Asymptotic Retarded van der Waals Forces Derived from Classical Electrodynamics with Classical Electromagnetic Zero-Point Radiation

The large-separation asymptotic forms for the retarded van der Waals forces between a neutral polarizable particle and a conducting wall, and between two neutral polarizable particles, are derived from classical electromagnetism under the assumption that the universe contains fluctuating classical electromagnetic radiation with a Lorentz-invariant spectrum (classical electromagnetic zero-point radiation). These forces were first calculated by Casimir and Polder from quantum electrodynamics, and then recalculated by Casimir using ideas of zero-point energy. The present calculation involves purely classical electromagnetic attractions between classical oscillators driven by fluctuating classical radiation.