arXiv subjects
Publications and source records attributed to H. Ichie.
We present first results on the dynamics of monopoles in full QCD with N_f=2 flavors of dynamical quarks. Among the quantities being studied are the monopole density and the monopole screening length, the static potential as well as the profile of the color electric flux tube. Furthermore, we derive the low-energy effective monopole action.
Based on the dual-superconductor picture, we study the confinement physics in QCD in terms of the monopole in the maximally abelian (MA) gauge using the SU(2) lattice QCD. In the MA gauge, the off-diagonal gluon component is forced to be small, and hence microscopic abelian dominance on the link variable is observed in the lattice QCD for the whole region of $β$. From the gluon-propagator analysis in the lattice QCD, the origin of abelian dominance for the long-range physics is interpreted as the effective mass $m_{ch} \simeq 0.9 {\rm GeV}$ of the charged gluon induced by the MA gauge fixing. In the MA gauge, there appears the macroscopic network of the monopole world-line covering the whole system, which would be identified as monopole condensation at a large scale. Using the dual Wilson loop in the MA gauge, we find the effective mass of the dual gluon field, $m_B \simeq $0.5GeV, which is the evidence of the dual Higgs mechanism by monopole condensation. The large fluctuation of off-diagonal gluons remains around the monopole in the MA gauge, and this charged-gluon rich region would provide the effective monopole size as the critical scale of the abelian projected QCD. Instantons are expected to appear in the charged-gluon rich region around the monopole world-line in the MA gauge, which leads to the local correlation between monopoles and instantons.
We study the nonperturbative QCD in terms of topological objects, i.e., QCD-monopoles and instantons. In the 't Hooft abelian gauge, QCD is reduced into an abelian gauge theory with QCD-monopoles, and the confinement mechanism can be understood with the dual superconductor picture. Regarding the flux-tube ring as the glueball, we study the glueball properties by combining the dual Ginzburg-Landau theory and the Nambu-Goto action. We find the strong correlations between instantons and monopole world-lines both in the continuum theory and in the lattice QCD. The nonperturbative QCD vacuum is filled with instantons and monopoles, and dense instantons generate a macroscopic network of the monopole world-line, which would be responsible for the confinement force in the infrared region.
We study the surface tensions in the mixed phase of QCD in the dual Ginzburg-Landau theory, where the QCD-monopole condensate is the order parameter on the confinement. First, we consider the thermal mixed phase, and derive the analytical expressions for the surface tension and the boundary thickness in terms of the shape of the effective potential. We study also the properties of the spherical hadron bubble in the quark-gluon-plasma phase at finite temperature. Second, we study the surface tension in the mixed phase with the external color-electric field at zero temperature. In the type-II dual superconductor, the individual flux tubes with unit color flux are stable. On the other hand, the flux tubes tend to melt into a huge tube, which is energetically favored, in the type-I case.
We study the relation between instantons and monopoles in the abelian gauge. First, we investigate the monopole in the multi-instanton solution in the continuum Yang-Mills theory using the Polyakov gauge. At a large instanton density, the monopole trajectory becomes highly complicated, which can be regarded as a signal of monopole condensation. Second, we study instantons and monopoles in the SU(2) lattice gauge theory both in the maximally abelian (MA) gauge and in the Polyakov gauge. Using the $16^3 \times 4$ lattice, we find monopole dominance for instantons in the confinement phase even at finite temperatures. A linear-type correlation is found between the total monopole-loop length and the integral of the absolute value of the topological density (the total number of instantons and anti-instantons) in the MA gauge. We conjecture that instantons enhance the monopole-loop length and promote monopole condensation.
We study the QCD phase transition at finite temperature and discuss the hadron bubble formation in the dual Ginzburg-Landau theory, which is an effective theory of QCD and describes the color confinement via QCD-monopole condensation. We formulate the effective potential at various temperatures and find that thermal effects reduce the QCD-monopole condensate and bring a first-order deconfinement phase transition. Based on this effective potential at finite temperature, we investigate properties of hadron bubbles created in the early Universe and discuss the hadron bubble formation process.
We study the system of multi color-flux-tubes in terms of the dual Ginzburg -Landau theory. We consider two ideal cases, where the directions of all the color-flux-tubes are the same in one case and alternative in the other case for neighboring flux-tubes. We formulate the system of multi color-flux -tubes by regarding it as the system of two color-flux-tubes penetrating through a two dimensional sphere surface. We find the multi flux-tube configuration becomes uniform above some critical flux-tube number density $ρ_c = 1.3 \sim 1.7 {\rm fm}^{-2}$. On the other hand, the inhomogeneity on the color electric distribution appears when the flux-tube density is smaller than $ρ_c$. We discuss the relation between the inhomogeneity in the color-electric distribution and the flux-tube number density in the multi-flux-tube system created during the QGP formation process in the ultra-relativistic heavy-ion collision.
Nonperturbative QCD is studied with the dual Ginzburg-Landau theory, where color confinement is realized through the dual Higgs mechanism by QCD-monopole condensation. We obtain a general analytic formula for the string tension. A compact formula is derived for the screened inter-quark potential in the presence of light dynamical quarks. The QCD phase transition at finite temperature is studied using the effective potential formalism. The string tension and the QCD-monopole mass are largely reduced near the critical temperature, $T_c$. The surface tension is estimated from the effective potential at $T_c$. We propose also a new scenario of the quark-gluon-plasma creation through the color-electric flux-tube annihilation. Finally, we discuss a close relation between instantons and QCD-monopoles.