General Covariance and Background Independence in Quantum Gravity

TL;DR

This paper discusses the importance of general covariance and background independence in formulating quantum gravity, proposing definitions and examining their presence in string theory and loop quantum gravity.

Contribution

It offers a clear definition of general covariance and background independence and analyzes their implementation in leading quantum gravity approaches.

Findings

String theory partially aligns with these principles.

Loop quantum gravity and spin foams adhere closely to these principles.

The principles guide the development of consistent quantum gravity theories.

Abstract

The history of general relativity suggests that in absence of experimental data, constructing a theory on philosophical first principles can lead to a very useful theory as well as to ground-breaking insights about physical reality. The two related concepts of general covariance and background independence are some of these principles and play a central role in general relativity. A definition for them will be proposed and discussed. Constructing a theory of quantum gravity -- the sought-after unification of general relativity and quantum mechanics -- could profit from the same approach. Two popular research areas of quantum gravity, string theory and loop quantum gravity together with spin foams, are being examined whether they comply with these principles.