A minimal quasiparticle approach for the QGP and its large- N c limits

We propose a quasiparticle approach allowing to compute the equation of state of a generic gauge theory with gauge group SU(N_c) and quarks in an arbitrary representation. Our formalism relies on the thermal quasiparticle masses (quarks and gluons) computed from perturbative techniques, in which the standard two-loop running coupling constant is used. Our model is minimal in the sense that we do not allow any extra ansatz concerning the temperature-dependence of the running coupling. We first show that it is able to reproduce the most recent equations of state computed on the lattice for temperatures typically higher than 2T_c. Well above T_c indeed, an ideal-gas framework with thermal masses is expected to be relevant. Then we study the accuracy of various inequivalent large-N_c limits concerning the description of the QCD results, as well as the equivalence between the QCD_AS limit and the $\mathcal{N}=1$ SUSY Yang–Mills theory.