New 'phase' of quantum gravity

Abstract

The emergence of loop quantum gravity over the past two decades has stimulated a great resurgence of interest in unifying general relativity and quantum mechanics. Amongst a number of appealing features of this approach are the intuitive picture of quantum geometry using spin networks and powerful mathematical tools from gauge field theory. However, the present form of loop quantum gravity suffers from a quantum ambiguity, due to the presence of a free (Barbero-Immirzi) parameter. Following recent progress on the conformal decomposition of gravitational fields, we present a new phase space for general relativity. In addition to spin-gauge symmetry, the new phase space also incorporates conformal symmetry making the description parameter free. The Barbero-Immirzi ambiguity is shown to occur only if the conformal symmetry is gauge-fixed prior to quantization. By withholding its full symmetries, the new phase space offers a promising platform for the future development of loop quantum gravity. This paper aims to provide an exposition, at a reduced technical level, of the above theoretical advances and their background developments. Further details are referred to cited references.

17 pages, 6 figures, To appear in the 2006 Christmas Issue of Phil. Trans. Roy. Soc. A

References in corpus (16)

• Background Independent Quantum Gravity: A Status Report
• Real Ashtekar Variables for Lorentzian Signature Space-times
• Quantum Spin Dynamics (QSD)
• Spin Networks and Quantum Gravity
• Quantum Gravity: a Progress Report
• Real and complex connections for canonical gravity
• Anomaly-free formulation of non-perturbative, four-dimensional Lorentzian quantum gravity
• Quantum Gravity, Torsion, Parity Violation and all that
• Physical effects of the Immirzi parameter
• The Immirzi parameter in quantum general relativity
• SU(2) Loop Quantum Gravity seen from Covariant Theory
• SO(4,C)-covariant Ashtekar-Barbero gravity and the Immirzi parameter
• Quantum gravitational decoherence of matter waves
• Conformal geometrodynamics: True degrees of freedom in a truly canonical structure
• Unambiguous spin-gauge formulation of canonical general relativity with conformorphism invariance
• Towards conformal loop quantum gravity

Cited by in corpus (4)

• Quantum principle of sensing gravitational waves: From the zero-point fluctuations to the cosmological stochastic background of spacetime
• Quantum coherence, radiance, and resistance of gravitational systems
• Closing the gaps in quantum space and time: Conformally augmented gauge structure of gravitation
• Immirzi parameter without Immirzi ambiguity: Conformal loop quantization of scalar-tensor gravity