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Title: Quantum propagation in Smolin’s weak coupling limit of 4D Euclidean gravity
Authors: Varadarajan, Madhavan
Keywords: General Relativity and Quantum Cosmology
High Energy Physics - Theory
Issue Date: 15-Sep-2019
Publisher: American Physical Society
Citation: Physical Review D, 2019, Vol.100, p066018
Abstract: Two desirable properties of a quantum dynamics for loop quantum gravity (LQG) are that its generators provide an anomalyfree representation of the classical constraint algebra and that physical states which lie in the kernel of these generators encode propagation. A physical state in LQG is expected to be a sum over graphical S U (2 ) spin network states. By propagation we mean that a quantum perturbation at one vertex of a spin network state propagates to vertices which are "many links away" thus yielding a new spin network state which is related to the old one by this propagation. A physical state encodes propagation if its spin network summands are related by propagation. Here we study propagation in an LQG quantization of Smolin's weak coupling limit of Euclidean gravity based on graphical U (1 )3 "charge" network states. Building on our earlier work on anomalyfree quantum constraint actions for this system, we analyse the extent to which physical states encode propagation. In particular, we show that a slight modification of the constraint actions constructed in our previous work leads to physical states which encode robust propagation. Under appropriate conditions, this propagation merges, separates and entangles vertices of charge network states. The "electric" diffeomorphism constraints introduced in previous work play a key role in our considerations. The main import of our work is that there are choices of quantum constraint constructions through LQG methods which are consistent with vigorous propagation thus providing a counterpoint to Smolin's early observations on the difficulties of propagation in the context of LQG type operator constructions. Whether the choices considered in this work are physically appropriate is an open question worthy of further study.
Description: Open Access
ISSN: 2470-0010
2470-0029 (online)
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Copyright: 2019 American Physical Society
Appears in Collections:Research Papers (TP)

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