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Estimate of the primordial magnetic field helicity

Tanmay Vachaspati
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Abstract

Electroweak baryogenesis proceeds via changes in the non-Abelian Chern-Simons number. It is argued that these changes generate a primordial magnetic field with left-handed helicity. The helicity density of the primordial magnetic field today is then estimated to be given by $\sim 10^2 n_b$ where $n_b\sim 10^{-6}$ /cm$^3$ is the present cosmological baryon number density. With certain assumptions about the inverse cascade we find that the field strength at recombination is $\sim 10^{-13}$ G on a comoving coherence scale $\sim 0.1$ pc.

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Tanmay Vachaspati. 2001-11-01. Estimate of the primordial magnetic field helicity. https://doi.org/10.1103/physrevlett.87.251302

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