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ENRICO FERMI AND ETTORE MAJORANA: SO STRONG, SO DIFFERENT Francesco Guerra, (Department of Physics, Sapienza University of Rome and INFN, Rome Section ) Nadia Robotti, (Department of Physics, University of Genova, Italy ) Abstract By exploiting primary sources we will analyze some of the aspects of the very complex relationship between Enrico Fermi and Ettore Majorana, from 1927 (first contacts of Majorana with the Institute of Physics of Rome, and with Fermi) until 1938 (disappearance of Majorana). The relationship between Fermi and Majorana can not be interpreted in the simple scheme Teacher-Student. Majorana, indeed, played an important role in the development of research in Rome in the field of the statistical model for the atom and in nuclear physics. Our current research concerns the development of Nuclear Physics in Italy in the Thirties of XXth Century, and is based exclusively on primary sources (archive documents, scientific literature printed on the journals of the time, and so on). In this framework, we will try to outline some aspects of the complex topic concerning the relationship between Enrico Fermi and Ettore Majorana. Of course, this paper will touch only some of the most important issues. For convenience, our exposure will be connected to a periodization of Majorana scientific activity, which we used in previous works. One of our important results is the reassessment of the role played by Majorana for the decisive orientation of the research in Rome (statistical model of the atom, nuclear physics). This role is obscured in discussions which place emphasis on the (alleged) "genius" of Majorana, usually associated with his (alleged) "lack of common sense". Perhaps we could summarize, in a very concise and expressive manner, the nature of the relationship between Majorana and Fermi, and in general the Physical Institute of Rome, presenting these two important documents stored in the “Archive Heisenberg”, at the Max Planck Institute of Munich. On November 9, 1933, the Sweden Academy of Sciences announced that the Nobel Prize for Physics for the year 1932 was awarded to Werner Heisenberg. Immediately, all the exponents of world culture send their congratulations, in various forms. Heisenberg stored in a folder of his personal archive all received messages. Among them, a telegram by the Deutsche Reichspost, from Rome and dated 11-XI-33 (Fig.1) written in a very cold and formal style, in German: “MOST CORDIAL CONGRATULATIONS CORBINO FERMI RASETTI SEGRE AMALDI WICK” We note the order of signing according to the close rank of academic seniority at the Institute of Physics in Rome (Orso Mario Corbino, Enrico Fermi, Franco Rasetti, Emilio Segre’, Edoardo Amaldi, Gian Carlo Wick). Fig.1. “Roma” Congratulations (Heisenberg Archive, Max Planck Institut, Munchen) Ettore Majorana (who is in Rome) is not included in the list, not even at the very last place. But Majorana, who had left Leipzig in early August, sends his "Gratulationen", according to his style. He sends a small personal business card, dated Rome, 11.11.1933 (Fig. 2) with the title "Dr." canceled by hand, written in a poignant Italian. It is a very intense letter. “Dear Professor, Let me (if you have not forgotten me !) allow to express my greetings on the occasion of the new formal recognition of your prodigious work. With deep admiration Yours Ettore Majorana”. Fig.2 Majorana Congratulations (Heisenberg Archive, Max Planck Institut, Munchen) 1.The formation years until the doctoral degree (1929) The scientific research activities of Ettore Majorana develop immediately at the highest international standard, while it is still a university student at the School of Engineering, in 1928. His first research concern the applications, the improvement, and the extension of the statistical model for atoms, introduced by Enrico Fermi at the end of 1927, only few months before! (Fermi 1927). This model is now known as the “Thomas-Fermi model”. As it is well known, Enrico Fermi was called as full Professor in Theoretical Physics in Rome in 1927, through the effort of the Director of the Institute Orso Mario Corbino to develop advanced modern physics in Rome. The main Fermi achievements concern: the so called “Fermi-Dirac statistics”, the statistical model for the atom, the theory of weak interactions, the discovery of the neutron-induced radioactivity, the effect of the slowing down of neutrons, (after the 1938 Nobel Prize and the emigration to the U.S.A.) the atomic pile, the Manhattan project, the elementary particle physics, the computers, and so on). The first involvement of Majorana on the statistical model subject is a paper in collaboration with his friend Giovanni Gentile jr., published on the Proceedings of the “Accademia dei Lincei”, presented on