Editing Ettore Majorana (section)

==Life and work==
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 [[Galileo Galilei|Galilei]] and [[Isaac Newton|Newton]]. Majorana was one of these."<ref>{{cite web |title=Ettore Majorana: genius and mystery |url=https://cerncourier.com/a/ettore-majorana-genius-and-mystery/ |website=CERN Courier |date=24 July 2006 |access-date=19 July 2021}}</ref>

Majorana was an enthusiastic and devout [[Catholic]].<ref name="Zichichi">{{cite web |last=Zichichi |first=Antonino |author-link=Antonino Zichichi |date=24 July 2006 |title=Ettore Majorana: genius and mystery |url=https://cerncourier.com/a/ettore-majorana-genius-and-mystery/ |website=CERN Courier |access-date=February 19, 2025 |quote=Majorana was an enthusiastic and devout Catholic and, moreover, he withdrew his savings from the bank a week before his disappearance.}}</ref><ref name="frontiers">{{cite web |last=Leonard |first=Mary |date=2015 |title=The Majorana mystery |url=https://frontiersmagazine.org/post-02/ |website=Frontiers Magazine |access-date=February 19, 2025 |quote=Sciascia rules this out on the grounds that Majorana was a devout Catholic.  Majorana’s family and his priest Monsignor Francesco Riccieri also rule out suicide, favouring the option of spiritual retreat.}}</ref>

===Gifted in mathematics===
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]].<ref name="digest1991">{{cite book |title=Great Mysteries of the Past |publisher=[[Reader's Digest]] Association |place=Pleasantville, New York |year=1991 |isbn=0-89577-377-5 |url-access=registration |url=https://archive.org/details/greatmysteriesof00read }}</ref>{{rp|69–72}} He was very young when he joined [[Enrico Fermi]]'s team in [[University of Rome La Sapienza|Rome]] as one of the "[[Via Panisperna boys]]", who took their name from the street address of their laboratory.<ref>{{citation |last=Sciascia |first=Leonardo |page=137 |title=The Moro Affair ; And, the Mystery of Majorana |date=1987 |publisher=Carcanet |isbn=978-0-85635-700-8 |language=en}}</ref>  

===First published academic papers===
[[File:Majorana Equazinfcomp.jpg|thumb|200px|Handwritten notes for the equation in infinite components]]
Majorana's first [[Academic paper|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 [[Cesium|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 Victor Auger|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.<ref>It is discussed in detail by {{cite journal |first=D.M. |last=in |journal=Am. J. Phys. |volume=34 |pages=314–318 |year=1966 |title=Comments on a Paper by Majorana Concerning Elementary Particles|issue=4 |doi=10.1119/1.1972947 |bibcode=1966AmJPh..34..314F |citeseerx=10.1.1.522.8279 }}</ref>

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]]. [[Enrico Fermi|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.<ref>{{cite web |url=http://cerncourier.com/cws/article/cern/29664 |title=Ettore Majorana: genius and mystery |publisher=[[CERN]] |website=CERN Courier|date=24 July 2006 }}</ref>

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."<ref name=digest1991/>{{rp|71}} 

The [[Nazi]]s had come to power in Germany as Majorana arrived there. He worked on a theory of the [[atomic nucleus|nucleus]] (published in German in 1933) which, in its treatment of [[exchange interaction|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.<ref name="Francese2010">{{cite journal |last=Francese |first=Joseph |year=2010 |title=Leonardo Sciascia and The Disappearance of Majorana |journal=Journal of Modern Italian Studies |volume=15 |issue=5 |pages=715–733 |doi=10.1080/1354571X.2010.523541}}</ref>{{rp|p=718}} A month before disappearing, he wrote to his mother:

{{bq|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!<ref name="Recami1975b">{{cite journal |last=Recami |first=Erasmo |year=1975 |title=I nuovi documenti sulla scomparsa del fisico Ettore Majorana |journal=Scientia |volume=110 |pages=577–588}}</ref>}}

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:<ref name="Recami2008"/>{{rp|p=147-157}}

{{bq|[[Hitler]] seems to know what he is doing. Probably the fascist example is of great help to him.<ref name="Gentile1988">{{cite journal |last=Gentile |first=Giovanni, Jr |year=1988 |title=Lettere inedite di Ettore Majorana a Giovanni Gentile, Jr. |journal=Giornale critico della filosofia italiana |pages=145–153}}</ref>{{rp|p=148}}}}

Majorana recommended to his mother, who wanted to learn German, a newspaper that "became fascist overnight after Hitler imposed changes in the editorial board".<ref name="Recami2008"/>{{rp|p=163}}

Majorana endorsed antisemitic views by suggesting that discrimination against Jews was justified as a means to "repress a socially harmful mentality,"<ref name="Recami2008">{{cite book |last=Recami |first=Erasmo |year=2008 |title=Il caso Majorana: epistolario, documenti, testimonianze |publisher=Di Renzo |pages=170}}</ref> implying that such measures were necessary to make room for a new generation. Majorana wrote:

{{bq|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.<ref name="Recami2008"/>{{rp|p=170}}}}

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.<ref name="Francese2010">{{cite journal |last=Francese |first=Joseph |year=2010 |title=Leonardo Sciascia and The Disappearance of Majorana |journal=Journal of Modern Italian Studies |volume=15 |issue=5 |pages=715–733 |doi=10.1080/1354571X.2010.523541}}</ref>

===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."<ref name=digest1991/>{{rp|71}}

===Final work===
During these years, in which he published few articles, Majorana wrote many small works on [[geophysics]], [[electrical engineering]], [[mathematics]], and [[Theory of relativity|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 [[electron]]s and [[positron]]s. He predicted that in the class of particles known as fermions, there should be particles that are their own antiparticles. 
Solution of the [[Majorana equation]] yields those particles, now referred to as [[Majorana fermion]]s.  There has been speculation that at least some part of the [[dark matter|"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 32, 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".<ref name="Holstein2">{{cite web |last=Holstein |first=B. |date=16 May 2008 |title=The mysterious disappearance of Ettore Majorana |url=http://astr.psc.sc.edu/CISNP/workshop/Holstein-majorana.pdf |access-date=5 April 2009 |publisher=USC Neutrino Symposium}}</ref><ref>{{Cite journal |last=Holstein |first=Barry R |date=2009-06-01 |title=The mysterious disappearance of Ettore Majorana |journal=Journal of Physics: Conference Series |volume=173 |issue=1 |pages=012019 |bibcode=2009JPhCS.173a2019H |doi=10.1088/1742-6596/173/1/012019 |issn=1742-6596 |doi-access=free}}</ref>

===Work on neutrino masses===
Majorana did prescient theoretical work on [[neutrino mass]]es, an active subject of research {{as of|2017|lc=y}}.<ref>{{cite arXiv |author=Barranco, J.|author2=Delepine, D. |author3=Napsuciale, M. |author4=Yebra, A. |title=Distinguishing Dirac and Majorana neutrinos with astrophysical fluxes |year=2017 |eprint=1704.01549 |class=hep-ph}}</ref>