Discovering Relic Gravitational Waves in Cosmic Microwave Background Radiation

TL;DR

This paper discusses the theoretical basis and observational prospects for detecting relic gravitational waves in the cosmic microwave background, emphasizing their quantum origin, properties, and the potential for near-future discovery.

Contribution

It provides a detailed justification for the existence of relic gravitational waves, critiques inflationary predictions, and outlines observational strategies focusing on CMB polarization correlations.

Findings

Relic gravitational waves are theoretically justified and expected to be detectable soon.

The temperature-polarization TE correlation function is a promising detection method.

Detection of relic gravitational waves could occur within a few years.

Abstract

The authority of J. A. Wheeler in many areas of gravitational physics is immense, and there is a connection with the study of relic gravitational waves as well. I begin with a brief description of Wheeler's influence on this study. One part of the paper is essentially a detailed justification of the very existence of relic gravitational waves, account of their properties related to the quantum-mechanical origin, derivation of the expected magnitude of their effects, and reasoning why they should be detectable in the relatively near future. This line of argument includes the comparison of relic gravitational waves with density perturbations of quantum-mechanical origin, and the severe criticism of methods and predictions of inflationary theory. Another part of the paper is devoted to active searches for relic gravitational waves in cosmic microwave background radiation (CMB). Here, the emphasis is on the temperature-polarization TE cross-correlation function of CMB. The expected numerical level of the correlation, its sign, statistics, and the most appropriate interval of angular scales are identified. Other correlation functions are also considered. The overall conclusion is such that the observational discovery of relic gravitational waves looks like the matter of a few coming years, rather than a few decades.