Intermediate Scale Accidental Axion and ALPs

We discuss the problem of constructing models containing an axion and axion-like particles, motivated by astrophysical observations, with decay constants at the intermediate scale ranging from $10^9$GeV to $10^{13}$GeV. We present examples in which the axion and axion-like particles arise accidentally as pseudo Nambu-Goldstone bosons of automatic global chiral symmetries, in models having exact discrete symmetries.Comment: 4 pages. To appear in the Proceedings of the 10th Patras Workshop on Axions, WIMPs and WISPs, CERN, 29 June - 04 July 201

Grand Unification and Proton Stability Near the Peccei-Quinn Scale

We show that in an $SU(2)\otimes U(1)$ model with a DSF-like invisible axion it is possible to obtain (i) the convergence of the three gauge coupling constants at an energy scale near the Peccei-Quinn scale; (ii) the correct value for $\sin^2\hat{\theta}_W(M_Z)$; (iii) the stabilization of the proton by the cyclic $Z_{13}\otimes Z_3$ symmetries which also stabilize the axion as a solution to the strong CP problem. Concerning the convergence of the three coupling constants and the prediction of the weak mixing angle at the $Z$-peak, this model is as good as the minimal supersymmetric standard model with $\mu_{\rm SUSY}=M_Z$. We also consider the standard model with six and seven Higgs doublets. The main calculations were done in the 1-loop approximation but we briefly consider the 2-loop contributions.Comment: 12 pages, 4 figure