Phenomenological Quantum Gravity

TL;DR

This paper reviews phenomenological approaches to quantum gravity, exploring their connections to observational anomalies, high-energy cosmic rays, varying constants, and cosmological puzzles, highlighting open problems and recent models.

Contribution

It provides a pedagogic overview of phenomenological quantum gravity topics, including non-linear relativity, varying constant models, and their links to observational data and unresolved issues.

Findings

Non-linear relativity relates to loop quantum gravity and cosmic rays.

Varying constant models connect to high-redshift data and cosmological puzzles.

Open problems and exercises are presented for further research.

Abstract

These notes summarize a set of lectures on phenomenological quantum gravity which one of us delivered and the other attended with great diligence. They cover an assortment of topics on the border between theoretical quantum gravity and observational anomalies. Specifically, we review non-linear relativity in its relation to loop quantum gravity and high energy cosmic rays. Although we follow a pedagogic approach we include an open section on unsolved problems, presented as exercises for the student. We also review varying constant models: the Brans-Dicke theory, the Bekenstein varying $\alpha$ model, and several more radical ideas. We show how they make contact with strange high-redshift data, and perhaps other cosmological puzzles. We conclude with a few remaining observational puzzles which have failed to make contact with quantum gravity, but who knows... We would like to thank Mario Novello for organizing an excellent school in Mangaratiba, in direct competition with a very fine beach indeed.