Probing Primordial Magnetism with Off-Diagonal Correlators of CMB Polarization

Research paper by Amit P. S. Yadav, Levon Pogosian, Tanmay Vachaspati

Indexed on: 14 Mar '13Published on: 14 Mar '13Published in: arXiv - Astrophysics - Cosmology and Nongalactic Astrophysics


Primordial magnetic fields (PMF) can create polarization $B$-modes in the cosmic microwave background (CMB) through Faraday rotation (FR), leading to non-trivial 2-point and 4-point correlators of the CMB temperature and polarization. We discuss the detectability of primordial magnetic fields using different correlators and evaluate their relative merits. We have fully accounted for the contamination by weak lensing, which contributes to the variance, but whose contribution to the 4-point correlations is orthogonal to that of FR. We show that a Planck-like experiment can detect scale-invariant PMF of nG strength using the FR diagnostic at 90GHz, while realistic future experiments at the same frequency can detect 10^{-10} G. Utilizing multiple frequencies will improve on these prospects, making FR of CMB a powerful probe of scale-invariant PMF.