Comments on a Paper by Majorana Concerning Elementary Particles ∗

An early paper (1932) by Majorana, that has received but scant attention, is reexamined in light of later developments. This pioneering paper constructs a relativistically invariant theory of arbitrary spin particles, develops and utilizes infinite dimensional representations of the homogeneous Lorentz group, and provides a mass spectrum for elementary particles. The relevance of Majorana’s approach and results to later and current research is explained. Reprinted with permission from the AMERICAN JOURNAL OF PHYSICS, Volume 34, Issue 4, pp. 314-318. Copyright 1966, American Association of Physics Teachers. We reproduce here the historical D. M. Fradkin 1966 paper whose role among the physicists of high energy was decisive; since then espressions like ”Majorana mass”, ”Majorana spinors” and ”Majorana neutrino” have become usual. The paper is based upon the work Teoria di Particelle con Momento Intrinseco Arbitrario, translated by Italiam from Edoardo Amaldi. Ignazio Licata†‡ c © Electronic Journal of Theoretical Physics. All rights reserved.