# Berlin’s Math Maker

## Professor Günter M. Ziegler does research and teaches at Freie Universität Berlin. He sees collaboration between three city universities as the great strength of mathematics in Berlin.

Jun 13, 2017

When Günter M. Ziegler arrived in Berlin as a young researcher in 1992, a whole new world opened up for him. “I saw back then how the great minds of Berlin mathematics – Martin Grötschel at Technische Universität Berlin, Peter Deuflhard at Freie Universität, and Jürgen Sprekels at Humboldt-Universität – collaborated on research activities and launched joint projects. When leading researchers spread such a collaborative mindset, the effect is infectious.” Twenty-five years later, mathematician Günter Ziegler is himself one of the leading team players in collaborations between Freie Universität, Technische Universität Berlin, and Humboldt-Universität. He refers to the German capital as “a unique setting.”

Part of that setting relates to the collaborative projects between Freie Universität, Technische Universität Berlin, and Humboldt-Universität. “I can set more in motion here than anywhere else,” says the 54-year-old. Ziegler is University Professor at Freie Universität Institute of Mathematics, where he heads the Discrete Geometry group. In May 2017 he was additionally appointed an adjunct professor at Technische Universität Berlin. That professorship takes him back to the venue of his first years in Berlin. It was at Technische Universität Berlin where he completed his *Habilitation* in 1992 and worked as a lecturer before serving as professor of mathematics from 1995 to 2011. He then switched to Freie Universität.

Günter Ziegler has launched or helped with large numbers of research collaborations in Berlin. He is among the founder-members of *Matheon*, which was established in 2002 as a research center of the German Research Foundation (DFG). *Matheon* has since grown to become an internationally acknowledged platform for application-oriented mathematics and – after the maximum period for DFG funding expired – has been funded since 2012 by the Einstein Foundation Berlin.

At *Matheon*, researchers from the universities, the Weierstrass Institute for Applied Analysis and Stochastics (WIAS), and the Zuse Institute Berlin (ZIB) use mathematics to develop new methods for key technologies in areas such as health care, logistics, and visualization. Günter Ziegler was first spokesperson of the Methods for Discrete Structures research training group and in 2008, as president of the German Mathematical Society (DMV), had a major hand in planning and staging the German Year of Mathematics. This project led to the establishment of the DMV Mathematics Media Office, which is now located at Freie Universität and promotes mathematics in the media.

## “Together we can achieve so much more”

Working in collaboration with colleagues, in the first round of the German government’s Excellence Initiative in 2006, Günter Ziegler succeeded in winning one of the first graduate schools for Berlin: the *Berlin Mathematical School* (BMS), ), a joint institution of Technische Universität Berlin, Freie Universität, and Humboldt-Universität where he served as founding chair from 2006 to 2007. The BMS program, which is highly regarded internationally, enables students from all over the world to progress directly in the space of just a few years from bachelor’s to doctorate. A total of 233 doctorates were awarded at the graduate school up to March 2017. The chair of BMS alternates every two years between Technische Universität Berlin, Humboldt-Universität, and Freie Universität; Ziegler is once again the current chair.

“Together we can achieve so much more than with everyone working on their own,” says Ziegler, going on to enumerate the wealth of expertise that comes together at BMS: Technische Universität Berlin with its four focus areas in stochastics, numerics, optimization, and geometry; Humboldt-Universität with its knowhow in areas such as algebra, number theory, and nonlinear optimization; and Freie Universität with focus areas including mathematics in the life sciences and discrete mathematics. “In my research area at Freie Universität we look into many different questions of discrete geometry and especially the theory of polytopes,” explains Ziegler. At this point he breaks off and laughs. “But without a geometry lecture that isn’t very easy to understand.” For Ziegler, *Matheon* and the BMS are key institutions for networking in mathematics.

At the beginning of his academic career he never would have thought that he would one day be an accomplished team player, Ziegler relates, saying he started out very much as a go-it-aloner. He recalls his studies as a turbocharged part of his career. “I hit university at 18 and had my doctorate at 24.” Looking back, he says he was over-eager and over-ambitious. “I wanted to show everyone I could do it.” He was a loner who after his *Vordiplom* in mathematics and physics at Ludwig-Maximilians-Universität in Munich went to the Massachusetts Institute of Technology (MIT) in the USA to do his doctorate and then on to the University of Augsburg. There, from 1987 to 1991, he held a postdoc position under Martin Grötschel – today’s president of the Berlin-Brandenburg Academy of Sciences and Humanities – until Grötschel accepted a professorship at Technische Universität Berlin. In 1991, Ziegler went to Sweden for a research year studying combinatorics at the Mittag-Leffler Institute in Djursholm. A year later he completed his *Habilitation* in Berlin. It was there that he experienced the collaboration between Grötschel, Deuflhard, and Sprekels that he found so inspiring.

Ziegler also passes on his enthusiasm for mathematics in book form. His latest book, ironically entitled *Mathematik – Das ist doch keine Kunst!* (roughly translated, “Mathematics? There’s no art to that!”), entertainingly describes Ziegler’s science with the aid of 24 works of art: as an art that creates art, as a playground for ambitious adventurers, and also as a major driver of progress.