Cosmic Magnetic Fields and the CMB
Abstract
Description
I describe the imprint of primordial magnetic fields on the CMB. I show that these are observable only if the field amplitude is of the order of $B\gsim 10^{-9}G$ on Mpc scale. I further argue that such fields are strongly constrained by the stochastic background of gravity waves which they produce. Primordial magnetic fields, which are strong enough to be seen in the CMB, are compatible with the nucleosynthesis bound, only if their spectrum is close to scale invariant, or maybe if helical magnetic fields provoke an inverse cascade. For helical fields, the CMB signature is especially interesting. It contains parity violating T-B and E--B correlations.
12 pages, 6 figures, Contribution to the proceedings of the Francesco Melchiorri Memorial conference, Rome, April 2006
12 pages, 6 figures, Contribution to the proceedings of the Francesco Melchiorri Memorial conference, Rome, April 2006