Journal of Physical Studies 11(2), 200–209 (2007) DOI: https://doi.org/10.30970/jps.11.200 INFRARED BEHAVIOR OF THE RESPONSE OF STRONGLY INTERACTING BOSE SYSTEMS A. Chumachenko{1}, S. Vilchynskyy{1}, M. Weyrauch{2} {1}National Taras Shevchenko University, Kyiv, Ukraine {2}Physikalisch-Technische Bundesanstalt, D–38116 Braunschweig, Federal Republic of Germany

We discuss field-theoretical foundations of Landau's quasi-particle concept for strongly interacting Bosons. The historical development starting from Belyaev's field theory up to modern renormalization group theory is briefly reviewed with a particular emphasis on the problem of infrared divergences. It is shown in detail that the correlation functions obtained in Popov's functional integral approach based on a hydrodynamic action agrees precisely with recent renormalization group analysis. The phonon decay is also discussed.

PACS number(s): 67.40.-w, 11.30.Qc, 11.10.Gh

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