  The one-loop effective energy density of a pure SU(2) Yang-Mills theory in
the Savvidy background, at finite temperature and chemical potential is
examined with emphasis on the unstable modes. After identifying the stable and
unstable modes, the stable modes are treated in the quadratic approximation.
For the unstable modes, the full expansion including the cubic and the quartic
terms in the fluctuations is used. The functional integrals for the unstable
modes are evaluated and added to the results for the stable modes. The
resulting energy density is found to be {\it{real}}, coinciding with the real
part of the energy density in the quadratic approximation of earlier study.
There is now {\it{no imaginary part.}} Numerical results are presented for the
variation of the energy density with temperature for various choices of the
chemical potential.
