Cosmological aspects of inflation in a supersymmetric axion model
  We show that the hybrid inflation is naturally realized in the framework of a supersymmetric axion model, which is consistent with the WMAP observation if the Peccei-Quinn symmetry breaking scale is around 10^{15}GeV. By solving the post inflationary scalar dynamics, it is found that the scalar partner of the axion, saxion, oscillates with large amplitude and its decay produces a huge entropy and dilutes the axion. As a result, the axion coherent oscillation can be the dominant component of the dark matter in the Universe. Cosmological gravitino and axino problems are solved. 
Masahiro Kawasaki, Naoya Kitajima and Kazunori Nakayama
hep-ph astro-ph.CO