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78-835: QCD exhibits three salient properties: Physicist Murray Gell-Mann coined the word quark in its present sense. It originally comes from the phrase "Three quarks for Muster Mark" in Finnegans Wake by James Joyce . On June 27, 1978, Gell-Mann wrote a private letter to the editor of the Oxford English Dictionary , in which he related that he had been influenced by Joyce's words: "The allusion to three quarks seemed perfect." (Originally, only three quarks had been discovered.) The three kinds of charge in QCD (as opposed to one in quantum electrodynamics or QED) are usually referred to as " color charge " by loose analogy to

156-451: A {\displaystyle \left(D_{\mu }\right)_{ij}=\partial _{\mu }\delta _{ij}-ig\left(T_{a}\right)_{ij}{\mathcal {A}}_{\mu }^{a}\,} couples the quark field with a coupling strength g {\displaystyle g\,} to the gluon fields via the infinitesimal SU(3) generators T a {\displaystyle T_{a}\,} in the fundamental representation. An explicit representation of these generators

234-404: A meson contains a term that increases in proportion to the distance between the quark and anti-quark ( ∝ r {\displaystyle \propto r} ), which represents some kind of "stiffness" of the interaction between the particle and its anti-particle at large distances, similar to the entropic elasticity of a rubber band (see below). This leads to confinement   of

312-409: A , b and c running from 1 {\displaystyle 1} to 8 {\displaystyle 8} ; and f abc are the structure constants of SU(3) (the generators of the adjoint representation). Note that the rules to move-up or pull-down the a , b , or c indices are trivial , (+, ..., +), so that f = f abc = f bc whereas for the μ or ν indices one has

390-543: A Yang-Mills theory of "quark color," and coined the term quantum chromodynamics (QCD) as the gauge theory of the strong interaction. The quark model is a part of QCD, and it has been robust enough to accommodate in a natural fashion the discovery of new " flavors " of quarks, which has superseded the eightfold way scheme. Gell-Mann was responsible, with Pierre Ramond and Richard Slansky , and independently of Peter Minkowski , Rabindra Mohapatra , Goran Senjanović , Sheldon Glashow , and Tsutomu Yanagida, for proposing

468-439: A closed loop W ; i.e. ⟨ P W ⟩ {\displaystyle \,\langle P_{W}\rangle } is proportional to the area enclosed by the loop. For this behavior the non-abelian behavior of the gauge group is essential. Further analysis of the content of the theory is complicated. Various techniques have been developed to work with QCD. Some of them are discussed briefly below. This approach

546-408: A corresponding antiquark, of which the charge is exactly opposite. They transform in the conjugate representation to quarks, denoted 3 ¯ {\displaystyle {\bar {\mathbf {3} }}} . According to the rules of quantum field theory , and the associated Feynman diagrams , the above theory gives rise to three basic interactions: a quark may emit (or absorb)

624-408: A field theory model in which quarks interact with gluons. Perhaps the first remark that quarks should possess an additional quantum number was made as a short footnote in the preprint of Boris Struminsky in connection with the Ω hyperon being composed of three strange quarks with parallel spins (this situation was peculiar, because since quarks are fermions , such a combination is forbidden by

702-415: A field theory. The difference between Feynman's and Gell-Mann's approaches reflected a deep split in the theoretical physics community. Feynman thought the quarks have a distribution of position or momentum, like any other particle, and he (correctly) believed that the diffusion of parton momentum explained diffractive scattering . Although Gell-Mann believed that certain quark charges could be localized, he

780-476: A force can themselves radiate further carrier particles. (This is different from QED, where the photons that carry the electromagnetic force do not radiate further photons.) The discovery of asymptotic freedom in the strong interactions by David Gross , David Politzer and Frank Wilczek allowed physicists to make precise predictions of the results of many high energy experiments using the quantum field theory technique of perturbation theory . Evidence of gluons

858-427: A gluon, a gluon may emit (or absorb) a gluon, and two gluons may directly interact. This contrasts with QED , in which only the first kind of interaction occurs, since photons have no charge. Diagrams involving Faddeev–Popov ghosts must be considered too (except in the unitarity gauge ). Detailed computations with the above-mentioned Lagrangian show that the effective potential between a quark and its anti-quark in

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936-523: A member of Jonathan Edwards College . At Yale, he participated in the William Lowell Putnam Mathematical Competition and was on the team representing Yale University (along with Murray Gerstenhaber and Henry O. Pollak ) that won the second prize in 1947. Gell-Mann graduated from Yale with a bachelor's degree in physics in 1948 and intended to pursue graduate studies in physics. He sought to remain in

1014-425: A meson. However, the numerical sign problem makes it difficult to use lattice methods to study QCD at high density and low temperature (e.g. nuclear matter or the interior of neutron stars). A well-known approximation scheme, the 1 ⁄ N expansion , starts from the idea that the number of colors is infinite, and makes a series of corrections to account for the fact that it is not. Until now, it has been

1092-561: 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 rules confirmed by experiment, and provided starting points underpinning the development of the Standard Model (SM), the widely accepted theory of elementary particles. In 1972 Gell-Mann, while on sabbatical leave to CERN, together with Harald Fritzsch , Heinrich Leutwyler and William A. Bardeen , considered

1170-471: A novel classification scheme, in 1961, for hadrons . A similar scheme had been independently proposed by Yuval Ne'eman , and has come to be explained by the quark model. Gell-Mann referred to the scheme as the eightfold way , because of the octets of particles in the classification (the term is a reference to the Eightfold Path of Buddhism ). Gell-Mann, along with Maurice Lévy, developed

1248-613: A nuclear research facility in Switzerland, among others as a John Simon Guggenheim Memorial Foundation fellow in 1972. In 1984 Gell-Mann was one of several co-founders of the Santa Fe Institute —a non-profit theoretical research institute in Santa Fe, New Mexico intended to study various aspects of a complex system and disseminate the notion of a separate interdisciplinary study of complexity theory. He wrote

1326-579: A popular science book about physics and complexity science, The Quark and the Jaguar: Adventures in the Simple and the Complex (1994). The title of the book is taken from a line of a poem by Arthur Sze : "The world of the quark has everything to do with a jaguar circling in the night". The author George Johnson has written a biography of Gell-Mann, Strange Beauty: Murray Gell-Mann, and

1404-460: A preeminent role in the development of the theory of elementary particles . Gell-Mann introduced the concept of quarks as the fundamental building blocks of the strongly interacting particles, and the renormalization group as a foundational element of quantum field theory and statistical mechanics . He played key roles in developing the concept of chirality in the theory of the weak interactions and spontaneous chiral symmetry breaking in

1482-416: A serious experimental blow to QCD. But, as of 2013, scientists are unable to confirm or deny the existence of glueballs definitively, despite the fact that particle accelerators have sufficient energy to generate them. Murray Gell-Mann Murray Gell-Mann ( / ˈ m ʌr i ˈ ɡ ɛ l ˈ m æ n / ; September 15, 1929 – May 24, 2019) was an American theoretical physicist who played

1560-455: A son. Margaret died in 1981, and in 1992 he married Marcia Southwick , whose son became his stepson. In 2011, Gell-Mann attended an event on Jeffrey Epstein 's private island, Little Saint James , known as the "Mindshift Conference", hosted by Epstein and Al Seckel . Gell-Mann's extensive interests outside of physics included archaeology , numismatics , birdwatching and linguistics . Along with S. A. Starostin , he established

1638-712: Is chiral perturbation theory or ChiPT, which is the QCD effective theory at low energies. More precisely, it is a low energy expansion based on the spontaneous chiral symmetry breaking of QCD, which is an exact symmetry when quark masses are equal to zero, but for the u, d and s quark, which have small mass, it is still a good approximate symmetry. Depending on the number of quarks that are treated as light, one uses either SU(2) ChiPT or SU(3) ChiPT. Other effective theories are heavy quark effective theory (which expands around heavy quark mass near infinity), and soft-collinear effective theory (which expands around large ratios of energy scales). In addition to effective theories, models like

