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2 votes
1 answer
137 views

Indicability of $\mathrm{Out}(F_n)$

A group $G$ is said to be indicable if it surjects onto $\mathbb{Z}$. If $n=1$: $\mathrm{Out}(F_1)=\mathbb{Z}/2\mathbb{Z}$ and no finite group surjects onto an infinite group. If $n\geq 4$: $\...
Marcos's user avatar
  • 911
9 votes
1 answer
377 views

Morse theory on outer space via the lengths of finitely many conjugacy classes

Let $F_n$ be the free group on letters $\{x_1,\ldots,x_n\}$ and let $X_n$ be the (reduced) outer space of rank $n$. Points of $X_n$ thus correspond to pairs $(G,\mu)$, where $G$ is a finite connected ...
Sarah's user avatar
  • 93
4 votes
1 answer
338 views

outer automorphism classification

I am trying to understand Bestvina's "A Bers-like proof of the existence of train tracks for free group automorphisms". I'm going to ask a probably trivial question ... Here we go: The automorphism $\...
1123581321's user avatar
7 votes
0 answers
319 views

How does Outer Space look like without a simplex?

Considering the simplicial structure of Culler and Vogtmanns Outer Space $CV_n$. The question is now: Let $\Delta \subset CV_n$ be a closed simplex of dimension $3n-4$ or $3n-5$, how does $CV_n \...
ctst's user avatar
  • 255
7 votes
1 answer
523 views

$\operatorname{Out}(F_n)$ is not linear for $n > 3$

The paper The Tits alternative for $\operatorname{Out}(F_n)$ I by Bestvina, Feighn and Handel and the paper Automorphisms of free groups and Outer space by Vogtmann both state that $\operatorname{Aut}(...
Student's user avatar
  • 275
4 votes
1 answer
151 views

Genericity of irreducible automorphisms of free groups

I have seen in the literature that Irreducible outer automorphisms of a free group $F_n$ are "generic". I would like to ask that if for example : it is true that for any generating set $X$ of $Out(...
user75691's user avatar
  • 339