FIZIKA A 14 (2005) 1 , 29-46

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Ruđer Bošković Institute, P.O.B. 180, 10 002 Zagreb, Croatia
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Dedicated to the memory of Professor Vladimir Šips

Received 7 January 2005;  revised manuscript received    2 May 2005
Accepted 13 June 2005   Online 21 October 2005

We discuss some implications of a very recently obtained result for the force on a slab in a planar cavity based on the calculation of the vacuum Lorentz force [C. Raabe and D.-G. Welsch, Phys. Rev. A 71 (2005) 013814]. We demonstrate that, according to this formula, the total force on the slab consists of a medium-screened Casimir force and, in addition to it, a medium-assisted force. The sign of of the medium-assisted force is determined solely by the properties of the cavity mirrors. In the Lifshitz configuration, this force is proportional to 1/d at small distances and is very small compared with the corresponding van der Waals force. At large distances, however, it is proportional to 1/d4 and comparable with the Casimir force, especially for denser media. The exponents in these power laws decrease by 1 in the case of a thin slab. The formula for the medium-assisted force also describes the force on a layer of the cavity medium, which has similar properties. For dilute media, it implies an atom-mirror interaction of the Coulomb type at small and of the Casimir-Polder type at large atom-mirror distances. For a perfectly reflecting mirror, the latter force is effectively only three-times smaller than the Casimir-Polder force.

PACS numbers: 12.20.Ds, 42.50.Nn, 42.60.Da
UDC 535.14, 535.417.2

Keywords: Casimir effect, Lorentz-force approach, medium-assisted force

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