PERFECT LATTICE TOPOLOGY - THE QUANTUM ROTOR AS A TEST-CASE

Lattice actions and topological charges that are classically and quant um mechanically perfect (i.e. free of lattice artifacts) are construct ed analytically for the quantum rotor. it is demonstrated that the Man ton action is classically perfect while the Villain action is quantum perfect. The geometric construction for the topological charge is only perfect at the classical level. The quantum perfect lattice topology associates a topological charge distribution, not just a single charge , with each lattice field configuration. For the quantum rotor with th e classically perfect action and topological charge, the remaining cut -off effects are exponentially suppressed. (C) 1997 Published by Elsev ier Science B.V.