S-matrix in de Sitter spacetime from general boundary quantum field theory

A new quantization scheme for a massive scalar field in de Sitter spacetime is proposed, based on the general boundary formulation of quantum field theory. We show that the general interacting theory can be consistently described in terms of the S-matrix for spatial asymptotic states. The new S-matrix results to be equivalent to the standard one in situations where both apply. This is due to the existence of an isomorphism between the corresponding asymptotic state spaces.