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Monthly Archives: August 2011
Notes of Enric Ventura’s talk
On the difficulty of inverting automorphisms of free groups Joint work with Pedro Silva and Manuel Ladra 1. Motivation I will give an application of the asymetry of the metric on Outer space. Question [Myasnikov]: Can you find a group … Continue reading
Notes of Ashot Minasyan’s talk
Residual finiteness of outer automorphism groups of relatively hyperbolic groups Joint work with Gilbert Levitt and Denis Osin. I like relatively hyperbolic groups, since combinatorial and geometric group theory meet there. 1. Residual finiteness 1.1. Definition Definition 1 A group … Continue reading
Notes of Martin Bridson’s lecture 3
1. Torsion in and applications Skipping train tracks and mapping tori. 1.1. Finite subgroups Theorem 1 has finitely many classes of finite subgroups. question: Does this holds in arbitrary finitely presented linear groups ? 1.2. Proof Prove a fixed point … Continue reading
Notes of Saul Schleimer’s talk
The structure theorem for train track splitting sequences joint work with Howard Masur and Lee Mosher. Related to recent work of Bestvina and Feighn on folding sequences in the . 1. Introduction Consider surface of genus and boundary components. There … Continue reading
Notes of Martin Bridson lecture 2
Recall denotes the spine of Outer space. 1. Plan revisited The plan I gave yesterday is for a one year course. After discussing with people, I decided on more realistic contents. In this talk, I intend to discuss various definitions … Continue reading
Notes of Arnaud Hilion’s talk
Automorphisms of free groups and free Burnside groups Joint work with Rémi Coulon 1. Rémi Coulon’s results on free Burnside groups The free Burnside group of rank and exponent , , is the group on generators, with relators all the … Continue reading
Notes of Armando Martino’s talk
The Lipschitz metric on Outer space and spectral rigidity 1. The Lipschitz metric I sometimes consider unprojectivized Culler Vogtmann space, i.e. the space of marked metric graphs of genus up to equivalence (isometry and homotopy). Alternatively, it is the space … Continue reading
Notes of Thierry Coulbois’ talk
Botanic of Trees in Outer Space Joint work with Arnaud Hilion I am interested in particular examples of trees with isometric actions of a free group . These are real trees, action is minimal (all orbits are dense), very small … Continue reading
Notes of Chris Cashen’s lecture
Quasiisometries of mapping tori of free group automorphisms Joint work with Natalia Macura 1. The problem Definition 1 Let . The corresponding mapping torus group is the semi-direct product . It depends only on the class . Goal: classify these … Continue reading
Notes of Martin Bridson’s first lecture
1. Plan Outer space and its spine, connectedness, folding, change of marking, contractibility, local structure and symmetries, isoperimetric inequalities, curvature. Lipschitz metric, classification of isometries, existence of train tracks, relative train tracks, refinements, selected applications. Growth, isometric inequality for . … Continue reading
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