| Abstract: |
We will discuss natural inflation models in supergravity motivated by the string theory, in which a heavy string theoretic axion plays a role in an inflaton. The models are controlled by an approximate shift symmetry originating from a gauge symmetry in the string theory, and will require a decay constant larger than the Planck scale for the inflation models to be consistent with CMB observations such as Planck and BICEP2. In order to obtain such an axion decay constant, we will require a large number of D-branes or an alignment mechanism among winding numbers of branes wrapping on the extra dimension. We discuss also the reheating temperature and its consequences after the inflation. |
