A criterion for covariance in complex sequential growth models
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.
 Publication:

Classical and Quantum Gravity
 Pub Date:
 October 2020
 DOI:
 10.1088/13616382/ab987f
 arXiv:
 arXiv:2003.11311
 Bibcode:
 2020CQGra..37s5030S
 Keywords:

 quantum gravity;
 discrete spacetime;
 measure theory;
 covariant observables;
 Mathematical Physics;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Theory;
 Quantum Physics
 EPrint:
 Latex 25 pages, 1 figure