Speaker
Description
Precise measurements at small angles of the cosmic microwave background (CMB) angular power spectrum (APS), done by the Planck collaboration, have stimulated accurate analyses of the lensing amplitude parameter $A_L$ to confirm if it satisfies the value expected by the flat $\Lambda$CDM concordance model, i.e. $A_L = 1$.
We discuss a possible excess in the Planck APS not accounted by the $\Lambda$CDM APS. Firstly, we test the hypothesis that the residual APS (i.e., the measured APS minus the $\Lambda$CDM APS) is white noise, or not. Then we quantify how much lensing amplitude is lacking in the Planck analyses of the flat $\Lambda$CDM concordance model (with $A_L = 1$ as a premise). We find that, indeed, there is a residual gravitational lensing signal that is well explained as a lacking lensing amplitude, in the $\Lambda$CDM APS, of around 15%.