  We show that if one chooses the Einstein Static Universe as the metric on the
conformal boundary of Kerr-AdS spacetime, then the Casimir energy of the
boundary conformal field theory can easily be determined. The result is
independent of the rotation parameters, and the total boundary energy then
straightforwardly obeys the first law of thermodynamics. Other choices for the
metric on the conformal boundary will give different, more complicated,
results. As an application, we calculate the Casimir energy for free self-dual
tensor multiplets in six dimensions, and compare it with that of the
seven-dimensional supergravity dual. They differ by a factor of 5/4.
