitude flows to the value given by the exact solution of the model. We also discuss the emergence of the Goldstone boson in this approach.