J.D. Jackson passed away on May 20, 2016. His book “Classical Electrodynamics” is a classic textbook. Like all physicists of my generation I have spent hundreds of hours studying classical electrodynamics from his book.
The paper by J.D. Jackson and L.B. Okun on the history of gauge invariance is an important document. This paper is also a significant document for reminding us about the contributions of L.V. Lorenz and H.A. Lorentz.
Most of us are in awe of H.A. Lorentz because of his contributions to the electromagnetic theory and him being the harbinger of the Special Relativity theory. He received the Nobel Prize in Physics in 1902. Einstein had a great respect for H.A. Lorentz.
In their paper, J.D. Jackson and L.B. Okun remind us that before H.A. Lorentz there was another pioneer by the name of L.V. Lorenz.
“The beginning of the last third of the 19th century saw Maxwell’s masterly creation of the correct complete set of equations governing electromagnetism, unfortunately expressed in a way that many found difficult to understand (Maxwell, 1865). Immediately after, the Danish physicist Ludvig V. Lorenz, apparently independently of Maxwell, brilliantly developed the same basic equations and conclusions about the kinship of light and the electromagnetism of charges and currents (Lorenz, 1867b). From the point of view of gauge invariance, Lorenz’s contributions are most significant. He introduced the so-called retarded scalar and vector potentials and showed that they satisfied the relation almost universally known as the Lorentz condition, though he preceded the Dutch physicist H. A. Lorentz by more that 25 years.”
“By the turn of the century, thanks to, among others, Clausius, Heaviside, Hertz, and Lorentz, who invented what we now call microscopic electromagnetism, with localized charges in motion forming currents, the formal structure of electromagnetic theory, the role of the potentials, the interaction with charged particles, the concept of gauge transformations, not yet known by that name, were in place. Lorentz’s encyclopedia articles (Lorentz, 1904a, b) and his book (Lorentz, 1909) established him as an authority in classical electrodynamics, to the exclusion of earlier contributors such as Lorenz.”
I addition to the photograph above I would like to remind you that H.A. Lorentz is the distinguished gentleman in the center of the photograph below (1927 Solvay Conference)
This is a colorized photo. The original photograph looks like this: