Casimir Surface Force on a Dilute Dielectric Ball
Abstract
The Casimir surface force density F on a dielectric dilute spherical ball of radius a, surrounded by a vacuum, is calculated at zero temperature. We treat (n-1) (n being the refractive index) as a small parameter. The dispersive properties of the material are taken into account by adopting a simple dispersion relation, involving a sharp high frequency cutoff at omega = omega0. For a nondispersive medium there appears (after regularization) a finite, physical, force Fnondisp which is repulsive. By means of a uniform asymptotic expansion of the Riccati-Bessel functions we calculate Fnondisp up to the fourth order in 1/nu. For a dispersive medium the main part of the force Fdisp is also repulsive. The dominant term in Fdisp is proportional to (n-1)2omega03/a, and will under usual physical conditions outweigh Fnondisp by several orders of magnitude.
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