Quark Confinement Physics from Lattice QCD

摘要

We study quark confinement physics using lattice QCD. In the maximally abelian (MA) gauge, the off-diagonal gluon amplitude is strongly suppressed, and then the off-diagonal gluon phase shows strong randomness, which leads to a large effective off-diagonal gluon mass, M_(off) approx= 1.2GeV. Due to the large off-diagonal gluon mass in the MA gauge, low-energy QCD is abelianized like nonabelian Higgs theories. In the MA gauge, there appears a macroscopic network of the monopole world-line covering the whole system. We extract and analyze the dual gluon field B_μ from the monopole-current system in the MA gauge, and evaluate the dual gluon mass as m_B = 0.4 ～ 0.5GeV in the infrared region, which is a lattice-QCD evidence of the dual Higgs mechanism by monopole condensation. Even without explicit use of gauge fixing, we can define the maximal abelian projection by introducing a "gluonic Higgs field" φ(x), whose hedgehog singularities lead to monopoles. Prom infrared abelian dominance and infrared monopole condensation, infrared QCD is describable with the dual Ginzburg-Landau theory. In relation to the color-flux-tube picture for baryons, we study the three-quark (3Q) ground-state potential V_(3Q) in SU(3)_c lattice QCD at the quenched level, with the smearing technique for enhancement of the ground-state component. With accuracy better than a few %, V_(3Q) is well described by a sum of the two-body Coulomb part and the three-body linear confinement part σ_(3Q)L_(min), where L_(min) denotes the minimal value of the total length of the color flux tube linking the three quarks. Comparing with the Q-Q potential, we find a universal feature of the string tension as σ_(3Q) approx= σ_(QQ) and the OGE result for the Coulomb coefficient as A_(3Q) approx= 1/2A_(QQ).