Quantum Spacetime, from a Practitioner's Point of View

TL;DR

This paper discusses how Causal Dynamical Triangulations provide a nonperturbative, background-independent quantum gravity model that produces an emergent de Sitter universe and reveals quantum properties at Planck scales.

Contribution

It demonstrates that Causal Dynamical Triangulations yield a dynamically derived quantum spacetime with realistic large-scale and quantum-scale features from minimal inputs.

Findings

Emergent de Sitter universe in four dimensions

Quantum properties at Planckian scales

Numerical methods enable study of quantum spacetime

Abstract

We argue that theories of quantum gravity constructed with the help of (Causal) Dynamical Triangulations have given us the most informative, quantitative models to date of quantum spacetime. Most importantly, these are derived dynamically from nonperturbative and background-independent quantum theories of geometry. In the physically relevant case of four spacetime dimensions, the ansatz of Causal Dynamical Triangulations produces - from a fairly minimal set of quantum field-theoretic inputs - an emergent spacetime which macroscopically looks like a de Sitter universe, and on Planckian scales possesses unexpected quantum properties. Important in deriving these results are a regularized version of the theory, in which the quantum dynamics is well defined, can be studied with the help of numerical Monte Carlo methods and extrapolated to infinite lattice volumes.