CMB bispectrum of scalar, vector and tensor modes sourced from primordial magnetic fields
Shiraishi, Maresuke (Nagoya University)

If the seed magnetic fields exist in the early Universe, their anisotropic stresses generate additional fluctuations of the cosmic microwave background (CMB) radiation. Because these fluctuations deviate largely from the Gaussian statistics due to the quadratic dependence on the strength of the Gaussian magnetic field, not only the power spectrum but also the higher-order correlations have reasonable signals. With these motives, we calculate the CMB bispectrum of scalar, vector and tensor modes induced from the seed magnetic fields. By comparing these results with the current observational constraint on the primordial non-Gaussianity, we find that the upper bound on the PMF strength is 2.6nG when the magnetic spectrum has nearly scale-invariant shape. This value is tighter than the current bounds obtained by the CMB power spectra. In this talk, I present our calculation and results.