title: Superfluid phase transition with activated velocity fluctuations: Renormalization group approach.
abstract: A quantum field model that incorporates Bose-condensed systems near their phase transition into a superfluid phase and velocity fluctuations is proposed. The stochastic Navier-Stokes equation is used for a generation of the velocity fluctuations. As such this model generalizes model F of critical dynamics. The field-theoretic action is derived using the Martin-Siggia-Rose formalism and path integral approach. The regime of equilibrium fluctuations is analyzed within the perturbative renormalization group method. The double (ε,δ)-expansion scheme is employed, where ε is a deviation from space dimension 4 and δ describes scaling of velocity fluctuations. The renormalization procedure is performed to the leading order. The main corollary gained from the analysis of the thermal equilibrium regime suggests that one-loop calculations of the presented models are not sufficient to make a definite conclusion about the stability of fixed points. We also show that critical exponents are drastically changed as a result of the turbulent background and critical fluctuations are in fact destroyed by the developed turbulence fluctuations. The scaling exponent of effective viscosity is calculated and agrees with expected value 4/3.
authors: Institute of Experimental Physics, SAS, Košice, Slovakia.|Joint Insitute for Nuclear Research, Dubna, Russia.
authors: Michal
authors: M
authors: Dančo
authors: Institute of Experimental Physics, SAS, Košice, Slovakia.|Joint Insitute for Nuclear Research, Dubna, Russia.|Faculty of Sciences, P.J. Šafarik University, Košice, Slovakia.
authors: Michal
authors: M
authors: Hnatič
authors: Department of Theoretical Physics, St. Petersburg University, Ulyanovskaya 1, St. Petersburg, Petrodvorets, 198504 Russia.
authors: Marina V
authors: MV
authors: Komarova
authors: Faculty of Sciences, P.J. Šafarik University, Košice, Slovakia.|Fakultät für Physik, Universität Duisburg-Essen, D-47048 Duisburg, Germany.
authors: Tomáš
authors: T
authors: Lučivjanský
authors: Department of Theoretical Physics, St. Petersburg University, Ulyanovskaya 1, St. Petersburg, Petrodvorets, 198504 Russia.
authors: Mikhail Yu
authors: MY
authors: Nalimov