Gambling with a theory of quarks

The aim of the game recently in quantum chromodynamics has been to find a single theory that describes both the short‐range and the long‐range interaction of quarks (PHYSICS TODAY, July 1976, page 17). The principal obstacle is that the coupling of quarks changes with the size scale: Gauge theories applied to the short range have predicted that the quark coupling there is weak, going to zero logarithmically with quark spacing. In this phenomenon of asymptotic freedom, the quarks behave as nearly free particles. By contrast, gauge theories applied to the long range have indicated that strong coupling would confine the quarks to bound states. The challenge is to bridge the gap between these two regions and to demonstrate that the longrange, strong‐coupling property of confinement persists even when the shortrange couplings are weak. The application of Monte Carlo techniques to a lattice gauge theory has moved the players ahead one step in this direction. The game will be advanced by several more steps if theorists have luck in extending the same procedure to calculate the masses of the lowest lying quark bound states such as the pi or rho mesons.

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