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Current information:


Dates: Monday, 10:00 (c.t.) -12:00 and Thursday, 10:00 (c.t.) - 12:00;  Room: SR 10 (Geb. 2.4)

Lecturers: Prof. Dr. Laurent Bartholdi and Prof. Dr. Gabriela Weitze-Schmithüsen

Contact: weitze[at], bartholdi[at]

Teaching assistant: Christian Steinhart

Contact: steinhart[at]
Office hours: By appointment, or just check at room 303, Building E 2.4
Problem session: Monday, 12:00 (s.t.) in SR 10 (directly after the lecture)



The Geometric group theory is a relatively new mathematical discipline which builds interesting connections between group theory and geometry. Its goal is to study groups using geometric methods. There are two main approaches:

  • Study how a group acts on a suitable geometric space.
  • Consider the group itself as a geometric space.

The interaction of these two fields has  lead to a series of mathematical breakthroughs in the last 50 years, among them Gromov's program to classify finitely generated groups, the systematic study of closed three manifolds by William Thurston, the solution of the isomorphism problem of word hyperbolic groups by Sela and the proof of the Haken conjecture by Ian Agol. The theory of automata groups closely links geometric group theory to computer sciences.

This lecture is a first introduction to geometric group theory. We will introduce Cayley graphs, the theory of quasi-isometries and the so-called coase geometry. Some highlights will be the theorem of Schwarz and Milnor which relates geometric properties of the group to  geometric spaces on which it acts in a good way, as well as examples of groups which play an eminent role in current research. This will offer insights into a rich world between algebra and geometry.

The lecture is a new Stammvorlesung which gives access to the mathematical disciplines of the two lecturer. It is aimed at bachelor and master students. With its algorithmic aspects it can also be an interesting lecture for students in computer sciences.



  • Free groups, presentations of groups, Cayley graphs
  • Fundamental groups and covering theory
  • Coarse geometry, quasi-isometries ad the theorem of Milnor and Schwarz
  • Gromov hyperbolicity
  • Optional: Growth of groups, space of ends, Fuchsian groups, Example of geometric spaces as Teichmüller space, translation surfaces and outer space.


Linear Algebra I und II and Algebra (recommended).


  • Pierre de la Harpe: Topics in Geometric Group Theory, Chicago Lectures in Mathematics 2003

  • Clara Löh: Geometric Group Theory, Springer-Verlag 2017


Problems and notes:

You can hand in your solutions directly in person mondays in the lecture/problem session, put them in the corresponding box in the basement in E 2.4 or hand it directly to Christian Steinhart in paper or digitally via E-Mail or Teams.

Problem sheet
Exercise Sheet 1
Exercise Sheet 2
Exercise Sheet 3
Exercise Sheet 4
Exercise Sheet 5
Exercise Sheet 6
Exercise Sheet 7
Exercise Sheet 8
Exercise Sheet 9
Exercise Sheet 10
Exercise Sheet 11
Exercise Sheet 12
Exercise Sheet 13