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  • Cited by 7
  • Print publication year: 2012
  • Online publication date: August 2012

13 - Causal dynamical triangulations and the quest for quantum gravity

Summary

Quantum gravity by causal dynamical triangulation has over the last few years emerged as a serious contender for a nonperturbative description of the theory. It is a nonperturbative implementation of the sum-overhistories, which relies on few ingredients and initial assumptions, has few free parameters and – crucially – is amenable to numerical simulations. It is the only approach to have demonstrated that a classical universe can be generated dynamically from Planckian quantum fluctuations. At the same time, it allows for the explicit evaluation of expectation values of invariants characterizing the highly nonclassical, short-distance behaviour of spacetime. As an added bonus, we have learned important lessons on which aspects of spacetime need to be fixed a priori as part of the background structure and which can be expected to emerge dynamically.

Quantum gravity – taking a conservative stance

Many fundamental questions about the nature of space, time and gravitational interactions are not answered by the classical theory of general relativity, but lie in the realm of the still-searched-for theory of quantum gravity: What is the quantum theory underlying general relativity, and what does it say about the quantum origins of space, time and our universe? What is the microstructure of spacetime at the shortest scale usually considered, the Planck scale lPl = 10-35m, and what are the relevant degrees of freedom determining the dynamics there?

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