Hausdorff Center for Mathematics

Only Moscow performed better: Bonn maths students enjoy great success at the IMC once again

At this year’s International Mathematics Competition for University Students (IMC) in Blagoevgrad, Bulgaria—held from July 27 to August 3, 2026—the Rheinische Friedrich-Wilhelms-Universität Bonn took second place in the unofficial team ranking. The seven-person Bonn team managed to finish ahead of the previously dominant Saint Petersburg State University, though the Moscow Institute of Physics and Technology proved even stronger this year, taking first place by a wide margin. In the individual ranking, Lennart Christian Grabbel achieved an outstanding fourth place. All seven participants from Bonn took home medals.

The International Mathematics Competition for University Students has been held annually since 1994. This year, 447 students from 135 universities around the world participated. The University of Bonn team also achieved outstanding results in the individual competition: Lennart Christian Grabbel placed fourth in the ranking and, like Samuel Meyer, won a coveted Grand First Prize. Boldiszàr Mann, Paul Jakob Schmidt, and David Streun were awarded gold medals; Cedric Friedrich received a silver medal; and Birgit Veldi was awarded a bronze medal.

We would like to extend our sincere thanks to Lawk Mineh, a postdoctoral researcher at the Mathematical Institute at the University of Bonn, who served as team captain for the Bonn team, graded the problems, and filed appeals on behalf of the German team regarding the scoring.

Almost every year, the team of math students from Bonn is among the top five teams at the IMC in Blagoevgrad. In recent years, many of its current members have represented Germany at the annual International Mathematical Olympiad (IMO) for school students and then decided to study mathematics in Bonn. The Bonn team is supported by the Hausdorff Center for Mathematics (HCM) and by QuantCo. At the HCM, excellent support for young talent at all career levels is of high priority, from early support for children in the Bonn Math Club to the Hausdorff School for doctoral students and postdocs to the Bonn Junior Fellows.

English version below

Beim Tanz Mathematik neu entdecken
Schüler*innenwoche ermöglicht Jugendlichen drei Tage lang Einblicke in höhere Mathematik

Information and Registration:
https://www.mathematics.uni-bonn.de/de/outreach/oeffentliche-veranstaltungen/veranstaltungen/schuelerinnenwoche-2026

Wir laden Schüler*innen ab der zehnten Klasse ein, spannende Einblicke in die Mathematik und das Mathestudium zu bekommen. Ort ist das Hörsaalzentrum in der Friedrich-Hirzebruch-Allee 5 in Bonn. Die Veranstaltung beginnt nach den Sommerferien am Donnerstag, 10. September, mit einem fünfteiligen Workshop und endet mit einer Rallye über den Campus am Samstag, 12. September. Die Anmeldung ist bis zum 20. August möglich.

Mathematik hat sehr viel mehr zu bieten, als man im Schulunterricht vermuten würde. Ob man ein Mathematikstudium anstrebt oder sich in seiner Freizeit einfach gerne der Mathematik widmet: Die Schüler*innenwoche, die nach den Sommerferien vom 10. bis 12. September stattfindet, macht Spaß und ermöglicht einen spannenden Einblick in die Materie. Für den Donnerstag und Freitag ist eine Befreiung vom regulären Schulunterricht erforderlich, was aber erfahrungsgemäß kein Problem darstellt.

Thema in diesem Jahr ist „John Conways Tangletanz – eine mathematische Brücke zwischen Topologie und Algebra“. Beim Tangletanz stehen vier Personen in einem Quadrat so angeordnet, dass jeweils zwei sich gegenüberstehende Tanzende ein Seil halten. Jede Person wird ihr Seilende bis zum Ende des Tanzes festhalten. Die Teilnehmenden dürfen nun nach vorgegebenen Regeln ihre Plätze tauschen. In diesem interaktiven Workshop werden die Jugendlichen nach und nach sehen, dass sich hinter diesem zunächst sehr übersichtlich wirkenden Tanz eine ganze mathematische Welt verbirgt, die es zu erforschen gilt, mit Einblicken in die mathematischen Teilgebiete der Topologie, Geometrie, Arithmetik und Algebra.

