In memoriam Rolf Jeltsch

Obituary of the lecturers of the Seminar for Applied Mathematics

We say farewell to

Professor Rolf Jeltsch

who passed away on 28 June 2024, at the age of 79.

Rolf Jeltsch graduated with a PhD in mathematics from ETH Zurich in 1972. His advisor was Peter Henrici at the Seminar for Applied Mathematics (SAM). He did a postdoc in Canada, then worked as an assistant professor in the US, and in 1976 he joined Ruhr-Universität Bochum as lecturer and was later promoted to senior scientist and professor. After stays at Stanford and Helsinki, RWTH Aachen hired him as full professor in 1979 and he was appointed director of the Institute for Geometry and Applied Mathematics. In 1989 he accepted an offer of ETH Zurich, where he was full professor of mathematics until his retirement in 2011.

Rolf Jeltsch's research area was computational mathematics with a focus on differential equations and scientific computing, encompassing both theory and applications. Initially, he worked on numerical methods for ordinary differential equations and then on numerical methods for conservation laws for the simulation of compressible flows, in particular for the Euler equations, the Navier-Stokes equations and magnetohydrodynamic models.

Rolf Jeltsch was a high-profile mathematician and served the scientific community in many ways, with utmost commitment and dedication, as a member of committees, panels, and leader. He was president of the Leonard Euler Center, of the Swiss pilot center of the European Community on Flow, Turbulence, and Combustion (ERCOFTAC), of the European Mathematical Society (EMS), the Swiss Mathematical Society (SMG), of the International Council on Industrial and Applied Mathematics (ICIAM), and vice president of the Gesellschaft für Angewandte Mathematik und Mechanik (GAMM). He was chairman of the scientific Council of the Stefan Banach Center in Warsaw, organizer of the ICIAM Congress 2007 in Zurich and acted as scientific advisor for various European research institutions.

Also at ETH Zurich Rolf Jeltsch shouldered important responsibilities. Shortly after his arrival he became head of the Seminar for Applied Mathematics, expanded the institute and had a leading role until 2009. From 1991 through 1993 he was Head of the Department of Mathematics (D-MATH).

Throughout his career Rolf Jeltsch fully committed himself to teaching, advising, and mentoring of students and young scientists. He had a total of 38 doctoral students, and was one of the founders and a driving force of the Computational Science and Engineering (CSE) study programme at ETH Zurich. He served as Director of Studies for this programme from 1997 through 2008. He believed that academic education in mathematics must have a strong application-oriented and inter-disciplinary focus and that it must enable graduates thrive outside academia and to collaborate successfully with partners in engineering sciences and industry.

Rolf Jeltsch was and still is a role model for many of his former undergraduate and graduate students, and for many of his former colleagues. He has left a lasting impression both as a scientist, a leader, and as a person, though he never put himself first, but always tried to promote what he thought was right. This made him treat other people with kindness, respect, and trust. This is what we will remember about Rolf Jeltsch and these memories will live on.