Perturbation of the Electromagnetic Vacuum by Atoms and Molecules

One of the most surprising facets of the world-view presented by quantum field theory is the nature and the potency of the vacuum. To the layman it is quite unexpected that the state consisting of no particles is non-trivial and efficacious. In this lecture these circumstances are examined in the context of the electromagnetic field as an introduction to the salient concern of the conference. Starting with elementary quantum mechanics we build up the structures required to (i) obtain, and (ii) use the wave functional for the electromagnetic vacuum. We demonstrate some physical consequences of vacuum fluctuations in such diverse topics as colloidal stability and the Lamb shift. Involved in these calculations are perturbations on the vacuum due to atoms/molecules. Changes in the vacuum due to confinement are discussed in a non-perturbative fashion. A re-look at Jaynes' neoclassical electrodynamics will be mentioned. The lecture will finish with an introduction to the Heisenberg form for the electromagnetic fields in the neighbourhood of molecules.