The Instanton Molecule Liquid and "Sticky Molasses" Above T_c

The main objective of this work is to explore the evolution in the structure of the quark-antiquark bound states in going down in the chirally restored phase from the so-called "zero binding points" T_zb to the QCD critical temperature T_c at which the Nambu-Goldstone and Wigner-Weyl modes meet. In doing this, we adopt the idea recently introduced by Shuryak and Zahed for charmed $\bar c c$, light-quark $\bar q q$ mesons $\pi, \sigma, \rho, A_1$ and gluons that at T_zb, the quark-antiquark scattering length goes through infinity at which conformal invariance is restored, thereby transforming the matter into a near perfect fluid behaving hydrodynamically, as found at RHIC. We show that the binding of these states is accomplished by the combination of (i) the color Coulomb interaction, (ii) the relativistic effects, and (iii) the interaction induced by the instanton-anti-instanton molecules. The spin-spin forces turned out to be small. While near T_zb all mesons are large-size nonrelativistic objects bound by Coulomb attraction, near T_c they get much more tightly bound, with many-body collective interactions becoming important and making the $\sigma$ and $\pi$ masses approach zero (in the chiral limit). The wave function at the origin grows strongly with binding, and the near-local four-Fermi interactions induced by the instanton molecules play an increasingly more important role as the temperature moves downward toward T_c.Comment: Contribution to QM2004 proceedings, 4 page

News from Lattice QCD on Heavy Quark Potentials and Spectral Functions of Heavy Quark States

We discuss recent lattice results on in-medium properties of hadrons and focus on thermal properties of heavy quark bound states. We will clarify the relation between heavy quark free energies and potentials used to analyze the melting of heavy quark bound states. Furthermore, we present calculations of meson spectral functions which indicate that the charmonium ground states, J/psi and eta_c, persist in the quark gluon plasma as well defined resonances with no significant change of their zero temperature masses at least up to T ~ 1.5 T_c. We also briefly comment on the current status of lattice calculations at non-vanishing baryon number density.Comment: Plenary talk at the 17th International Conference on Ultra Relativistic Nucleus-Nucleus Collisions (Quark Matter 2004), Oakland, California, 11-17 Jan 2004. Submitted to J.Phys.