Four variations on Theoretical Physics

Probably, the highest appraisal received by the work of Ettore Majoranawas expressed by the Nobel Prize Enrico Fermi in several occasions [1], butsuch opinions could appear as overstatements or unjustified (especially be-cause they are expressed by a great physicist as Fermi), when compared withthe spare (known) Majorana’s scientific production, just 9 published papers.However, today the name of Majorana is largely known to the nuclear andsubnuclear physicist’s community: Majorana neutrino, Majorana-Heisenbergexchange forces, and so on are, in fact, widely used concepts.In this paper, we focus on the less-known (or completely unknown) workby this scientist, aimed to shed some light on the peculiar abilities of Ma-jorana that were well recognized by Fermi and his coworkers. The wideunpublished scientific production by Majorana is testified by a large amountof papers [2], almost all deposited at the Domus Galilaeana in Pisa; thoseknown, in Italian, as “Volumetti” has been recently collected and translatedin a book [3], and we refer the interested reader to this book for further study.Here we have chosen to discuss only four topics dealt with by Majoranain different areas of Physics, just to give a sample of his very deep intuitionsand skilfulness, together with the relevance of the results obtained.1