  Contribution of the quark back reaction to the deconfinement phase transition
is studied in the thermodynamical potential of the gluonic sector which
consists of the gluon and ghost propagators calculated in the lattice QCD
simulations. Starting from QCD thermodynamic potential, we define the gluonic
potential in the leading-order of the 2PI formalism, which can describe the
deconfinement phase transition. Then the gluonic potential can be written by
using the microscopic characters; the gluon and ghost propagators in Landau
gauge fixing. To include effects of the quark back reaction, we calculate the
gluon propagators in lattice QCD simulations with two-flavored dynamical
quarks. Fitting the lattice data by the Gribov-Stingl form and investigating
the phase transition of the gluonic potential, we find that enhancement of the
quark back reaction reduces the critical temperature of the deconfinement phase
transition.
