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A Note on the Cosmic Evolution of the Axion in a Strong Magnetic Field

L. Campanelli, M. Giannotti

astro-pharXiv:astro-ph/0512324

Abstract

It has been pointed out in the literature that in the presence of an external magnetic field the axion mass receives an electromagnetic contribution. We show that if a magnetic field with energy density larger than ~10-8 times the energy density of the Universe existed at temperatures of a few GeV, that contribution would be dominant and consequently the cosmic evolution of the axion field would change substantially. In particular, the expected axion relic abundance would be lowered, allowing a small relaxation of the present cosmological bound on the Peccei-Quinn constant.

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