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Naturally light invisible axion in models with large local discrete symmetries
We show that by introducing appropriate local symmetries in
electroweak models it is possible to implement an automatic Peccei-Quinn
symmetry keeping at the same time the axion protected against gravitational
effects. Although we consider here only an extension of the standard model and
a particular 3-3-1 model, the strategy can be used in any kind of electroweak
model. An interesting feature of this 3-3-1 model is that if: {\it i)} we add
right-handed neutrinos, {\it ii)} the conservation of the total lepton number,
and {\it iii)} a symmetry, the and the chiral Peccei-Quinn
are both accidental symmetries in the sense that they are not
imposed on the Lagrangian but they are just the consequence of the particle
content of the model, its gauge invariance, renormalizability and Lorentz
invariance. In addition, this model has no domain wall problem.Comment: Some changes and a new reference added, 7 page
Naturally light invisible axion and local Z_{13} times Z_3 symmetries
We show that by imposing local symmetries in an
electroweak model we can implement an invisible axion in
such a way that (i) the Peccei-Quinn symmetry is an automatic symmetry of the
classical Lagrangian; and (ii) the axion is protected from semi classical
gravitational effects. In order to be able to implement such a large discrete
symmetry, and at the same time allow a general mixing in each charge sector, we
introduce right-handed neutrinos and enlarge the scalar sector of the model.
The domain wall problem is briefly considered.Comment: PQ charges and typos correcte
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