Memory and the Infrared

Understand

Memory effects in scattering processes are described in terms of the asymptotic retarded fields.

• These fields are completely determined by the scattering data and the zero mode part is set by the soft photon theorem.
• The dressed asymptotic states defining an infrared finite S- matrix for charged particles can be defined as quantum coherent states using the corpuscular resolution of the asymptotic retarded fields.
• Im- posing that the net radiated energy in the scattering is zero leads to the new set of conservation laws for the scattering S-matrix which are equivalent to the decoupling of the soft modes.