KITP Director Awarded 2004 Nobel Prize in Physics

October 5, 2004

Santa Barbara, Calif.—David J. Gross, director of the Kavli Institute for Theoretical Physics (KITP) and the first incumbent of the Frederick W. Gluck Chair in Theoretical Physics at the University of California at Santa Barbara, has been awarded the 2004 Nobel Prize in Physics for solving in 1973 the last great remaining problem of what has since come to be called "the Standard Model" of the quantum mechanical picture of reality.  He and his co-recipients discovered how the nucleus of atoms works.

Gross shares the prize with Frank Wilczek, now a physics professor at Massachusetts Institute of Technology, who was Gross's graduate student at Princeton University, when the pair completed the calculation that resulted in the discovery for which they have received the Nobel Prize.  The other recipient, H. David Politzer, a physics professor at the California Institute of Technology, was working independently on a similar calculation.

Gross was awoken shortly after 2:30 a.m. PST by a call from the Royal Swedish Academy of Sciences and participated by phone in the press conference under way in Stockholm.  Not known as a man of few words, Gross, who described his initial reaction as "shock," was hard-pressed to put his feelings into words, but the two words he chose were "honored" and "surprised."

Gross said, "This Nobel Prize recognizes the efforts not only by us but also the community of high energy physics.  Scientific explorations into fundamental reality are no longer the province of the lone genius such as Galileo or Newton or Einstein, but a collaborative effort by a community of scientists.  Hundreds of experimental physicists at the world's accelerator laboratories have designed and run the experiments that gave us early hints about how the strong force operates and then, after we published our theory, proved it.  The effort to explore the subtleties of the nuclear force continues today; we still have many implications of the theory to work out."

The Swedish Academy cited the winners "for the discovery of asymptotic freedom in the theory of the strong interaction."

Gross and Wilczek and independently Politzer made the key discovery of how the "strong" force works to bind the constituent elements, called quarks, of protons and neutrons (the particles that make up the nucleus of atoms).  The other three forces of nature--electromagnetism, the weak force (responsible for radioactive decay), and gravity all diminish in strength with distance.  They discovered that the strong force grows stronger with distance.

This discovery called "asymptotic freedom" means that attempts to pull the quarks inside protons and neutrons apart increase the strength of the force binding them.  This finding has had enormous implications for the design and conduct of experiments at the world's large accelerator facilities because it has enabled physicists to calculate what the results of the experiments should be.  Discrepancies from those calculated results in turn provide the invaluable clues to new physics—i.e., physics beyond the Standard Model.

The flip side of "asymptotic freedom" has been described as "infra-red slavery."  Since the force that binds quarks inside protons and neutrons grows stronger with distance, protons and neutrons can't be dismantled into constituent quarks.  This part of the Gross-Wilczek discovery is called "confinement."

The discovery of asymptotic freedom led Gross and Wilczek to propose a comprehensive theory of the strong or nuclear force called Quantum ChromoDynamics (QCD), whose three color charges are analogous to the positive and negative charges in the theory of the electromagnetic force or Quantum Electrodynamics (QED).  Because QCD bears remarkable mathematical similarity to QED and also to the theory of the weak force, the key discovery of asymptotic freedom has brought "physics one step closer to fulfilling a grand dream, to formulate a unified theory comprising gravity as well—a theory of everything," according to the announcement by the Swedish Academy.

After obtaining his Ph.D. from UC Berkeley in 1966, Gross was invited to join the select group of junior fellows at Harvard.  Having accepted an appointment as assistant professor at Princeton in 1969, he was promoted to professor in 1972 and later named to two endowed chairs: first as Eugene Higgins Professor of Physics and then as Thomas Jones Professor of Mathematical Physics.

In addition to heading for Stockholm in December for the awarding of the Nobel Prize, Gross will attend ceremonies Nov. 23 in Paris where he will receive France's highest scientific honor, the Grande Médaille D'Or (the Grand Gold Medal).