Memoirs of the American Mathematical Society 1997; 126 pp; softcover Volume: 126 ISBN10: 0821805959 ISBN13: 9780821805954 List Price: US$45 Individual Members: US$27 Institutional Members: US$36 Order Code: MEMO/126/604
 This work presents a systematic study of decision problems for equational theories of algebras of binary relations (relation algebras). For example, an easily applicable but deep method, based on von Neumann's coordinatization theorem, is developed for establishing undecidability results. The method is used to solve several outstanding problems posed by Tarski. In addition, the complexity of intervals of equational theories of relation algebras with respect to questions of decidability is investigated. Using ideas that go back to Jónsson and Lyndon, the authors show that such intervals can have the same complexity as the lattice of subsets of the set of the natural numbers. Finally, some new and quite interesting examples of decidable equational theories are given. The methods developed in the monograph show promise of broad applicability. They provide researchers in algebra and logic with a new arsenal of techniques for resolving decision questions in various domains of algebraic logic. Readership Graduate students, research mathematicians and computer scientists interested in questions of computability in algebra, logic and computer science. Table of Contents  Introduction
 Preliminaries
 Undecidability
 A lattice embedding that preserves decidability and undecidability
 A finitely generated, infinite, simple relation algebra with a decidable equational theory
 Bibliography
 Index of symbols
 Index of names and subjects
