A note on the inverse scattering problem in quantum field theory
Detlev Buchholz, Klaus Fredenhagen
February 23, 1977
We study the set of local fields $\phi$ describing the dynamics of a scalar, massless particle. It turns out that these fields are relatively local to the free, massless, scalar field $A$ if the massless particle does not interact. This leads to a simple algebraic characterisation of interacting fields in the above framework.