# IN MEMORIAM

**PETER DEUFLHARD****Professor of Numerical Mathematics****FREIE UNIVERSITÄT BERLIN and ZUSE INSTITUTE BERLIN ****1944 – 2019**

On September 22, 2019, Professor Peter Deuflhard passed away at the age of 75. Berlin mathematics lost one of its leaders, a highly respected colleague and wonderful person.

After a diploma in physics at the Technical University of Munich and a doctorate in mathematics with Roland Bulirsch on Newton methods at the University of Cologne, Deuflhard habilitated in 1977 at the Technical University of Munich with a thesis on multiple shooting techniques. At the age of 34, he was appointed as full professor for Numerical Mathematics at the Ruprecht-Karls-Universität Heidelberg, until he took up the chair in Scientific Computing at Freie Universität Berlin in 1986. He authored the pioneering green paper that led to the foundation of the Zuse Institute Berlin (ZIB) as the first German institute for Scientific Computing in 1986. He headed ZIB for more than 25 years as its president and made it a worldwide role model for interdisciplinary mathematical research. In 2002, he was one of the founders of the Berlin-based research center MATHEON that established ongoing successful cooperation of all Berlin universities and mathematical research institutes. Under the motto “Mathematics for key technologies”, MATHEON was the forerunner of the Cluster of Excellence MATH+. He was also a member of the Berlin-Brandenburg Academy of Sciences and Humanities (BBAW) since 2001.

Looking at the long and wide-ranging list of monographs, textbooks, and scientific papers by Peter Deuflhard, an unaware contemporary could believe that “Deuflhard” were the pseudonym of a whole interdisciplinary collaborative group consisting of scientists from mathematics, physics, chemistry, medicine, engineering, and the humanities. At his heart, however, Peter was a mathematician. In 2007, on the occasion of the award ceremony for SIAM’s Maxwell prize for “a mathematician who has demonstrated originality in applied mathematics”, SIAM’s prize committee published the following laudation: “Professor Peter Deuflhard's contributions to applied mathematics have a breadth, depth and originality that is almost without parallel. His contributions to algorithm-oriented numerical analysis are fundamental and range from highly nonlinear algebraic systems through large-scale ordinary and partial differential equations to Markov chains. Within these fields, they cover direct and inverse problems, optimization aspects and optimal control. Characteristic of his work is that he always lays a firm, often innovative, mathematical basis on which he constructs highly efficient algorithms for hard real-life problems in science and technology. His style of research has revolutionized scientific computing, a large number of highly reputed scholars follow his tracks.”

Peter supervised more than thirty doctoral students in mathematics and many of them used ZIB for a career in academia. He collaborated intensively with engineers, physicians, practitioners, and scientists in many different fields. He was quintessential in forming modern scientific computing as a field integrating a wide range of applied mathematicians, computer and other scientists aiming at a fundamental understanding of phenomena and processes by combining mathematics and computing technology. The variety of application areas in which Peter contributed is stunning. They range from spacecraft mission design, chemical engineering, nano-optics, systems biology, medicine, bioinformatics, molecular dynamics, and drug design to the humanities.

Peter never dropped a subject; he transformed it by identifying hidden structures into a source of possible future developments, maybe in other fields. As a result, he was able to build bridges between completely different areas. For, example, he applied ideas from the numerics of partial differential equations to model-supported operation planning in head surgery, found an intriguing way to connect the results to the studies of beautiful faces and started to contribute to research in the humanities. Although Peter appreciated his international recognition, he even more enjoyed the personal interaction that he had with so many colleagues and students, to whose careers he made extraordinary contributions.

We are so grateful and mourn the loss of a wonderful member of the scientific community. Our thoughts are with his family in these hours of grief.