arXiv subjects

Hiroshi Toki

Publications and source records attributed to Hiroshi Toki.

101 records · Page 6Linked to original sources

arXiv1996

Monopole Dominance for Nonperturbative QCD

Monopole dominance for the nonperturbative features in QCD is studied both in the continuum and the lattice gauge theories. First, we study the dynamical chiral-symmetry breaking (D$χ$SB) in the dual Higgs theory using the effective potential formalism. We find that the main driving force for D$χ$SB is brought from the confinement part in the nonperturbative gluon propagator rather than the short-range part, which means monopole dominance for D$χ$SB. Second, the correlation between instantons and QCD-monopoles is studied. In the Polyakov-like gauge, where $A_4(x)$ is diagonalized, the QCD-monopole trajectory penetrates the center of each instanton, and becomes complicated in the multi-instanton system. Finally, using the SU(2) lattice gauge theory with $16^4$ and $16^3 \times 4$, the instanton number is measured in the singular (monopole-dominating) and regular (photon-dominating) sectors, respectively. Instantons and anti-instantons only exist in the monopole sector both in the maximally abelian gauge and in the Polyakov gauge, which means monopole dominance for the topological charge.

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arXiv1996

Chiral Symmetry Breaking in the Dual Ginzburg-Landau Theory

Confinement and chiral symmetry breaking are the most fundamental phenomena in Quark Nuclear Physics, where hadrons and nuclei are described in terms of quarks and gluons. The dual Ginzburg-Landau (DGL) theory, which contains monopole fields as the most essential degrees of freedom and their condensation in the vacuum, is modeled to describe quark confinement in strong connection with QCD. We then demonstrate that the DGL theory is able to describe the spontaneous break down of the chiral symmetry.

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arXiv1995

Off-shell pion structure function and flavor asymmetry in the nucleon sea

We study off-shell effects of the pion cloud on the sea quark distribution in the nucleon. The structure function of the off-mass-shell pion is obtained within the Nambu and Jona-Lasinio model, where the shape of the distribution function depends on the pion momentum. By using the momentum dependent pion structure function, the SU(2) flavor asymmetry in the nucleon see is reexamined within the pionic model, in which the sea quark distribution of the nucleon is given as a convolution of the off-shell pion structure function. We calculate experimentally observed quantities related to the SU(2) asymmetry of the nucleon sea such as the Gottfried sum and the Drell-Yan cross section ratios, and find these quantities are insensitive to the off-shell effects of the pions structure function. However, the $x$ dependence of $\bar{u}-\bar{d}$ calculated with the off-shell structure function shows a clear deviation from the result with the on-shell one. We evaluate also the cross section of semi-inclusive lepton-nucleon process with a slow nucleon production to demonstrate the off-shell effect to be checked experimentally.

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arXiv1995

Chiral Symmetry Restoration at Finite Temperature in the Dual Ginzburg-Landau Theory

We study the relation between QCD-monopole condensation and dynamical chiral-symmetry breaking in the dual Ginzburg-Landau Theory, which realizes the color confinement due to the dual Meissner effect. Solving the Schwinger-Dyson equation at finite temperature numerically, we find the chiral symmetry is restored at high temperature. The critical temperature of the chiral symmetry restoration is strongly correlated with the string tension.

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arXiv1995

Dual Ginzburg-Landau Theory for Quark Confinement and Dynamical Chiral-Symmetry Breaking

Nonperturbative features of QCD are studied using the dual Ginzburg-Landau (DGL) theory with QCD-monopoles. The linear quark potential appears in the QCD-monopole condensed vacuum. We find that QCD-monopole condensation plays an essential role to the dynamical chiral-symmetry breaking. We also investigate the QCD phase transition at finite temperature in the DGL theory.

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arXiv1995

QCD Phase Transition at Finite Temperature in the Dual Ginzburg-Landau Theory

We study the pure-gauge QCD phase transition at finite temperatures in the dual Ginzburg-Landau theory, an effective theory of QCD based on the dual Higgs mechanism. We formulate the effective potential at various temperatures by introducing the quadratic source term, which is a new useful method to obtain the effective potential in the negative-curvature region. Thermal effects reduce the QCD-monopole condensate and bring a first-order deconfinement phase transition. We find a large reduction of the self-interaction among QCD-monopoles and the glueball masses near the critical temperature by considering the temperature dependence of the self-interaction. We also calculate the string tension at finite temperatures.

