Effective Lagrangian in de Sitter Spacetime

TL;DR

This paper constructs an effective Lagrangian in de Sitter spacetime that captures the impact of super-horizon metric fluctuations, revealing local infrared quantum effects that make fundamental couplings time-dependent while maintaining gauge invariance.

Contribution

It introduces a Lorenz-invariant effective Lagrangian in de Sitter space that accounts for quantum fluctuations and fixes gauge ambiguities to produce unique physical predictions.

Findings

Infrared quantum effects are local and induce time dependence in couplings.

Imposing Lorenz invariance fixes quantization ambiguities and yields unique predictions.

Gauge parameter dependence cancels out, ensuring gauge-invariant evolution of couplings.

Abstract

Scale invariant fluctuations of metric are universal feature of quantum gravity in de Sitter spacetime. We construct an effective Lagrangian which summarizes their implications on local physics by integrating super-horizon metric fluctuations. It shows infrared quantum effects are local and render fundamental couplings time dependent. We impose Lorenz invariance on the effective Lagrangian as it is required by the principle of general covariance. We show that such a requirement leads to unique physical predictions by fixing the quantization ambiguities. We explain how the gauge parameter dependence of observables is canceled. In particular the relative evolution speed of the couplings are shown to be gauge invariant.