Seminar Talks

List of seminar talks (pdf) since 1999.


Title: Planar Cayley graphs and Kleinian groups
Speaker: Prof. Agelos Georgakopoulos (University of Warwick)
Date: Wednesday, July 1st, 2020, 16:15 (virtual coffee break beginning 15:45)
Room: Webex meeting

Kleinian groups are a classical topic. I will give an overview
and explain their relationship to groups having planar Cayley graphs.
Moreover, I will show that if a finitely generated group G acts faithfully
and properly discontinuously by homeomorphisms on a planar surface, then G
admits such an action that is in addition co-compact.

Link to preprint:}

Webex meeting number: 137 170 6111

Password: iUMCF5Pb6M5


UPDATE: Strukturtheorie-Seminar

Title: Cayley-Abels graphs of totally disconnected locally compact groups
Speaker: Prof. Rögnvaldur Möller + Dr. Waltraud Lederle (University of Iceland + Université Catholique de Louvain)
Date: Wednesday 10 June 2020, 16:15 (virtual coffee break beginning 15:45)
Room: Webex meeting

The Cayley-Abels graph of a compactly generated totally disconnected locally compact group is an analogue of the ordinary Cayley graph for a finitely generated group.   Given a compactly generated totally disconnected locally compact group G, what is the lowest possible valency of a Cayley-Abels graph?  How does the valency relate to other properties of the group?  Is there something special about graphs that have this lowest possible valency? 

Joint work with Arnbjörg Soffia Arnadottir (Waterloo, Canada)

Webex meeting number: 321 855 198

Password: ZNpTHv9PT27

Join by video system:


Title: Poisson type limit theorems for a noncommutative independence associated with positive symmetric cones
Speaker: Lahcen Oussi (Intitut für Diskrete Mathematik, TU Graz)
Date: Mittwoch, 13.5.2020, 16:15

We present an analogue of the classical Law of Small Numbers, formulated for a noncommutative independence (the bm-independence), where the random variables are indexed by elements of positive symmetric cones in Euclidean spaces, including $\mathbb{R}^{d}_{+}$, the Lorentz cone in Minkowski spacetime and positive definite real symmetric matrices. The geometry of the cones plays an important role in the study as the volume characteristic sequences of each cone, related to the growth of volumes of intervals in the cone, appears in our final formulas. Also the combinatorics of ordered partitions is crucial for our study as one of the main tools for performed computations.

Colloquium of the Institute of Discrete Mathematics

Title: Infinite bridges for tree-valued Markov chains
Speaker: Prof. Anton WAKOLBINGER (Universität Frankfurt)
Date: Wednesday, 11 March 2020, 16:15
Room: Lecture room BE01, Steyrergasse 30, ground floor

For a few examples of tree-valued Markov chains (Rémy’s tree growth chain, the radix sort chain and the PATRICIA chain), we discuss representations of their Doob-Martin boundary that are obtained from their extremal “bridges to infinity”
(and thus from a conditioning on their remote future).

The talk is based on joint work with Steve Evans (Berkeley) and Rudolf Grübel (Hannover).

EGW, Doob-Martin boundary of Rémy's tree growth chain, Ann. Probab. 45b (2017), 225-277.

EW1, Radix sort trees in the large, Electron. Commun. Probab. 22 (2017).

EW2, PATRICIA bridges. In: Genealogies of Interacting Particle Systems, eds.
M. Birkner, R. Sun and J. Swart, pp. 233-267, World Scientific 2020.

Selection procedure for assistant position

Title: Short talks by several candidates
Speaker: K. Heuer / K. Kolesko / A. Muranova / C. Alves / F. Tonti ()
Date: 29 + 30. + 31.1.2020, afternoon

Assistant position (with PhD) - selection procedure

20 minutes' scientific talks (titles below) followed by

20 Minuten Lehrvortrag (Deutsch), Thema
``Die Eulersche Zahl e''

Wednesday, 29.1.2020, seminar room A306 (Steyrergasse 30, 3rd floor):

14:00 Karl HEUER (Berlin): Forcing Hamiltonicity in locally finite graphs via forbidden induced subgraphs

15:30 Konrad KOLESKO (Innsbruck): Limit theorems in branching processes

Thursday, 30.1., seminar room AE06 (Steyrergasse 30, ground floor):

13:30 Anna MURANOVA (Bielefeld): On the notion of effective impedance for networks

15:00 Caio ALVES (Leipzig): Decoupling inequalities in loop percolation

Friday, 31.1., seminar room AE02 (Steyrergasse 30, ground floor):

13:30 Fabio TONTI (Vienna): A new proof of Thoma's theorem