Spectral and Transport Properties of a Non-Perturbative Quark-Gluon Plasma.

Non-perturbative methods play an important role in quantum many-body systems, especially in situations with an interplay of continuum and bound states and/or large coupling strengths between the constituents. We here employ the Luttinger-Ward functional (LWF) to compute the equation of state (EoS) of the quark-gluon plasma (QGP) using fully dressed self-consistent 1- and 2-body propagators.The ladder diagram series of the LWF is resummed using a "matrix log" technique which accounts for dynamically formed bound and resonant states. The in-medium interaction kernel is constrained by lattice QCD and the pertinent pressure of the QGP is fitted with an effective parton mass parameter. We find that, as the pseudo-critical temperature ($T_{\rm pc}$) is approached from above, the quasi-particle peaks in the parton spectral functions dissolve as a consequence of large scattering rates, which in turn are driven by dynamically formed pre-hadronic states. Our results suggest that a gradual emergence of hadronic states is intricately related to the strongly coupled nature of the QGP near $T_{\rm pc}$. This is further corroborated by computing the temperature dependent viscosity-to-entropy ratio and heavy-flavor diffusion coefficient.