Peccei-Quinn mechanism in gravity and the nature of the Barbero-Immirzi parameter.
A general argument provides the motivation to consider the Barbero-Immirzi parameter as a field. The specific form of the geometrical effective action allows one to relate the value of the Barbero-Immirzi parameter to other quantum ambiguities through the analog of the Peccei-Quinn mechanism.
Institute for Gravitation and the Cosmos, The Pennsylvania State University, Physics Department, Whitmore Lab, University Park, Pennsylvania 16802, USA. mercuri@gravity.psu.edu
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