# History of the Institute

### Background

In 1919, the Physikalisches Staatsinstitut (founded in 1885) was integrated into the newly founded Universität Hamburg. Then, in 1921, Wilhelm Lenz was appointed to the first professorship for theoretical physics. One of his first assistants was Wolfgang Pauli—indeed, it was here that Pauli first discovered his exclusion principle for which he was later conferred the Nobel Prize in Physics. Hans Daniel Jensen was another Hamburg-based Nobel Prize winner working in theoretical physics.

Pascual Jordan came to Hamburg after the Second World War and set up a group that examined general relativity. One prominent member of this group was Jürgen Ehlers, who went on to found the Max Planck Institute for Gravitational Physics (Albert Einstein Institute).

### Establishment of the II. Institute for Theoretical Physics

In 1956, Willibald Jentschke was appointed as the chair for experimental physics. It was under his aegis that the Deutsches Elektronensynchroton (DESY) was established. In theoretical physics, Harry Lehmann succeeded Wilhelm Lenz as the chair. He was already a leading figure in the field of quantum field theory by the time of his appointment. To facilitate the collaboration with experimental particle physics, the theory institute was divided into two, and Harry Lehmann and his colleagues moved to the DESY site. The DESY Theory group was founded in parallel to the II. Institute for Theoretical Physics, whereby the two cooperated closely in the time that followed. Its first head was Hans Joos.

### The Institute’s Development Until the Late 1990s

Under Harry Lehmann’s leadership, the institute evolved into a leading center for quantum field theory and its application in elementary particle physics.

In quantum field theory, the fundamental relationship between time-ordered functions and the S-matrix was elucidated using the LSZ reduction formula—thus named after Harry Lehmann, Kurt Symanzik, and Wolfhart Zimmermann.

In quantum field theory, a new research focus was set in 1966 with the appointment of Rudolf Haag. Mathematical physics and algebraic quantum field theory were thus established as research focuses. It was during this time that Sergio Doplicher, Rudolf Haag, and John Roberts completed their work on the superselection structure of quantum field theory. Klaus Pohlmeyer and Gert Roepstorff also worked on the mathematical analysis of quantum field theory until they were offered appointments in Heidelberg and Aachen, respectively. The close collaboration with Kurt Symanzik, who joined the DESY theory department in 1968 and contributed essential input with his work on the renormalization group (Callan-Symanzik equation), was also decisive.

With the appointment of Gerhard Mack in 1975, new research focuses in conformal field theory and lattice gauge theory were added to the institute’s portfolio. These would later provide the basis for a general theory of complex systems. The expertise in algebraic quantum field theory was reinforced through the 1979 appointment of Detlev Buchholz. He left the institute in 1996 to take up an appointment in Göttingen.

Harry Lehman, who was granted emeritus status in 1985, was succeeded by Hermann Nicolai. Appointed in 1987, Nicolai established supersymmetry as a research focus. Rudolf Haag was granted emeritus status in 1987 and succeeded by Klaus Fredenhagen (1990), whose work investigated the renormalization of quantum field theories on curved spacetimes. Hermann Nicolai, who had previously declined an appointment in Karlsruhe, left the institute in 1995 to become director of the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) in Golm.

In addition to the more formal aspects of quantum field theory, the application of quantum field theory to experimental elementary particle physics was established at the institute as a key research focus. The emphasis lay in the development of methods of quantum field theoretical perturbation theory and the evaluation of experimental data, especially from the DESY ring accelerator and later from DORIS, PETRA, and, finally, HERA.

Following preliminary work completed by Peter Stichel (from 1959), the appointment of Gustav Kramer in 1961 led to the establishment of a larger research group in the field of phenomenology. This group was later expanded through the appointment of further professors (Kurt Meetz in 1965, Bruno Renner in 1970, Frank Steiner in 1974, Jochen Bartels in 1978). Stichel, Meetz, and Steiner later pursued appointments in Bielefeld, Bonn, and Ulm, respectively. Renner died in an accident. Kramer and Bartels were also offered appointments elsewhere — in Wuppertal and Leipzig, respectively — but chose to decline these.

Important contributions on the description of photoproduction processes were made early on, whereby Regge theory played a central role. Following the formulation in the early 1970s of quantum chromodynamics (QCD) as the field theory of strong interaction, the focus shifted to the perturbation-theoretical evaluation of non-Abelian gauge theories, especially QCD. Particularly the 3-jet calculations in electron-positron annihilation, which have contributed significantly to the experimental proof of the gluon in the PETRA ring, should be highlighted here. During operation of the HERA ring, the phenomenology group was mainly involved in the analysis of structure and fragmentation functions. The analysis of the jet production remained of great interest, both for photoproduction and electrical production. One theoretical focus of HERA physics was the investigation of small-x physics, the behavior of structural functions in small Bjorken x values.

