  (2+1) dimensional gravity is equivalent to an exactly soluble non-Abelian
Chern-Simons gauge field theory (E Witten 1988). Regarding this as the
topological phase of quantum gravity in (2+1)d, we suggest a topological
symmetry breaking by introducing a mass term for the gauge fields, which
carries a space-time metric and local dynamical degrees of freedom. We consider
the finite temperature behavior of the symmetry broken phase, and claim a
restoration of the topological invariance at some critical temperature. The
phase transition is shown of the zeroth order.
