The Casimir effect in a wormhole spacetime

We consider the Casimir effect for a quantized massive scalar field with non-conformal coupling ξ in a wormhole spacetime whose throat is surrounded by a spherical shell. In the framework of the zeta-regularization approach we calculate the zero-point energy of the scalar field. We find that depending on values of the coupling ξ, a mass of field m and/or the throat's radius a, the Casimir force may be both attractive and repulsive, and even equals zero.