REAL-TIME FINITE-TEMPERATURE GREEN-FUNCTIONS FOR NONUNIFORM NONEQUILIBRIUM MEDIA

A nonequilibrium generating functional for Green functions and finite-temperature diagrams for a nonuniform nonstationary scalar field are constructed as an expansion in powers of the temperature gradients. It is shown that time arguments of operators in the nonequilibrium case may be defined on the same contour as in the equilibrium case. The expressions for propagators and vertices up to first-order corrections in temperature gradients are given. It is shown that they are free from pinch singularities. The renormalization of mass and coupling constant is the same as at zero temperature only if the energy-momentum tensor is chosen in an improved form. The change of the local phase transition temperature in a spontaneously broken scalar field theory due to gradients and time derivatives of temperature is calculated. The free energy density in the low and high temperature limits is computed. © 1992.