CMB anisotropies caused by gravitational waves: A parameter study

TL;DR

This paper investigates how primordial gravitational waves influence cosmic microwave background anisotropies across various dark matter models, considering inflationary origins and anisotropic stresses, to understand their dependence on cosmological parameters.

Contribution

It provides a comprehensive parameter study of CMB anisotropies caused by gravitational waves in different dark matter and cosmological constant scenarios, including effects of anisotropic stresses.

Findings

Dependence of CMB anisotropy spectrum on dark matter composition.

Impact of cosmological constant on gravitational wave signatures.

Role of anisotropic stresses from massless particles.

Abstract

Anisotropies in the cosmic microwave background radiation due to gravity waves are investigated. An initial spectrum of gravity waves may have been induced during an epoch of inflation. We study the propagation of such a spectrum in a Friedmann background of hot and cold dark matter, radiation and (possibly) a cosmological constant. We finally calculate its imprint as anisotropies on the cosmic microwave background. We also take into account that massless particles can source gravity waves by their anisotropic stresses. We consider general mixed dark matter models with and without cosmological constant. For a given, scale invariant input spectrum of gravity we determine the dependence of the resulting spectrum of CMB anisotropies on the different model parameters.