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Subgroup Decomposition in $\mathsf {Out}(F_n)$

About this Title

Michael Handel, Lehman College, CUNY and Lee Mosher, Rutgers University, Newark

Publication: Memoirs of the American Mathematical Society
Publication Year: 2020; Volume 264, Number 1280
ISBNs: 978-1-4704-4113-5 (print); 978-1-4704-5802-7 (online)
DOI: https://doi.org/10.1090/memo/1280
Published electronically: April 20, 2020
MSC: Primary 20F28; Secondary 20E05, 20F65, 57M07

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Table of Contents

Chapters

  • Introduction to Subgroup Decomposition

1. Geometric Models

  • Introduction to Part I
  • 1. Preliminaries: Decomposing outer automorphisms
  • 2. Geometric EG strata and geometric laminations
  • 3. Vertex groups and vertex group systems

2. A relative Kolchin theorem

  • Introduction to Part II
  • 4. Statements of the main results
  • 5. Preliminaries
  • 6. An outline of the relative Kolchin theorem
  • 7. $IA_n(\mathbb {Z}/3)$ periodic conjugacy classes
  • 8. $IA_n(\mathbb {Z}/3)$ periodic free factors
  • 9. Limit Trees
  • 10. Carrying asymptotic data: Proposition
  • 11. Finding Nielsen pairs: Proposition

3. Weak Attraction Theory

  • Introduction to Part III
  • 12. The nonattracting subgroup system
  • 13. Nonattracted lines

4. Relatively irreducible subgroups

  • Introduction to Part IV
  • 14. Ping-pong on geodesic lines
  • 15. Proof of Theorem C
  • 16. A filling lemma

Abstract

In this work we develop a decomposition theory for subgroups of $\mathsf {Out}(F_n)$ which generalizes the decomposition theory for individual elements of $\mathsf {Out}(F_n)$ found in work of Bestvina, Feighn, and Handel, and which is analogous to the decomposition theory for subgroups of mapping class groups found in work of Ivanov.

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