  We study topologically massive (2+1)-dimensional gravity with a negative
cosmological constant. The masses of the linearized curvature excitations about
AdS_3 backgrounds are not only shifted from their flat background values but,
more surprisingly, split according to chirality. For all finite values of the
topological mass, we find a single bulk degree of freedom with positive energy,
and exhibit a complete set of normalizable, finite-energy wave packet
solutions. This model can also be written as a sum of two higher-derivative
SL(2,R) Chern--Simons theories, weighted by the central charges of the boundary
conformal field theory. At two particular "critical" values of the couplings,
one of these central charges vanishes, and linearized topologically massive
gravity becomes equivalent to topologically massive electromagnetism; however,
the physics of the bulk wave packets remains unaltered here.
