119223418
Color screening potential at finite density in two-flavor lattice QCD with Wilson fermions
We investigate the chemical-potential ($\ensuremath{\mu}$) dependence of static-quark free energies in both the real and imaginary $\ensuremath{\mu}$ regions, performing lattice QCD simulations at imaginary $\ensuremath{\mu}$ and extrapolating the results to the real-$\ensuremath{\mu}$ region with analytic continuation. Lattice QCD calculations are done on a ${16}^{3}\ifmmode\times\else\texttimes\fi{}4$ lattice with 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 correlation functions in the deconfinement phase. To perform the analytic continuation, the potential calculated at imaginary $\ensuremath{\mu}=i{\ensuremath{\mu}}_{\mathrm{I}}$ is expanded into a Taylor expansion series of $i{\ensuremath{\mu}}_{\mathrm{I}}/T$ up to fourth order and the pure imaginary variable $i{\ensuremath{\mu}}_{\mathrm{I}}/T$ is replaced by the real one ${\ensuremath{\mu}}_{\mathrm{R}}/T$. At real $\ensuremath{\mu}$, the fourth-order term sizably weakens the $\ensuremath{\mu}$ dependence of the potential. At long distance, all of the color-singlet and -nonsinglet potentials tend to twice the single-quark free energy, indicating that the interactions between static quarks are fully color screened for finite $\ensuremath{\mu}$. For both real and imaginary $\ensuremath{\mu}$, the color-singlet $q\overline{q}$ and the color-antitriplet $qq$ interactions are attractive, whereas the color-octet $q\overline{q}$ and the color-sextet $qq$ interactions are repulsive. The attractive interactions have a stronger $\ensuremath{\mu}/T$ dependence than the repulsive interactions. The color-Debye screening mass is extracted from the color-singlet potential at imaginary $\ensuremath{\mu}$, and the mass is extrapolated to real $\ensuremath{\mu}$ by analytic continuation. The screening mass thus obtained has a stronger $\ensuremath{\mu}$ dependence than the prediction of hard-thermal-loop perturbation theory at both real and imaginary $\ensuremath{\mu}$.
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.
22209692
Color confinement and the Faddeev-Popov ghosts in Coulomb gauge QCD
We investigate the Gribov-Zwanziger scenario in the Coulomb gauge using a SU(3) quenched lattice gauge simulation. The dressing function of the ghost propagator diverges in the infrared limit. This result is expected from the fact that the Faddeev-Popov eigenvalue density gets concentrated near the vanishing eigenvalue compared to that in the abelian gauge theory. The turnover of the transversal gluon propagator is not observed up to the largest lattice volume explored in this study. The instantaneous part of the time-time component of the gluon propagator which corresponds to the color-Coulomb potential in the continuum limit diverges stronger than the simple pole. Furthermore, we observe that the ghost propagator show good scaling while both components of the gluon propagator do not show scaling in the considered range of the lattice spacing.
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
43999878
Scalar mesons in lattice QCD
Recently there has been renewed and growing interestin scalarmesons[1, 2]. Oneofthe mostnoteworthydevel-opments in this ﬁeld is the re-identiﬁcation of the σ(600)after some twenty years. The results of re-analyses of theπ-π scattering phase shift of the scattering (S) matrixstrongly suggest the existence of the pole of the σ mesonwith I = 0 and J
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.
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.
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