Neben der Vermittlung von fachlichem Wissen beantworten Dozierende und Studierende der Universität Bonn auch Fragen rund um das Studium: Was ist eine Vorlesung, eine Übung oder ein Seminar? Oder was macht man eigentlich im Mathematikstudium? Darüber hinaus gibt es ein Mathematisches Pubquiz, bei dem Teams gegeneinander antreten und die begehrten gelben HCM-Shirts gewinnen können, sowie eine Führung durch das Arithmeum. Bei der abschließenden Rallye über den Poppelsdorfer Campus gibt es die Möglichkeit, die Uni noch auf eine ganz andere Art und Weise kennenzulernen. Die Veranstaltung ist kostenlos, und auch für das leibliche Wohl ist gesorgt. Bis zum 20. August sind noch Anmeldungen möglich.

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Rediscover Math Through Dance
Students' week gives young people a three-day introduction to higher mathematics

We invite high school students in 10th grade and above to gain exciting insights into mathematics and studying math. The event will take place at the Lecture Hall Center at Endenicher Allee 19c in Bonn. The event begins after summer break on Thursday, September 10, with a five-part workshop and concludes with a campus scavenger hunt on Saturday, September 12. Registration is open until August 20.

Mathematics has much more to offer than one might expect from school classes. Whether you’re planning to major in mathematics or simply enjoy spending your free time with math: The "Schüler*innenwoche", which takes place after summer break from September 10 to 12, is fun and provides an exciting glimpse into the subject. Exemption from regular school classes is required for Thursday and Friday, but experience has shown that this is not a problem.

This year’s topic is “John Conway’s Tangletanz—a mathematical bridge between topology and algebra.” In the Tangletanz, four people stand in a square arranged so that two dancers facing each other hold one end of a rope. Each person will hold onto their end of the rope until the end of the dance. The participants may now switch places according to specified rules. In this interactive workshop, the students will gradually discover that behind this dance—which at first glance seems very straightforward—lies an entire mathematical world waiting to be explored, offering insights into the mathematical fields of topology, geometry, arithmetic, and algebra.

In addition to sharing subject-specific knowledge, faculty and students from the University of Bonn will also answer questions about university life: What is a lecture, a tutorial, or a seminar? Or what do you actually do as a math degree student? There will also be a math pub quiz where teams can compete against each other to win the coveted yellow HCM T-shirts, as well as a guided tour of the Arithmeum. The concluding scavenger hunt across the Poppelsdorf campus offers the chance to get to know the university in a whole new way. The event is free, and refreshments will be provided. Registration is open until August 20.

We are looking to appoint up to four

🔥🔥 W2 Professorships (Bonn Junior Fellows)🔥🔥

to be filled as soon as possible.

These are temporary appointments for a period of five years. Some positions may be endowed with tenure-track, and, in exceptional cases, a position may be tenured immediately.

Deadline: September 27, 2026

The professorships👩‍🏫👨‍🏫
The professorships intend to encourage independent research by outstanding early career researchers. The professorships are endowed with travel and guest funds during the initial period. Bonn Junior Fellows also have access to additional resources of the Hausdorff Center. Bonn Junior Fellows are encouraged to supervise doctoral students.

The candidates 🧔🏾👱‍♀️👩🏿‍🦳👨🏻
We are looking for early career researchers holding a doctoral degree who are developing their own research agenda. Suitable candidates should have already demonstrated scientific independence with relevant publications. Candidates should have some international research experience. They will contribute to our advanced teaching program. German language skills are not required.

MathJobs: https://www.mathjobs.org/jobs/list/28548

More information on the Bonn Junior Fellows positions: https://www.mathematics.uni-bonn.de/hcm/opportunities/bonn-junior-fellows

Two weeks ago, the Bonn Mathematical Society ("Bonner Mathematische Gesellschaft") organized a fairy-tale evening “Alice and Bob in Wonderland” in the Poppelsdorf Mensa in cooperation with the "Studierendenwerk" and us. During the event, mathematics professor "R. Can-That", lured by a geometry puzzle, fell into the trap of the evil dragon Calculus. To free him, a series of mystical mathematical and moral challenges had to be solved. Together with Alice and Bob, the audience embarked on a fairy-tale journey during which all the virtues of studying mathematics were put to the test, moderated by the storyteller ("Märchenonkel") Thoralf Räsch. In the end, they succeeded in freeing the professor. We had so much fun with the puzzles and riddles, and with all the many wordplays and references. 😀 Thank you so much to all people involved, so many helping hands - fantastic! 🫶

