Some Inconvenient Truths

TL;DR

This paper critically examines claims that infrared divergences in graviton propagators are gauge artifacts, arguing instead that de Sitter breaking secular growth may be physically observable in quantum gravity effects.

Contribution

It challenges prior assertions by Fröb that infrared divergences are gauge artifacts, providing evidence that de Sitter breaking effects are physically meaningful and observable.

Findings

Infrared divergences are not merely gauge artifacts.

De Sitter breaking secular growth may be observable.

Recent vacuum polarization results support this view.

Abstract

A recent paper by Fr\"ob employs the linearized Weyl-Weyl correlator to construct the tensor power spectrum. Although his purpose was to argue that infrared divergences and secular growth in the graviton propagator are gauge artefacts, a closer examination of the problem leads to the opposite conclusion. The analogies with the BMS symmetries of graviton scattering on a flat background, and with the Aharonov-Bohm effect of quantum mechanics, suggest that de Sitter breaking secular growth is likely to be observable in graviton loop effects. And a recent result for the vacuum polarization does seem to show it.