Near actions of groups (Yves Cornulier, Lyon 1)

20.02.2018 10:30

A near permutation of a set is a bijection between two cofinite subsets, modulo coincidence on smaller cofinite subsets. Near permutations of a set form a group, and group homomorphisms into this group yield the notion of a near action. Given a near action, we introduce and study the realizability problem, which asks whether it is induced by a genuine action; we study various obstructions to realizability. The talk will be an introduction to these questions and will present several examples in which near actions occur, including groups of interval exchange transformations (near acting on the interval), and Thompson groups (near acting on a tree).


Room 623, Séminaire "Groupes et Géométrie"

Organisé par

Section de mathématiques


Yves de Cornulier, Lyon 1

entrée libre


Catégorie: Séminaire

Mots clés: groupes et géométrie