I won't start a new thread, but can someone explain this unparticle stuff to me. I read part of Georgi's paper. This is my take on the part I read, please correct me since I know I'm wrong.
What is a particle? In particle physics you consider cross sections of scattering events. You have some set of non interacting in particles they do something and you calculate the cross sections of the non interacting out particles. What could be argued is that the whole definition of a particle is truly dependent on the non interacting part. That is the thing of importance is the fields and particles are just the states created by the asymptotic limits of these fields.
Now, how do you define fields? Fields that create massive timelike particles are defined by how they transform under the poincare group. Massless null particles have a larger isometry group which is the poincare and the conformal group. The conformal group is usually scale invariant.
Is what Georgi is saying is that there may be fields that transform locally under conformal symmetries that do not represent the fields of particles?
