Casimir force on amplifying bodies

TL;DR

This paper develops a unified macroscopic QED approach to analyze the Casimir force on amplifying bodies, showing it can be expressed as a sum over Casimir--Polder forces on excited atoms, with a specific example calculation.

Contribution

It introduces a method to include amplification in Casimir force calculations within macroscopic QED, extending the understanding of forces on amplifying systems.

Findings

Force on amplifying objects can be expressed as a sum over Casimir--Polder forces.

Resonant force between excited atomic gas and a mirror is calculated.

The approach unifies absorption and amplification effects in Casimir force analysis.

Abstract

Based on a unified approach to macroscopic QED that allows for the inclusion of amplification in a limited space and frequency range, we study the Casimir force as a Lorentz force on an arbitrary partially amplifying system of linearly locally responding (isotropic) magnetoelectric bodies. We demonstrate that the force on a weakly polarisable/magnetisable amplifying object in the presence of a purely absorbing environment can be expressed as a sum over the Casimir--Polder forces on the excited atoms inside the body. As an example, the resonant force between a plate consisting of a dilute gas of excited atoms and a perfect mirror is calculated.