Axions at the intermediate mass scale in SUSY SU(5) models

On the basis of supersymmetric SU(5) scheme, axion models are investigated by taking into account constraints extracted from cosmology (domain wall problem) and astrophysics (invisibility of axion). A global U(1) axial symmetry is assumed to break down spontaneously at an intermediate mass scale in the tree approximation. Two minimal cases are examined by working the Peccei-Quinn mechanism in R-symmetry peculiar to SUSY theories and in the ordinary chiral phase transformations. The former case suggests the number of generations to be four, while the latter yields a certain relation among P-Q charges, in order to get rid of the domain structure. (author)