On finding gravitational waves from anisotropies of the Cosmic Microwave Background

TL;DR

This paper explores how gravitational waves can be detected through anisotropies in the Cosmic Microwave Background caused by the integrated Sachs-Wolfe effect, focusing on the inverse problem of identifying primordial gravitational perturbations.

Contribution

It demonstrates that primordial gravitational perturbations, especially their polarizations in the TT gauge, can be inferred from local observations of the ISW effect, advancing gravitational wave detection methods.

Findings

Primordial gravitational perturbations can be identified from CMB anisotropies.

Polarizations in the TT gauge are key to detecting gravitational waves.

The inverse problem approach links CMB observations to gravitational wave properties.

Abstract

The integrated Sachs-Wolfe (ISW) effect describes how photons are gravitationally redshifted, producing anisotropies in the Cosmic Microwave Background. We study the inverse problem and show that primordial gravitational perturbations, in particular their polarizations in the transversally traceless (TT) gauge can be identified from the local observation of the ISW effect.