July 24th, 1928 by Orso Mario Corbino. (Gentile, Majorana 1928). They calculate the splitting of the spectroscopic energy levels due to the hypothesis of the spinning electrons as recently developed by Dirac. It is a well received paper, developed completely in the frame of Fermi aproach. Then Majorana continues his research alone, with full autonomy and effectiveness. He proposes an improvement of the model (he changes the expression of the effective potential acting on the optical electron) and includes also positive ions (it is the first treatment made). Some of the results are communicated to the XXII General Meeting of the Italian Society of Physics (Rome, 28-30 December 1928). At that time Majorana was still a student, and had recently officially moved from Engineering to Physics. The communication was presented by Majorana in front of an audience of famous Physicists and Mathematicians, as O.M. Corbino, T. Levi Civita, V. Volterra, G. Polvani, Q. Majorana, A. Carrelli, E. Fermi, (he was not a timid person!) This communication is regularly published on “Il Nuovo Cimento”, the Journal of the Society (Majorana 1929), but it has been never mentioned in any scientific paper, nor by any of the many historians who wrote on the life and activity of Majorana. Historical analysis is in a paper by F.G. and N.R. (Guerra, Robotti 2008). The acknowledgements are very interesting: “The A. thanks Professor Fermi, for the advice and suggestions around new applications of this statistical method that has thrown much light on the atomic physics, and whose fertility, appears far from exhausted, still waiting to be ventured into investigation of fields of larger scope and more full of promise. " The results contained in Majorana notebooks (at Domus Galiaeana in Pisa) and in the communication show that Majorana reached a fully developed scientific personality, completely independent from Fermi. However, Majorana does not publish the results announced in the communication, nor the other results contained in his notebooks. An enlarged paper on the subject would have given a complete representation of the statistical model, his applications and extensions. As a matter of fact, Majorana does not work anymore on these subjects. Fermi convinces himself of Majorana improvement only in late 1933 and puts it at the basis of the monumental conclusive paper of the Rome School, co-authored by Fermi and Amaldi in 1934, without any reference to Majorana (Fermi, Amaldi 1934). It is amazing to note that all formulas of the general Fermi-Amaldi paper (1934) coincide with the corresponding formulas of Majorana communication (1929). Majorana earns his doctoral degree in Physics (July 6th, 1929) with a Thesis on Nuclear Physics (with the title "On the mechanics of radioactive nuclei"). Fermi is the supervisor. Majorana Thesis is the first work on Nuclear Physics in Rome, and also in Italy. Majorana gives a rigorous justification to Gamow model of alpha decay based on the quantum tunnel effect. Anyway, even if original and internationally competitive results are achieved, they are not published. 2. From the doctoral degree to the private professorship (1929-1932) After graduating a short period of silence: he does not deal at the moment with Nuclear Physics, but maturates new lines of research (Atomic Physics, Molecular Physics and Elementary Particle Physics) in complete autonomy from Fermi ( which deals with Quantum Electrodynamics and Hyperfine Structure of Atomic Spectra). Then follows a very intense activity, oriented toward the “Il Nuovo Cimento”. Between the end of 1930 and January 1931 there are ready two papers (Majorana 1931 A, B) on the quantum explanation of the chemical bond (formation of Helium molecular ion and Hydrogen molecule). The first is presented by Corbino at Accademia dei Lincei, December 7, 1930: "I warmly thank Professor Enrico Fermi, who gave me precious advice and aid” . Majorana becomes a pioneer in Theoretical Chemistry (this discipline will develop in Italy only in the 50s of XX Century). In 1931, other two papers will be published, this time in Spectroscopy. Majorana provides a theoretical interpretation of two new lines of Helium, recently discovered (Majorana 1931 C) and some triplets of calcium (Majorana 1931 D). These two works are appreciated as elegant examples of applications of group theory. In reality they have a direct physical interest: for the first time the role of the phenomenon of self-ionization of atoms is recognized in Spectroscopy. Follows a very important work (published in 1932): "Atoms oriented in magnetic field" (Majorana 1932 A). In this paper, he proposes an optimal arrangement of the magnetic field to show the sudden flip in the spatial quantization of the spin of atoms, and other related
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