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Perturbing a quantum gravity condensate

Gielen, Steffen


Steffen Gielen


In a recent proposal using the group field theory approach, a spatially homogeneous (generally anisotropic) universe is described as a quantum gravity condensate of
“atoms of space”, which allows the derivation of an effective cosmological Friedmann equation from the microscopic quantum gravity dynamics. Here we take a first step towards the study of cosmological perturbations over the homogeneous background. We consider a state in which a single “atom” is added to an otherwise homogeneous condensate. Backreaction of the perturbation on the background is negligible and the background dynamics can be solved separately. The dynamics for the perturbation takes the form of a quantum cosmology Hamiltonian for a “wave function”, depending on background and perturbations, of the product form usually assumed in a Born-Oppenheimer approximation. We show that the perturbation we consider corresponds to a spatially homogeneous metric perturbation, and for this case derive the usual procedures in quantum cosmology from fundamental quantum gravity.


Gielen, S. (2015). Perturbing a quantum gravity condensate. Physical Review D - Particles, Fields, Gravitation and Cosmology, 91(4), Article 043526.

Journal Article Type Article
Acceptance Date Jan 8, 2015
Online Publication Date Feb 20, 2015
Publication Date Feb 15, 2015
Deposit Date Oct 23, 2018
Publicly Available Date Oct 23, 2018
Journal Physical Review D
Print ISSN 1550-7998
Electronic ISSN 1550-2368
Publisher American Physical Society
Peer Reviewed Peer Reviewed
Volume 91
Issue 4
Article Number 043526
Public URL
Publisher URL


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