Distortion of the acoustic peaks in the CMBR due to a primordial   magnetic field
  In this paper we study the effect of a magnetic field on the fluctuation spectrum of the cosmic microwave background. We find that upcoming measurements might give interesting bounds on large scale magnetic fields in the early Universe. If the effects are seen, it might be possible to establish the presence of different fields in different patches of the sky. Absence of any effect, will provide by one order of magnitude a better limit for a primordial field, now given by nucleosynthesis. 
Jenni Adams, Ulf H. Danielsson, Dario Grasso and H\'ector Rubinstein   (Uppsala University)