Talk presented by Sunao Sakai

Parallel Session: Finite Temperature and Density IV

Friday July 2nd, 17.20 - 17.40, Room 7

Anisotropic properties of Improved Actions

Abstract: The results for the anisotropic properties of the improved actions will be reported. The improved actions studied in this work consist of plaquette plus rectangular loops with up to 6 links, which covers Symanzik's, Iwasaki's and QCDTARO's improved actions. In the weak coupling region, they have been studied by perturbative method and we have reported that the $\eta(=g_{\tau}/g_{\sigma}) $ becomes less than $1$ and the derivatives of the coupling constants with respect to the anisotropy parameter, $\partial g_{\tau}/\partial \xi$ and $\partial g_{\sigma}/\partial \xi$, change sign for Iwasaki's and QCDTARO's actions, where $\xi= a_{s}/a_{\tau}. The study of the $\eta(=g_{\tau}/g_{\sigma})$ parameters are proceeded in the medium coupling region by numerical method. In this talk, we will report global features for the $\eta$ parameters as a function of the coefficients of rectangular 6-link loops, which defines the improved action. It is found that the $\eta$ parameter, which is calculated by the ratio $\xi_{renormalied}/\xi_{bare}$ in numerical simulations, shows weaker beta dependences for improved actions. And for the Iwasaki's action the $\eta$ parameter remains close to unity in the wide range of $\beta$, which means that quantum corrections for the anisotropy parameters are small for those improved actions.

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