CRPC-TR94460 Title: An Algebraic Schwarz Theory Authors: Michael Holst Date: June 1994 Of the authors listed above, please indicate which are: Minority authors: Female authors: Student authors: Keywords (list up to 8): Multigrid, Domain Decomposition, Schwarz, Convergence Theory, Operator Theory. Abstract: In this paper, we discuss the general theory of additive and multiplicative Schwarz methods for self-adjoint positive linear operator equations, representative methods of particular interest here being multigrid and domain decomposition. We examine closely one of the most useful and elegant modern convergence theories for these methods, following closely the recent work of Dryja and Widlund, Xu, and their colleagues. Our motivation is to fully understand this theory, and then to develop a variation of the theory in a slightly more general setting, which will be useful in the analysis of algebraic multigrid and domain decomposition methods, when little or no finite element structure is available. Using this approach we can show some convergence results for a very broad class of fully algebraic domain decomposition methods, without regularity assumptions about the continuous problem. Although we cannot at this time use the theory to provide a ``good'' convergence theory for algebraic multigrid methods, we believe that with additional analysis it may be possible to do so using this framework, as well as to use the framework to guide the design of the coarse problems. The language we employ throughout is algebraic, and can be interpreted abstractly in terms of operators on Hilbert spaces, or in terms of matrix operators. Publication History: Submitted to: Published in: