title: Production of axions by cosmic magnetic helicity.
abstract: We investigate the effects of an external magnetic helicity production on the evolution of the cosmic axion field. It is shown that a helicity larger than (few x 10(-15) G)2 Mpc, if produced at temperatures above a few GeV, is in contradiction with the existence of the axion, since it would produce too much of an axion relic abundance.
authors.affiliation: Dipartimento di Fisica, Università di Ferrara, I-44100 Ferrara, Italy. campanelli@fe.infn.it
authors.forename: L
authors.initials: L
authors.lastname: Campanelli
authors.forename: M
authors.initials: M
authors.lastname: Giannotti