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1716-550: Is spontaneously broken by the QCD vacuum to the vector (L+R) SU V ( N f ) with the formation of a chiral condensate . The vector symmetry, U B (1) corresponds to the baryon number of quarks and is an exact symmetry. The axial symmetry U A (1) is exact in the classical theory, but broken in the quantum theory, an occurrence called an anomaly . Gluon field configurations called instantons are closely related to this anomaly. There are two different types of SU(3) symmetry: there

1794-405: Is based on asymptotic freedom, which allows perturbation theory to be used accurately in experiments performed at very high energies. Although limited in scope, this approach has resulted in the most precise tests of QCD to date. Among non-perturbative approaches to QCD, the most well established is lattice QCD . This approach uses a discrete set of spacetime points (called the lattice) to reduce

1872-496: Is deduced from observations. These can be QCD is a non-abelian gauge theory (or Yang–Mills theory ) of the SU(3) gauge group obtained by taking the color charge to define a local symmetry. Since the strong interaction does not discriminate between different flavors of quark, QCD has approximate flavor symmetry , which is broken by the differing masses of the quarks. There are additional global symmetries whose definitions require

1950-510: Is given by T a = λ a / 2 {\displaystyle T_{a}=\lambda _{a}/2\,} , wherein the λ a ( a = 1 … 8 ) {\displaystyle \lambda _{a}\,(a=1\ldots 8)\,} are the Gell-Mann matrices . The symbol G μ ν a {\displaystyle G_{\mu \nu }^{a}\,} represents

2028-435: Is part of the first generation of matter, has an electric charge of + ⁠ 2 / 3 ⁠   e and a bare mass of 2.2 +0.5 −0.4   MeV/ c . Like all quarks , the up quark is an elementary fermion with spin ⁠ 1 / 2 ⁠ , and experiences all four fundamental interactions : gravitation , electromagnetism , weak interactions , and strong interactions . The antiparticle of

2106-406: Is practically no interaction between the particles. This is in contrast – more precisely one would say dual – to what one is used to, since usually one connects the absence of interactions with large  distances. However, as already mentioned in the original paper of Franz Wegner, a solid state theorist who introduced 1971 simple gauge invariant lattice models, the high-temperature behaviour of

2184-488: Is the gauge covariant derivative ; the γ are Gamma matrices connecting the spinor representation to the vector representation of the Lorentz group . Herein, the gauge covariant derivative ( D μ ) i j = ∂ μ δ i j − i g ( T a ) i j A μ

2262-402: Is the quark field, a dynamical function of spacetime, in the fundamental representation of the SU(3) gauge group , indexed by i {\displaystyle i} and j {\displaystyle j} running from 1 {\displaystyle 1} to 3 {\displaystyle 3} ; D μ {\displaystyle D_{\mu }}

2340-420: Is the symmetry that acts on the different colors of quarks, and this is an exact gauge symmetry mediated by the gluons, and there is also a flavor symmetry that rotates different flavors of quarks to each other, or flavor SU(3) . Flavor SU(3) is an approximate symmetry of the vacuum of QCD, and is not a fundamental symmetry at all. It is an accidental consequence of the small mass of the three lightest quarks. In

2418-718: The Evolution of Human Languages project at the Santa Fe Institute . As a humanist and an agnostic , Gell-Mann was a Humanist Laureate in the International Academy of Humanism . Novelist Cormac McCarthy saw Gell-Mann as a polymath who "knew more things about more things than anyone I've ever met...losing Murray is like losing the Encyclopædia Britannica ." Gell-Mann died on May 24, 2019, at his home in Santa Fe, New Mexico. Gell-Mann

Quantum chromodynamics - Misplaced Pages Continue

2496-683: The Greek word χρῶμα ( chrōma , "color") is applied to the theory of color charge, "chromodynamics". With the invention of bubble chambers and spark chambers in the 1950s, experimental particle physics discovered a large and ever-growing number of particles called hadrons . It seemed that such a large number of particles could not all be fundamental . First, the particles were classified by charge and isospin by Eugene Wigner and Werner Heisenberg ; then, in 1953–56, according to strangeness by Murray Gell-Mann and Kazuhiko Nishijima (see Gell-Mann–Nishijima formula ). To gain greater insight,

