1304.7277 (Maresuke Shiraishi et al.)

First observational constraints on tensor non-Gaussianity sourced by
primordial magnetic fields from cosmic microwave background    [PDF]

Maresuke Shiraishi, Toyokazu Sekiguchi

Primordial magnetic fields (PMFs) create a large squeezed-type non-Gaussianity in tensor perturbation, which generates non-Gaussian temperature fluctuations in the cosmic microwave background (CMB). We for the first time derive an observational constraint on such tensor non-Gaussianity from observed CMB maps. Analyzing temperature maps of the WMAP 7-year data, we find such tensor non-Gaussianity is consistent with zero. This gives an upper bound on PMF strength smoothed on $1 ~ {\rm Mpc}$ as $B_{1 ~ \rm Mpc} < 3.2 {\rm nG}$ at 95% CL. We discuss some difficulties in constraining tensor non-Gaussianity due to spin and angle dependence of resultant CMB bispectrum.

View original: http://arxiv.org/abs/1304.7277