Quantum Chromodynamics

Claudio Rebbi

A crucial component of the scientific process consists of deriving quantitative predictions from assumed theoretical models. The power of modern computers has added a new dimension to this aspect of research. Today, physicists can use advanced numerical techniques to simulate the behavior of very complex systems and thus solve problems that defy the more traditional methods of mathematical analysis. Scientists in the particle theory group have been applying forefront computational methods to the study of quantum chromodynamics (QCD, the theory of interacting quarks and gluons) and to other particle models. Space-time is approximated by a lattice of points, and the fundamental fields, defined over this lattice, are represented by an extremely large collection of numbers stored in the memory of a supercomputer. Calculating at the rate of billions of operations per second, the computer simulates the effects of quantum fluctuations of the fields. From such techniques, one can calculate fundamental observables such as particle masses or the temperature at which quarks and gluons become unbound and evaluate matrix elements crucial for the interpretation of collider experiments. Students, research staff, and faculty working on these problems avail themselves of the supercomputer resources and support structure of the Center for Computational Science. While doing research in the fascinating and challenging field of subatomic particles, students also acquire invaluable expertise in the use of the most modern and powerful supercomputer technologies.