### More Recent Developments: String Theory and Astroparticle Physics

With the appointment of Jan Louis in 2000 as Hermann Nicolai’s successor, the institute’s research areas were complemented with string theory. Following the retirement of Gerhard Mack, theoretical astroparticle physics was also added as a new research area with the appointment of Günter Sigl in 2007. This group collaborates closely with observational astroparticle physics. The research into phenomenology was continued with the appointment of Bernd Kniehl in 1999 as Gustav Kramer’s successor and of Sven-Olaf Moch in 2012 as Jochen Bartels’ successor. Special emphasis lies in precision calculations in electroweak theory and QCD. Two new DESY funded professorships were established for which Gudrid Moortgat-Pick (2009) and Geraldine Servant (2014) were appointed. Gudrid Moortgat-Pick looks at the physics of a future electron-positron linear accelerator. Geraldine Servant considers the applications of elementary particle physics in cosmology. In 2014, Gleb Arutyunov succeeded Fredenhagen as the chair for quantum field theory and mathematical physics. He primarily concerns himself with integrable structures in quantum field theory.

### Participation in University and DESY Management

After the faculty structure was abolished in 1970 and replaced with departments, Gustav Kramer, Harry Lehmann, and Gerhard Mack acted as department spokespersons. After the faculties were reintroduced in 2006, Jochen Bartels served as head of the department, as well as after him Jan Louis and Günter Sigl. Since summer 2016, Jan Louis has been one of the vice presidents of Universität Hamburg. Harry Lehmann and Gustav Kramer both served in DESY management committees for many years.

### Research Training Groups, Collaborative Research Centers, and Cooperations

The institute established two DFG Research Training Groups: “Theoretical Elementary Particle Physics” (1990–1999; spokespersons: Hermann Nicolai, Klaus Fredenhagen) and “Future Developments in Particle Physics” (2000–2009; spokesperson: Jochen Bartels). It has also been instrumental in the Collaborative Research Center “Particles, Strings and the Early Universe” (2006–2018; spokespersons: Jan Louis, Johannes Haller) and currently is in the Cluster of Excellence “Quantum Universe” (since 2019; spokespersons: Jan Louis, Peter Schleper, Geraldine Servant).

The institute has been involved in the Center for Mathematical Physics since 2003 (together with the Department of Mathematics and the DESY Theory group) and in the Wolfgang Pauli Centre for Theoretical Physics since 2013 (together with the I. Institute for Theoretical Physics and the DESY Theory group).

### Awards

Current and former members of the institute have been conferred numerous prizes. These include the Max Planck Medal of the German Physical Society, which has been awarded to Harry Lehmann, Rudolf Haag, Martin Lüscher (doctorate at the institute in 1976), and Detlev Buchholz. Harry Lehmann received the Dannie Heineman Prize for Mathematical Physics, and Rudolf Haag won the Henri Poincaré Prize of the International Association of Mathematical Physics (IAMP). Gerhard Mack and Hermann Nicolai were conferred the Klung Wilhelmy Science Award, and Klaus Pohlmeyer, Detlev Buchholz, Klaus Fredenhagen, Hans Werner Wiesbrock (research associate at the institute 1987–89), and Volker Schomerus (assistant at the institute 1995–2000) have all been honored with the physics prize of the Göttingen Academy of Sciences and Humanities. Gustav Kramer was a visiting scientist at Argonne National Laboratory in 1968–69 and a distinguished visiting professor at Ohio State University in 1983–84. Klaus Fredenhagen acted as Leibniz professor at the University of Leipzig in 1997. Jochen Bartels was granted an honorary professorship by the Faculty of Physics at St. Petersburg State University (Russia) in 2011 and accorded the Abate-Molina (Humboldt) Prize for excellence in science from the Chilean National Commission for Scientific and Technological Research (CONICYT) in 2012.

### Institute Professors

- Harry Lehmann 1956–1986 (emeritated)
- Peter Stichel 1959–1970 (appointment in Bielefeld)
- Gustav Kramer 1961–1998 (emeritated)
- Kurt Meetz 1965–1967 (appointment in Bonn)
- Rudolf Haag 1967–1987 (emeritated)
- Bruno Renner 1970–1973 (deceased)
- Gert Roepstorff 1972–1974 (appointment in Aachen)
- Klaus Pohlmeyer 1972–1975 (appointment in Heidelberg)
- Frank Steiner 1974–1995 (appointment in Ulm)
- Gerhard Mack 1975–2005 (emeritated)
- Jochen Bartels 1978–2011 (emeritated)
- Detlev Buchholz 1979–1997 (appointment in Göttingen)
- Hermann Nicolai 1987–1995 (appointment at the Max Planck Institute for Gravitational Physics [Albert Einstein Institute] in Golm)
- Klaus Fredenhagen 1990–2013 (emeritated)
- Bernd Kniehl (since 1999)
- Jan Louis (since 2000)
- Günter Sigl (since 2007)
- Gudrid Moortgat-Pick (since 2009)
- Sven-Olaf Moch (since 2012)
- Gleb Arutyunov (since 2014)
- Geraldine Servant (since 2014)
- Timo Weigand (since 2020)

(Sources: Prof. Dr. Jochen Bartels, Prof. Dr. Klaus Fredenhagen, Prof. Dr. Gustav Kramer)