Density Dependence of the Mass and Decay Constant of Pion in Nuclear Matter in the Dyson--Schwinger Equation Approach of QCD

With the Dyson--Schwinger equation formalism at finite chemical potential, we study the density dependence of the mass and decay constant of pion in nuclear matter. The calculated results indicate that both the mass and the decay constant remain almost constant at small chemical potential. As the chemical potential gets quite large, the decay constant increases and the mass decreases with the increasing of the chemical potential, and both of them vanish suddenly as a critical value is reached.