Shear Viscosities from Kubo Formalism

Focusing on the properties of quark-gluon plasma, this thesis explores its behavior as a nearly perfect fluid in heavy-ion collisions. Utilizing a two-flavor Nambu-Jona-Lasinio model, it calculates shear viscosity based on temperature and chemical potential. A novel Kubo formula is introduced, addressing the complete Dirac structure of the quark spectral function. The study reveals that mesonic fluctuations at the Fock level are the primary source of dissipation, leading to a parameter-free ratio that decreases with temperature and chemical potential, showing a minimum above the AdS/CFT benchmark.