S-Matrix for AdS from General Boundary QFT
  The General Boundary Formulation (GBF) is a new framework for studying quantum theories. After concise overviews of the GBF and Schr\"odinger-Feynman quantization we apply the GBF to resolve a well known problem on Anti-deSitter spacetime where due to the lack of temporally asymptotic free states the usual S-matrix cannot be defined. We construct a different type of S-matrix plus propagators for free and interacting real Klein-Gordon theory. 
Daniele Colosi, Max Dohse and Robert Oeckl
hep-th math-ph math.MP quant-ph