Fluctuative Mechanism of Vortex Nucleation in the Flow of $^4He$

TL;DR

This paper introduces a new mechanism for vortex nucleation in superfluid helium-4 involving critical fluctuations and plasma of half-vortex rings, deriving scaling laws and critical exponents near the transition temperature.

Contribution

It proposes a novel vortex nucleation mechanism based on plasma of half-vortex rings and derives associated scaling laws and critical exponents.

Findings

Critical velocity scales as V_c ~ V_0(1 - T/T_c)

Critical exponent p is found to be 1

Mechanism explains vortex nucleation near walls in superfluid helium-4

Abstract

We propose a mechanism of a vortex nucleation in a flow of a superfluid $^4He$. The mechanism is related to the creation by critical fluctuations of a "plasma" of half-vortex rings located near the wall. The "plasma" screens the attraction of the vortex to the wall and permits vortex nucleation. In the spirit of Williams-Shenoy theory we derive the scaling laws in the critical region and estimate the scaling relation and the critical exponent $p$ for critical velocity; we find $V_c\sim V_{0}(1-T/T_c)$, so that $p=1$. Various applications of the obtained results are discussed.