Pictures: Ronny Bittner / BMG

Today, a “Stolperstein” was laid at the former residence of Otto Toeplitz, at Wittelsbacher Ring 1. Two of Otto Toeplitz’s grandchildren, Tamar Vital and Ronnie Toeplitz, were in attendance; they had traveled from Israel especially for the occasion. In addition, many students from the nearby Ernst-Moritz-Arndt-Gymnasium and numerous professors and students from the Hausdorff Center for Mathematics took part.

A Stolperstein (“stumbling block”) is a ten-centimeter cube bearing a brass plate inscribed with the name and dates of birth and death of victims of N**i extermination or persecution. The Stolpersteine project aims to commemorate individuals at the last place they freely chose to live, work, or study before they fell victim to N**i terror, forced euthanasia, eugenics, or deportation to a concentration or extermination camp, or escaped persecution through emigration or su***de.

Special thanks go to the students of the Ernst-Moritz-Arndt-Gymnasium (which will be renamed the Felix-Hausdorff-Gymnasium in a few months). In May 2024, students there published a special edition of the school newspaper titled “Stolpersteine – Frieden durch Erinnerung.” The editorial team researched biographies, reviewed historical sources, conducted interviews with experts, and brought to light the fates of people who lived in Bonn and were disenfranchised, displaced, or murdered as a result of N**i persecution. This journalistic commitment eventually led to something more: the student editorial team wanted not only to remember, but also to make their own contribution to the culture of remembrance in our city. Through the sale of the special edition and additional donations, a total of 2,520 euros was raised. This sum will now be used to fund 22 Stolpersteine, which will be laid today and in three days’ time in the Bonn city area.

Otto Toeplitz was born in Breslau in 1881, the son of mathematician Emil Toeplitz and his wife Pauline. He studied mathematics in Berlin and Breslau, where he earned his doctorate in 1905 with a dissertation on algebraic geometry. In 1907, he qualified as a professor in Göttingen, became a full professor in Kiel in 1920, and was appointed to Bonn in 1928. In Bonn, he was friends with Felix Hausdorff. After the National Socialists came to power, everything changed in the Toeplitz family’s life as well. Otto Toeplitz was forced into retirement in 1935 at the age of 53. The family had to leave their home on Wittelsbacher Ring and move in 1936 to a small apartment in the house of the widow of a Jewish colleague at 102 Koblenzer Straße. In 1938, Otto Toeplitz had been invited to give a lecture at the University of Jerusalem in order to secure a position there. Prior to this, the Gestapo had summoned him and pressured him to return to Bonn. After the November pogrom, he received a renewed job offer from the University of Jerusalem. Consequently, the Toeplitz couple left Bonn in 1939 and traveled via Switzerland to Jerusalem. Otto Toeplitz soon fell ill with typhus and died in 1940.

Following his dissertation, his main area of research became the theory of linear operators (which he still treated as infinite matrices) in normed spaces. Today, this field is part of functional analysis. Furthermore, Toeplitz made significant contributions to function theory. His conjecture that a square can be inscribed in every closed Jordan curve has to date neither been proven nor refuted (Toeplitz conjecture). The conjecture holds for a class of special Jordan curves. Three of his works in functional analysis have gained particular significance and should therefore be mentioned separately here. For the five-year period 1988–1992, Peter Lax (Courant Institute, New York) analyzed the data from the “Mathematical Reviews” and found that 394 papers from this period mention Toeplitz in the title and that Toeplitz is cited in the text of 1,191 papers. The vast majority of all these references pertain to Toeplitz’s nearly two-page article “On the Fourier Expansion of Positive Functions” from 1911. In this article, Toeplitz introduced the matrices that are now named after him and used these matrices to solve a problem posed by Constantin Carathéodory (1873–1950). The theory of these matrices and their generalizations found application in various branches of mathematics such as Fourier analysis, particle differential equations, time series analysis, random walks, and the development of fast algorithms, but also far beyond mathematics into crystallography, statistical mechanics, quantum mechanics, and quantum chromodynamics.

