118146301
Heavy quark potential at finite imaginary chemical Potential
We investigate chemical-potential (μ) dependence of static-quark free energies in both the real and imaginary μ regions, using the clover-improved two-flavor Wilson fermion action and the renormalization-group improved Iwasaki gauge action. Static-quark potentials are evaluated from the Polyakov-loop correlator in the deconfinement phase and the imaginary μ = iμI region and extrapolated to the real μ region with analytic continuation. As the analytic continuation, the potential calculated at imaginary μ = iμI is expanded into a Taylor-expansion series of iμI/T up to 4th order and the pure imaginary variable iμI/T is replaced by the real one μR/T . At real μ , the 4th-order term weakens μ dependence of the potential sizably. Also, the color-Debye screening mass is extracted from the color-singlet potential at imaginary μ , and the mass is extrapolated to real μ by analytic continuation. The screening mass thus obtained has stronger μ dependence than the prediction of the leading-order thermal perturbation theory at both real and imaginary μ . This talk is based on [1].
15579258
Transport Coefficients of Gluon Plasma from Lattice QCD
In this report we present our calculation of the transport coefficient of gluon system on $24^3\times 8$ lattice in the quench approximation. Simulations are carried out in the range, $1.4 \le T/T_c \le 24$. In the temperature region slightly above the transition, where the perturbative calculation is not applicable, the shear viscosity($\eta$) is smaller than typical hadron masses. The bulk viscosity is consistent with zero within the range of error bars in $1.4 \le T/T_c \le 24$. We compare our results with the perturbative calculations in large $T/T_c$ region. It is found that the lattice and perturbative results are consistent with each other there. The ratio $\eta/s$ is around $0.1-0.4$ in $T/T_c < 3$ region and satisfies the KSS bound\cite{KSS}. In order to estimate the contribution from high frequency part of the spectral function, we study the effects of a term $\rho^{high}$ proposed by Aarts and Resco\cite{Aarts}. It is found that until the threshold mass becomes small, its effect is quite small, and that viscosity decreases as the threshold decreases. From these studies we think that although our result is obtained under an assumptions for the spectral function, it gives a reasonable estimation for $\eta$($=\pi d\rho/d\omega$ at $\omega=0$), and qualitative results will not be changed when the accurate spectral function is obtained.
125144577
Lattice calculation of the QGP viscosities - Present results and Next Project -
119191322
QCD Phase Diagram with Imaginary Chemical Potential
We report our recent results on the QCD phase diagram obtained from the lattice QCD simulation. The location of the phase boundary between hadronic and QGP phases in the two-flavor QCD phase diagram is investigated. The imaginary chemical potential approach is employed, which is based on Monte Carlo simulations of the QCD with imaginary chemical potential and analytic continuation to the real chemical potential region.
118183371
Wilson fermions with imaginary chemical potential
It is of prime interest to understand QCD at ﬁnite temperatur e and density. The lattice QCDwith a non-zero baryon density suffers from a sign problem, where the determinant of the quarkmatrix becomes complex and Monte Carlo simulations become unavailable. Because of this, it isstill challenge to understand the QCD at ﬁnite density. Seve ral approaches have been investigatedto overcome or circumvent the sign problem: multi-parameter reweighting, canonical approaches,imaginary chemical potentials, and so on.If the chemical potential is pure imaginary µ= µ
121904969
Elastic Pion-Deuteron Scattering and Dibaryon Resonances
We show that effects of dibaryon resonances can be clearly seen in the data on the differential cross section of red elastic scattering. Giving the formulation of the Glauber model with the resonance formation term in red direct channel in detail and analyzing all the data presently available by this model, we find that at least two resonances are needed in red direct channel in order to explain the data. One of them may be 'F, (2. 25 GeV) state of two nucleons which was found at Argonne and the other has mass value around ~.5GeV. The data are not enough to determine the spin-parity of the latter but ()' seems somewhat preferable. The branching ratios of the resonances into red system are also given.
119211078
Aharonov-Bohm scattering by vortices of dimensionally-reduced Yang-Mills field
If two dimensions of six-dimensional space-time are compactified, a topological configuration of Yang-Mills gauge field appears as a cosmic string in four dimensions, whose thickness is of the same order as the size of the compact space. We consider scattering of low-energy fermions by this object.