http://arxiv.org/abs/1712.03288
The lack of power of large–angle CMB anisotropies is known to increase its statistical significance at higher Galactic latitudes, where a string–inspired pre–inflationary scale $\Delta$ can also be detected. Considering the Planck 2015 data, and relying largely on a Bayesian approach, a novelty for CMB anomalies, we show that the effect is mostly driven by the \emph{even}–$\ell$ harmonic multipoles with $\ell \lesssim 20$, which appear sizably suppressed in a way that is robust with respect to Galactic masking, along with the corresponding detections of $\Delta$. On the other hand, the first \emph{odd}–$\ell$ multipoles are only suppressed at high Galactic latitudes. We investigate this behavior in different sky masks, constraining $\Delta$ through even and odd multipoles, and we elaborate on possible implications. We include systematically low–$\ell$ polarization data, which are currently noise limited and yet help in attaining confidence levels of about 3 $\sigma$ in the detection of $\Delta$. We also show by direct forecasts that a future all–sky $E$–mode cosmic–variance–limited polarization survey may push the constraining power for $\Delta$ beyond 5 $\sigma$.
A. Gruppuso, N. Kitazawa, M. Lattanzi, et. al.
Tue, 12 Dec 17
25/78
Comments: 49 pages, 20 figures