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Cosmological perturbations from full quantum gravity

Gielen, Steffen; Oriti, Daniele

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Steffen Gielen

Daniele Oriti


The early universe provides an opportunity for quantum gravity to connect to observation by explaining the large-scale structure of the Universe. In the group field theory (GFT) approach, a macroscopic universe is described as a GFT condensate; this idea has already been shown to reproduce a semiclassical large universe under generic conditions, and to replace the cosmological singularity by a quantum bounce. Here we extend the GFT formalism by introducing additional scalar degrees of freedom that can be used as a physical reference frame for space and time. This allows, for the first time, the extraction of correlation functions of inhomogeneities in GFT condensates: in a way conceptually similar to inflation, but within a quantum field theory of both geometry and matter, quantum fluctuations of a homogeneous background geometry become the seeds of cosmological inhomogeneities. We find approximately scale-invariant initial quantum fluctuations in the local volume, with naturally small amplitude; this behaviour extends to other quantities such as the matter density. These results confirm the potential of GFT condensate cosmology to provide a purely quantum gravitational foundation for the understanding of the early universe.


Gielen, S., & Oriti, D. (2018). Cosmological perturbations from full quantum gravity. Physical Review D, 98(10), Article 106019.

Journal Article Type Article
Acceptance Date Nov 6, 2018
Online Publication Date Nov 26, 2018
Publication Date Nov 26, 2018
Deposit Date Nov 27, 2018
Publicly Available Date Jan 31, 2019
Journal Physical Review D
Print ISSN 2470-0010
Electronic ISSN 2470-0029
Publisher American Physical Society
Peer Reviewed Peer Reviewed
Volume 98
Issue 10
Article Number 106019
Keywords Physics and Astronomy (miscellaneous)
Public URL
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