From May 3, 2021 to May 7, 2021, Professor O. Kharlampovich from City University of New York will teach a mini course on Groups acting on Trees. Due to the current situation caused by the corona virus disease, the mini course will take place virtually. Bass-Serre theory relates group actions on trees with decomposing groups as iterated applications of the operations of amalgamated product and HNN extension, via the notion of the fundamental group of a graph of groups. One…