Reduced bispectrum seeded by helical primordial magnetic fields

Understand

In this paper, we investigate the effects of helical primordial magnetic fields (PMFs) on the cosmic microwave background (CMB) reduced bispectrum.

• We derive the full three-point statistics of helical magnetic fields and numerically calculate the even contribution in the collinear configuration.
• We then numerically compute the CMB reduced bispectrum induced by passive and compensated PMF modes on large angular scales.
• There is a negative signal on the bispectrum due to the helical terms of the fields and we also observe that the biggest contribution to the bispectrum comes from the non-zero IR cut-off for causal fields, unlike the two-point correlation case.