Thermal Casimir Effect in the Plane-Sphere Geometry

TL;DR

This paper investigates the thermal Casimir effect in plane-sphere geometry, revealing how material models and geometry influence force magnitude, including repulsive thermal photon contributions and negative entropy at certain distances.

Contribution

It provides exact numerical and analytical analysis of the thermal Casimir force in plane-sphere geometry, highlighting geometry's impact on force ratios and thermal photon effects.

Findings

The force ratio decreases from 2 to 1.5 in plane-sphere geometry.

Thermal photons can contribute repulsively to the Casimir force.

Negative entropy values are observed at intermediate distances.

Abstract

The thermal Casimir force between two metallic plates is known to depend on the description of material properties. For large separations the dissipative Drude model leads to a force a factor of 2 smaller than the lossless plasma model. Here we show that the plane-sphere geometry, in which current experiment are performed, decreases this ratio to a factor of 3/2, as revealed by exact numerical and large distance analytical calculations. For perfect reflectors, we find a repulsive contribution of thermal photons to the force and negative entropy values at intermediate distances.