2574-600: The Ivy League for his graduate education and applied to Princeton University as well as Harvard University . He was rejected by Princeton and accepted by Harvard, but the latter institution was unable to offer him needed financial assistance. He was accepted by the Massachusetts Institute of Technology (MIT) and received a letter from Victor Weisskopf urging him to attend MIT and become Weisskopf's research assistant. This would provide Gell-Mann with

2652-477: The Nambu–Jona-Lasinio model and the chiral model are often used when discussing general features. Based on an Operator product expansion one can derive sets of relations that connect different observables with each other. The notion of quark flavors was prompted by the necessity of explaining the properties of hadrons during the development of the quark model . The notion of color was necessitated by

2730-457: The Pauli exclusion principle ): Three identical quarks cannot form an antisymmetric S-state. In order to realize an antisymmetric orbital S-state, it is necessary for the quark to have an additional quantum number. Boris Struminsky was a PhD student of Nikolay Bogolyubov . The problem considered in this preprint was suggested by Nikolay Bogolyubov, who advised Boris Struminsky in this research. In

2808-529: The QCD vacuum there are vacuum condensates of all the quarks whose mass is less than the QCD scale. This includes the up and down quarks, and to a lesser extent the strange quark, but not any of the others. The vacuum is symmetric under SU(2) isospin rotations of up and down, and to a lesser extent under rotations of up, down, and strange, or full flavor group SU(3), and the observed particles make isospin and SU(3) multiplets. The approximate flavor symmetries do have associated gauge bosons, observed particles like

2886-435: The baryon number , which is 1 ⁄ 3 for each quark, hypercharge and one of the flavor quantum numbers . Gluons are spin-1 bosons that also carry color charges , since they lie in the adjoint representation 8 of SU(3). They have no electric charge, do not participate in the weak interactions, and have no flavor. They lie in the singlet representation 1 of all these symmetry groups. Each type of quark has

2964-446: The original model , e.g. the strong decay of correlations at large distances, corresponds to the low-temperature behaviour of the (usually ordered!) dual model , namely the asymptotic decay of non-trivial correlations, e.g. short-range deviations from almost perfect arrangements, for short distances. Here, in contrast to Wegner, we have only the dual model, which is that one described in this article. The color group SU(3) corresponds to

3042-553: The quark model , then consisting only of up, down , and strange quarks . However, while the quark model explained the Eightfold Way, no direct evidence of the existence of quarks was found until 1968 at the Stanford Linear Accelerator Center . Deep inelastic scattering experiments indicated that protons had substructure, and that protons made of three more-fundamental particles explained

3120-475: The quark–gluon plasma is a non-perturbative test bed for QCD that still remains to be properly exploited. One qualitative prediction of QCD is that there exist composite particles made solely of gluons called glueballs that have not yet been definitively observed experimentally. A definitive observation of a glueball with the properties predicted by QCD would strongly confirm the theory. In principle, if glueballs could be definitively ruled out, this would be

3198-523: The 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. Gell-Mann was a proponent of the consistent histories approach to understanding quantum mechanics, which he advocated in papers with James Hartle . Gell-Mann won numerous awards and honours including

Quantum chromodynamics - Misplaced Pages Continue

3276-420: The sigma model of pions , which describes low-energy pion interactions. In 1964, Gell-Mann and, independently, George Zweig went on to postulate the existence of quarks , particles which make up the hadrons 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

3354-536: The strong interactions , which controls the physics of the light mesons . In the 1970s he was a co-inventor of quantum chromodynamics (QCD) which explains the confinement of quarks in mesons and baryons and forms a large part of the Standard Model of elementary particles and forces. Murray Gell-Mann received the 1969 Nobel Prize in Physics for his work on the theory of elementary particles. Gell-Mann

3432-427: The violation of parity by Chien-Shiung Wu , as suggested theoretically by Chen-Ning Yang and Tsung-Dao Lee . Gell-Mann's work in the 1950s involved recently discovered cosmic ray particles that came to be called kaons and hyperons . Classifying these particles led him to propose that a quantum number , called strangeness , would be conserved by the strong and the electromagnetic interactions, but not by

