Force That Holds Nucleus Together Is Recognized

The 2004 Nobel Prize in Physics has been awarded to three U.S. physics professors for their contributions to theories describing forces that govern the interactions of quarks. These subatomic particles are the fundamental building blocks of protons and neutrons.

David J. Gross, 63, of the University of California, Santa Barbara; H. David Politzer, 55, of California Institute of Technology; and Frank A. Wilczek, 53, of Massachusetts Institute of Technology, discovered, through theoretical investigations, that the intensity of the so-called strong interaction--the force that holds atomic nuclei together--weakens as the distance between quarks decreases and strengthens as the separation between quarks increases.

The surprising phenomenon, first reported in 1973, is termed "asymptotic freedom." The unexpected nature of the force causes quarks to behave as free particles at infinitesimally small separations. The theoretical result led to the development of quantum chromodynamics, which is recognized by physicists as an important piece of the Standard Model. That model accounts for the electromagnetic forces between charged particles in addition to the weak and strong forces that are active in atomic nuclei.

The prize money, nearly $1.4 million, will be divided equally among the three laureates.