Equation of state in the PNJL model with the entanglement interaction

The equation of state and the phase diagram in two-flavor QCD are investigated by the Polyakov-loop extended Nambu--Jona-Lasinio (PNJL) model with an entanglement vertex between the chiral condensate and the Polyakov-loop. The entanglement-PNJL (EPNJL) model reproduces LQCD data at zero and finite chemical potential better than the PNJL model. Hadronic degrees of freedom are taken into account by the free-hadron-gas (FHG) model with the volume-exclusion effect due to the hadron generation. The EPNJL+FHG model improves agreement of the EPNJL model with LQCD data particularly at small temperature. The quarkyonic phase survives, even if the correlation between the chiral condensate and the Polyakov loop is strong and hadron degrees of freedom are taken into account. However, the location of the quarkyonic phase is sensitive to the strength of the volume exclusion.Comment: 9 pages, 7 figure

Scaling Study of Pure Gauge Lattice QCD by Monte Carlo Renormalization Group Method

The scaling behavior of pure gauge SU(3) in the region $\beta=5.85 - 7.60$ is examined by a Monte Carlo Renormalization Group analysis. The coupling shifts induced by factor 2 blocking are measured both on 32$^4$ and 16$^4$ lattices with high statistics. A systematic deviation from naive 2-loop scaling is clearly seen. The mean field and effective coupling constant schemes explain part, but not all of the deviation. It can be accounted for by a suitable change of coupling constant, including a correction term ${\cal O}(g^7)$ in the 2-loop lattice $\beta$-function. Based on this improvement, $\sqrt{\sigma}/\Lambda_{\overline {MS}}^{n_f=0}$ is estimated to be $2.2(\pm 0.1)$ from the analysis of the string tension $\sigma$.Comment: 4 pages of A4 format including 7-postscript figure

Quenched charmonium spectrum

We study charmonium using the standard relativistic formalism in the quenched approximation, on a set of lattices with isotropic lattice spacings ranging from 0.1 to 0.04 fm. We concentrate on the calculation of the hyperfine splitting between eta_c and J/psi, aiming for a controlled continuum extrapolation of this quantity. The splitting extracted from the non-perturbatively improved clover Dirac operator shows very little dependence on the lattice spacing for $a \leq 0.1$ fm. The dependence is much stronger for Wilson and tree-level improved clover operators, but they still yield consistent extrapolations if sufficiently fine lattices, $a \leq 0.07$ fm ($a M(\eta_c) \leq 1$), are used. Our result for the hyperfine splitting is 77(2)(6) MeV (where Sommer's parameter, r_0, is used to fix the scale). This value remains about 30% below experiment. Dynamical fermions and OZI-forbidden diagrams both contribute to the remainder. Results for the eta_c and J/psi wave functions are also presented.Comment: 22 pages, 7 figure