Pseudo-Cartesian coordinates in a model of Causal Dynamical Triangulations

• Published in: Nuclear physics. B Vol. 943; p. 114626
• Main Authors: Ambjørn, J., Drogosz, Z., Gizbert-Studnicki, J., Görlich, A., Jurkiewicz, J.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.06.2019; Elsevier
• ISSN: 0550-3213; 1873-1562
• DOI: 10.1016/j.nuclphysb.2019.114626

Causal Dynamical Triangulations is a non-perturbative quantum gravity model, defined with a lattice cut-off. The model can be viewed as defined with a proper time but with no reference to any three-dimensional spatial background geometry. It has four phases, depending on the parameters (the coupling constants) of the model. The particularly interesting behavior is observed in the so-called de Sitter phase, where the spatial three-volume distribution as a function of proper time has a semi-classical behavior which can be obtained from an effective mini-superspace action. In the case of the three-sphere spatial topology, it has been difficult to extend the effective semi-classical description in terms of proper time and spatial three-volume to include genuine spatial coordinates, partially because of the background independence inherent in the model. However, if the spatial topology is that of a three-torus, it is possible to define a number of new observables that might serve as spatial coordinates as well as new observables related to the winding numbers of the three-dimensional torus. The present paper outlines how to define the observables, and how they can be used in numerical simulations of the model.