Dark energy and QCD axion from approximate U(1) de & U(1) PQ
Dark energy and QCD axion from approximate U(1) de & U(1) PQ JEK, Phys. Rev. Lett. 111 (2013) 031801; JEK, Phys. Lett. B726 (2013) 450; JEK+H. P. Nilles,
