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Emergent Friedmann dynamics with a quantum bounce from quantum gravity condensates

MPS-Authors
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Oriti,  Daniele
Microscopic Quantum Structure & Dynamics of Spacetime, AEI-Golm, MPI for Gravitational Physics, Max Planck Society;

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Sindoni,  Lorenzo
Microscopic Quantum Structure & Dynamics of Spacetime, AEI-Golm, MPI for Gravitational Physics, Max Planck Society;

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Wilson-Ewing,  Edward
Quantum Gravity & Unified Theories, AEI-Golm, MPI for Gravitational Physics, Max Planck Society;

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1602.05881.pdf
(Preprint), 504KB

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Citation

Oriti, D., Sindoni, L., & Wilson-Ewing, E. (2016). Emergent Friedmann dynamics with a quantum bounce from quantum gravity condensates. Classical and Quantum Gravity, 33(22): 224001. doi:10.1088/0264-9381/33/22/224001.


Cite as: http://hdl.handle.net/11858/00-001M-0000-002A-181D-B
Abstract
We study the effective cosmological dynamics, emerging as the hydrodynamics of simple condensate states, of a group field theory model for quantum gravity coupled to a massless scalar field and reduced to its isotropic sector. The quantum equations of motion for these group field theory condensate states are given in relational terms with respect to the scalar field, from which effective dynamics for spatially flat, homogeneous and isotropic space-times can be extracted. The result is a generalization of the Friedmann equations, including quantum gravity modifications, in a specific regime of the theory. The classical Friedmann equations of general relativity are recovered in a suitable semi-classical limit for some range of parameters of the microscopic dynamics. An important result is that the quantum geometries associated with these GFT condensate states are non-singular: a bounce generically occurs in the Planck regime. For some choices of condensate states, these modified Friedmann equations are very similar to those of loop quantum cosmology.