Amplification of hypercharge electromagnetic fields by a cosmological pseudoscalar - art. no. 023508

If, in addition to the standard model fields, a new pseudoscalar field exis ts and couples to the hypercharge topological number density, it can expone ntially amplify hyperelectric and hypermagnetic fields in the symmetric pha se of the electroweak plasma, while coherently rolling or oscillating. We p resent equations describing the coupled system of a pseudoscalar field and hypercharge electromagnetic fields in an electroweak plasma at temperatures above the electroweak phase transition, and discuss approximations to the equations and their validity. We then solve the approximate equations using assorted analytical and numerical methods, and determine the parameters fo r which hypercharge electromagnetic fields can be exponentially amplified. [S0556-2821(99)03012-X].