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Lattice calculation of the QGP viscosities - Present results and Next Project -

Presenter: Sunao Sakai — Yamagata University

Sunao Sakai and Atsushi Nakamura

On isotropic 243 8 lattice, we have carried out high statistic measurements of Matsubara Green's functions: for Iwasaki's Improved action numbers of measurements amount to 4.5 106, and for standard action they are about 12 106. From improved action data, we could determine bulk and shear viscosities in 1.5 < T/Tc < 24 region. The bulk viscosity is about one order of magnitude smaller than the shear viscosity. While in the case of the standard action, the fluctuations of Matsubara green's functions are still large that the transport coefficients have large errors. But they are consistent with the ones determined by improved action. The lattice result on shear viscosity is consistent with the perturbative one in high temperature region. For more accurate determination of viscosities using MEM, we will adopt anisotropic lattice. Before carrying out the calculation on large lattice, we have started calculations on smaller lattices with η=2. The preliminary results will be reported. Further, we are trying to reduce the fluctuation of Matsubara Green's function of energy momentum tensor. A study using the clover type operator for the definition of it will be reported.