CMB and matter power spectra from cross correlations of primordial
  curvature and magnetic fields
  A complete numerical calculation of the temperature anisotropies and the
polarization of the cosmic microwave background (CMB) is presented for a non
zero cross correlation of a stochastic magnetic field with the primordial
curvature perturbation. Such a cross correlation results, for example, if the
magnetic field is generated during inflation by coupling electrodynamics to a
scalar field which is identified with the curvaton. For a nearly scale
invariant magnetic field of 1 nG it is found that at low multipoles the
contribution due to the cross correlation dominates over that of the pure
magnetic mode. A similar behaviour on large scales is found for the linear
matter power spectrum.
