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General Relativity and Quantum Cosmology, gr-qc,High Energy Physics - Theory, hep-th
Abstract:
The condensate cosmology programme of group field theory quantum gravity has
produced several interesting results. The key idea is in the suggestion that a
macroscopic homogeneous spacetime can be approximated by a dynamical condensate
phase of the underlying microscopic system of an arbitrarily large number of
candidate quanta of geometry. In this work, we extend the standard treatments
in two ways: by using a class of thermal condensates, the coherent thermal
states, which encode statistical fluctuations in quantum geometry; and, by
introducing a suitable class of smearing functions as non-singular,
well-behaved generalisations for relational clock frames in group field theory.
In particular, we investigate an effective relational cosmological dynamics for
homogeneous and isotropic spacetimes, extracted from a class of free group
field theory models, and subsequently investigate aspects of its late and early
times evolution. We find the correct classical limit of Friedmann equations at
late times, with a bounce and accelerated inflationary expansion at early
times. Specifically, we find additional correction terms in the evolution
equations corresponding to the statistical contribution of the new thermal
condensates in general; and, a higher upper bound on the number of e-folds,
even without including any interactions.
