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Groups & dynamics seminar: Noam Kolodner (HUJI) - Surjectivity of morphisms of labeled core-graph under the action of automorphisms of a free group | Einstein Institute of Mathematics

Groups & dynamics seminar: Noam Kolodner (HUJI) - Surjectivity of morphisms of labeled core-graph under the action of automorphisms of a free group

Date: 
Thu, 20/06/201910:00-11:00
For a finitely generated subgroup H of the free group F_r, the Stallings graph of H is a finite combinatorial graph, whose edges are labeled by r letters (and their inverses), so that paths in the graphs correspond precisely to the words in H. Furthermore, there is a map between the graphs of two subgroups H and J, precisely when one is a subgroups of the other. Stallings theory studies the algebraic information which is encoded in the combinatorics of these graphs and maps. We focus on the question whether H is contained in a free factor of J (which is called a "non-algebraic extension"), and give new algorithms and examples which answer some open questions in the field. No prior knowledge is required.