Topological Currents in Neutron Stars: Kicks, Precession, Toroidal Fields, and Magnetic Helicity

TL;DR

This paper explores how topological currents arising from parity-violating processes in neutron stars can explain phenomena like stellar kicks, magnetic field configurations, and precession, linking these effects through underlying topological physics.

Contribution

It demonstrates that topological currents in dense matter can account for multiple neutron star phenomena, providing a unified physical explanation.

Findings

Topological currents can generate neutron star kicks.

They contribute to toroidal magnetic fields and magnetic helicity.

These effects stem from P-odd topological phenomena.

Abstract

The effects of anomalies in high density QCD are striking. We consider a direct application of one of these effects, namely topological currents, on the physics of neutron stars. All the elements required for topological currents are present in neutron stars: degenerate matter, large magnetic fields, and P-parity violating processes. These conditions lead to the creation of vector currents capable of carrying momentum and inducing magnetic fields. We estimate the size of these currents for many representative states of dense matter in the neutron star and argue that they could be responsible for the large proper motion of neutron stars (kicks), the toroidal magnetic field and finite magnetic helicity needed for stability of the poloidal field, and the resolution of the conflict between type-II superconductivity and precession. Though these observational effects appear unrelated, they likely originate from the same physics -- they are all P-odd phenomena that stem from a topological current generated by parity violation.