3 U.S. Physicists Win Nobel for Research on the ‘Strong Force’

Researchers from Caltech, UC Santa Barbara and MIT will share the 2004 Nobel Prize in physics for their studies of the “strong force,” the powerful and mysterious energy that holds the nuclei of atoms together even as the electrical charges on protons try to blow them apart.

The Nobel Foundation said Tuesday that the award would go to H. David Politzer, 55, of Caltech; David J. Gross, 63, of UC Santa Barbara; and Frank Wilczek, 55, of the Massachusetts Institute of Technology for their development of a crucial part of the theory now known as quantum chromodynamics.

It was the fourth Nobel for UC Santa Barbara in the last six years, marking that university’s emergence as a leading research institution.

The development of quantum chromodynamics -- so called because researchers arbitrarily assign different types of quarks different colors in the same way that electrons and protons were arbitrarily assigned charges -- is widely considered a major step toward the physicist’s Holy Grail, the “Theory of Everything” that would use a single, simple set of equations to explain everything from the forces holding atoms together to the gravitational fields that hold planets in orbit.

The trio explained the mystifying characteristics of the strong force, which holds together the fundamental building blocks of nature called quarks to form protons and neutrons, two of the basic components of atoms.

Experiments in which physicists bombarded atoms with high-energy particles indicated that the then-theoretical quarks in protons and neutrons were held together only very loosely. Nonetheless, no matter what researchers did, they could not blow the elementary particles apart to produce isolated quarks.

“The history of understanding matter is taking things apart,” said cosmologist Michael Turner of the National Science Foundation. “How could it be that they are made of quarks and you can’t get them out? It was a deep conundrum.”

At the time of their prize-winning work, Politzer was a graduate student at Harvard University and Wilczek a graduate student in Gross’ lab at Princeton University. Independently, they developed the theory and the mathematical equations to show that quarks were held together by the strong force, which, unlike any other force in the universe, gets stronger as the quarks get further apart -- a concept now known as “asymptotic freedom.”

The simplest analogy is to a rubber band encircling two objects. When the objects are close together, the rubber band fits loosely. But as they are drawn apart, the rubber band stretches, trying to push them back together.

Electromagnetic interactions, the weak force (responsible for radioactivity) and gravity, in contrast, get much weaker as two objects get further apart.

With the publication of their work, “overnight, the strong nuclear force went from a mystery to a solved problem,” said physicist Joseph Polchinski of UC Santa Barbara.

The theory initially seemed outlandish, MIT’s Wilczek said Tuesday, but it has subsequently held up to multiple tests, and the derivation of the mathematics is now widely used as a homework problem in physics classes. The Nobel recognition came as “a great relief,” he added.

Quantum chromodynamics “basically explains 99% of all physics and chemistry at a very fundamental level,” said the National Science Foundation’s Turner. “It explains protons and neutrons, how they are held together, how electrons are held in orbits around the nucleus. It’s the completion of the understanding of matter in ordinary circumstances. It also changed how we thought about the earliest moments of the universe.”

Before the Nobel laureates’ work, cosmologists couldn’t explain the first 1/100,000th of a second of creation, because they did not understand how protons and neutrons could overcome their mutual repulsion and be compacted together. But quantum chromodynamics predicts that the quarks from which protons and neutrons are formed could be tightly compacted, leading to the current idea of the early cosmos as a “quark soup.”

“It came as no surprise that this group was awarded the prize,” said theoretical physicist Mark Wise of Caltech. Their work “impacts our understanding of the laws of nature in a fundamental way.”

The new laureates’ names “will rank right up there with Newton and Coulomb,” said UC Santa Barbara Chancellor Henry T. Yang. Newton formulated the laws of gravity, Charles-Augustin de Coulomb those of electromagnetic interaction.

Caltech called a news conference Tuesday morning for Politzer but, to everyone’s surprise, he did not show up. “He’s shy,” said Jill Perry, director of media relations. “He’s just going to take this in his own quiet way -- with family and friends.”

David Baltimore, Caltech’s president, said he had twisted Politzer’s arm “as much as you can over the phone” to attend, but with no success.

Colleagues were surprised, because Politzer is not a recluse. He even played the part of a physicist in “Fat Man and Little Boy,” a movie about the Manhattan Project.

“He’s a very regular guy, except a lot smarter than most of us,” Wise said.

Gross is the director of the Kavli Institute of Theoretical Physics at UC Santa Barbara, which coincidentally is celebrating its 25th anniversary this week. “We invited 12 Nobel laureates,” he said. “Now it looks like we will have 14.”

The notification came via “the proverbial call in the middle of the night,” he said. “I haven’t had a drop of sleep since.”

People have been telling him for years that he would win the Nobel, he said, and “I even began to believe it.” But it was a long time coming, he added -- 31 years after their paper’s publication, to be exact.

Wilczek was in the shower when he got the phone call at 5:30 a.m., said his wife, Betsy Devine. “It was this person with a beautiful accent,” she said, “and it was so early, so I was immediately hopeful. Frank came in, dripped all over the floor, and talked to half the Swedish Academy.”

The three laureates will share the $1.35-million prize equally.

Caltech and MIT have won numerous Nobel Prizes over the decade.

UC Santa Barbara has now won five. In addition to Gross, the other recipients are: Herbert Kroener, chemistry, 2000; Alan J. Heeger, chemistry, 2000; Walter Kohn, chemistry, 1998; and J. Robert Schrieffer, physics, 1972.

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Times staff writer Usha Lee McFarling contributed to this report.