The 't Hooft interaction at finite T and $\mu$: Beyond the mean field   theory
  We use the N-quantum approach (NQA) to quantum field theory to construct a solution of the two flavor effective instanton induced `t Hooft interaction model valid for any temperature (T) and chemical potential ($\mu$) beyond the mean field theory. The model contains only the $\bar{q}q$ channels. In constructing this solution we calculate the masses, widths and coupling constants of bound $\sigma$ and resonant color $\bar{3}$ scalar diquark states. We find that the chemical potential induced by the interaction cancel exactly for all values of T in contrast to the Nambu-Jona-Lasinio model. Our method can also be extended to include the qq channels in the model Lagrangian and we discuss how the NQA can be used to study the properties of bound diquark states at finite T and $\mu$. 
Yasuo Umino and Vicente Vento