  We study infrared abelian dominance and the dual Higgs mechanism in the
maximally abelian (MA) gauge using the lattice QCD Monte Carlo simulation. In
the MA gauge, the off-diagonal gluon phase tends to be random, and the
off-diagonal gluon $A_\mu^\pm$ acquires the effective mass as $M_{\rm off}
\simeq$ 1.2 GeV. From the monopole current in the MA gauge, we extract the dual
gluon field $B_\mu$ and estimate the dual gluon mass as $m_B \simeq $ 0.5 GeV.
The QCD-monopole structure is also investigated in terms of off-diagonal
gluons. From the lattice QCD in the MA gauge, the dual Ginzburg-Landau (DGL)
theory can be constructed as a realistic infrared effective theory based on
QCD.

High Energy Physics - Lattice