出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：The shear and bulk viscosities of gluon plasma are calculated by accumulating a large amount of
data for the Matsubara Green function (Gb (tm)) on isotropic 243 8 and 163 8 lattices. In the
case of Iwasaki’s improved action, Gb (tm) is calculated on roughly 6 million configurations, while
for the standard action the calculation is carried out on more than 16 million configurations. The
shear viscosities increase roughly with T 3, and h=s ratios are close to the KSS lower bound in the
region where 1 < T=Tc < 25. Using these data the bulk viscosities are also determined in the region
where T=Tc <2. They are roughly one order of magnitude smaller than the shear viscosities.
Our next target is to determine the transport coefficients more precisely by a maximum-entropy
method. For this purpose the most effective method may be to adopt an anisotropic lattice. In
this report, we study the possible systematic error due to the deformation of the anisotropic lattice
at short distances. Near the critical temperature, it is found that the standard action suffers from
a large deformation on the anisotropic lattice at short distances, while the deformation is slight
for Iwasaki’s improved action. To reduce the fluctuation of the Matsubara Green function, the
improvement of the energy momentum tensor operator by using clover-type loops is promising.
We are also attempting to apply the multi-level algorithm to reduce fluctuation.
