Geoffrey Chew (born 1924) is an American theoretical physicist. Professor of Physics, UC Berkeley, since 1957, Emeritus since 1991. PhD in theoretical particle physics, 1944-1946, from University of Chicago. Physics faculty member at the University of Illinois, 1950-56. Member, National Academy of Sciences and American Academy of Arts and Science. Hughes Prize of the American Physics Society for bootstrap theory of strong interactions, 1962. Lawrence Prize, 1969.

Chew was a student of Enrico Fermi, and his students include David Gross and John H. Schwarz. He was known as a leader of the S-matrix approach to the strong interaction and the associated bootstrap principle, a theory whose popularity peaked in the 1960s when he led an influential theory group at UC Berkeley. S-matrix theorists sought to understand the strong interaction by using the analytic properties of the scattering matrix to calculate the interactions of bound-states without assuming that there is a point-particle field theory underneath. The S-matrix approach did not provide a local space-time description, and although it was not immediately appreciated by the practitioners, it was a natural framework in which to produce a quantum theory of gravity.

Chew's central contribution to the program came in 1960. Along with collaborator Steven Frautschi, they noted that the mesons fall into families where the square of the mass is linearly proportional to the spin, with the same constant of proportionality for each of the families. Since bound states in quantum mechanics naturally fall into families of this sort, their conclusion, quickly accepted, was that none of the strongly interacting particles were elementary. The conservative point of view was that the bound states were made up of elementary particles, but Chew's more far reaching vision was that there would be a new type of theory which describes the interactions of bound-states which have no point-like constituents at all. This approach was sometimes called nuclear democracy, since it avoided singling out certain particles as elementary.

Although the S-matrix approach to the strong interactions was largely abandoned by the particle physics community in the 1970s in favor of quantum chromodynamics, a consistent theory for the scattering of bound-states on straight-line trajectories was eventually constructed and is nowadays known as string theory. Within string theory, Edward Witten reinterpreted S-matrix theory as a flat-space statement of the holographic principle.

Professor Chew has also participated in religion and science discussions. He has stated that an "appeal to God may be needed to answer the 'origin' question: 'Why should a quantum universe evolving toward a semiclassical limit be consistent?'" [1]