3510-456: The Δ baryon ; in the quark model, it is composed of three up quarks with parallel spins. In 1964–65, Greenberg and Han – Nambu independently resolved the problem by proposing that quarks possess an additional SU(3) gauge degree of freedom , later called color charge. Han and Nambu noted that quarks might interact via an octet of vector gauge bosons : the gluons . Since free quark searches consistently failed to turn up any evidence for

3588-545: The 1950s. The relationships between each of them were unclear until 1961, when Murray Gell-Mann and Yuval Ne'eman (independently of each other) proposed a hadron classification scheme called the Eightfold Way , or in more technical terms, SU(3) flavor symmetry . This classification scheme organized the hadrons into isospin multiplets , but the physical basis behind it was still unclear. In 1964, Gell-Mann and George Zweig (independently of each other) proposed

3666-703: The Revolution in 20th-Century Physics (1999), which was shortlisted for the Royal Society Book Prize . Although Gell-Mann himself criticized Strange Beauty for some inaccuracies, with one interviewer reporting him wincing at the mention of it, the book was acclaimed by a number of his colleagues. A revised second edition was published in 2023 by the Santa Fe Institute Press with a foreword by Douglas Hofstadter . In 2012 Gell-Mann and his companion Mary McFadden published

3744-501: The analytically intractable path integrals of the continuum theory to a very difficult numerical computation that is then carried out on supercomputers like the QCDOC , which was constructed for precisely this purpose. While it is a slow and resource-intensive approach, it has wide applicability, giving insight into parts of the theory inaccessible by other means, in particular into the explicit forces acting between quarks and antiquarks in

3822-510: The beginning of 1965, Nikolay Bogolyubov , Boris Struminsky and Albert Tavkhelidze wrote a preprint with a more detailed discussion of the additional quark quantum degree of freedom. This work was also presented by Albert Tavkhelidze without obtaining consent of his collaborators for doing so at an international conference in Trieste (Italy), in May 1965. A similar mysterious situation was with

3900-512: The behavior of Wilson loops can distinguish confined and deconfined phases. Quarks are massive spin- 1 ⁄ 2 fermions that carry a color charge whose gauging is the content of QCD. Quarks are represented by Dirac fields in the fundamental representation 3 of the gauge group SU(3) . They also carry electric charge (either − 1 ⁄ 3 or + 2 ⁄ 3 ) and participate in weak interactions as part of weak isospin doublets. They carry global quantum numbers including

3978-461: The book Mary McFadden: A Lifetime of Design, Collecting, and Adventure . 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 chiral structures of the weak interaction of physics and developed the V-A theory (vector minus axial vector theory). This work followed the experimental discovery of

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4056-442: The data (thus confirming the quark model ). At first people were reluctant to describe the three bodies as quarks, instead preferring Richard Feynman 's parton description, but over time the quark theory became accepted (see November Revolution ). Despite being extremely common, the bare mass of the up quark is not well determined, but probably lies between 1.8 and 3.0  MeV/ c . Lattice QCD calculations give

4134-448: The financial assistance he required. Unaware of MIT's eminent status in physics research, Gell-Mann was "miserable" with the fact that he would not be able to attend Princeton or Harvard and in characteristic dark irony, said he considered suicide. Gell-Mann stated that he realized he could try to first enter MIT and commit suicide afterwards if he found it to be truly terrible. However, he couldn't first choose suicide and then attend MIT;

4212-537: The following: Universities that gave Gell-Mann honorary doctorates include Cambridge , Columbia , the University of Chicago , Oxford and Yale . Up quark The up quark or u quark (symbol: u) is the lightest of all quarks , a type of elementary particle , and a significant constituent of matter . It, along with the down quark , forms the neutrons (one up quark, two down quarks) and protons (two up quarks, one down quark) of atomic nuclei . It

4290-475: The gauge invariant gluon field strength tensor , analogous to the electromagnetic field strength tensor , F , in quantum electrodynamics . It is given by: where A μ a ( x ) {\displaystyle {\mathcal {A}}_{\mu }^{a}(x)\,} are the gluon fields , dynamical functions of spacetime, in the adjoint representation of the SU(3) gauge group, indexed by

