Open/Closed Topological CP1 Sigma Model Revisited
  We consider the topological sigma-model on Riemann surfaces with genus g and h holes, and target space CP1. We calculate the correlation functions of bulk and boundary operators, and study the symmetries of the model and its most general deformation. We study the open/closed topological field theory (TFT) correspondence by summing up the boundaries. We argue that this summation can be understood as a renormalization of the closed TFT. We couple the model to topological gravity and derive constitutive relations between the correlation functions of bulk and boundary operators. 
Shmuel Elitzur, Yaron Oz, Eliezer Rabinovici, Johannes Walcher
hep-th