Angular Power Spectrum of B-mode Polarization from Cosmic String Wakes

TL;DR

This paper calculates the angular power spectrum of B-mode polarization caused by cosmic string wakes, finding the signal too weak for current surveys but suggesting position space map analysis as a better detection method.

Contribution

It extends previous work by computing the power spectrum for a distribution of string wakes and discusses the detectability challenges and alternative analysis techniques.

Findings

Signal amplitude too small for first-generation surveys

Spectral shape similar to gravitational lensing

Position space map analysis may better constrain cosmic strings

Abstract

Cosmic string wakes produce direct B-mode polarization at leading order in cosmological perturbation theory, as worked out in a previous publication \cite{BDH} in the case of a single string wake. Here we compute the angular power spectrum of B-mode polarization from a scaling distribution of string wakes. We find that the averaging which enters in computing the power spectrum renders the signal, which is distinctive in position space maps, too small in amplitude to be detectable with the first generation B-mode surveys. In addition, the spectral shape is similar to that of gravitational lensing, making it additionally difficult to detect the cosmic string signal from the angular power spectrum. Hence, a more promising way to constrain cosmic strings using B-mode polarization is by analyzing position space maps using novel algorithms such as the Canny algorithm.