Cosmological Alfv\'en waves in the recent CMB data, and the observational bound on the primordial vector perturbation

TL;DR

This paper investigates the effects of primordial magnetic fields on cosmic microwave background anisotropies, providing observational bounds on primordial vector perturbations through analysis of WMAP data, and finds evidence for cosmological Alfvén waves at 3 sigma confidence.

Contribution

It presents the first observational constraint on primordial vector perturbations induced by cosmological Alfvén waves using recent CMB data.

Findings

3 sigma evidence for cosmological Alfvén waves

Lower bound on primordial vector perturbation amplitude: 4*10^-12

Imposed constraints based on WMAP data analysis

Abstract

In the presence of the primordial magnetic field, initial vector (vorticity) perturbations produce cosmological Alfven waves and leave imprints on cosmic microwave background (CMB) temperature and polarization anisotropy. We have investigated imprints of cosmological Alfven 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 3 sigma evidence of cosmological Alfven waves. Using the 3 sigma limit from our analysis and the Alfven velocity limit from the total energy density constraint, we impose a lower bound on the amplitude of primordial vector perturbation: 4*10^-12 at k_0=0.002/Mpc.