Causal sets: discreteness without symmetry breaking

Joe Henson

doi:10.1017/CBO9780511920998.016

16 - Causal sets: discreteness without symmetry breaking

Published online by Cambridge University Press: 05 August 2012

Edited by

Amanda Weltman and

Joe Henson: Affiliation:
Perimeter Institute
Jeff Murugan: Affiliation:
University of Cape Town
Amanda Weltman: Affiliation:
University of Cape Town
George F. R. Ellis: Affiliation:
University of Cape Town

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Summary

Causal sets are a discretisation of spacetime that allow the symmetries of GR to be preserved in the continuum approximation. One proposed application of causal sets is to use them as the histories in a quantum sum-over-histories, i.e. to construct a quantum theory of spacetime. It is expected by many that quantum gravity will introduce some kind of ‘fuzziness’, uncertainty and perhaps discreteness into spacetime, and generic effects of this fuzziness are currently being sought. Applied as a model of discrete spacetime, causal sets can be used to construct simple phenomenological models which allow us to understand some of the consequences of this general expectation.

Introduction: seeing atoms with the naked eye

At present, one of the most important tasks in theoretical physics is to understand the nature of spacetime at the Planck scale. Various indications from our current most successful theories point to this scale: quantum effects are to be expected to invalidate the general theory of relativity here. What should replace our current best understanding of spacetime? This question remains controversial as no theory of quantum gravity can yet be claimed to be complete. For example, some researchers are convinced that the kinematical structure used to replace the continuous manifolds of GR should be discrete, but others do not adhere to this requirement. George Ellis' great contribution to our understanding of spacetime, and his interest in the issue of spacetime discreteness, make this a very appropriate topic for these proceedings.

Type: Chapter
Information: Foundations of Space and Time
Reflections on Quantum Gravity
, pp. 385 - 409

DOI: https://doi.org/10.1017/CBO9780511920998.016 [Opens in a new window]

Publisher: Cambridge University Press

Print publication year: 2012

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16 - Causal sets: discreteness without symmetry breaking

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