Pairwise Summation Approximation of Casimir energy from first principles

TL;DR

This paper derives the Pairwise Summation Approximation (PSA) of Casimir energy from first principles, showing its validity at large distances and extending it to the full electromagnetic case, providing a new theoretical insight.

Contribution

It introduces a first-principles derivation of the PSA for Casimir energy, including the electromagnetic coupling, for the first time.

Findings

PSA is an asymptotic approximation valid at large distances.

PSA has been extended to include electromagnetic coupling.

Complete PSA limit for the full electromagnetic Casimir energy has been achieved.

Abstract

We obtain the Pairwise Summation Approximation (PSA) of the Casimir energy from first principles in the soft dielectric and soft diamagnetic limit, so we find that the PSA is an asymptotic approximation of the Casimir energy valid for large distances between the objects. We also obtain the PSA for the electromagnetic coupling part of the Casimir energy, so we are able to complete the PSA limit at a first time for the complete electromagnetic field.