Comment on "Transverse Force on a Quantized Vortex in a Superfluid"

TL;DR

This paper discusses the discrepancy between theoretical predictions and experimental observations of transverse forces on vortices in superfluids, emphasizing the importance of the Iordanskii and spectral flow forces in resolving the contradiction.

Contribution

It highlights the necessity of including the Iordanskii and spectral flow forces to accurately describe vortex dynamics in superfluids, correcting previous theoretical models.

Findings

The Iordanskii force explains negative transverse force at low temperatures.

Spectral flow contributes to the transverse force approaching unity at high temperatures.

Theoretical models must incorporate these forces to match experimental results.

Abstract

The result of Thouless, Ao and Niu (TAN), that the mutual friction parameter $d_\perp =0$, contradicts to the experiments made in rotating 3He-B by Manchester group. The Manchester group observed that $d_\perp <0$ at low temperature and approaches 1 at high temperature. The reason of the contradiction is that TAN did not take into account the Iordanskii force on the vortex and the spectral flow force, which comes from the anomaly related to the low-energy bound states of fermions in cores of quantized vortices. The Iordanskii force is responsible for the negative $d_\perp <0$ at low temperature, while due to the spectral flow $d_\perp$ approaches 1 at high temperature. Relation of the spectral flow anomaly with the paradoxes of the linear and angular momenta in gapless superfluids is discussed.