Analytical solution of the Sommerfeld-Page equation

Abstract

The Sommerfeld-Page equation describes the non-relativistic dynamics of a classical electron modeled by a sphere of finite size with a uniform surface charge density. The Sommerfeld-Page equation is a delay differential equation, and almost no exact results on solutions of this equation was known. However, the progress has been made, especially in the last few years, and recently an analytical solution was found for an almost identical delay differential equation, which arose in the context of mathematical modeling of COVID-19 epidemics. Inspired by this research, we offer a pedagogical exposition of how one can find an analytical solution of the Sommerfeld-Page equation.