Editing Murray Gell-Mann (section)

==Scientific contributions==

In 1958, Gell-Mann in collaboration with [[Richard Feynman]], in parallel with the independent team of [[E. C. George Sudarshan]] and [[Robert Marshak]], discovered the [[Chirality (physics)|chiral]] structures of the [[weak interaction]] of physics and developed the V-A theory (vector minus axial vector theory).<ref>{{Cite journal|last1=Sudarshan|first1=E. C. G.|last2=Marshak|first2=R. E.|date=June 1, 2016|title=Origin of the Universal V-A theory|journal=AIP Conference Proceedings|volume=300|issue=1|pages=110–124|doi=10.1063/1.45454|issn=0094-243X|hdl=2152/29431|s2cid=10153816 |hdl-access=free}}</ref> This work followed the experimental discovery of the [[parity (physics)|violation of parity]] by [[Chien-Shiung Wu]], as suggested theoretically by [[Yang Chen-Ning|Chen-Ning Yang]] and [[Tsung-Dao Lee]].<ref>{{cite book |last=Gleick |first=James |author-link=James Gleick |title=Genius: The Life and Science of Richard Feynman |publisher=[[Pantheon Books]] |year=1992 |isbn=0-679-40836-3|oclc=243743850}}</ref>

Gell-Mann's work in the 1950s involved recently discovered [[cosmic ray]] particles that came to be called [[kaon]]s and [[hyperon]]s. Classifying these particles led him to propose that a [[quantum number]], called [[strangeness]], would be conserved by the [[strong interaction|strong]] and the [[electromagnetic interaction|electromagnetic]] interactions, but not by the weak interaction.<ref>{{cite journal|last=Gell-Mann |first=M. |title=The Interpretation of the New Particles as Displaced Charge Multiplets |journal=[[Il Nuovo Cimento]] |year=1956 |volume=4 |number=supplement 2 |pages=848–866 |doi=10.1007/BF02748000|bibcode=1956NCim....4S.848G |s2cid=121017243 }}</ref> Another of Gell-Mann's ideas is the [[Gell-Mann–Okubo mass formula|Gell-Mann–Okubo]] formula, which was, initially, a formula based on empirical results, but was later explained by his [[quark model]].<ref>{{cite book|last=Georgi |first=Howard |author-link=Howard Georgi |title=Lie Algebras in Particle Physics: from Isospin to Unified Theories |publisher=Perseus Books |year=1999 |edition=2nd |isbn=9780738202334 |oclc=479362196}}</ref> Gell-Mann and [[Abraham Pais]] were involved in explaining this puzzling aspect of the [[neutral kaon mixing]].<ref>{{Cite web|url=https://www.britannica.com/science/quantum-mechanics-physics/Applications-of-quantum-mechanics#ref77525|title=Quantum mechanics – Applications of quantum mechanics – Decay of the Kaon|last=Squires|first=Gordon Leslie|date=July 26, 1999|website=[[Encyclopedia Britannica]]|access-date=May 27, 2019|archive-date=March 28, 2023|archive-url=https://web.archive.org/web/20230328223015/https://www.britannica.com/science/quantum-mechanics-physics/Applications-of-quantum-mechanics#ref77525|url-status=live}}</ref>

