This is a website for the reading group on Bass-Serre theory that we are doing in the Spring semester 2022/23 in Ljubljana.
The main reference is J. P. Serre, Trees, Springer, 1980.
Each participant chooses a topic and prepares a one-hour lecture for the group. You do not need to cover the whole material in great detail and it is completely OK to only explain the main ideas (after all, you only have 1 hour).
If you decide to participate, send an email to urban.jezernik@fmf.uni-lj.si so that I mark the topic has been chosen.
Amalgams [pages 1-12].
Trees [pages 13-24].
Trees and free groups [pages 25-31].
Trees and amalgams [pages 32-40].
Structure of a group acting on a tree, part 1 [pages 41-50].
Structure of a group acting on a tree, part 2 [pages 50-57].
Amalgams and fixed points [pages 58-68].
The tree of SL2 over a local field, part 1 [pages 69-75].
The tree of SL2 over a local field, part 2 [pages 76-81].
The tree of SL2 over a local field, part 3 [pages 82-89].
The tree of SL2 over a local field, part 4 [pages 89-95].
We meet Tuesdays at 11.15 in classroom 3.07.
28/02/2023 Primož Moravec: Introduction to Bass-Serre theory [video (Passcode: R^Fp$%^4)]
14/03/2023 Jaka Smrekar: Amalgams [video (Passcode: Q04@q#10)]
21/03/2023 Izak Jenko: Trees [video (Passcode: T7L9E$c&)]
28/03/2023 Antonio Montero: Trees and free groups [video (Passcode: =ECdzM7m)]
04/04/2023 Nikola Kovačević: Trees and amalgams [video - no sound (Passcode: 5%9dAU8+)]
11/04/2023 Marko Čmrlec: Structure of a group acting on a tree, part 1 [video (Passcode: Gq&Az6*1)]
18/04/2023 Maruša Lekše: Structure of a group acting on a tree, part 2
25/04/2023 Tim Milanez: Amalgams and fixed points [video (Passcode: *7aF8b=s)]
09/05/2023 Urban Jezernik: The tree of SL2 over a local field, part 1 [video (Passcode: $T%t6kSN)]
16/05/2023 Primož Moravec: The tree of SL2 over a local field, part 2 [video (Passcode: nNqud4+.)]
23/05/2023 Nikola Kovačević: The tree of SL2 over a local field, part 3 [video (Passcode: VNiBQ5#9)]
30/05/2023 Marco Barbieri: The tree of SL2 over a local field, part 4 [video (Passcode: ^sjPc5!Q)]