Cosmological Alfvén waves in the recent CMB data , and the observational bound on the primordial vector perturbation

In the presence of the primordial magnetic field, initial vector (vorticity) perturbations produce cosmological Alfvén waves and leave imprints on cosmic microwave background (CMB) temperature and polarization anisotropy. We have investigated imprints of cosmological Alfvén waves in CMB anisotropy. For data constraints, we have used the power spectrum of the recent CMB observations, and correlations estimated from WMAP Internal Linear Combination (ILC) maps. Our analysis shows 3σ evidence of cosmological Alfvén waves. Using the 3σ limit from our analysis and the Alfvén velocity limit from the total energy density constraint, we impose a lower bound on the amplitude of primordial vector perturbation: 4× 10 at k0 = 0.002/Mpc. PACS numbers: 95.85.Sz, 98.70.Vc, 98.80.Cq, 98.80.Es, 98.80.-k