Preface ix Chapter 1. Orderable groups and their algebraic properties 1.1. Invariant orderings 1.2. Examples 1.3. Bi-orderable groups 1.4. Positive cone 1.5. Topology and the spaces of orderings 1.6. Testing for orderability 1.7. Characterization of left-orderable groups 1.8. Group rings and zero divisors 1.9. Torsion-free groups which are not left-orderable Chapter 2. Hölder's theorem, convex subgroups and dynamics 2.1. Hölder's Theorem 2.2. Convex subgroups 2.3. Bi-orderable groups are locally indicable 2.4. The dynamic realization of a left-ordering Chapter 3. Free groups, surface groups and covering spaces 3.1. Surfaces 3.2. Ordering free groups 3.3. Ordering surface groups 3.4. A theorem of Farrell Chapter 4. Knots 4.1. Review of classical knot theory 4.2. The Wirtinger presentation 4.3. Knot groups are locally indicable 4.4. Bi-ordering certain knot groups 4.5. Crossing changes: a theorem of Smythe Chapter 5. Three-dimensional manifolds 5.1. Ordering 3-manifold groups 5.2. Surgery 5.3. Branched Coverings 5.4. Bi-orderability and surgery Chapter 6. Foliations 6.1. Examples 6.2. The leaf space vii viii CONTENTS 6.3. Seifert fibred spaces 6.4. R-covered foliations 6.5. The universal circle Chapter 7. Left-orderings of the braid groups 7.1. Orderability properties of the braid groups 7.2. The Dehornoy ordering of B n 7.3. Thurston's orderings of B n 7.4. Applications of the Dehornoy ordering to knot theory Chapter 8. Groups of Homeomorphisms 8.1. Homeomorphisms of a space 8.2. PL homeomorphisms of the cube 8.3. Proof of Theorem 8.6 8.4. Generalizations 8.5. Homeomorphisms of the cube Chapter 9. Conradian left-orderings and local indicability 9.1. The defining property of a Conradian ordering 9.2. Characterizations of Conradian left-orderability Chapter 10. Spaces of orderings 10.1. The natural actions on LO(G) 10.2. Orderings of Z n and Sikora's theorem 10.3. Examples of groups without isolated orderings 10.4. The space of orderings of a free product 10.5. Examples of groups with isolated orderings 10.6. The number of orderings of a group 10.7. Recurrent orderings and a theorem of Witte-Morris Bibliography Index
PrefaceThe inspiration for this book is the remarkable interplay, expecially in the past few decades, between topology and the theory of orderable groups. Applications go in both directions. For example, orderability of the fundamental group of a 3manifold is related to the existence of certain foliations. On the other hand, one can apply topology to study the space of all orderings of a given group, providing strong algebraic applications. Many groups of special topological interest are now known to have invariant orderings, for example braid groups, knot groups, fundamental groups of (almost all) surfaces and many interesting manifolds in higher dimensions.There are several excellent books on orderable groups, and even more so for topology. The current book emphasizes the connections between these subjects, leaving out some details that are available elsewhere, although we have tried to include enough...