Can infrared gravitons screen $\Lambda$?

TL;DR

This paper investigates whether infrared gravitons in de Sitter space can cause a secular decrease in the effective cosmological constant, concluding that gauge-invariant measures do not support such screening.

Contribution

The authors demonstrate that previous indications of screening are gauge-dependent and show, using a gauge-invariant operator, that there is no secular screening of the curvature scalar.

Findings

Gauge-dependent tadpole corrections are not gauge invariant.

A gauge-invariant operator measuring the curvature scalar shows no secular screening.

No evidence of effective cosmological constant decay from infrared gravitons.

Abstract

It has been suggested that infrared gravitons in de Sitter space may lead to a secular screening of the effective cosmological constant. This seems to clash with the naive expectation that the curvature scalar should stay constant due to the Heisenberg equation of motion. Here, we show that the tadpole correction to the local expansion rate, which has been used in earlier analyses as an indicator of a decaying effective $\Lambda$, is not gauge invariant. On the other hand, we construct a gauge invariant operator which measures the renormalized curvature scalar smeared over an arbitrary window function, and we find that there is no secular screening of this quantity (to any given order in perturbation theory).