Lessons for loop quantum gravity from emergent modified gravity

TL;DR

This paper evaluates emergent modified gravity as a framework to interpret loop quantum gravity effects, clarifying ambiguities, ruling out some models, and unifying different modifications for a consistent space-time description.

Contribution

It introduces emergent modified gravity as a new approach to analyze loop quantum gravity, reducing ambiguities and unifying various modifications within a consistent geometric framework.

Findings

Restricts ambiguities in previous models

Rules out specific candidate modifications

Provides a unified treatment of holonomy modifications

Abstract

Most of the potential physical effects of loop quantum gravity have been derived in effective models that modify the constraints of canonical general relativity in specific forms. Emergent modified gravity evaluates important conditions that ensure the existence of a compatible geometrical space-time interpretation of canonical solutions, as well as phase-space covariance under different choices of canonical variables. This setting, specialized to modifications suggested by loop quantum gravity, is therefore an important contribution to physical evaluations of this approach to quantum gravity. Here, it is shown that emergent modified gravity restricts several ambiguities that existed in previous formulations, rules out several specific candidates, and provides a unified treatment of different types of (holonomy) modifications that had been thought to be physically distinct.