Near actions of groups, 2 (Yves Cornulier, Lyon 1)

21.02.2018 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).

Lieu

Room 624, Attn. unusual day & place, Séminaire "Groupes et Géométrie"

entrée libre