Quantization of fields over de Sitter space by the method of generalized   coherent states. I. Scalar field
  A system of generalized coherent states for the de Sitter group obeying Klein-Gordon equation and corresponding to the massive spin zero particles over the de Sitter space is considered. This allows us to construct the quantized scalar field by the resolution over these coherent states; the corresponding propagator can be computed by the method of analytic continuation to the complexified de Sitter space and coincides with expressions obtained previously by other methods. We show that this propagator possess the de Sitter-invariance and causality properties. 
Semyon Pol'shin