We study the temperature dependence of the effective bag constant, the mass,
and the radius of a nucleon in the formalism of the simple global color
symmetry model in the Dyson-Schwinger equation approach of QCD with a
Gaussian-type effective gluon propagator. We obtain that, as the temperature is
lower than a critical value, the effective bag constant and the mass decrease
and the radius increases with the temperature increasing. As the critical
temperature is reached, the effective bag constant and the mass vanish and the
radius tends to infinity. At the same time, the chiral quark condensate
disappears. These phenomena indicate that the deconfinement and the chiral
symmetry restoration phase transitions can take place at high temperature. The
dependence of the critical temperature on the interaction strength parameter in
the effective gluon propagator of the approach is given.Comment: 10 pages, 9 figure
