Open Strings in PP-Wave Background from Defect Conformal Field Theory
  We consider open strings ending on a D5-brane in the pp-wave background, which is realized in the Penrose limit of $AdS_5 \times S^5$ with an $AdS_4\times S^2$ brane. A complete list of gauge invariant operators in the defect conformal field theory is constructed which is dual to the open string states. 
Peter Lee and Jongwon Park (Caltech)