Seminar “Theory of Condensed Matter”

Date and Time: Tuesday, 1 March 2022, at 4:00 PM

Venue: Blokhintsev lecture hall, Bogoliubov Laboratory of Theoretical Physics, online seminar on Zoom

Link to join the seminar via Zoom

Seminar topic: “Critical Dynamics of the phase transition to the superfluid state”

Speaker: Iurii Molotkov (Faculty of Physics, SPbSU)

Abstract:

The most generally accepted statement in superfluidity research is that the dynamics of the corresponding phase transition is described by the stochastic model F or E. However, the dynamic critical exponent z has not been yet evaluated even in the leading order of perturbation theory. Instead of dealing with phenomenological stochastic theories, we propose a microscopic theory of the time-dependent Green functions at finite temperature. This framework allows one to construct an effective infrared (IR) theory for phase transition to the superfluid state and to prove multiplicative renormalizability of this theory. This theory has only one IR stable fixed point and the dynamic critical exponent z corresponding to this fixed point is equal to the critical exponent z calculated in a 2-component A model of stochastic dynamics.

In this talk, I briefly develop framework of the time-dependent Green function at finite temperature, discuss the apparent IR divergence and methods of regularization of the model. Then, with aid of this framework, I construct the IR effective large-scale theory and discuss its renormalizability. Moreover, I speculate on the stability of fixed point in the third order of perturbation theory and also on the technique of the calculation of Feynman diagrams, which allows for this model to receive answers in the form of quadratures.