Studying the high energy regime of QCD is a problem that can be tackled by perturbation theory. This is a consequence of asymptotic freedom, which states that the coupling constant of QCD decreases when increasing the energy. The low energy regime (often called the “nonperturbative regime”) is much more difficult to access, mainly because the standard perturbation theory is not applicable anymore.
Nonetheless, I will discuss the possibility of studying the low-energy regime of QCD perturbatively. The main idea is to perform perturbation theory not around the usual Faddeev-Popov action, but around a simple extension of the latter, known as the Curci-Ferrari model. I will discuss the properties of this model and present several 1-loop calculations a) for correlation functions 2) for the phase diagram of QCD. Comparison with lattice data show that all these quantities can be reproduced with a precision of the order of 15-20%.
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