D3/D7 Inflation in a Type-0B String Background
  The D3/D7 inflation is studied in the framework of Type 0B string theory. Due to the presence of the closed string tachyon, the constant gauge field flux on the transverse worldvolume of D7-brane is almost arbitrary in having an attractive inflaton potential energy. Besides, a positive cosmological constant appears in this model whose magnitude is related to the volume modulus of the D7-brane transverse worldvolume. 
Huan-Xiong Yang