Volume 82, Number 5, June 2008
Article Number 53001
Number of page(s) 6
Section Atomic, Molecular and Optical Physics
Published online 28 May 2008
EPL, 82 (2008) 53001
DOI: 10.1209/0295-5075/82/53001

Frequency spectrum of the Casimir force: Interpretation and a paradox

S. A. Ellingsen

Department of Energy and Process Engineering, Norwegian University of Science and Technology N-7491 Trondheim, Norway

received 4 January 2008; accepted in final form 16 April 2008; published June 2008
published online 28 May 2008

The frequency spectrum of the Casimir force between two plates separated by vacuum as it appears in the Lifshitz formalism is reexamined and generalised as compared to previous works to allow for imperfectly reflecting plates. As previously reported by Ford (Phys. Rev. A, 48 (1993) 2962), the highly oscillatory nature of the frequency dependence of the Casimir force points to possibilities for very large and indeed negative Casimir forces if the frequency-dependent dielectric response, $\epsilon(\omega)$, of the materials could be tuned. A paradox occurs, however, because an alternative calculation of the effect of a perturbation of $\epsilon(\omega)$ involving a Wick rotation to imaginary frequencies indicates only very modest effects. A recent experiment appears to convincingly rule out the reality of Ford's optimistic predictions, although given the enormous technological promise of such frequency effects, further theoretical and experimental study is called for.

34.20.-b - Interatomic and intermolecular potentials and forces, potential energy surfaces for collisions.
12.20.-m - Quantum electrodynamics.
03.70.+k - Theory of quantized fields.

© EPLA 2008