Nonperturbative quantum gravity unlocked through computation

TL;DR

This paper discusses how lattice quantum gravity, especially causal dynamical triangulations, enables nonperturbative computations of quantum spacetime, providing new insights into quantum gravity and early universe physics.

Contribution

It introduces the use of Lorentzian lattice quantum gravity with causal dynamical triangulations as a successful approach to nonperturbative quantum gravity.

Findings

Lattice quantum gravity produces new physical results from numerical experiments.

Incorporating Lorentzian structure into lattices is crucial for success.

Computational methods are reshaping understanding of quantum spacetime.

Abstract

Being able to perform explicit computations in a nonperturbative, Planckian regime is key to understanding quantum gravity as a fundamental theory of gravity and spacetime. Rather than a variety of different approaches to quantum gravity, what we primarily need is a gravitational analogue of the highly successful lattice treatment of nonperturbative quantum chromodynamics. Unsurprisingly, however, lattice quantum gravity is not simple. The crucial insight that has finally led to success is to build the dynamical and Lorentzian nature of spacetime into the lattices from the outset. Lattice quantum gravity based on causal dynamical triangulations (CDT) puts this idea into practice and is producing new and exciting physical results from numerical experiments. This largely nontechnical account describes the challenges and achievements of modern lattice quantum gravity, which has opened an unprecedented computational window on quantum spacetime in a Planckian regime and is reshaping our understanding of what it means to "solve" quantum gravity. This methodology is well placed to unlock the physics of the early universe from first principles. Related topics discussed are the difference between lattice and discrete quantum gravity, and the role of spacetime emergence in the light of computational results.