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Gell-Mann, Murray

particles institute elementary theory

(1929– ) US theoretical physicist: applied group theory to understanding of elementary particles.

Gell-Mann was educated at Yale University and Massachusetts Institute of Technology, gaining his PhD at 22. Work with followed and he then moved to California Institute of Technology, where he became professor of theoretical physics in 1967.

At 24, Gell-Mann made a major contribution to the theory of elementary particles by introducing the concept of ‘strangeness’, a new quantum number which must be conserved in any so-called ‘strong’ nuclear interaction event. Using strangeness Gell-Mann and (independently) neatly classified elementary particles into multiplets of 1, 8, 10 or 27 members. The members of the multiplets are then related by symmetry operations, specifically unitary symmetry of dimensions 3, or SU. The omega-minus particle was predicted by this theory and was observed in 1964, to considerable acclaim. Their book on this work was entitled The Eightfold Way , a pun on the Buddhist eightfold route to nirvana (loosely, heaven).

Gell-Mann and G Zweig (1937–) introduced in 1964 the concept of quarks, which have one-third or two-thirds integral charge and baryon number. From these the other nuclear particles (hadrons) can be made. The name is an invented word, associated with a line in Joyce’s Finnegan’s Wake : ‘Three quarks for Muster Mark!’ Six types of quark are now recognized. Five were detected indirectly after 1964, but the sixth (‘top’) quark eluded detection until 1995.

Another major contribution was Gell-Mann’s introduction (with ) of currents for understanding the weak interaction. For all this work he was awarded the Nobel Prize for physics in 1969.

In his 70s he worked at the Santa Fe Institute in New Mexico, studying how complexity can arise from simplicity in nature.

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