Nell'ambito del ciclo "Insalate di matematica", lunedì 21 Ottobre alle ore 10.30 in aula 3014 (edificio U5) Giulia dal Verme, dottoranda presso l'Università di Milano-Bicocca, terrà un seminario dal titolo:
"An introduction to a Bass-Serre theory for groupoids"
Abstract:
The so-called Bass-Serre theory gives a complete and satisfactory description of groups acting on trees via the structure theorem.
Roughly speaking, a graph of groups consists of a graph \Gamma together with a group for each vertex and edge of \Gamma, and monomorphisms from each edge group to the adjacent vertex groups. Any group action on a tree (satisfying some mild hypotheses) induces a graph of groups, while any graph of groups has a canonical associated group, called the fundamental group, and a tree, called the Bass-Serre tree, such that the fundamental group acts on the Bass-Serre tree. The so-called Fundamental Theorem of Bass-Serre Theory says that these processes are mutually inverse, so that graphs of groups "encode'' group actions on trees.
Following these ideas, we try to build the appropriate analogue of the Bass-Serre theory for groupoids.
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