Polarization bispectrum for measuring primordial magnetic fields

Understand

We examine the potential of polarization bispectra of the cosmic microwave background (CMB) to constrain primordial magnetic fields (PMFs).

• We compute all possible bispectra between temperature and polarization anisotropies sourced by PMFs and show that they are weakly correlated with well-known local-type and secondary ISW-lensing bispectra.
• From a Fisher analysis it is found that, owing to E-mode bispectra, in a cosmic-variance-limited experiment the expected uncertainty in the amplitude of magnetized bispectra is 80% improved in comparison with an analysis in terms of temperature auto-bispectrum alone.
• In the $\mathit{Planck}$ or the proposed PRISM experiment cases, we will be able to measure PMFs with strength 2.6 or 2.2 nG.