06.09.2024In Memoriam: Günther Rasche, Wolfgang Jaus

Günther Rasche was born on 5 May 1934 in Mülheim an der Ruhr. He studied physics and business administration in Göttingen from 1953 to 1956. His in-depth knowledge of the latter would later have a positive impact on the well-being of the Institute of Theoretical Physics. In 1956, he moved to Zurich, where he graduated in experimental physics under Hans Staub in 1958. In 1961, he obtained his doctorate under Walter Heitler with the dissertation ‘Untersuchungen zum statistischen Modell der Mesontheorie’. He continued his academic career with postdoctoral positions in Dublin and London, but always returned to the University of Zurich. He became a private lecturer there in 1967, assistant professor in 1968, associate professor in 1969 and full professor of theoretical physics in 1977. In the following years until his retirement, he was several times in Canberra, Australia, as well as in Stockholm as visiting professor. In addition to his research in physics that focussed on nuclear and medium-energy physics, he has increasingly turned his interest to topics in history of science, where his long-standing contacts with Walter Heitler have revealed many interesting findings.

Günther Rasche was not only a dedicated researcher, but also an excellent teacher who took students' difficulties seriously. With his humanity, his straightforwardness and his interest in organisational issues, he was an outstanding head of the Institute of Theoretical Physics from 1989 to 2001 and Dean of the Faculty of Mathematics and Natural Sciences from 1992 to 1994. Many of his former students, staff and colleagues from all over the world came frequently back to Zurich for visits of their mentor and friend and exchange thoughts.

Günther Rasche's scientific interest was initially characterised by the striking developments in field theory in the 1950s on the one hand and their applications to mesons and nucleons, the strongly interacting elementary particles known at the time, on the other. The quark theory valid today was only in its early beginnings, as were the (non-)abelian gauge theories. In his doctoral thesis, he investigated a specific model for the meson-nucleon interaction with regard to its physical consistency. Rasche then turned to precision calculations for meson-nucleon interactions, often together with his long-time colleagues William Woolcock from Canberra and Geoffrey Oades from Aarhus. The aim of this work was (and still is) to find theoretical predictions or explanations for experiments with high accuracy. He also worked on general questions relating to the mathematical treatment of physical processes. Günther Rasche was always interested in current advances and findings in experimental physics and was a valued liaison for experimental groups, both at the Department of Physics at the University and at the Paul Scherrer Institute (PSI).

An important development began around 1970 in collaboration with Wolfgang Jaus. Together they developed a formalism to calculate the electromagnetic corrections to super-allowed beta decays. These decays make it possible to precisely measure one of the fundamental quantities in particle physics, the element Vud of the quark mixing matrix. This quantity is very sensitive to the effects of new (as yet undiscovered) particles and forces. It has been shown that the results of Jaus and Rasche are still valid today and are being further developed accordingly. For example, the fundamental article by Jaus and Rasche from 1970 has already been cited three times this year, 54 years after its publication.

Wolfgang Jaus was born on 14 January 1938 in Marbach am Neckar. After his school years in Konstanz, he began his physics studies in Tübingen and continued studying from 1960 at the University of Zurich under the influence of Walter Heitler. Wolfgang Jaus completed his studies in 1966 with a doctorate on the ‘Symmetry property of the state vector of two decaying particles’ under Heitler. He then continued his academic career at the UZH, which was not unusual at the time, occasionally interrupted by research stays in Ireland and later also in the USA. In 1971 he became a private lecturer and in 1978 titular professor. Wolfgang Jaus was not only a passionate scientist, he was also a very diligent teacher whose lectures were always clearly and systematically structured.

Wolfgang Jaus' scientific interests, similar to those of Günther Rasche, were initially driven by the striking developments in field theory in the 1950s on the one hand and their applications to mesons and nucleons on the other. Wolfgang Jaus's doctoral thesis dealt with a fundamental question, whether decaying particles obey the usual symmetry rules of stable particles, which are either bosons or fermions; Jaus showed that this was not the case. After his doctorate, Jaus then turned more and more to the details of the interactions of mesons and nucleons.  The aim of this work was to reveal the fundamental forces in the measurable processes through often complex calculations and thus determine their properties. In a 1968 paper, he dealt for the first time with electromagnetic radiation corrections to beta decay. This work was subsequently expanded in collaboration with Günther Rasche and led to the now established approach to electromagnetic precision predictions for beta decay. In his research activities, Wolfgang Jaus has continuously extended this approach and applied it to a large number of decay processes. 

Günther Rasche and Wolfgang Jaus, together with their colleagues Armin Thellung, Norbert Straumann and Günter Scharf, shaped the Institute of Theoretical Physics from the early 1970s until their retirement at the beginning of the 21st century and introduced generations of physics students to theoretical physics. Even after his retirement, Günther Rasche was an important contact person for his colleagues in matters of university policy, and with his wealth of experience and excellent knowledge of human nature, he made valuable contributions to the further development of the department of physics at the University of Zurich.

The University of Zurich, colleagues and former students honour the memory of Günther Rasche and Wolfgang Jaus in gratitude for their contributions to the success and well-being of our institute.