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Gravity, Superselection Rules and Axions
Author(s) -
Gómez César
Publication year - 2021
Publication title -
fortschritte der physik
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.469
H-Index - 71
eISSN - 1521-3978
pISSN - 0015-8208
DOI - 10.1002/prop.202000095
Subject(s) - superselection , axion , physics , theoretical physics , quantum field theory , charge (physics) , quantum gravity , quantum , gravitation , string (physics) , quantum mechanics , particle physics , dark matter
It is generally accepted that consistent coupling to quantum gravity implies that any low energy free parameter is in reality the vacuum expectation value of some local quantum field. In this note we present a modest attempt to prove this general claim using as key example the θ parameter of QCD and the Peccei‐Quinn axion solution of the strong CP problem. The gravitational emergence of the local axion field associated with the superselection θ parameter is worked out using as basic ingredients the quantum representation of classical geometries in terms of coherent states and the interpretation of the θ QCD superselection rule in quantum information terms as the lack of a quantum reference frame for topological charge. The formal connection with the model independent axion in string theory is briefly discussed.