Casimir effect for a D-dimensional sphere

The Casimir force on a D-dimensional sphere due to the confinement of a massless scalar field is computed as a function of D, where D is a continuous variable that ranges from -\infty to \infty. The dependence of the force on the dimension is obtained using a simple and straightforward Green's function technique. We find that the Casimir force vanishes as D\to +\infty (D non-even integer) and also vanishes when D is a negative even integer. The force has simple poles at positive even integer values of D