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FIZIKA A 14 (2005) 1 , 29-46
 
MEDIUM-ASSISTED VACUUM FORCE
M. S. TOMAŠ
Ruđer Bošković Institute, P.O.B. 180, 10 002 Zagreb, Croatia
E-mail address: tomas@thphys.irb.hr
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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