Exact Electromagnetic Casimir Energy of a Disk Opposite a Plane

Abstract

Building on work of Meixner [J. Meixner, Z. Naturforschung 3a, 506 (1948)], we show how to compute the exact scattering amplitude (or $T$-matrix) for electromagnetic scattering from a perfectly conducting disk. This calculation is a rare example of a non-diagonal $T$-matrix that can nonetheless be obtained in a semi-analytic form. We then use this result to compute the electromagnetic Casimir interaction energy for a disk opposite a plane, for arbitrary orientation angle of the disk, for separations greater than the disk radius. We find that the proximity force approximation (PFA) significantly overestimates the Casimir energy, both in the case of the ordinary PFA, which applies when the disk is parallel to the plane, and the "edge PFA," which applies when the disk is perpendicular to the plane.

13 pages, 4 .eps figures; v2: minor clarifications, expanded discussion in Sec. 4, version accepted for publication in PRA

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Cited by in corpus (2)

• Unifying Theory for Casimir Forces: Bulk and Surface Formulations
• Something Can Come of Nothing: Surface Approaches to Quantum Fluctuations and the Casimir Force