4368-438: The hadrons were sorted into groups having similar properties and masses using the eightfold way , invented in 1961 by Gell-Mann and Yuval Ne'eman . Gell-Mann and George Zweig , correcting an earlier approach of Shoichi Sakata , went on to propose in 1963 that the structure of the groups could be explained by the existence of three flavors of smaller particles inside the hadrons: the quarks . Gell-Mann also briefly discussed

4446-418: The local symmetry whose gauging gives rise to QCD. The electric charge labels a representation of the local symmetry group U(1), which is gauged to give QED : this is an abelian group . If one considers a version of QCD with N f flavors of massless quarks, then there is a global ( chiral ) flavor symmetry group SU L ( N f ) × SU R ( N f ) × U B (1) × U A (1). The chiral symmetry

4524-675: The new particles, and because an elementary particle back then was defined as a particle that could be separated and isolated, Gell-Mann often said that quarks were merely convenient mathematical constructs, not real particles. The meaning of this statement was usually clear in context: He meant quarks are confined, but he also was implying that the strong interactions could probably not be fully described by quantum field theory. Richard Feynman argued that high energy experiments showed quarks are real particles: he called them partons (since they were parts of hadrons). By particles, Feynman meant objects that travel along paths, elementary particles in

4602-476: The non-trivial relativistic rules corresponding to the metric signature (+ − − −). The variables m and g correspond to the quark mass and coupling of the theory, respectively, which are subject to renormalization. An important theoretical concept is the Wilson loop (named after Kenneth G. Wilson ). In lattice QCD, the final term of the above Lagrangian is discretized via Wilson loops, and more generally

4680-433: The notion of chirality , discrimination between left and right-handed. If the spin of a particle has a positive projection on its direction of motion then it is called right-handed; otherwise, it is left-handed. Chirality and handedness are not the same, but become approximately equivalent at high energies. As mentioned, asymptotic freedom means that at large energy – this corresponds also to short distances – there

4758-409: The particles as "aces", but Gell-Mann's name caught on. Quarks, antiquarks, and gluons 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. In the 1960s, he introduced current algebra as

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4836-479: The predictions are harder to make. The best is probably the running of the QCD coupling as probed through lattice computations of heavy-quarkonium spectra. There is a recent claim about the mass of the heavy meson B c . Other non-perturbative tests are currently at the level of 5% at best. Continuing work on masses and form factors of hadrons and their weak matrix elements are promising candidates for future quantitative tests. The whole subject of quark matter and

4914-440: The puzzle of the Δ . This has been dealt with in the section on the history of QCD . The first evidence for quarks as real constituent elements of hadrons was obtained in deep inelastic scattering experiments at SLAC . The first evidence for gluons came in three-jet events at PETRA . Several good quantitative tests of perturbative QCD exist: Quantitative tests of non-perturbative QCD are fewer, because

4992-486: The quarks to the interior of hadrons, i.e. mesons and nucleons , with typical radii R c , corresponding to former " Bag models " of the hadrons The order of magnitude of the "bag radius" is 1 fm (= 10 m). Moreover, the above-mentioned stiffness is quantitatively related to the so-called "area law" behavior of the expectation value of the Wilson loop product P W of the ordered coupling constants around

5070-409: The rho and the omega, but these particles are nothing like the gluons and they are not massless. They are emergent gauge bosons in an approximate string description of QCD . The dynamics of the quarks and gluons are defined by the quantum chromodynamics Lagrangian . The gauge invariant QCD Lagrangian is where ψ i ( x ) {\displaystyle \psi _{i}(x)\,}

5148-522: The source of qualitative insight rather than a method for quantitative predictions. Modern variants include the AdS/CFT approach. For specific problems, effective theories may be written down that give qualitatively correct results in certain limits. In the best of cases, these may then be obtained as systematic expansions in some parameters of the QCD Lagrangian. One such effective field theory

5226-400: The strong interactions. In 1973 the concept of color as the source of a "strong field" was developed into the theory of QCD by physicists Harald Fritzsch and Heinrich Leutwyler , together with physicist Murray Gell-Mann. In particular, they employed the general field theory developed in 1954 by Chen Ning Yang and Robert Mills (see Yang–Mills theory ), in which the carrier particles of

