Critical Dynamics of the Superfluid Phase Transition. Calculation of z Critical Exponent and Stability of the IR Fixed Point

Dynamic behaviour of weak interacting boson gas near the condensation transition in the symmetric phase is studied with the use of an effective large-scale model derived from time-dependent Green function at finite temperature. In three-loop calculation stability of the infra-red stable fixed point is showed. The method of calculation is demonstrate and discussed. Overall this result confirm the previous hypothesis about infra-red stability of an unique stable fixed point found in (Zhavoronkov et al. in Theor. Math. Phys. 200:1237–1251, 2019).