Quantum gravity, as a fundamental theory of space-time, is expected to reveal how the universe may have started, perhaps during or before an inflationary epoch. It may then leave a potentially observable (but probably miniscule) trace in cosmic large-scale structures that seem to match well with predictions of inflation models. A systematic quest to derive such tiny effects using one approach, loop quantum gravity, has, however, led to unexpected obstacles. Such models remain incomplete, and it is not clear whether loop quantum gravity can be consistent as a full theory. But some surprising effects appear to be generic and would drastically alter our understanding of space-time at large density. These new high-curvature phenomena are a consequence of a widening gap between quantum gravity and ordinary quantum-field theory on a background.
La gravité quantique, en tant que théorie fondamentale de l'espace-temps, est supposée fournir des scénarios décrivant le début de l'univers, peut-être pendant ou avant une ère inflationnaire. Elle a alors pu laisser des signatures potentiellement observables (mais probablement minuscules) dans les grandes structures, qui semblent être en bon accord avec les prédictions des modèles d'inflation. Une recherche systématique visant à dériver ces petits effets dans le cadre d'une théorie quantique de la gravitation, la gravitation quantique à boucle, s'est heurtée à des obstacles inattendus. Ces modèles sont incomplets, et il n'est pas évident que la théorie quantique à boucle soit cohérente en tant que théorie complète. Mais des effets surprenants, qui modifieraient radicalement notre conception de l'espace-temps à grande densité, semblent être génériques. Ces nouveaux effets à grande courbure sont la conséquence d'un décalage grandissant entre la gravité quantique et la théorie quantique des champs ordinaires en espace-temps courbe.
Mots-clés : Cosmologie quantique, Espace-temps, Théorie efficace, Anomalies
Martin Bojowald 1
@article{CRPHYS_2015__16_10_1012_0,
author = {Martin Bojowald},
title = {(Loop) quantum gravity and the inflationary scenario},
journal = {Comptes Rendus. Physique},
pages = {1012--1017},
publisher = {Elsevier},
volume = {16},
number = {10},
year = {2015},
doi = {10.1016/j.crhy.2015.08.007},
language = {en},
}
Martin Bojowald. (Loop) quantum gravity and the inflationary scenario. Comptes Rendus. Physique, Cosmic inflation / Inflation cosmique, Volume 16 (2015) no. 10, pp. 1012-1017. doi : 10.1016/j.crhy.2015.08.007. https://comptes-rendus.academie-sciences.fr/physique/articles/10.1016/j.crhy.2015.08.007/
[1] Using cosmology to establish the quantization of gravity, Phys. Rev. D, Volume 89 (2014) | arXiv
[2] Observational effects from quantum cosmology, Ann. Phys., Volume 525, 2012, pp. 323-338 | arXiv
[3] Observational issues in loop quantum cosmology, Class. Quantum Gravity, Volume 31 (2014) | arXiv
[4] General relativity as an effective field theory: the leading quantum corrections, Phys. Rev. D, Volume 50 (1994), pp. 3874-3888 | arXiv
[5] Quantum gravity in everyday life: general relativity as an effective field theory, Living Rev. Relativ., Volume 7 (2004), p. 5 http://www.livingreviews.org/lrr-2004-5 | arXiv
[6] The Dynamics of General Relativity, Wiley, New York, 1962 (reprinted in [32])
[7] Canonical Gravity and Applications: Cosmology, Black Holes, and Quantum Gravity, Cambridge University Press, Cambridge, 2010
[8] Geometrodynamics regained, Ann. Phys. (New York), Volume 96 (1976), pp. 88-135
[9] Groupoid symmetry and constraints in general relativity. 1: kinematics | arXiv
[10] Effective constraint algebras with structure functions | arXiv
[11] Loop space representation of quantum general relativity, Nucl. Phys. B, Volume 331 (1990), pp. 80-152
[12] Quantization of diffeomorphism invariant theories of connections with local degrees of freedom, J. Math. Phys., Volume 36 (1995) no. 11, pp. 6456-6493 | arXiv
[13] Anomaly-free formulation of non-perturbative, four-dimensional lorentzian quantum gravity, Phys. Lett. B, Volume 380 (1996), pp. 257-264 | arXiv
[14] Effective equations of motion for quantum systems, Rev. Math. Phys., Volume 18 (2006), pp. 713-745 | arXiv
[15] Effective constraints for quantum systems, Rev. Math. Phys., Volume 21 (2009), pp. 111-154 | arXiv
[16] Spherically symmetric loop quantum gravity: connections to 2-dimensional models and applications to gravitational collapse, The Pennsylvania State University, 2009 (Ph.D. thesis)
[17] Anomaly-free perturbations with inverse-volume and holonomy corrections in loop quantum cosmology, Class. Quantum Gravity, Volume 31 (2014), p. 125011 | arXiv
[18] Discreteness corrections and higher spatial derivatives in effective canonical quantum gravity, Phys. Rev. D, Volume 90 (2014) | arXiv
[19] Anomaly-free cosmological perturbations in effective canonical quantum gravity | arXiv
[20] Genericity of big bounce in isotropic loop quantum cosmology, Phys. Rev. Lett., Volume 94 (2005) | arXiv
[21] On the Hamiltonian constraint of loop quantum cosmology, Phys. Rev. D, Volume 71 (2005) | arXiv
[22] Quantum nature of the Big Bang: improved dynamics, Phys. Rev. D, Volume 74 (2006) | arXiv
[23] Large scale effective theory for cosmological bounces, Phys. Rev. D, Volume 75 (2007) | arXiv
[24] Quantum cosmology: effective theory, Class. Quantum Gravity, Volume 29 (2012), p. 213001 | arXiv
[25] Deformed general relativity and effective actions from loop quantum gravity, Phys. Rev. D, Volume 86 (2012) | arXiv
[26] Back to the beginning of quantum spacetime, Phys. Today, Volume 66 (2013), p. 35
[27] Signature change in loop quantum cosmology | arXiv
[28] Repertorium der Theorie der Differentialgleichungen, Springer Verlag, 1968
[29] A quantum gravity extension of the inflationary scenario, Phys. Rev. Lett., Volume 109 (2012) | arXiv
[30] Observational constraints on loop quantum cosmology, Phys. Rev. Lett., Volume 107 (2011) | arXiv
[31] Inflationary power spectra with quantum holonomy corrections | arXiv
[32] The dynamics of general relativity, Gen. Relativ. Gravit., Volume 40 (2008), pp. 1997-2027
Cited by Sources:
Comments - Policy