We are looking for a new team member. If you are interested in helping us coordinate and run the international guest researcher programs at our Hausdorff Research Institute, feel free to apply!

https://www.uni-bonn.de/de/universitaet/arbeiten-an-der-uni/stellenangebote/stellenausschreibungen/sachbearbeiter-in-im-bereich-programmkoordination-und-administration

Bonn PhD student Daniel Ebert receives first prize at the heureka Student Award

Daniel Ebert, a PhD student at the Research Institute for Discrete Mathematics, has been awarded the first prize at the 2025 heureka Student Award for his master’s thesis “Better Cost Allocations in Vehicle Routing” (advisor: Jens Vygen), along with a cash prize of 2,000 euros. In his thesis, he developed a new mathematical concept for the fair distribution of costs in delivery transport and demonstrated its practical utility in an industrial application.

The Student Award from the heureka Foundation aims to support young researchers by honoring outstanding master’s theses on the topics of “Mobility and the Environment” or “Mobility and Optimization,” with prizes of €2,000 (1st prize), €1,000 (2nd prize), and €500 (3rd prize). For the 2025 Student Award, 23 high-quality theses were submitted from 17 universities in Germany and Austria, covering a broad interdisciplinary spectrum of mobility-related topics ranging from mathematical optimization to engineering and the social sciences. The awards were presented at the Forum Neue Mobilitätsformen (FONEMO) conference.

Picture (c) heureka: Daniel Ebert (right) at the awards ceremony

Yesterday, Paul Klemperer (Edgeworth Professor of Economics at the University of Oxford) gave a public lecture at our Mathematics Center titled “What Really Matters in Auction Design,” as part of the trimester program “Advances in Mechanism Design,” which is currently running at the Hausdorff Research Institute for Mathematics. Paul Klemperer explained to the audience in the fully-booked Lipschitz Hall that an auction is essentially just another market to which the normal rules of economics apply. Since it is particularly simple, it serves as a sort of “model organism” for economics, similar to Drosophila in biomedicine. On the other hand, it also quickly became clear that auction design has not a “one-size-fits-all” solution and that the devil is in the details. For instance, the UK generated revenue of 650 euros per capita in its 3G auction, while the Netherlands achieved only 170 euros per capita. And this despite the fact that the Netherlands had copied the UK’s design! The situation was quite different, however: In the UK, 5 licenses were auctioned, and there were 4 strong bidders (incumbent operators). As a result, at least one license had to go to a new entrant. 9 new entrants bid, driving up the prices of all 5 licenses. The Netherlands, however, auctioned 5 licenses but had 5 strong bidders (incumbent operators). So why would any new entrant bother bidding? Instead of an ascending auction, the Netherlands should have preferred to choose a sealed-bid auction. Later in his presentation, Paul Klemperer showed us additional auction designs, including the product-mix auction, which he developed and wich is now regularly used by the Bank of England. Thank you for the very interesting lecture!

Over the past few days, 15 children from our Bonner Matheclub (Bonn Math Club) competed in the final round of the FEMO International Math Olympiad in Antalya, Turkey (grade 1-6). They made up the entire German team. The children had an incredible time and came home with many cultural and social experiences — as well as a few medals. 😎 In the individual competition, the following children from the Bonn Math Club recieved awards:

🥇Gold: Oliver Roubal (Grade 5)
🥈Silver: Linus Jender (Grade 4)
🥈Silver: Alexander Didenko (Grade 4)
🥈Silver: Larion Nett (Grade 2)
🥉Bronze: Platon Maslinkov (Grade 4)
🥉Bronze: Victor Liu (Grade 3)
🥉Bronze: Hannah Alashwal (Grade 2)
🥉Bronze: Michel Berk (Grade 2)

Congratulations!!🎊🎉🎈

Special recognition goes to Oliver Roubal, who achieved one of the best results in Grade 5 with 25 out of a possible 30 points — an awesome performance!! 👏🙏