INFRARED QCD

We prove that Nambu-Jona-Lasinio model is an exact description of infrared Quantum ChromoDynamics (QCD) deriving it from QCD Lagrangian. The model we obtain is renormalizable and confining but, taking very small momenta fixes completely all the parameters of the Nambu-Jona-Lasinio model through those of QCD. The choice of the infrared propagator is done consistently with recent numerical results from lattice and Dyson-Schwinger equations for Yang-Mills theory. The model we get coincides, once the ultraviolet contribution is removed, with the one proposed by Langfeld, Kettner and Reinhardt [Nucl. Phys. A608 (1996) 331]