  The dielectric function of nuclear matter excited by $\rho NN$ tensor
coupling has been studied in the framework of Finite temperature field theory.
The induced current mechanism has been introduced to explain the three extrema
on the dielectric function curve, of which one is in the space-like region and
the other two are in the time-like region. It points out that the tensor
coupling contributes much more large amplitude than the vector coupling and
plays a more important role on the time-like region compared with its effect on
the space-like region.
