Chiral models of composite axions and accidental Peccei-Quinn symmetry

We introduce a class of composite axion models that provide natural solution to the strong CP problem, and possibly account for observed dark matter abundance. The QCD arises as Nambu-Goldstone boson (NGB) from dynamics chiral gauge theory with strongly-interacting confining SU(N) factor weakly-interacting U(1), no fundamental scalar fields. Peccei-Quinn (PQ) symmetry is accidental all mass scales are generated dynamically. analyze specific where PQ broken only by operators dimension 12 or higher. also classify several other can be potentially protected up 15 18 level. Our framework easily extended scenario Standard Model (SM) unified into simple group, we discuss case non-supersymmetric SU(5) unification. GUT predict existence additional pseudo NGBs, parametrically lighter than scales, which could have an impact on cosmological evolution leave observable signatures. clarify selection rules under higher-dimensional PQ-violating generate potential in IR, discussion discrete symmetries associated number domain walls. These results general interest based QCD-like group.