Analytic Spectra of CMB Anisotropies and Polarization Generated by Relic Gravitational Waves with Modification due to Neutrino Free-Streaming

Understand

We present an analytical calculation of the spectra of CMB anisotropies and polarizations generated by relic gravitational waves (RGWs).

• As a substantial extension to the previous studies, three new ingredients are included in this work.
• Firstly, the analytic $C_l^{TT}$ and $C_l^{TE}$ are given; especially the latter can be useful to extract signal of RGWs from the observed data in the zero multipole method.
• Secondly, a fitting formula of the decaying factor on small scales is given, coming from the visibility function around the photon decoupling.