George Zweig

A Moscow childhood, a Pasadena thesis

George Zweig was born in Moscow on May 30, 1937, into a Jewish family that left the Soviet Union while he was still a small child. His father was a structural engineer, and the family settled eventually in the United States, where the young Zweig grew up reading mathematics texts the way other children read adventure novels. He enrolled at the University of Michigan in 1955 and took his bachelor’s degree in mathematics in 1959, with so many physics courses bolted on as electives that the distinction was largely a matter of which department printed the diploma.

He went on to the California Institute of Technology for graduate work, intending at first to do theoretical research in pure mathematics and finding himself instead drawn into the orbit of Richard Feynman, who was then in the middle of the lecturing tour that would become the Feynman Lectures on Physics. Feynman did not so much advise his students as detonate them. Zweig took the blast and reoriented toward particle physics. He finished his Caltech PhD in 1964, twenty-seven years old, and immediately moved to Geneva to begin a postdoctoral appointment at CERN.

George Zweig (; born May 30, 1937) is an American physicist of Russian-Jewish origin. He was trained as a particle physicist under Richard Feynman. He introduced, independently of Murray Gell-Mann, the quark model (although he named it "aces"). He later turned his attention to neurobiology. He has worked as a research scientist at Los Alamos National Laboratory and Massachusetts Institute of Technology, and in the financial services industry.

The aces paper

The particle zoo of the early 1960s was a mess. Cosmic ray experiments and the new accelerators at Brookhaven and Berkeley had piled up almost a hundred strongly interacting particles, each with its own mass, charge, spin, and a quantum number called strangeness that nobody could quite account for. Murray Gell-Mann at Caltech and Yuval Ne’eman in Israel had organized the lighter ones into geometric patterns they called the Eightfold Way, but the patterns themselves cried out for an explanation. Why octets? Why decuplets? Why those specific arrangements and no others?

In late 1963 and early 1964, working alone in Geneva and only a few months past his thesis defense, Zweig wrote two CERN preprints arguing that every hadron in the zoo could be built out of a small number of more fundamental constituents. He proposed three of them initially, with fractional electric charges of plus two-thirds, minus one-third, and minus one-third, and a fourth that he reserved for the still-mysterious charm-carrying states. He called them aces, after the four playing cards in a deck. Mesons were ace-antiace pairs. Baryons such as the proton and neutron were triplets of aces. The patterns of the Eightfold Way fell out as the arithmetic of how three aces could combine.

Gell-Mann, working independently at Caltech, reached almost the same conclusion at almost the same moment and gave the particles a different name that stuck. He had pulled it from a line in Finnegans Wake by James Joyce. Quarks were what they came to be called, and Zweig’s aces vanished into a footnote. The two papers nonetheless differed in style. Gell-Mann was cagey about whether his quarks were real objects or a mathematical bookkeeping device. Zweig wrote as though the aces were physical constituents you could in principle hold in your hand, fractional charges and all. In the subsequent technical literature, the distinction came to be phrased as current quarks (Gell-Mann’s bookkeeping) versus constituent quarks (Zweig’s heavy, near-classical objects). Both versions turned out to describe pieces of the truth.

The OZI rule and the silence that followed

One of the empirical clues that drove Zweig to his picture was an oddity in the decays of the phi meson. The phi was known to be a strange-antistrange composite, and it decayed mostly into two kaons rather than into three pions, even though the three-pion channel had more phase space available and ought, by rights, to have dominated. Zweig saw that if you drew a diagram of the quark lines flowing through the decay, the three-pion channel required the quark lines to disconnect and reconnect, while the two-kaon channel let them flow straight through. He proposed a rule: decays in which the quark lines must be cut are suppressed. The rule was independently noticed by Susumu Okubo and Jugoro Iizuka, and the three names together gave it the acronym it carries today. The Z in OZI is Zweig.

The aces papers themselves had a harder time. Zweig submitted the first version to Physical Review and was rejected. He has told the story since, with the sort of dry humor that physicists develop over thirty years of distance, that the referee found the idea of fractionally charged particles too speculative to publish. The preprints circulated at CERN but were not formally journaled for years. Gell-Mann published his version in Physics Letters almost immediately. By the late 1960s, when deep inelastic scattering experiments at SLAC revealed that protons really did contain hard pointlike scattering centers, both pictures had been vindicated. Gell-Mann received the 1969 Nobel Prize in Physics, with the citation listing his contributions to the classification of elementary particles. The official statement did not specifically mention quarks. By 1977, Feynman thought the omission egregious enough to nominate both Zweig and Gell-Mann again, jointly, for a second prize. The nomination failed. Zweig has never received the Nobel.

From quarks to cochleae

By the early 1970s the quark model had won, and Zweig, who had moved from CERN to a faculty position at Caltech, made one of the most striking career pivots in the history of theoretical physics. He left particle physics entirely and turned to the question of how the human ear converts pressure waves in air into electrical signals in the auditory nerve. He worked in the cochlea, the spiral fluid-filled structure inside the inner ear whose hair cells transduce sound into nerve impulses, and he asked what kind of mathematical transform the cochlea was actually performing.

In 1975, while working through the problem, he wrote down a continuous wavelet decomposition of the cochlear signal that anticipated by nearly a decade the formalism Yves Meyer, Ingrid Daubechies, and Stéphane Mallat would later develop into the modern theory of wavelets. Zweig’s version, which he called the cochlear transform, used a basis of damped oscillating wavelets matched to the response of individual cochlear positions. It did for hearing what Fourier analysis had done for steady tones: it pulled time and frequency information apart in a way that respected the physiology. He spent the rest of the 1970s and the 1980s at Los Alamos National Laboratory and at MIT, publishing on the cochlea, on auditory pitch perception, and on the mapping from frequency space onto the cortex.

A second turn, to Wall Street

The third act began in 2003, when Zweig left academic neuroscience and joined Renaissance Technologies, the secretive quantitative hedge fund founded by the former Cold War code breaker and Stony Brook mathematician James Simons. Renaissance had a long-standing habit of hiring physicists, astronomers, and number theorists for whom finance was a kind of applied statistical mechanics. Zweig fit the pattern exactly. He stayed seven years, left in 2010, served out a four-year non-compete, and then at the age of seventy-eight co-founded a new quantitative fund called Signition with two younger partners. They began trading in 2015.

His public honors include a MacArthur Prize Fellowship in 1981, election to the National Academy of Sciences in 1996, and the J. J. Sakurai Prize for Theoretical Particle Physics in 2015, awarded jointly with Gell-Mann fifty-one years after the aces preprints first circulated.

George Zweig is the rare theorist who proposed a piece of the deepest layer of physics, the constituents of matter itself, and then decided that the problem of how the ear hears was harder and more interesting. The aces became the quarks, the quarks became the Standard Model, and the OZI rule still gets drawn on blackboards whenever anyone tries to explain why some mesons decay quickly and others stubbornly do not. The quantum story owes him the fractional charges that nobody believed in, and the diagrammatic rule that bears his initial.