Journal
CLASSICAL AND QUANTUM GRAVITY
Volume 38, Issue 19, Pages -Publisher
IOP Publishing Ltd
DOI: 10.1088/1361-6382/ac1b44
Keywords
effective; spin; foam; models; Lorentzian; quantum; gravity
Categories
Funding
- Government of Canada through the Department of Innovation, Science and Economic Development Canada
- Province of Ontario through the Ministry of Colleges and Universities
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In this work, effective spin foam models are used to define the Lorentzian path integral, allowing for computation over discrete Lorentzian quantum geometric configurations. These models are computationally efficient and enable initial tests for determining the semi-classical regime.
Making the Lorentzian path integral for quantum gravity well-defined and computable has been a long standing challenge. In this work we adopt the recently proposed effective spin foam models to the Lorentzian case. This defines a path integral over discrete Lorentzian quantum geometric configurations, which include metric and torsion degrees of freedom. The torsion degrees of freedom arise due to an anomaly, which is parameterized by the Barbero-Immirzi parameter. Requiring a semi-classical regime constrains this parameter, but the precise bound has to be determined by probing the dynamics. The effective models provide the computationally most efficient spin foam models yet, which allows us to perform first tests for determining the semi-classical regime. This includes explorations specific to the Lorentzian case, e.g. investigating quantum geometries with null lengths and null areas as well as geometries that describe a change of spatial topology.
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