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arXiv1995

Dual Higgs Mechanism for Quarks in Hadrons

We study nonperturbative features of QCD using the dual Ginzburg-Landau (DGL) theory, where the color confinement is realized through the dual Higgs mechanism brought by QCD-monopole condensation. The linear confinement potential appears in the QCD-monopole condensed vacuum. We study the infrared screening effect to the confinement potential by the light-quark pair creation, and derive a compact formula for the screened quark potential. We study the dynamical chiral-symmetry breaking (D$χ$SB) in the DGL theory by solving the Schwinger-Dyson equation. QCD-monopole condensation plays an essential role to D$χ$SB. The QCD phase transition at finite temperature is studied using the effective potential formalism in the DGL theory. We find the reduction of QCD-monopole condensation and the string tension at high temperatures. The surface tension is calculated using the effective potential at the critical temperature. The DGL theory predicts a large mass reduction of glueballs near the critical temperature. We apply the DGL theory to the quark-gluon-plasma (QGP) physics in the ultrarelativistic heavy-ion collisions. We propose a new scenario of the QGP formation via the annihilation of color-electric flux tubes based on the attractive force between them.

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arXiv1994

Dynamical Chiral-Symmetry Breaking in the Dual Ginzburg-Landau Theory

We study the effect of QCD-monopole condensation on the dynamical chiral-symmetry breaking by using the dual Ginzburg-Landau theory of QCD. We formulate the Schwinger-Dyson equation and solve it numerically. The large enhancement is found for the chiral-symmetry breaking due to QCD-monopole condensation, which suggests the close relation between the color confinement and the chiral-symmetry breaking.

hep-ph↗

arXiv1994

Color Confinement and Dynamical Effect of Light Quarks in the Dual Ginzburg-Landau Theory

We study nonperturbative features of QCD using the dual Ginzburg-Landau theory. The color confinement is realized through the dual Higgs mechanism, which is brought by QCD-monopole condensation. We investigate the infrared screening effect on the color confinement due to the light-quark pair creation. By solving the Schwinger-Dyson equation, we find that the dynamical chiral-symmetry breaking is largely brought by the confining force.

hep-ph↗

arXiv1994

Heavy Quarkonium in the dual Ginzburg-Landau theory of QCD

We study the masses and the leptonic decay widths of heavy quarkonium in the dual Ginzburg-Landau (DGL) theory of QCD, in which the abelian monopole condensation plays an essential role for color confinement. The effect of color screening due to the light quark pair creation is introduced by the infrared momentum cutoff in the gluon propagator. We find that the color screening effect is important to reproduce the properties of the heavy quarkonium, in particular the leptonic decay width. We also discuss the underlying systematics of the heavy quark spectroscopy in the DGL theory.

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arXiv1994

Color Confinement, Quark Pair Creation and Dynamical Chiral-Symmetry Breaking in the Dual Ginzburg-Landau Theory

We study the color confinement, the $q$-$\bar q$ pair creation and the dynamical chiral-symmetry breaking of nonperturbative QCD by using the dual Ginzburg-Landau theory, where QCD-monopole condensation plays an essential role on the nonperturbative dynamics in the infrared region. As a result of the dual Meissner effect, the linear static quark potential, which characterizes the quark confinement, is obtained in the long distance within the quenched approximation. We obtain a simple expression for the string tension similar to the energy per unit length of a vortex in the superconductivity physics. The dynamical effect of light quarks on the quark confining potential is investigated in terms of the infrared screening effect due to the $q$-$\bar q$ pair creation or the cut of the hadronic string. The screening length of the potential is estimated by using the Schwinger formula for the $q$-$\bar q$ pair creation. We introduce the corresponding infrared cutoff to the strong long-range correlation factor in the gluon propagator as a dynamical effect of light quarks, and obtain a compact formula of the quark potential including the screening effect in the infrared region. We investigate the dynamical chiral-symmetry breaking by using the Schwinger-Dyson equation, where the gluon propagator includes the nonperturbative effect related to

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