5304-603: The theory is verified within lattice QCD computations, but is not mathematically proven. One of the Millennium Prize Problems announced by the Clay Mathematics Institute requires a claimant to produce such a proof. Other aspects of non-perturbative QCD are the exploration of phases of quark matter , including the quark–gluon plasma . Every field theory of particle physics is based on certain symmetries of nature whose existence

5382-417: The three kinds of color (red, green and blue) perceived by humans . Other than this nomenclature, the quantum parameter "color" is completely unrelated to the everyday, familiar phenomenon of color. The force between quarks is known as the colour force (or color force ) or strong interaction , and is responsible for the nuclear force . Since the theory of electric charge is dubbed " electrodynamics ",

5460-506: The two "didn't commute", as Gell-Mann said. He received his Ph.D. in physics from MIT in 1951 after completing a doctoral dissertation, titled "Coupling strength and nuclear reactions", under the supervision of Weisskopf. Subsequently, Gell-Mann was a postdoctoral fellow at the Institute for Advanced Study at Princeton in 1951, and a visiting research professor at the University of Illinois at Urbana–Champaign from 1952 to 1953. He

5538-419: The up quark is the up antiquark (sometimes called antiup quark or simply antiup ), which differs from it only in that some of its properties, such as charge have equal magnitude but opposite sign . Its existence (along with that of the down and strange quarks ) was postulated in 1964 by Murray Gell-Mann and George Zweig to explain the Eightfold Way classification scheme of hadrons . The up quark

5616-503: The weak interaction. Another of Gell-Mann's ideas is the Gell-Mann–Okubo formula, which was, initially, a formula based on empirical results, but was later explained by his quark model . Gell-Mann and Abraham Pais were involved in explaining this puzzling aspect of the neutral kaon mixing . Murray Gell-Mann's fortunate encounter with mathematician Richard Earl Block at Caltech, in the fall of 1960, "enlightened" him to introduce

5694-525: Was a visiting associate professor at Columbia University and an associate professor at the University of Chicago in 1954–1955, before moving to the California Institute of Technology , where he taught from 1955 until he retired in 1993. He was on sabbatical at the Collège de France for the academic year 1958–1959. Gell-Mann married J. Margaret Dow in 1955; they had a daughter and

5772-690: Was born in Lower Manhattan to a family of Jewish immigrants from the Austro-Hungarian Empire , specifically from Czernowitz in present-day Ukraine . His parents were Pauline (née Reichstein) and Arthur Isidore Gelman, who taught English as a second language . Propelled by an intense boyhood curiosity and love for nature and mathematics, he graduated valedictorian from the Columbia Grammar & Preparatory School aged 14 and subsequently entered Yale College as

5850-428: Was discovered in three-jet events at PETRA in 1979. These experiments became more and more precise, culminating in the verification of perturbative QCD at the level of a few percent at LEP , at CERN . The other side of asymptotic freedom is confinement . Since the force between color charges does not decrease with distance, it is believed that quarks and gluons can never be liberated from hadrons. This aspect of

5928-401: Was first observed by experiments at the Stanford Linear Accelerator Center in 1968. In the beginnings of particle physics (first half of the 20th century), hadrons such as protons , neutrons and pions were thought to be elementary particles . However, as new hadrons were discovered, the ' particle zoo ' grew from a few particles in the early 1930s and 1940s to several dozens of them in

6006-475: Was open to the possibility that the quarks themselves could not be localized because space and time break down. This was the more radical approach of S-matrix theory . James Bjorken proposed that pointlike partons would imply certain relations in deep inelastic scattering of electrons and protons, which were verified in experiments at SLAC in 1969. This led physicists to abandon the S-matrix approach for

6084-694: Was the Robert Andrews Millikan Professor of Theoretical Physics Emeritus at California Institute of Technology as well as a university professor in the physics and astronomy department of the University of New Mexico in Albuquerque, New Mexico , and the Presidential Professor of Physics and Medicine at the University of Southern California . He was a member of the editorial board of the Encyclopædia Britannica . Gell-Mann spent several periods at CERN ,

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