Magnetic fields from inflation?

TL;DR

This paper investigates the generation of primordial magnetic fields during inflation, revealing that back reaction effects impose strict limits on their strength, which are too weak for subsequent amplification to observable levels.

Contribution

The study demonstrates that back reaction effects significantly constrain the amplitude of inflation-generated primordial magnetic fields, challenging their role as seeds for cosmic magnetism.

Findings

Primordial magnetic field amplitude cannot exceed 10^{-32} G at Mpc scales.

Back reaction effects are crucial in limiting magnetic field strength during inflation.

Generated fields are too weak for galactic dynamo amplification.

Abstract

We consider the possibility of generation of the seeds of primordial magnetic field on inflation and show that the effect of the back reaction of this field can be very important. Assuming that back reaction does not spoil inflation we find a rather strong restriction on the amplitude of the primordial seeds which could be generated on inflation. Namely, this amplitude recalculated to the present epoch cannot exceed $10^{-32}G$ in $Mpc$ scales. This field seems to be too small to be amplified to the observable values by galactic dynamo mechanism.