Dresden 2011 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 12: Quantum Dynamics, Decoherence, and Quantum Information II

DY 12.3: Vortrag

Dienstag, 15. März 2011, 10:45–11:00, ZEU 255

Asymmetric Bethe-Salpeter equation for pairing and condensation — •Klaus Morawetz — University of Applied Science Münster, Stegerwaldstrasse 39, 48565 Steinfurt, Germany — International Institute of Physics (IIP), Universidade Federal do Rio grande do Norte - UFRN, Brazil

The Martin-Schwinger hierarchy of correlations are reexamined and the three-particle correlations are investigated under various partial summations. Besides the known approximations of screened, ladder and maximally crossed diagrams the pair-pair correlations are considered. It is shown that the recently proposed asymmetric Bethe-Salpeter equation to avoid unphysical repeated collisions is derived as a result of the hierarchical dependencies of correlations. Exceeding the parquet approximation we show that an asymmetry appears in the selfconsistent propagators. This form is superior over the symmetric selfconsistent one since it provides the Nambu-Gorkov equations and gap equation for fermions and the Beliaev equations for bosons while from the symmetric form no gap equation results. The selfenergy diagrams which account for the subtraction of unphysical repeated collisions are derived from the pair-pair correlation in the three-particle Greenfunction. It is suggested to distinguish between two types of selfconsistency, the channel-dressed propagators and the completely dressed propagators, with the help of which the asymmetric expansion completes the Ward identity and is Φ-derivable.

arXiv:1006.4695