Murray Gell-Mann's fortunate encounter with mathematician [[Richard Earl Block]] at Caltech, in the fall of 1960, "enlightened" him to introduce a novel classification scheme, in 1961, for [[hadron]]s.<ref>{{cite report |last=Gell-Mann |first=M. |author-link=Murray Gell-Mann |date=March 15, 1961 |title=The Eightfold Way: A Theory of Strong Interaction Symmetry |publisher=California Inst. of Tech., Synchrotron Laboratory |location=[[Pasadena, CA]] |doi=10.2172/4008239 |id=TID-12608 |url=https://www.osti.gov/scitech/servlets/purl/4008239 |via=[[Office of Scientific and Technical Information|OSTI.GOV]] |access-date=May 25, 2019 |archive-date=March 9, 2020 |archive-url=https://web.archive.org/web/20200309114449/https://www.osti.gov/biblio/4008239 |url-status=live }}</ref><ref>{{cite AV media |title=Murray Gell-Mann - Sheldon Glashow. The SU(2) times U1 theory: Part 2 (91/200) |url=https://m.youtube.com/watch?v=UoRm30T2058&t=2m32s  |archive-url=https://ghostarchive.org/varchive/youtube/20211211/UoRm30T2058| archive-date=2021-12-11 |url-status=live|date=May 19, 2016 |publisher=[[Web of Stories]] |via=YouTube |access-date=June 3, 2019}}{{cbignore}}</ref> A similar scheme had been independently proposed by [[Yuval Ne'eman]], and has come to be explained by the quark model.<ref>{{cite journal |last=Ne'eman |first=Y. |author-link=Yuval Ne'eman |date=August 1961 |title=Derivation of Strong Interactions from a Gauge Invariance |journal=[[Nuclear Physics (journal)|Nuclear Physics]] |publisher=North-Holland Publishing Co. |location=Amsterdam |doi=10.1016/0029-5582(61)90134-1 |volume=26 |issue=2 |pages=222–229|bibcode=1961NucPh..26..222N }}</ref> Gell-Mann referred to the scheme as the ''[[Eightfold way (physics)|eightfold way]]'', because of the ''octets'' of particles in the classification (the term is a reference to the [[Noble Eightfold Path|Eightfold Path]] of [[Buddhism]]).<ref name="tnyt" /><ref name=Guardian_obit>{{cite news |url=https://www.theguardian.com/science/2019/may/26/murray-gell-mann-nobel-prize-physicist-quarks-dies |title=Murray Gell-Mann, Nobel Prize-winning physicist who named quarks, dies at 89 |newspaper=The Guardian |date=26 May 2019 |access-date=27 May 2019 |archive-date=August 4, 2020 |archive-url=https://web.archive.org/web/20200804030901/https://www.theguardian.com/science/2019/may/26/murray-gell-mann-nobel-prize-physicist-quarks-dies |url-status=live }}</ref>

Gell-Mann, along with Maurice Lévy, developed the [[sigma model]] of [[pion]]s, which describes low-energy pion interactions.<ref>{{Cite journal
 | last1=Gell-Mann | first1=M.
 | last2=Lévy | first2=M.
 | year=1960
 | title=The axial vector current in beta decay
 | journal=[[Il Nuovo Cimento]]
 | volume=16 | issue=4
 | pages=705–726
 | doi=10.1007/BF02859738
| bibcode=1960NCim...16..705G| s2cid=122945049
 }}</ref>

In 1964, Gell-Mann and, independently, [[George Zweig]] went on to postulate the existence of [[quark]]s, particles which make up the [[hadron]]s of this scheme. The name "quark" was coined by Gell-Mann, and is a reference to the novel ''[[Finnegans Wake]]'', by [[James Joyce]] ("Three quarks for Muster Mark!" book 2, episode 4). Zweig had referred to the particles as "aces",<ref>{{Cite book |author=G. Zweig |orig-date=1964 |chapter=An SU(3) model for strong interaction symmetry and its breaking II |chapter-url=http://cdsweb.cern.ch/search.py?recid=570209&ln=en |editor1=D. Lichtenberg |editor2=S. Rosen |year=1980 |title=Developments in the Quark Theory of Hadrons |volume=1 |pages=22–101 |publisher=Hadronic Press |doi=10.17181/CERN-TH-412 }}</ref> but Gell-Mann's name caught on. Quarks, antiquarks, and [[gluon]]s were soon established as the underlying elementary objects in the study of the structure of hadrons. He was awarded a [[Nobel Prize in Physics]] in 1969 for his contributions and discoveries concerning the classification of elementary particles and their interactions.<ref>[http://nobelprize.org/nobel_prizes/physics/laureates/1969/ Simple listing of Nobel Prize in Physics, 1969] {{Webarchive|url=https://web.archive.org/web/20120713083609/http://www.nobelprize.org/nobel_prizes/physics/laureates/1969/ |date=July 13, 2012 }} Retrieved February 15, 2017</ref>

