On Type IIA String Theory on the PP-wave Background
  We study type IIA superstring theory on a PP-wave background with 24 supercharges. This model can exactly be solved and then quantized. The open string in this PP-wave background is also studied. We observe that the theory has supersymmetric Dp-branes for p=2,4,6,8. 
Mohsen Alishahiha, Mohammad A. Ganjali, Ahmad Ghodsi, Shahrokh Parvizi