## Details

Khuri, in 1995, considered potential scattering for a model where one spatial coordinate in compactified on the circle. He adopted Greens function method to study analyticity property of scattering amplitude. His conclusion was that forward scattering amplitude does not satisfy dispersion relations in certain cases; whereas in potential models (without a compact dimension) analyticity holds. If this result was true for relativistic QFT it will be a matter of concern. I consider a massive scalar field field theory in D=5 Minkowski space. Then one spatial cordinate is compactified on a circle. Analyticity property of scattering amplitude in the compactified theory is studied in general field theoretic framework such as LSZ formalism. It is shown that forward scattering amplitude and nonforward amplitude satisfy dispersion relations.