The origin of cosmological magnetic fields is an unresolved
issue. Most scenarios for a primordial origin of these fields
predict most power on microscopic scales, but very weak
fields on cosmologically relevant scales. In this case, observed
large scale and galactic fields would have to have either
a secondary origin, for example from battery effects,
or one has to assume that primordial fields were enhanced
by dynamo effects.
However, parity-odd interactions which are present in
certain particle physics scenarios and also in string
theory can lead to injection of magnetic helicity.
In combination with a dynamo acting on small
scales some of the magnetic energy originally produced
at microscopic scales can cascade to large scales where
it may lead to observable effects or be dissipated.
I am working on quantitative calculations of such effects.
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