Primordial magnetic fields and their interaction with gravity waves.

by Ms Elisa Fenu (University of Geneva)

Wednesday 11 Feb 2009, 11:00 → 12:00 Europe/Zurich

1/1-025 (CERN)

I briefly review some kind of imprints that a primordial magnetic field can leave on the CMB and I show that these can be observed only if their amplitude is greater than 10^-9 Gauss on the Mpc scale. Then, I explain how they can be strongly constrained by a stochastic background of gravity waves, going into the details of the so-called gravito-magnetic interaction: the energy momentum tensor of a magnetic field always contains a spin-2 component in its anisotropic stress and therefore generates gravitational waves. This gravitional wave production can be very strong and back-reaction cannot be neglected. Moreover, given a gravitational wave background which affects the evolution of magnetic fields, it has been argued in the literature that this can lead to a very strong amplification of a primordial magnetic field. I will finally revisit these claims and study back-reaction to second order.

Reference:

• C. Caprini and R. Durrer, Phys. Rev. D 65, 023517 (2001)
• C.G.Tsagas, P.K.S.Dunsby and M.Marklund, "Gravitational wave amplification of seed magnetic fields", Phys. Lett. B 561, 17 (2003) [arXiv:astro-ph/0112560]
• C. Tsagas, "Resonant amplification of magnetic seed fields by gravitational waves in the early universe", Phys. Rev. D 72, 123509 (2005) [arXiv:astro-ph/0508556]
• E.Fenu and R.Durrer, "Interactions of cosmological gravity waves and magnetic fields", arXiv:0809.1383 [astro-ph]