Quark-Gluon Systems at Extreme Condition: International Collaboration for High Temperature and Density QCD

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1) At RBHIC, a new form of matter was created. It is important to understand this new matter by lattice QCD, the first-principle calculation. We calculated the shear viscosity of quark-gluon plasma in detail by lattice QCD and found that it is very small and the matter is almost perfect fluid, which is suggested by experiments.2) We proceed the above calculation, and showed that the bulk-viscosity is very small but positive definite.3) We calculated quark-propagators in both the confinement and the deconfinement phases. We observed that the spectrum is not positive definite in the confinement phase. Quark mass is difkent in the confinement and deconfmment phases. Especially in the deconfinement phase, a standard form does not work.4) At very high temperature, the confinement is expected to be broken. To understand this phenomena, it is important to understand the confinement mechanism at zero temperature. For this purpose, using the Coulomb gauge, which is the physical gauge, we calculated the color-Coulomb form numerically. We observed that the confinement force comes from the color-Coulomb force, and relates to the behavior of eigen values of the Fadddev-Popov operators. However, the temperature behavior of the eigen values is different from what was expected, ie., the condensation of the eigen-values near zero does not disappear. The confinement/deconfinement transition is very non-trivial.5) We developed a Lattice QCD code on the CELTLL which is a new architecture of high-performance computers.