Massless graviton in a model of quantum gravity with emergent spacetime

TL;DR

This paper demonstrates that in a quantum gravity model with emergent spacetime, a massless graviton naturally arises when the Hilbert space is partitioned into largely unentangled local clocks, linking quantum matter to gravitational phenomena.

Contribution

It shows the emergence of a massless graviton in a quantum gravity model based on specific Hilbert space decompositions supporting local clocks.

Findings

Massless graviton appears in the emergent spacetime.

Emergence depends on Hilbert space partitioning.

Local clocks facilitate graviton emergence.

Abstract

In the model of quantum gravity proposed in JHEP 2020, 70 (2020), dynamical spacetime arises as a collective phenomenon of underlying quantum matter. Without a preferred decomposition of the Hilbert space, the signature, topology and geometry of an emergent spacetime depend upon how the total Hilbert space is partitioned into local Hilbert spaces. In this paper, it is shown that the massless graviton emerges in the spacetime realized from a Hilbert space decomposition that supports a collection of largely unentangled local clocks.