How Inflationary Gravitons Affect Gravitational Radiation

TL;DR

This paper investigates how quantum effects from inflationary gravitons influence gravitational waves, revealing potential observable corrections in the tensor power spectrum after extensive inflation periods.

Contribution

It provides explicit calculations of one-loop quantum corrections to gravitational wave propagation during inflation, highlighting their significance over long inflationary epochs.

Findings

One-loop corrections are enhanced by the number of inflationary e-foldings.

Perturbation theory breaks down during very long inflation.

Potential observability of quantum corrections in future cosmological measurements.

Abstract

We include the single graviton loop contribution to the linearized Einstein equation. Explicit results are obtained for one loop corrections to the propagation of gravitational radiation. Although suppressed by a minuscule loop-counting parameter, these corrections are enhanced by the square of the number of inflationary e-foldings. One consequence is that perturbation theory breaks down for a very long epoch of primordial inflation. Another consequence is that the one loop correction to the tensor power spectrum might be observable, in the far future, after the full development of 21cm cosmology.