Magnetic fields from inflation: the transition to the radiation era

Understand

We compute the contribution to the scalar metric perturbations from large-scale magnetic fields which are generated during inflation.

• We show that apart from the usual passive and compensated modes, the magnetic fields also contribute to the constant mode from inflation.
• This is different from the causal (post inflationary) generation of magnetic fields where such a mode is absent and it might lead to significant, non-Gaussian CMB anisotropies.