About
On the occasion of the 60th birthday of Oswin Aichholzer, a colloquium will take place on the morning of March 28th, 2026 in Hagen (Germany), as a satellite event of EuroCG 2026. After the colloquium, we will have lunch together.
Schedule
| 09:00 – 09:05 | Opening |
| 09:05 – 09:50 |
Ruy Fabila-Monroy: Extremal Point Set Theory The key questions in extremal graph theory ask what global structures emerge when one maximizes the number of edges subject to some constraint. For example, the triangle-free graph with the largest number of edges is the complete bipartite graph. In this talk, I will use this perspective to study point sets that maximize the number of certain subconfigurations. For instance, point sets that minimize crossings in rectilinear drawings of Kn can equivalently be viewed as maximizing non-convex 4-tuples. We explore what "extremal" point sets look like under such constraints. |
| 09:50 – 10:20 | Cake Break |
| 10:20 – 11:05 |
Maarten Löffler: Playing with Proofs The research fields of discrete mathematics and theoretical computer science, and the design of fun and challenging games and puzzles, share a rich and symbiotic history. The analysis of games often leads to new fundamental insights in mathematics, and conversely, proof techniques can inspire new games that are fun to play, also for non-mathematicians. We will highlight a few examples of this two-way street that I have had the honour to work on with Oswin throughout the years. 
|
| 11:05 – 11:15 | Short Break |
| 11:15 – 12:00 |
Günter Rote: Enumeration and Counting of Pseudoline Arrangements I will report how we managed to count the number of simple pseudoline arrangements with up to 16 lines. Related objects and side questions, like abstract order types of point sets, or how to sweep a rope over a pseudoline arrangement, are also counted and touched upon. |
| 12:00 – 12:30 | Personal Remarks |
| 12:30 – 12:35 | Closing |
| 12:35 – 13:00 | Walk to Lunch |
| 13:00 | Lunch |
About Oswin Aichholzer
Oswin was born in 1965 Spittal an der Drau in Carinthia, Austria. He received his PhD under the supervision of Franz Aurenhammer at TU Graz in 1997. Oswin is an expert in computational and combinatorial geometry. He is well known for his exhaustive data bases of all realizable order types and rotation systems of small cardinality, where the former even allowed queries via email for a long time, a service which has been extensively used and appreciated. He has supervised 13 PhD students (2 currently under supervision and 11 graduated), several of whom now pursue a career in academia. Oswin loves cycling, hiking, puzzles, and games. He has a soft spot for sweets, helping him to re-earn the calories for his ourdoor activities.
Registration
While there is no official registration, we would be grateful if you indicate your interest in attendence in this form on Google Forms or send us a short e-mail to oswinfest@vogtenhuber.org. This will help us to estimate the number of participants.
There is no registration fee. Lunch will be self-paid by the participants.
Venue
The Oswinfest takes place at FernUniversität in Hagen, Universitätsstraße 11, 58097 Hagen, Germany. It will be held in the Ellipse room, located in Building 3, ground floor (Openstreetmap; Google Maps).
Lunch will take place at the Bavarian restaurant Humpert am Höing, Fleyerstraße 123, 58097 Hagen. (Openstreetmap; Google Maps).