  We put forward a formalism to calculate the relativistic particle - hole and
delta - hole excitation polarization insertion for pion propagator by using the
particle - hole - antiparticle representation of nucleon and delta propagators
in nuclear matter. The real and the imaginary part of the polarization
insertion and the dispersion relation for pion propagator are calculated
numerically. We find that the short range correlation enhances the delta - hole
excitation but suppresses the particle - hole excitation, it also suppresses
the pion condensation. We find that the effect of the short range correlation
on the pion dispersion relation depends very much on the form of the short
range correlation and the parameters involved.
