Scattering of Phonons by a Vortex in a Superfluid

TL;DR

This paper challenges previous assumptions about phonon scattering by vortices in superfluids, showing that the resulting transverse force is smaller than previously thought and emphasizing the need for a different analytical approach.

Contribution

It corrects a common derivation of the transverse force on vortices, demonstrating that the force is significantly smaller and proposing that alternative methods are necessary.

Findings

The transverse force on a vortex due to phonon scattering is smaller than previously believed.

A common derivation of the transverse force contains errors.

A different analytical approach is required for accurate force calculation.

Abstract

Recent work gives a transverse force on an isolated moving vortex which is independent of the normal fluid velocity, but it is widely believed that the asymmetry of phonon scattering by a vortex leads to a transverse force dependent on the relative motion of the normal component and the vortex. We show that a widely accepted derivation of the transverse force is in error, and that a careful evaluation leads to a much smaller transverse force. We argue that a different approach is needed to get the correct expression. \pacs{67.40.Vs,67.57.Fg,47.37.+q,47.32.Cc}