COMPUTATION OF THE RUNNING COUPLING IN THE SU(2) YANG-MILLS THEORY

A finite-size scaling technique is applied to the SU(2) gauge theory (without matter fields) to compute a non-perturbatively defined running coupling alpha(q) for a range of momenta q given in units of the string tension K. We find that already at rather low q, the evolution of alpha(q) is well described by the 2-loop approximation to the Callan-Symanzik beta-function. At the highest momentum reached, q = 20 x square-root K, we obtain alpha(MSBAR)(q) = 0.187+/-0.005+/-0.009 for the running coupling in the MSBAR scheme of dimensional regularization.