83 research outputs found

    Thermodynamic Lattice Study for Preconformal Dynamics in Strongly Flavored Gauge Theory

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    By using the lattice Monte-Carlo simulation, we investigate the finite temperature (T) chiral phase transition at color SU(3) gauge theories with various species of fundamental fermions, and discuss the signal of the (pre-)conformality at large Nf (num. of flavors.) via their comparisons. As Nf increases, we observe stronger fermion screening effects which result from a larger fermion multiplicity. We investigate a finite T step-scaling associated with a uniqueness of the critical temperature (Tc) at each Nf, then the vanishing step-scaling indicates the emergence of the conformality around Nf* = 10 - 12. Further, motivated by the functional renormalization group analyses, we examine the Nf dependence of Tc, whose vanishing behavior indicates the onset of conformal window around Nf* = 9 - 10.Comment: 5 pages, 5 figures, Proceedings for Extreme QCD 201

    Chiral and deconfinement transitions in strong coupling lattice QCD with finite coupling and Polyakov loop effects

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    We investigate chiral and deconfinement transitions in the framework of the strong coupling lattice QCD for color SU(3) with one species of unrooted staggered fermion at finite temperature and quark chemical potential. We take account of the leading order Polyakov loop terms as well as the next-to-next-to-leading order (1/g^4) fermionic terms of the strong coupling expansion in the effective action. We investigate the Polyakov loop effects by comparing two approximation schemes, a Haar measure method (no fluctuation from the mean field) and a Weiss mean-field method (with fluctuations). The effective potential is obtained in both cases, and we analytically clarify the Polyakov loop contributions to the effective potential. The Polyakov loop is found to suppress the chiral condensate and to reduce the chiral transition temperature at mu=0, and the chiral transition temperature roughly reproduces the Monte Carlo results at beta=2N_c/g^2 \lesssim 4. The deconfinement transition is found to be the crossover and first order for light (am_0 \lesssim 4 at beta=4) and heavy quark masses, respectively.Comment: 13 pages, 15 figures. v2; More dicussions added, figures improved, and typos correcte

    Another mean field treatment in the strong coupling limit of lattice QCD

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    We discuss the QCD phase diagram in the strong coupling limit of lattice QCD by using a new type of mean field coming from the next-to-leading order of the large dimensional expansion. The QCD phase diagram in the strong coupling limit recently obtained by using the monomer-dimer-polymer (MDP) algorithm has some differences in the phase boundary shape from that in the mean field results. As one of the origin to explain the difference, we consider another type of auxiliary field, which corresponds to the point-splitting mesonic composite. Fermion determinant with this mean field under the anti-periodic boundary condition gives rise to a term which interpolates the effective potentials in the previously proposed zero and finite temperature mean field treatments. While the shift of the transition temperature at zero chemical potential is in the desirable direction and the phase boundary shape is improved, we find that the effects are too large to be compatible with the MDP simulation results.Comment: Talk given at 28th International Symposium on Lattice Field Theory (Lattice 2010), Villasimius, Sardinia, Italy, 14-19 June, 201

    Quarkyonic matter in lattice QCD at strong coupling

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    We study the phase diagram of quark matter at finite temperature and density in the strong coupling lattice QCD with one species of unrooted staggered fermions including finite coupling (1/g21/g^2) effects for color SU(NcN_c). We find that we may have partially chiral restored medium density matter at Nc=3N_c=3, which would correspond to the quarkyonic matter suggested at large NcN_c.Comment: 9 pages, 4 figure

    Schwinger-Dyson Study for Walking/Conformal Dynamics with IR Cutoffs

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    Motivated by recent progress on many flavor QCD on a lattice, we investigate conformal/walking dynamics by using Schwinger-Dyson (SD) equation within an improved ladder approximation for two-loop running coupling. By numerically solving the SD equation, we obtain a pole mass mpm_{p}, pion decay constant fπf_{\pi}, and investigate the chiral symmetry breaking and mass anomalous dimension γm\gamma_{m} in the presence of IR cutoffs ΛIR\Lambda_{\mathrm{IR}}. We find that the chiral symmetry breaking is suppressed \ if IR cutoff ΛIR\Lambda_{\mathrm{IR}} becomes larger than the critical \ value near the dynamical mass (ΛIR\Lambda_{\mathrm{IR}} mD\simeq m_{D}) In the conformal phase the γm\gamma_{m} is strongly suppressed by IR cutoffs for ΛIR\Lambda _{\mathrm{IR}} mp\simeq m_{p}. We, then, obtain finite size hyperscaling (FSS) relation by adapting a linearized approximation for the SD equation, and examine the γm\gamma_{m} The results offer valuable insight and suggestion for analyses in lattice gauge theories.Comment: 5 pages,2 figures; Presented at Sakata Memorial KMI Workshop on "Origin of Mass and Strong Coupling Gauge Theories" (SCGT15