title: Limit on primordial small-scale magnetic fields from cosmic microwave background distortions
abstract: Spatially varying primordial magnetic fields may be efficiently dissipated prior to the epoch of recombination due to the large viscosity of the baryon-photon fluid. We show that this dissipation may result in observable chemical potential &mgr; and Compton y distortions in the cosmic microwave background spectrum. Current upper limits on &mgr; and y from FIRAS constrain magnetic fields to have strength B0<3x10(-8) G (scaled to the present) between comoving coherence length approximately 400 pc and approximately 0.6 Mpc. These represent the strongest upper limits on small-scale primordial magnetic fields to date.
authors.affiliation: Max-Planck-Institut fur Astrophysik, 85748 Garching bei Munchen, Germany.
authors.initials: K
authors.lastname: Jedamzik
authors.initials: V
authors.lastname: Katalinic
authors.initials: AV
authors.lastname: Olinto