Critical slowing down of topological modes

We investigate the critical slowing down of the topological modes using local updating algorithms in lattice 2d CpN-1 models. We show that the topological modes experience a critical slowing down that is much more severe than the one of the quasi-Gaussian modes relevant to the magnetic susceptibility, which is characterized by tau(mag) similar to 7 with z approximate to 2. We argue that this may be a general feature of Monte Carlo simulations of lattice theories with non-trivial topological properties, such as QCD, as also suggested by recent Monte Carlo simulations of 4d SU(N) lattice gauge theories. (C) 2004 Published by Elsevier B.V.