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Centro de Astrofísica da Universidade do Porto
22-26 August 2011, Porto, Portugal

 

Helical magnetic fields from inflation
Jain, Rajeev (Department of Theoretical Physics, University of Geneva)

I shall discuss the generation of helical magnetic fields in single field inflation induced by an axial coupling of the electromagnetic field to the inflaton. In slow roll inflation, such a coupling always leads to a blue spectrum of the magnetic fields with P_B ~ k. Moreover, even a short deviation from slow roll does not result in strong modifications to the shape of the spectrum. I shall also discuss the subsequent evolution of the spectrum during the inverse cascade and viscous damping of the helical magnetic fields in the radiation era after inflation. Although the power is transferred from small to large scales, the magnetic fields generated in this scenario are too weak to provide the seeds for the observed fields in galaxies and clusters; except for low scale inflation with very strong axial coupling, a case where the perturbative treatment of the theory may break down.