Signature change of the metric in CDT quantum gravity?

• Published in: The journal of high energy physics Vol. 2015; no. 8; pp. 1 - 17
• Main Authors: Ambjørn, J., Coumbe, D. N., Gizbert-Studnicki, J., Jurkiewicz, J.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.08.2015; Springer Nature B.V
• Subjects: Bifurcations; Classical and Quantum Gravitation; Constants; Coupling; Elementary Particles; High energy physics; Order parameters; Phase diagrams; Phases; Physics; Physics and Astronomy; Quantum Field Theories; Quantum Field Theory; Quantum gravity; Quantum Physics; Regular Article - Theoretical Physics; Relativity Theory; String Theory; Wicks; Lattice Models of Gravity; Models of Quantum Gravity
• ISSN: 1029-8479; 1029-8479
• DOI: 10.1007/JHEP08(2015)033

A bstract We study the effective transfer matrix within the semiclassical and bifurcation phases of CDT quantum gravity. We find that for sufficiently large lattice volumes the kinetic term of the effective transfer matrix has a different sign in each of the two phases. We argue that this sign change can be viewed as a Wick rotation of the metric. We discuss the likely microscopic mechanism responsible for the bifurcation phase transition, and propose an order parameter that can potentially be used to determine the precise location and order of the transition. Using the effective transfer matrix we approximately locate the position of the bifurcation transition in some region of coupling constant space, allowing us to present an updated version of the CDT phase diagram.