On the bound states of the massless free field in two space-time dimensions

Abstract

We point out the peculiar kinematics of zero-mass fields in two space-time dimensions by showing that the n-fold tensor product of one-particle representations of the Poincaré group for n ⩾ 2 contains a countable infinity of discrete, zero-mass representations. We relate this result to the well-known “bound” states in every charge sector of the fermion Fock space.