Hadronic axion model in gauge-mediated supersymmetry breaking and the cosmology of the saxion

Recently we proposed a simple hadronic axion model within gauge-mediated supersymmetry breaking. In this paper we discuss various cosmological consequences of the model in great detail. Particular attention is paid to the saxion, a scalar partner of the axion, which is produced as a coherent oscillation in the early universe. We show that our model is cosmologically viable if the reheating temperature of inflation is sufficiently low. We also discuss the late decay of the saxion which gives a preferable power spectrum of the density fluctuation in the standard cold dark matter model when compared with observations. [S0556-2821(99)01910-4].