Magnetic fields in a hot dense neutrino plasma and the Gravitational Waves

TL;DR

This paper investigates how magnetic instability in a neutrino-rich plasma can generate primordial gravitational waves, potentially detectable by future radio telescope observations, and compares these results with previous models excluding magnetic effects.

Contribution

It introduces a new mechanism for primordial gravitational wave generation via magnetic instability in a neutrino plasma, highlighting its potential observability.

Findings

Magnetic instability produces a helical magnetic field on large scales.

Anisotropic stress from magnetic fields sources primordial GWs at matter-neutrino decoupling.

Predicted GWs may be detectable by SKA or PTA observations.

Abstract

In the present work, we have studied the spectrum of the primordial gravitational waves due to magnetic instability in the presence of neutrino asymmetry. The magnetic instability generates a helical magnetic field on a large scale. The anisotropic stress generated by the magnetic field shown to be a source of primordial gravitational waves (GWs) at the time of matter-neutrino decoupling. We expect that the theoretically predicted GWs by this mechanism may be detected by Square Kilometer Array (SKA) or pulsar time array (PTA) observations. We also compare our findings with the results obtained by the earlier work where the effect of magnetic instability was not considered.