A criterion for covariance in complex sequential growth models. (16th September 2020)

• Record Type: Journal Article
• Authors: Surya, Sumati; Zalel, Stav
• Is Part Of: Classical and quantum gravity. Volume 37:Number 19(2020:Oct.)
• Publication Date: 2020-09-16
• Subjects: quantum gravity -- discrete spacetime -- measure theory -- covariant observables; Quantum gravity -- Periodicals; Gravitation -- Periodicals; Relativity (Physics) -- Periodicals; Space and time -- Periodicals; Periodicals; 521.1
• DOI: 10.1088/1361-6382/ab987f
• Languages: English
• ISSNs: 0264-9381

Abstract

Abstract: The classical sequential growth model for causal sets provides a template for the dynamics in the deep quantum regime. This growth dynamics is intrinsically temporal and causal, with each new element being added to the existing causal set without disturbing its past. In the quantum version, the probability measure on the event algebra is replaced by a quantum measure, which is Hilbert space valued. Because of the temporality of the growth process, in this approach, covariant events (or observables) are measurable only if the quantum measure extends to the associated sigma algebra of events. This is not always guaranteed. In this work we find a criterion for extension (and thence covariance) in complex sequential growth models for causal sets. We find a large family of models in which the measure extends, so that all covariant events/observables are measurable.