Walter Thirring, a pioneer of modern mathematical physics, passed away in Vienna on August 18, 2014 at age 87. Born in Vienna on April 29, 1927, he was the son of the well known physicist Hans Thirring (Lense-Thirring frame dragging effect in GR). Walter was originally destined for a career as a musician, but took up the study of physics at the University of Innsbruck where he obtained his PhD in 1949 at the age of 22. The following ten years were spent at various research institutions in Europe and the USA: The Institute for Advanced Studies in Dublin, the University of Glasgow, the Max Planck Institute in Göttingen, the ETH Zürich, the University of Bern, the IAS in Princeton, MIT and the University of Washington. He met Shrödinger, Heisenberg, Pauli and Einstein during this period.
In 1959 Walter became professor of theoretical physics at the University of Vienna; he retired in 1995. His contributions in particle physics led to his appointment as Head of the Theory Division of CERN in Geneva from 1968 to 1971. This critical period in the life of CERN is well described in his autobiography The Joy of Discovery.
Walter played an important role in the international physics community. He was a force behind the founding of the International Association of Mathematical Physics (IAMP) in the 1970s and from 1976-1978 he was its first President. A notable aspect of IAMP is that it is one of the few international scientific organizations whose members are individual scientists. Walter was also the founding president (1993-1996) and first director of the International Erwin Shrödinger Institute for Mathematical Physics (ESI) in Vienna. ESI has proved to be a major meeting place of mathematicians and physicists.
Walter's scientific life was impressively broad and deep. The Selected papers of Walter E. Thirring (American Mathematical Society Collected Works series, 1998) grant a panoramic view of his work.
Walter's earliest interests were in high energy physics. Important papers include the first rigorous proof of divergence of perturbation series in a quantum field theory and the discovery and exactly soluble model in relativistic quantum field theory, known as the Thirring model. This work, not Tomonaga's paper as occasionally alleged, was the source of Luttinger's far reaching model in condensed matter physics. Walter's monograph on QED was highly influential. The remarkable papers 'On the number of fundamental fields' and 'Three-field theory of strong interactions' contain ideas pointing to the eightfold way and the theory of quarks developed later by Gell-Mann and Ne'eman.
In the 1960s Walter's research interests broadened, first in the areas of GR and statistical physics and subsequently to condensed matter physics and the physics of atoms and molecules. At the same time his papers became more mathematical and he developed his distinctive style, using modern mathematics to solve hard problems in physics. He was one of the first to use the concepts and notation of modern differential geometry in GR. In other areas he used sophisticated techniques of functional analysis and the theory of operator algebras. Remarkably quickly he absorbed and applied these methods, which were not part of the mathematics curriculum for physics students during his studies. Despite his mathematical skills his motivation always came from physics, and his work guided by deep physical insight and intuition about the tools that would be appropriate for the physical problem at hand. In the 1970s Walter became interested in the quantum theory of many-body systems with Coulomb forces. This resulted in our joint work on stability of matter, which led to developments in physic and mathematics.
Thirring's Course on Mathematical Physics is a lasting legacy reflecting his role as a researcher and teacher. This work comprises four volumes covering classical mechanics, classical field theory, the quantum physics of atoms and molecules and the quantum theory of large systems. It is a true classic with a breathtaking wealth of information and insights that will continue to educate and inspire many future generations of mathematical physicists. He had many students who made careers in several areas of physics.
Walter received numerous awards and honors recognizing his scientific work. In addition to the Henri Poincaré Prize of the IAMP, he was recipient of the Max Planck Medal, the highest award of the German Physical Society, and the highly selective Austrian Decoration for Science and Art. He was a member of the Austrian Academy of Sciences, the U.S. National Academy of Sciences, the Pontifical Academy, and the Hungarian Academy of Sciences and he held several honorary doctorates.
Physics was not Walter's only intellectual passion. He composed for organ, piano and violin. He was also genuinely interested in a dialogue between science and religion as witnessed by several books on the subject. The passing of this great master of modern mathematical physics closes a chapter in the intellectual history of the last seventy years.
Elliott Lieb, Princeton University
