Wilfrid Hodges

Ian Chiswell

Mathematical Logic (Oxford Texts in Logic)

Assuming no previous study in logic, this informal yet rigorous text covers the material of a standard undergraduate first course in mathematical logic, using natural deduction and leading up to the completeness theorem for first-order logic. At each stage of the text, the reader is given an intuition based on standard mathematical practice, which is subsequently developed with clean formal mathematics. Alongside the practical examples, readers learn what can and can't be calculated; for example the correctness of a derivation proving a given sequent can be tested mechanically, but there is no general mechanical test for the existence of a derivation proving the given sequent. The undecidability results are proved rigorously in an optional final chapter, assuming Matiyasevich's theorem characterising the computably enumerable relations. Rigorous proofs of the adequacy and completeness proofs of the relevant logics are provided, with careful attention to the languages involved. Optional sections discuss the classification of mathematical structures by first-order theories; the required theory of cardinality is developed from scratch. Throughout the book there are notes on historical aspects of the material, and connections with linguistics and computer science, and the discussion of syntax and semantics is influenced by modern linguistic approaches. Two basic themes in recent cognitive science studies of actual human reasoning are also introduced. Including extensive exercises and selected solutions, this text is ideal for students in Logic, Mathematics, Philosophy, and Computer Science.

Mathematical Logic

The theory of o-trees has its origin in the work of Lyndon on length functions in groups. The first definition of an R -tree was given by Tits in 1977. The importance of o-trees was established by Morgan and Shalen, who showed how to compactify a generalisation of Teichmller space for a finitely generated group using R -trees. In that work they were led to define the idea of a o-tree, where o is an arbitrary ordered abelian group. Since then there has been much progress in understanding the structure of groups acting on R -trees, notably Rips'' theorem on free actions. There has also been some progress for certain other ordered abelian groups o, including some interesting connections with model theory. Introduction to o-Trees will prove to be useful for mathematicians and research students in algebra and topology. Contents: o-Trees and Their Construction; Isometries of o-Trees; Aspects of Group Actions on o-Trees; Free Actions; Rips'' Theorem. Readership: Mathematicians and research students in algebra and topology."

Introduction to [lambda]-trees

The theory of ?-trees has its origin in the work of Lyndon on length functions in groups. The first definition of an R-tree was given by Tits in 1977. The importance of ?-trees was established by Morgan and Shalen, who showed how to compactify a generalisation of Teichmller space for a finitely generated group using R-trees. In that work they were led to define the idea of a ?-tree, where ? is an arbitrary ordered abelian group. Since then there has been much progress in understanding the structure of groups acting on R-trees, notably Rips' theorem on free actions. There has also been some progress for certain other ordered abelian groups ?, including some interesting connections with model theory.Introduction to ?-Trees will prove to be useful for mathematicians and research students in algebra and topology.

Thomas Müller

Thomas Wolfgang Müller

This coherent introduction provides a new perspective on group actions on R-trees.

A Universal Construction for Groups Acting Freely on Real Trees

School of Mathematical Sciences Wilfrid Hodges

Assuming no previous study in logic, this informal yet rigorous text covers the material of a standard undergraduate first course in mathematical logic, using natural deduction and leading up to the completeness theorem for first-order logic. At each stage of the text, the reader is given an intuition based on standard mathematical practice, which is subsequently developed with clean formal mathematics. Alongside the practical examples, readers learn what can and can't becalculated; for example the correctness of a derivation proving a given sequent can be tested mechanically, but there is no general mechanical test for the existence of a derivation proving the given sequent. The undecidability results are proved rigorously in an optional final chapter, assumingMatiyasevich's theorem characterising the computably enumerable relations. Rigorous proofs of the adequacy and completeness proofs of the relevant logics are provided, with careful attention to the languages involved. Optional sections discuss the classification of mathematical structures by first-order theories; the required theory of cardinality is developed from scratch. Throughout the book there are notes on historical aspects of the material, and connections with linguistics andcomputer science, and the discussion of syntax and semantics is influenced by modern linguistic approaches. Two basic themes in recent cognitive science studies of actual human reasoning are also introduced. Including extensive exercises and selected solutions, this text is ideal for students in Logic,Mathematics, Philosophy, and Computer Science.

Ian Chiswell

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