Detecting relic gravitational waves in the CMB: Comparison of different methods

TL;DR

This paper compares different methods for detecting relic gravitational waves in the CMB, showing that considering all power spectra improves signal detection and is less affected by noise or parameter variations.

Contribution

It provides a comparative analysis of detection methods for relic gravitational waves using CMB data, emphasizing the benefits of including all power spectra.

Findings

Considering all power spectra improves signal-to-noise ratio.

Including all spectra reduces impact of increased noise.

Parameter variations have minimal effect on detection sensitivity.

Abstract

In this paper, we discuss the constraint on the relic gravitational waves by both temperature and polarization anisotropies power spectra of cosmic microwave background radiation. Taking into account the instrumental noises of Planck satellite, we calculate the signal-to-noise ratio $S/N$ by the simulation and the analytic approximation methods. We find that, comparing with the $BB$ channel, the value of $S/N$ is much improved in the case where all the power spectra, $TT$, $TE$, $EE$ and $BB$, are considered. If the noise power spectra of Planck satellite increase for some reasons, the value of $S/N$ in $BB$ channel is much reduced. However, in the latter case where all the power spectra of cosmic microwave background radiation are considered, the value of $S/N$ is less influenced. We also find that the free parameters $A_s$, $n_s$ and $n_t$ have little influence on the value of $S/N$ in both cases.