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Register a new userFinite temperature QCD with two flavors of dynamical quarks on 24^3*10 lattice
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We present results obtained in QCD with two flavors of non-perturbatively improved Wilson fermions at finite temperature on $16^3 times 8$ and $24^3 times 10$ lattices. We determine the transition temperature in the range of quark masses $0.6<m_pi/m_rho<0.8$ at lattice spacing a$approx$0.1 fm and extrapolate the transition temperature to the continuum and to the chiral limits.
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We present results obtained in QCD with two flavors of non-perturbatively improved Wilson fermions at finite temperature on $16^3 times 8$ and $24^3 times 10$ lattices. We determine the transition temperature in the range of quark masses $0.6<m_pi/m_rho<0.8$ at lattice spacing a$approx$0.1 fm and extrapolate the transition temperature to the continuum and to the chiral limits. We also discuss the order of phase transition.
We study the dynamics of SU(2) gauge theory with NF=6 Dirac fermions by means of lattice simulation to investigate if they are appropriate to realization of electroweak symmetry breaking. The discrete analogue of beta function for the running coupling constant defined under the Schroedinger functional boundary condition are computed on the lattices up to linear size of L/a=24 and preclude the existence of infrared fixed point below 7.6. Gluonic observables such as heavy quark potential, string tension, Polyakov loop suggest that the target system is in the confining phase even in the massless quark limit.
We present a study of the topological susceptibility in lattice QCD with two degenerate flavors of dynamical quarks. The topological charge is measured on gauge configurations generated with a renormalization group improved gauge action and a mean field improved clover quark action at three values of $beta=6/g^2$, corresponding to lattice spacings of $a approx 0.22$, 0.16 and 0.11 fm, with four sea quark masses at each $beta$. The study is supplemented by simulations of pure SU(3) gauge theory with the same gauge action at 5 values of $beta$ with lattice spacings 0.09 fm$simlt a simlt$0.27 fm. We employ a field theoretic definition of the topological charge together with cooling. For the topological susceptibility in the continuum limit of pure SU(3) gauge theory we obtain $chi_t^{1/4} = 197^{+13}_{-16}$ MeV where the error shows statistical and systematic ones added in quadrature. In full QCD $chi_t$ at heavy sea quark masses is consistent with that of pure SU(3) gauge theory. A decrease of $chi_t$ toward light quark masses, as predicted by the anomalous Ward-Takahashi identity for U(1) chiral symmetry, becomes clearer for smaller lattice spacings. The cross-over in the behavior of $chi_t$ from heavy to light sea quark masses is discussed.
We present results of a first study of equation of state in finite-temperature QCD with two flavors of Wilson-type quarks. Simulations are made on lattices with temporal size $N_t=4$ and 6, using an RG-improved action for the gluon sector and a meanfield-improved clover action for the quark sector. The lines of constant physics corresponding to fixed values of the ratio $m_{rm PS}/m_{rm V}$ of the pseudo-scalar to vector meson masses at zero temperature are determined, and the beta functions which describe the renormalization-group flow along these lines are calculated. Using these results, the energy density and the pressure are calculated as functions of temperature along the lines of constant physics in the range $m_{rm PS}/m_{rm V} = 0.65$--0.95. The quark mass dependence in the equation of state is found to be small for $m_{rm PS}/m_{rm V} simlt 0.8$. Comparison of results for $N_t=4$ and $N_t=6$ lattices show significant scaling violation present in the $N_t=4$ results. At high temperatures the results for $N_t=6$ are quite close to the continuum Stefan-Boltzmann limit, suggesting the possibility of a precise continuum extrapolation of thermodynamic quantities from simulations at $N_tsimgt 6$.
We present results of a numerical calculation of lattice QCD with two degenerate flavors of dynamical quarks, identified with up and down quarks, and with a strange quark treated in the quenched approximation. The lattice action and simulation parameters are chosen with a view to carrying out an extrapolation to the continuum limit as well as chiral extrapolations. Gauge configurations are generated with a renormalization-group improved gauge action and a mean field improved clover quark action at three values of $beta$ and four sea quark masses. The sizes of lattice are chosen so that the physical spatial size is kept constant. Hadron masses, light quark masses and meson decay constants are measured at five valence quark masses. We also carry out complementary quenched simulations with the same improved actions. The quenched spectrum from this analysis agrees well in the continuum limit with the one of our earlier work using the standard action. We find the two-flavor full QCD meson masses in the continuum limit to be much closer to experimental meson masses than those from quenched QCD. We take these results as manifestations of sea quark effects in two-flavor full QCD. For baryon masses full QCD values for strange baryons are in agreement with experiment, while they differ increasingly with decreasing strange quark content, resulting in a nucleon mass higher than experiment. The pattern suggests finite size effects as a possible origin for this deviation. For light quark masses in the continuum limit we obtain values which are reduced by about 25% compared to the values in quenched QCD. We also present results for decay constants where large scaling violations obstruct a continuum extrapolation. Need for a non-perturbative estimate of renormalization factors is discussed.
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