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arXiv · 1005.1291

The Immirzi Parameter as an Instanton Angle

Simone Mercuri·Andrew Randono
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Abstract

The Barbero-Immirzi parameter is a one parameter quantization ambiguity underpinning the loop approach to quantum gravity that bears tantalizing similarities to the theta parameter of gauge theories such as Yang-Mills and QCD. Despite the apparent semblance, the Barbero-Immirzi field has resisted a direct topological interpretation along the same lines as the theta-parameter. Here we offer such an interpretation. Our approach begins from the perspective of Einstein-Cartan gravity as the symmetry broken phase of a de Sitter gauge theory. From this angle, just as in ordinary gauge theories, a theta-term emerges from the requirement that the vacuum is stable against quantum mechanical tunneling. The Immirzi parameter is then identified as a combination of Newton's constant, the cosmological constant, and the theta-parameter.

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Simone Mercuri, Andrew Randono. 2010-05-07. The Immirzi Parameter as an Instanton Angle. https://doi.org/10.1088/0264-9381/28/2/025001

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