B-mode Power Spectrum of CMB via Polarized Compton Scattering

TL;DR

This paper investigates how polarized Compton scattering, influenced by electron asymmetry, can generate and amplify B-mode polarization in the CMB, potentially affecting measurements of primordial gravitational waves.

Contribution

It introduces the calculation of B-mode power spectrum generated by polarized Compton scattering due to electron asymmetry, highlighting its significance in future CMB polarization observations.

Findings

Amplification of B-mode spectrum at large scales for ^{-6}  ^{-5} in 

Polarized Compton scattering can suppress the tensor-to-scalar ratio r

Contamination from this effect can be comparable to primordial signals

Abstract

In this work, according to some evidence from being an asymmetry in the number density of left and right-handed electrons, $\delta_L$, in-universe motivate us to calculate the dominated contribution of this asymmetry in the generation of B-mode power spectrum $C_{ B\,l}^{(S)}$. Note, in the standard cosmological scenario, Compton scattering in the presence of scalar matter perturbation can not generate magnetic like pattern in linear polarization while in the case of polarized Compton scattering, we have shown $C_{B\,l}^{(S)}\propto \delta_L^2$. We add up the spectrum of the B-mode generated by the polarized Compton scattering to the spectra produced by weak lensing effects and Compton scattering in the presence of tensor perturbations. The results show a significant amplification in $C_{B\,l}$ in large scale $l<500$ for $\delta_L>10^{-6}$ which will be observable in future high resolution B-mode polarization detection. Finally, we have shown that $C_{ B\,l}^{(S)}$ generated by polarized Compton scattering can suppress the tensor to scalar ratio, $r$ parameter so that this contamination can be comparable to a primordial tensor-to-scalar ratio spatially for $\delta_L>10^{-5}$.