Volume 123, Number 1, July 2018
|Number of page(s)||6|
|Published online||02 August 2018|
From coarse-graining to holography in loop quantum gravity
Univ Lyon, ENS de Lyon, Univ Claude Bernard, CNRS, LPENSL - 69007 Lyon, France
Received: 2 July 2018
Accepted: 17 July 2018
We discuss the relation between coarse-graining and the holographic principle in the framework of loop quantum gravity and ask the following question: when we coarse-grain arbitrary spin network states of quantum geometry, are we integrating out physical degrees of freedom or gauge degrees of freedom? Since the distinction between physical and gauge degrees of freedom is encoded in the dynamics of the theory, this highlights the crucial role of the dynamics in understanding the coarse-graining. Focusing on how bulk spin network states for bounded regions of space are projected onto boundary states, we show that all possible boundary states can be recovered from bulk spin networks with a single vertex in the bulk and a single internal loop attached to it. This partial reconstruction of the bulk from the boundary leads us to the idea of realizing the Hamiltonian constraints at the quantum level as a gauge equivalence reducing arbitrary spin network states to one-loop bulk states. This proposal of “dynamics through coarse-graining” would lead to a one-to-one map between equivalence classes of physical states under gauge transformations and boundary states, thus defining holographic dynamics for loop quantum gravity.
PACS: 04.60.Pp – Loop quantum gravity, quantum geometry, spin foams / 04.60.Nc – Lattice and discrete methods / 04.60.Ds – Canonical quantization
© EPLA, 2018
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