118532418
EoS of finite density QCD with Wilson fermions by multi-parameter reweighting and Taylor expansion
A bstractThe equation of state (EoS), quark number density and susceptibility at nonzero quark chemical potential μ are studied in lattice QCD simulations with a clover improved Wilson fermion of 2-flavors and RG-improved gauge action. To access nonzero μ, we employ two methods: a multi-parameter reweighting (MPR) in μ and β and Taylor expansion in μ/T. The use of a reduction formula for the Wilson fermion determinant enables to study the reweighting factor in MPR explicitly and higher-order coefficients in Taylor expansion free from errors of noise method, although calculations are limited to small lattice size. As a consequence, we can study the reliability of the thermodynamical quantities through the consistency of the two methods, each of which has different origin of the application limit. The thermodynamical quantities are obtained from simulations on a 83 × 4 lattice with an intermediate quark mass(mPS/mV = 0.8). The MPR and Taylor expansion are consistent for the EoS and number density up to μ/T ~ 0.8 and for the number susceptibility up to μ/T ~ 0.6. This implies within a given statistics that the overlap problem for the MPR and truncation error for the Taylor expansion method are negligible in these regions. In order to make MPR methods work, the fluctuation of the reweighting factor should be small. We derive the equation of the reweighting line where the fluctuation is small, and show that the equation of the reweighting line is consistent with the fluctuation minimum condition.
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
119503968
Anisotropic improved actions
The studies of the quantum corrections for the anisotropy parameter, η(= ξR/ξB), for the improved actions, β(C0L(Plaq.) + C1L(Rect.)), are proceeded in the medium to strong coupling region on anisotropic lattices. The global features for the η parameters as a function of β and the coefficient C1 have been clarified. It has been found by the perturbative analysis that as C1 decreases, the slope of the η(β) becomes less steep and for the actions whose C1 is less than −0.160, η decreases as β decreases, contrary to the case of the standard action. In the medium to strong coupling region, the η parameter begins to increase as β decreases for all C1. This means that for the actions with C1 < −0.160, the one-loop perturbative results for η break down qualitatively and the η parameters have a dip. As a result of this dip structure the η for Iwasaki's action remains close to unity in the wide range of β, which means that quantum corrections for the anisotropy parameters are small for it.
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].
17570795
Phase fluctuation of fermion determinant in lattice QCD at finite density
Abstract Once the quark chemical potential μ is introduced in finite density QCD, the fermion determinant appeared in the path integral measure becomes complex. In order to investigate the phase effect of SU (3) lattice QCD (2-flavors), we calculated the fluctuation of the phase of det Δ(μ) on a 8 3 × 4 lattice at μ = 0.1 and 0.2. Then we calculated the chiral condensate and Polyakov line in the no phase and reweighted cases. There is little difference between these two cases at μ = 0.1 and 0.2. We consider a possible reason for this result below μ ≤ 0.27 in terms of Z 3 symmetry.
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.
123256260
Is the Stochastic Gauge-Fixing a Consistent Method for Reducible Gauge Theories?
By using the Stochastic Gauge-Fixing term derived in a previous paper, we stochastically quantize the Non-Abelian Antisymmetric Tensor Field theory as an example of the Reducible Gauge Theories. Though all the quantities are finitely computed and the induced vertex really reproduces the full ghost contributions, the uninterpretable terms still remain