Joint constraint on primordial gravitational waves and polarization rotation angle with current CMB polarization data

TL;DR

This paper analyzes current CMB polarization data to jointly constrain primordial gravitational waves and polarization rotation angles, providing tighter limits on tensor-to-scalar ratio and CPT violation signatures.

Contribution

It presents the first comprehensive joint analysis of tensor-to-scalar ratio and polarization rotation angles using multiple CMB datasets, improving constraints on CPT violation effects.

Findings

Isotropic rotation angle $ar{eta} = -0.01^\u00b0 \, extpm \, 0.37^\u00b0$ at 68% CL

Variance of anisotropic rotation angles $C^{eta}(0)<0.0032$ rad$^2$

Upper limit on tensor-to-scalar ratio $r<0.057$ at 95% CL

Abstract

Cosmological CPT violation will rotate the polarized direction of CMB photons, convert partial CMB E mode into B mode and vice versa. It will generate non-zero EB, TB spectra and change the EE, BB, TE spectra. This phenomenon gives us a way to detect the CPT-violation signature from CMB observations, and also provides a new mechanism to produce B mode polarization. In this paper, we perform a global analysis on tensor-to-scalar ratio $r$ and polarization rotation angles based on current CMB datasets with both low $\ell$ (Planck, BICEP2/Keck Array) and high $\ell$ (POLARBEAR, SPTpol, ACTPol). Benefited from the high precision of CMB data, we obtain the isotropic rotation angle $\bar{\alpha} = -0.01^\circ \pm 0.37^\circ $ at 68% C.L., the variance of the anisotropic rotation angles $C^{\alpha}(0)<0.0032\,\mathrm{rad}^2$, the scale invariant power spectrum $D^{\alpha\alpha}_{\ell \in [2, 350]}<4.71\times 10^{-5} \,\mathrm{rad}^2$ and $r<0.057$ at 95% C.L.. Our result shows that with the polarization rotation effect, the 95% upper limit on $r$ gets tightened by 17%.