CMB lensing forecasts for constraining the primordial perturbations: adding to the CMB temperature and polarization information

Understand

We forecast how current ({\planck}) and future ({\prism}) cosmic microwave background (CMB) experiments constrain the adiabatic mode and its admixtures with primordial isocurvature modes, using measurements of the reconstructed CMB lensing potential and lensing-induced CMB B-mode polarization anisotropies in combination with the CMB temperature and E-mode polarization anisotropies.

• We first study the characteristic features of the CMB temperature, polarization and lensing spectra for adiabatic and isocurvature modes.
• We then consider how lensing-induced B-mode polarization and lensing potential information can improve constraints on an admixture of adiabatic and three correlated isocurvature modes.
• We find that the CMB lensing spectrum improves constraints on isocurvature modes by at most 10% for the {\planck} and {\prism} experiments, with the limited improvement a result of the low amplitude of isocurvature lensing spectra and cancellations between these spectra rendering them only slightly detectable.