Loop quantum cosmology of Bianchi type I models

Abhay Ashtekar and Edward Wilson-Ewing
Phys. Rev. D 79, 083535 – Published 29 April 2009

Abstract

The “improved dynamics” of loop quantum cosmology is extended to include anisotropies of the Bianchi type I model. As in the isotropic case, a massless scalar field serves as a relational time parameter. However, the extension is nontrivial because one has to face several conceptual subtleties as well as technical difficulties. These include a better understanding of the relation between loop quantum gravity and loop quantum cosmology, handling novel features associated with the nonlocal field strength operator in presence of anisotropies, and finding dynamical variables that make the action of the Hamiltonian constraint manageable. Our analysis provides a conceptually complete description that overcomes limitations of earlier works. We again find that the big-bang singularity is resolved by quantum geometry effects but, because of the presence of Weyl curvature, Planck scale physics is now much richer than in the isotropic case. Since the Bianchi I models play a key role in the Belinskii, Khalatnikov, Lifshitz conjecture on the nature of generic spacelike singularities in general relativity, the quantum dynamics of Bianchi I cosmologies is likely to provide considerable intuition about the fate of generic spacelike singularities in quantum gravity. Finally, we show that the quantum dynamics of Bianchi I cosmologies projects down exactly to that of the Friedmann model. This opens a new avenue to relate more complicated models to simpler ones, thereby providing a new tool to relate the quantum dynamics of loop quantum gravity to that of loop quantum cosmology.

  • Figure
  • Received 20 March 2009

DOI:https://doi.org/10.1103/PhysRevD.79.083535

©2009 American Physical Society

Authors & Affiliations

Abhay Ashtekar* and Edward Wilson-Ewing

  • Institute for Gravitation and the Cosmos, and Physics Department, The Pennsylvania State University, University Park, Pennsylvania 16802, USA

  • *ashtekar@gravity.psu.edu
  • wilsonewing@gravity.psu.edu

See Also

Loop quantum cosmology of Bianchi type II models

Abhay Ashtekar and Edward Wilson-Ewing
Phys. Rev. D 80, 123532 (2009)

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Vol. 79, Iss. 8 — 15 April 2009

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