Cosmological perturbation theory and quantum gravity

TL;DR

This paper demonstrates how cosmological perturbation theory naturally emerges from a fully quantized quantum gravity framework using gauge-invariant local observables, recovering known linear results and providing new second order expressions.

Contribution

It introduces a non-perturbative approach to gauge-invariant observables that generate perturbative invariants in quantum gravity, connecting to cosmological perturbation theory.

Findings

Recovery of linear gauge-invariant observables from quantum gravity.

Explicit second order gauge-invariant expressions provided.

Framework unifies quantum gravity with cosmological perturbation analysis.

Abstract

It is shown how cosmological perturbation theory arises from a fully quantized perturbative theory of quantum gravity. Central for the derivation is a non-perturbative concept of gauge-invariant local observables by means of which perturbative invariant expressions of arbitrary order are generated. In particular, in the linearised theory, first order gauge-invariant observables familiar from cosmological perturbation theory are recovered. Explicit expressions of second order quantities are presented as well.