Magnetic Field Transfer From A Hidden Sector

TL;DR

This paper investigates how primordial magnetic fields in a hidden dark sector can be transferred to the visible sector through gauge kinetic mixing, highlighting the conditions and efficiency of this process and its implications for observed intergalactic magnetic fields.

Contribution

It demonstrates the conditions under which magnetic field transfer occurs from a dark sector to the visible sector and analyzes the factors affecting its efficiency, providing new insights into dark magnetogenesis.

Findings

Transfer occurs during dissipation-dominated magnetic evolution.

Transfer efficiency is suppressed by gauge coupling and conductivity-to-momentum ratio.

Without dynamo amplification, the transferred magnetic fields are insufficient to explain observed intergalactic fields.

Abstract

Primordial magnetic fields in the dark sector can be transferred to magnetic fields in the visible sector due to a gauge kinetic mixing term. We show that the transfer occurs when the evolution of magnetic fields is dominated by dissipation due to finite electric conductivity, and does not occur at later times if the magnetic fields evolve according to magnetohydrodynamics scaling laws. The efficiency of the transfer is suppressed by not only the gauge kinetic mixing coupling but also the ratio between the large electric conductivity and the typical momentum of the magnetic fields. We find that the transfer gives nonzero visible magnetic fields today. However, without possible dynamo amplifications, the field transfer is not efficient enough to obtain the intergalactic magnetic fields suggested by the gamma-ray observations, although there are plenty of possibilities for efficient dark magnetogenesis, which are experimentally unconstrained.