Astronomy and Astrophysics – Astrophysics
Scientific paper
2007-12-11
Phys.Rev.D77:063517,2008
Astronomy and Astrophysics
Astrophysics
9 pages, 1 figure; minor corrections and additions; accepted for publication in Physical Review D
Scientific paper
10.1103/PhysRevD.77.063517
We analyse the possibility that topological defects can act as a source of magnetic fields through the Harrison mechanism in the radiation era. We give a detailed relativistic derivation of the Harrison mechanism at first order in cosmological perturbations, and show that it is only efficient for temperatures above T ~ 0.2 keV. Our main result is that the vector metric perturbations generated by the defects cannot induce vorticity in the matter fluids at linear order, thereby excluding the production of currents and magnetic fields. We show that anisotropic stress in the matter fluids is required to source vorticity and magnetic fields. Our analysis is relevant for any mechanism whereby vorticity is meant to be transferred purely by gravitational interactions, and thus would also apply to dark matter or neutrinos.
Caprini Chiara
Crittenden Robert
Hollenstein Lukas
Maartens Roy
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