paper

Helical Magnetic Fields from Inflation

arXiv:0805.0575 · doi:10.1142/S0218271809015175

Abstract

We analyze the generation of seed magnetic fields during de Sitter inflation considering a non-invariant conformal term in the electromagnetic Lagrangian of the form , where is a pseudoscalar function of a non-trivial background field . In particular, we consider a toy model, that could be realized owing to the coupling between the photon and either a (tachyonic) massive pseudoscalar field and a massless pseudoscalar field non-minimally coupled to gravity, where follows a simple power-law behavior during inflation, while it is negligibly small subsequently. Here, is a positive dimensionless constant, the wavenumber, the conformal time, and a real positive number. We find that only when and astrophysically interesting fields can be produced as excitation of the vacuum, and that they are maximally helical.

17 pages, 1 figure, subsection IIc and references added; accepted for publication in IJMPD

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