Ettore Majorana

The Majorana equation, Majorana fermions, and Microsoft's device attempting to create topological qubits, Majorana 1, are named after him. In 2006, the Majorana Prize was established in his memory.

In 1938, Enrico Fermi was quoted as saying about Majorana: "There are several categories of scientists in the world; those of second or third rank do their best but never get very far. Then there is the first rank, those who make important discoveries, fundamental to scientific progress. But then there are the geniuses, like Galilei and Newton. Majorana was one of these."

He disappeared under mysterious circumstances after purchasing a ticket to travel by ship from Palermo to Naples. An investigation concluded in 2015 found evidence suggesting Majorana lived in Valencia, Venezuela, between 1955 and 1959. The case was officially closed with the conclusion that he had emigrated.

Life and work

Early and personal life

Majorana was born in Catania, Sicily. Majorana's uncle Quirino Majorana was also a physicist. Mathematically gifted, Majorana began his university studies in engineering in 1923, but switched to physics in 1928 at the urging of Emilio Segrè. He was very young when he joined Enrico Fermi's team in Rome as one of the "Via Panisperna boys", who took their name from the street address of their laboratory.

Majorana was an enthusiastic and devout Catholic.

First published academic papers

Majorana's first papers dealt with problems in atomic spectroscopy. His first paper, published in 1928, was written when he was an undergraduate and it was coauthored by Giovanni Gentile, Jr., a junior professor at the Institute of Physics in Rome. This work was an early quantitative application to atomic spectroscopy of Fermi's statistical model of atomic structure (now known as the Thomas–Fermi model, due to its contemporaneous description by Llewellyn Thomas).

In this paper, Majorana and Gentile performed first-principles calculations within the context of this model that gave a good account of experimentally-observed core electron energies of gadolinium and uranium, and of the fine structure splitting of caesium lines observed in optical spectra. In 1931, Majorana published the first paper on the phenomenon of autoionization in atomic spectra, which he called "spontaneous ionization"; an independent paper in the same year, published by Allen Shenstone of Princeton University, called it "auto-ionization", a name first used by Pierre Auger. This name, without the hyphen, has since become the conventional term for the phenomenon.

Majorana earned his Laurea in physics at the University of Rome La Sapienza in 1929. In 1932, he published a paper in the field of atomic spectroscopy concerning the behaviour of aligned atoms in time-varying magnetic fields. This problem, also studied by I. I. Rabi and others, led to development of an important sub-branch of atomic physics, that of radio-frequency spectroscopy. In the same year, Majorana published his paper on a relativistic theory of particles with arbitrary intrinsic momentum, in which he developed and applied infinite dimensional representations of the Lorentz group, and gave a theoretical basis for the mass spectrum of elementary particles. Like most of Majorana's papers, written in Italian, it languished in relative obscurity for several decades.

Experiments in 1932 by Irène Joliot-Curie and Frédéric Joliot showed the existence of an unknown particle that they suggested was a gamma ray. Majorana was the first to interpret correctly the experiment as requiring a new particle that had a neutral charge and a mass about the same as the proton; this particle is the neutron. Fermi advised him to write an article on the topic, but Majorana did not. James Chadwick proved the existence of the neutron by experiment later that year, and he was awarded the Nobel Prize for this discovery.

Majorana was known for not seeking credit for his discoveries, considering his work to be trivial. He wrote only nine papers in his lifetime.

Work with Heisenberg and Bohr

"At Fermi's urging, Majorana left Italy early in 1933 on a grant from the National Research Council. In Leipzig, Germany, he met Werner Heisenberg. In letters he subsequently wrote to Heisenberg, Majorana revealed that he had found in him, not only a scientific colleague, but a warm personal friend."

The Nazis had come to power in Germany as Majorana arrived there. He worked on a theory of the nucleus (published in German in 1933) which, in its treatment of exchange forces, represented a further development of Heisenberg's theory of the nucleus. Majorana also travelled to Copenhagen that year, where he worked with Niels Bohr, another Nobel Prize winner, and a friend and mentor of Heisenberg.

Political and ideological affiliations

Majorana was a member of the National Fascist Party (PNF), having joined on 31 July 1933. A month before disappearing, he wrote to his mother:

Today they will give me a better room, on via Depretis, from which I will be able to see, three months from now, Hitler pass by!

In another letter from Copenhagen to a member of Enrico Fermi's group Giovannino, he expressed support for Nazi policies and applauded Hitler's sacking of civil servants from local administrations and his replacement of them with nationalist cadre:

Hitler seems to know what he is doing. Probably the fascist example is of great help to him.

Majorana recommended to his mother, who wanted to learn German, a newspaper that "became fascist overnight after Hitler imposed changes in the editorial board".

Majorana endorsed antisemitic views by suggesting that discrimination against Jews was justified as a means to "repress a socially harmful mentality," implying that such measures were necessary to make room for a new generation. Majorana wrote:

In truth, not only the Jews, but even the communists and in general all adversaries of the regime are being eliminated from social life. In sum, what the government is doing comes in response to an historical necessity: that of making room for a new generation that risks being suffocated by economic stagnation.

Professor of Italian Joseph Francese contends that Leonardo Sciascia's narrative regarding Majorana's disappearance is primarily a literary construct designed to stimulate debate over the ethical responsibilities of scientists rather than an accurate historical account. According to Francese, the story of Majorana's disappearance was a later dramatization by Sciascia that obscured the fact that Majorana was actively involved in the nationalist politics of the 1930s.

Illness and isolation

"In the fall of 1933, Majorana returned to Rome in poor health, having developed acute gastritis in Germany and apparently suffering from nervous exhaustion. Put on a strict diet, he grew reclusive and became harsh in his dealings with his family. To his mother, with whom he had previously shared a warm relationship, he had written from Germany that he would not accompany her on their customary summer vacation by the sea. Appearing at the institute less frequently, he soon was scarcely leaving his home; the promising young physicist had become a hermit. For nearly four years he shut himself off from friends and stopped publishing."

Final work

During these years, in which he published few articles, Majorana wrote many small works on geophysics, electrical engineering, mathematics, and relativity. These unpublished papers, preserved in Domus Galileiana in Pisa, have been edited by Erasmo Recami and Salvatore Esposito.

Majorana's last-published paper, in 1937, was an elaboration of a symmetrical theory of electrons and positrons. This corresponds to modern field theory methods, and predicts that the particles that, as the electron, have electric charge and obey Dirac equations, should be fermions and have distinct antiparticles. Particles without charge, such as the neutrinos, could coincide with their own antiparticles, and are called Majorana fermions. There has been speculation that at least some part of the "missing mass" in the universe, which cannot be detected except by inference from its gravitational influence, may be composed of Majorana particles.

In 1938, at the age of 31, he became a full professor of theoretical physics at the University of Naples independently of the competition rules, without needing to take an examination because of his "high fame of singular expertise reached in the field of theoretical physics".