S-matrix at spatial infinity

Understand

We provide a new method to construct the S-matrix in quantum field theory.

• This method implements crossing symmetry manifestly by erasing the a priori distinction between in- and out-states.
• It allows the description of processes where the interaction weakens with distance in space, but remains strong in the center at all times.
• It should also be applicable to certain spacetimes where the conventional method fails due to lack of temporal asymptotic states.