In the 1960s, he introduced [[current algebra]] as a method of systematically exploiting symmetries to extract predictions from quark models, in the absence of reliable dynamical theory. This method led to model-independent [[Sum rule in quantum mechanics|sum rules]] confirmed by experiment, and provided starting points underpinning the development of the [[Standard Model]] (SM), the widely accepted theory of elementary particles.<ref>{{cite conference|last=Ellis |first=John |title=Prospects for New Physics at the LHC |book-title=Proceedings of the Conference in Honour of Murray Gell-Mann's 80th Birthday: Quantum Mechanics, Elementary Particles, Quantum Cosmology and Complexity : Nanyang Technological University, Singapore, February 24–26, 2010 |publisher=World Scientific |year=2011 |isbn=9789814335607 |editor1-last=Fritzsch |editor1-first=Harald |editor2-last=Phua |editor2-first=K. K. |editor3-last=Baaquie |editor3-first=B. E.}}</ref><ref>{{cite book|last=Cao |first=Tian Yu |title=From Current Algebra to Quantum Chromodynamics: A Case for Structural Realism |year=2010 |publisher=Cambridge University Press |isbn=9781139491600}}</ref>

In 1972 Gell-Mann, while on sabbatical leave to CERN, together with [[Harald Fritzsch]], [[Heinrich Leutwyler]] and [[William A. Bardeen]], considered a Yang-Mills theory of "quark color," and coined the term [[quantum chromodynamics]] (QCD) as the [[gauge theory]] of the strong interaction.<ref>{{cite journal | last1 = Fritzsch | first1 = H. | last2 = Gell-Mann | first2 = M. | last3 = Leutwyler | first3 = H. | title = Advantages of the color octet gluon picture | journal = Physics Letters | volume = 47B | issue = 4| pages = 365–368 | year = 1973 | doi=10.1016/0370-2693(73)90625-4| bibcode = 1973PhLB...47..365F | citeseerx = 10.1.1.453.4712 }}</ref> The [[quark model]] is a part of QCD, and it has been robust enough to accommodate in a natural fashion the discovery of new "[[Flavour (particle physics)|flavors]]" of quarks, which has superseded the eightfold way scheme.<ref>{{cite web |url=http://math.ucr.edu/home/baez/qg-spring2003/eightfold/ |title=The Eightfold Way |last=Baez |first=John C. |author-link=John C. Baez |year=2003 |website=Quantum Gravity Seminar — Spring 2003 |publisher=[[University of California, Riverside]] |access-date=2019-05-28 |archive-date=February 15, 2019 |archive-url=https://web.archive.org/web/20190215231205/http://math.ucr.edu/home/baez/qg-spring2003/eightfold/ |url-status=live }}</ref>

Gell-Mann was responsible, with [[Pierre Ramond]] and [[Richard Slansky]],<ref name="Gell-Mann1979">M. Gell-Mann, [[Pierre Ramond|P. Ramond]] and [[Richard Slansky|R. Slansky]], in ''Supergravity'', ed. by D. Freedman and P. Van Nieuwenhuizen, North Holland, Amsterdam (1979), pp. 315–321. {{ISBN|044485438X}}</ref> and independently of [[Peter Minkowski]], [[Rabindra Mohapatra]], [[Goran Senjanović]], [[Sheldon Glashow]], and Tsutomu Yanagida, for proposing the [[seesaw mechanism|seesaw theory of neutrino masses]]. This produces masses at the large scale in any theory with a right-handed neutrino. He is also known to have played a role in keeping [[string theory]] alive through the 1970s and early 1980s, supporting that line of research at a time when it was a topic of niche interest.<ref>{{cite book|last=Rickles |first=Dean |title=A Brief History of String Theory: From Dual Models to M-Theory |publisher=Springer Science & Business Media |year=2014 |isbn=9783642451287 |oclc=968779591}}</ref><ref name="sciencenews">{{cite web |url=https://www.sciencenews.org/node/205111 |title=Murray Gell-Mann gave structure to the subatomic world |last=Siegfried |first=Tom |website=[[Science News]] |date=May 24, 2019 |access-date=May 26, 2019 |archive-date=May 25, 2019 |archive-url=https://web.archive.org/web/20190525071755/https://www.sciencenews.org/node/205111 |url-status=dead }}</ref>

Gell-Mann was a proponent of the [[consistent histories]] approach to understanding quantum mechanics, which he advocated in papers with [[James Hartle]].<ref name="sciencenews"/><ref>{{cite journal|last=Kent |first=Adrian |title=Consistent Sets Yield Contrary Inferences in Quantum Theory |journal=[[Physical Review Letters]] |volume=78 |number=15 |date=April 14, 1997 |pages=2874–2877 |doi=10.1103/PhysRevLett.78.2874|bibcode=1997PhRvL..78.2874K |arxiv=gr-qc/9604012 |s2cid=16862775 }}</ref>