MULTIGRID ACCELERATION FOR ASYMPTOTICALLY FREE THEORIES

We present a multigrid Monte Carlo algorithm with piecewise-linear interpolation operator for nonlinear sigma-models with global chiral SU(N) x SU(N) symmetry or CP(N-1) manifold. We demonstrate its efficiency in the two-dimensional SU(3) x SU(3) chiral model and the CP3 nonlinear cr model for correlation length up to 77 in lattice units. On lattices up to size 512 x 512 we achieve almost complete elimination of critical slowing down in the CP3 case, with a dynamical critical exponent z(MGMC) = 0.2 +/- 0.1. Asymptotic scaling with the bare coupling does not appear to set in for the standard action of both models in the range of parameters studied.