Steffen Gielen
Group field theory and its cosmology in a matter reference frame
Gielen, Steffen
Authors
Abstract
While the equations of general relativity take the same form in any coordinate system, choosing a suitable set of coordinates is essential in any practical application. This poses a challenge in background-independent quantum gravity, where coordinates are not a priori available and need to be reconstructed from physical degrees of freedom. We review the general idea of coupling free scalar fields to gravity and using these scalars as a “matter reference frame”. The resulting coordinate system is harmonic, i.e., it satisfies the harmonic (de Donder) gauge. We then show how to introduce such matter reference frames in the group field theory approach to quantum gravity, where spacetime is emergent from a “condensate” of fundamental quantum degrees of freedom of geometry, and how to use matter coordinates to extract physics. We review recent results in homogeneous and inhomogeneous cosmology, and give a new application to the case of spherical symmetry. We find tentative evidence that spherically-symmetric group field theory condensates defined in this setting can reproduce the near-horizon geometry of a Schwarzschild black hole.
Citation
Gielen, S. (2018). Group field theory and its cosmology in a matter reference frame. Universe, 4(10), 103. https://doi.org/10.3390/universe4100103
Journal Article Type | Article |
---|---|
Acceptance Date | Sep 30, 2018 |
Online Publication Date | Oct 2, 2018 |
Publication Date | Oct 2, 2018 |
Deposit Date | Oct 4, 2018 |
Publicly Available Date | Mar 29, 2024 |
Journal | Universe |
Print ISSN | 2218-1997 |
Publisher | MDPI |
Peer Reviewed | Peer Reviewed |
Volume | 4 |
Issue | 10 |
Pages | 103 |
DOI | https://doi.org/10.3390/universe4100103 |
Keywords | quantum gravity; group field theory; harmonic coordinates; spherical symmetry |
Public URL | https://nottingham-repository.worktribe.com/output/1146454 |
Publisher URL | https://www.mdpi.com/2218-1997/4/10/103 |
Files
universe-04-00103
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Publisher Licence URL
https://creativecommons.org/licenses/by/4.0/
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