Murray Gell-Mann (September 15, 1929 – May 24, 2019) was an American theoretical physicist who won the 1969 Nobel Prize in physics for his work on the theory of elementary particles.

Gell-Mann introduced this idea of a “quantum number”, called strangeness, as well as that of charm and color. He has also developed the so-called “eightfold way” or classification scheme for particle physics.

**About Murray Gell-Mann**

Murray Gell-Mann – Nobel Prize in physics and introduction of strangeness theory

Gell-Mann’s work has been focused on fundamental particles of matter, such as the quarks and their interaction with each other. The quark model of the solid-state was advocated by Gell-Mann and Francis Crick before it was realized that the model does not predict that there should be three generations of quarks.

**Life of Gell-Mann**

**His birth**

Murray Gell-Mann was born in New York City, New York on September 15, 1929. His father was an executive for a steel company. He grew up in Cleveland, Ohio, where his parents owned a house in Shaker Square. His mother was a concert pianist who died when he was 16 years old.

**His education**

Murray Gell-Mann earned his B.S. in Chemistry at the University of California, Berkeley in 1948. He graduated with honors and won the prestigious year-long Herbert Smith Fellowship there at the end of his junior year from 1946 to 1947 (a truly fantastic achievement!).

**His personal life**

He married J. Margaret Dow, who died in 1981, in 1955. They had two daughters, Elizabeth, and Jane, and a son, Paul. In 1992 Murray Gell-Mann married his longtime partner and collaborator Marcia Southwick, who survives him.

**Career**

Murray Gell-Mann was a physicist at AT&T Bell Laboratories and the California Institute of Technology in the 1950s. He joined the physics faculty of the California Institute of Technology in 1959 and remained there with the exception of one year in 1968 when he took an academic sabbatical at Brandeis University while working with Richard Feynman on particle physics.

He worked as a senior staff physicist at Brookhaven National Laboratory before retiring to Santa Cruz, CA.

**Nuclear physics**

Murray Gell-Mann, along with his collaborators and a number of other bright young physicists, worked on the theories of high-energy nuclear processes. Gell-Mann’s early research involved the study of nuclear beta decay and decay into excited states of nuclei.

While working at Brookhaven National Laboratory in Long Island, NY., he worked on the theory behind the design of the first nuclear reactor using liquid deuterium as a fuel. This work was cited as a significant contribution by Lawrence Livermore National Laboratory Director Edward Teller when it came time to award the Nobel Prize in Physics to Gell-Mann and his colleagues for their work on particle physics.

**The notion of strangeness**

His work on the theory of weak and electromagnetic interactions led to a new classification scheme for hadrons or strongly interacting particles. It explained a phenomenon called “strangeness.” Gell-Mann postulated that the number of strange particles in a beam would indicate how much “strangeness” it carried. Murray Gell-Mann also noted the pattern in hadrons containing an odd number of either quarks or antiquarks, known as baryons and antibaryons, respectively. These structures were originally dub A (antiproton) and B (proton) by Gell-Mann based on their physical characteristics.

**The quark model**

Using the principle of the conservation of strangeness, Murray Gell-Mann and his collaborators constructed a model of baryons based on three fractionally charged objects called quarks. They proposed that the different baryons are composed of different combinations of quarks. For example, a proton contains two up quarks and one down quark while a neutron contains one up quark and two down quarks.

After publishing their original paper in 1964, Gell-Mann and collaborators worked to refine their model by including another type of particle called hyperons to explain other observed phenomena.

**The sigma model of pions**

In their study of the weak interactions, Gell-Mann’s collaborators at Brookhaven National Laboratory took note of what they called sigma particles. These particles are now know to be identical to the charge pions. The idea behind this was that the masses of the sigma particles and pions should be similar. This led to a new model for particle physics called “supersymmetry”. Pions are much heavier than previously thought, a fact discovered during Gell-Mann’s research at Brookhaven.

Murray Gell-Mann and his collaborators continued their studies on weak interactions by examining what would happen when two pions collided.

**Complexity science**

Gell-Mann has been active in the development of complexity science. Both as a scientific concept and as a field of study. Murray Gell-Mann is one of the founders of the Santa Fe Institute and has received its five-year research achievement award.

The Gell-Mann Amnesia effect

In 1964, Gell-Mann proposed that it should be possible to classify particles based on their strangeness number, ys. His collaborators at Brookhaven National Laboratory found that. There were many more baryons than could be account for using this theory. Gell-Mann called this phenomenon “the eightfold way”, or “octet rule”.

**Quantum foundations**

Gell-Mann is also known for his work on the foundations of quantum field theory. While working at Brandeis University together with Richard Feynman, Murray Gell-Mann first published a paper that formulated what is now called the Gell-Mann-Lewosky theorem, which states that “if the total spin S of all elementary particles in a model is an integer multiple of 2e (negative), then the theory cannot be renormalized”. In other words, this theorem shows that any well-defined quantum theory needs to be renormalizable if it is to describe elementary particles.

**Awards and Honors**

In 1960 Murray Gell-Mann was award a Sloan Fellowship and in 1969 he receive the Nobel Prize in Physics. Gell-Mann has received a number of honorary doctorates from other academies.

**Giving back to the community**

Gell-Mann is an active philanthropist who has been involve with his alma mater, Caltech, for over forty years. Murray Gell-Mann established the Gell-Mann Distinguished Scholar Award at Caltech to recognize outstanding research by members of its faculty. In addition, he served as chair of the board of trustees at Oxfam America from 1996 to 2004. While also remaining as a trustee of Yale’s board until his term expired in 2008.