Casimir repulsion in sphere-plate geometry

The electromagnetic vacuum energy is considered in the presence of a perfectly conducting plane and a ball with dielectric permittivity epsilon and magnetic permeability mu, mu not equal 1. The attention is focused on the Casimir repulsion in this system caused by the magnetic permeability of the sphere. In the case of a perfectly permeable sphere, mu = infinity, the vacuum energy is estimated numerically. The short- and long-distance asymptotes corresponding to the repulsive force and respective low-temperature corrections and high-temperature limits are found for a wide range of mu. The constraints on the Casimir repulsion in this system are discussed. DOI: 10.1103/PhysRevD.87.085031