Are primordial galactic magnetic fields created at the QCD scale?

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  • 6 April 2000
Abstract
In this letter, we propose a mechanism to generate large-scale magnetic fields with correlation lengths of 100 kpc. The seeds for these fields originate at the QCD phase transition through the alignment of the fields along axion domain walls. Axion domain walls provide the required Hubble size correlation at the QCD scale. Due to maximal CP violation across the domain walls (the so-called theta parameter is non-zero along the wall), both electric and magnetic dipole moments are induced generating electromagnetic fields with near maximal helicity (Chern-Simons). These fields support an inverse cascade which allows the initial correlations to grow to 100 kpc today. We calculate the generated electromagnetic fields in terms of the QCD parameters and discuss the effects of the resulting fields.

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