Cosmological perturbations from full quantum gravity

Gielen, Steffen; Oriti, Daniele

Abstract

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.

Citation

Gielen, S., & Oriti, D. (2018). Cosmological perturbations from full quantum gravity. Physical Review D, 98(10), Article 106019. https://doi.org/10.1103/physrevd.98.106019

• 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
• DOI: https://doi.org/10.1103/physrevd.98.106019
• Keywords: Physics and Astronomy (miscellaneous)
• Public URL: https://nottingham-repository.worktribe.com/output/1314021
• Publisher URL: https://journals.aps.org/prd/abstract/10.1103/PhysRevD.98.106019
• Contract Date: Nov 27, 2018