Some Comments on Multigrid Methods for Computing Propagators

Alan D. Sokal
Department of Physics
New York University
4 Washington Place
New York, NY 10003


I make three conceptual points regarding multigrid methods for computing propagators in lattice gauge theory: 1) The class of operators handled by the algorithm must be stable under coarsening. 2) Problems related by symmetry should have solution methods related by symmetry. 3) It is crucial to distinguish the vector space $V$ from its dual space $V^*$. All the existing algorithms violate one or more of these principles.

Contributed July 31, 1993.