Article
A 2D model of Causal Set Quantum Gravity: The emergence of the continuum
Classical and Quantum Gravity (Impact Factor: 3.56). 07/2007; DOI: 10.1088/02649381/25/10/105025
Source: arXiv

Article: Discovering the Discrete Universe
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ABSTRACT: This paper presents an brief review of some recent work on the causal set approach to quantum gravity. 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 sumoverhistories, 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. Comment: 24 pages, 4 figures. Based on a proceedings article for the "Foundations of Space and Time" conference, Cape Town, August 2009, in honour of George Ellis' 70th birthday.03/2010;  [Show abstract] [Hide abstract]
ABSTRACT: There are several indications (from different approaches) that Spacetime at the Plank Scale could be discrete. One approach to Quantum Gravity that takes this most seriously is the Causal Sets Approach. In this approach spacetime is fundamentally a discrete, random, partially ordered set (where the partial order is the causal relation). In this contribution, we examine how timelike and spacelike distances arise from a causal set (in the case that the causal set is approximated by Minkowski spacetime), and how one can use this to obtain geometrical information (such as lengths of curves) for the general case, where the causal set could be approximated by some curved spacetime. Comment: 8 pages, 2 figures, based on talk by P. Wallden at the NEB XIII conferenceJournal of Physics Conference Series 11/2008;  [Show abstract] [Hide abstract]
ABSTRACT: A 2d model of causal set quantum gravity is constructed using a continuuminspired dynamics. Apart from a restriction to causal set dimension and topology, the model is fully dynamical and includes all relevant 2d conformally flat degrees of freedom. Surprisingly, in the large N limit the partition function is dominated by causal sets that resemble 2d Minkowski spacetime. Thus, in this model the "entropy problem" of causal set theory is overcome and a sensible low energy limit is obtained.Journal of Physics Conference Series 06/2009; 174(1):2049.
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