Loop quantum gravity as an effective theory

TL;DR

This paper discusses how loop quantum gravity can be formulated as an effective theory, enabling meaningful phenomenology and addressing traditional quantum gravity problems through effective equations and corrections.

Contribution

It demonstrates that despite ambiguities, effective actions in loop quantum gravity allow for testable predictions and resolve key issues like anomaly and the problem of time.

Findings

Signature change at high density due to holonomy corrections

Falsifiability enabled by inverse-triad corrections

Effective equations provide consistent physical evaluations

Abstract

As a canonical and generally covariant gauge theory, loop quantum gravity requires special techniques to derive effective actions or equations. If the proper constructions are taken into account, the theory, in spite of considerable ambiguities at the dynamical level, allows for a meaningful phenomenology to be developed, by which it becomes falsifiable. The tradiational problems plaguing canonical quantum-gravity theories, such as the anomaly issue or the problem of time, can be overcome or are irrelevant at the effective level, resulting in consistent means of physical evaluations. This contribution presents aspects of canonical equations and related notions of (deformed) space-time structures and discusses implications in loop quantum gravity, such as signature change at high density from holonomy corrections, and falsifiability thanks to inverse-triad corrections.