Modified field theory for quark binding

We have investigated the structure of modified field theories. Higher derivatives are introduced into the Lagrangian in such a way that the bare propagator becomes $q^{-4\mathrm{}}$ rather than $q^{-2\mathrm{}}$. A modification of this type to the gluon propagator in a quark-gluon model gives the possibility of permanent quark binding. We find that such a model has difficulties with unitarity and with infrared divergences when treated in naive perturbation theory. If the problems associated with going beyond perturbation theory can be overcome, these difficulties may be eliminated.