Peter Gabriel Bergmann, who introduced general relativity into modern physics through his influential book Introduction to the Theory of Relativity (Prentice Hall, 1942), died on 19 October 2002 in Seattle, Washington, following a lengthy illness.
Peter was born in Berlin, Germany, on 24 March 1915. His mother was a pediatrician and his father would later be a professor of chemistry at the Rockefeller Institute for Medical Research. Peter began his undergraduate studies in theoretical physics at the University of Freiburg in 1931. Concerned that Peter would not be able to continue his studies in Nazi Germany, his mother secretly wrote to Albert Einstein in the summer of 1933 to ask whether he would consider accepting her son as a PhD candidate. Einstein demurred and suggested that Peter study with Wolfgang Pauli first. After studying at Freiburg for two years, Peter left Germany for Prague. He received his PhD in physics in 1936 under Philipp Frank at the German University in Prague. His thesis, “The Harmonic Oscillator in a Spherical Space,” began his work in general relativity.
Following a strong recommendation from Frank and without knowing of his mother’s earlier contact with Einstein, the 21-year-old postdoc arrived in Princeton, New Jersey, in 1936 and worked as a research assistant to Einstein at the Institute for Advanced Study until 1941. A fruit of their collaboration was their paper “On a Generalization of Kaluza’s Theory of Electricity,” which, unlike Theodore Kaluza’s 1919 paper, ascribed physical reality to the fifth dimension. The letters between Einstein and Peter during the time they worked on their paper reveal the seminal contributions of the young physicist who was introducing a new point of view.
In 1942, when Peter was 27, his book Introduction to the Theory of Relativity , with a foreword by Einstein, was published. Einstein wrote: “Much effort has gone into making this book logically and pedagogically satisfactory, and Dr. Bergmann has spent many hours with me which were devoted to this end.” This magisterial text, translated into several languages, remained for many years the canonical survey of Einstein’s ideas on special and general relativity and contains the first systematic development of Kaluza’s theory. Peter showed that gauge transformations were nothing else but coordinate transformations in the higher-dimensional space. And with a simple transformation, he made clear that Pauli’s projective relativity was nothing other than standard Kaluza theory.
After completing his appointment as research assistant to Einstein, Peter spent the year 1941–42 as an assistant professor at Black Mountain College in North Carolina and then from 1942 to 1944 as an assistant professor of physics at Lehigh University. For the next three years, he was engaged in war research on underwater sound at Columbia University and the Woods Hole Oceanographic Institution. In 1947, he was appointed assistant professor in the Syracuse University department of physics, where he rose to become professor in 1953. Except for the year 1963–64, when he was at Yeshiva University in New York City, Peter remained at Syracuse until his retirement in 1982. At that time, he was appointed visiting professor at New York University, a position he kept until shortly before his death.
When Peter began his career at Syracuse in 1947, no US physics department had a center for research in general relativity. Indeed, very few physicists considered the area worthy of their time. Within the Syracuse physics department, Peter created one of the first groups specifically concerned with studying the general theory of relativity with the intent of reconciling that field with quantum theory. The publication in the Physical Review of his 1949 paper “Nonlinear Field Theories” was the first fruit of Peter’s research program to unify general relativity and quantum theory. That paper contained the major conceptual ideas of nonperturbative canonical general relativity. Those ideas were the main thrust of his research for the rest of his career. He was concerned with the meaning of general covariance and introduced the search for observables whose commutation relations are essential for the successful quantization of gravity.
Up to the mid-1950s, Peter and his students were the major contributors to the literature in general relativity. Twenty years later, there were more than a dozen centers of active research in general relativity. Now, general relativity is in the mainstream of current physics research—in astrophysics and cosmology, in supergravity, in string theory, as well as in Einstein’s original theory. The field supports the international General Relativity and Gravitation Society, which organizes triennial conferences and publishes the journal General Relativity & Gravitation. Peter played a central role in that growth through his research and teaching. He also devoted time to the society through the informal international committee by helping to draft the constitution and structure of the present formal organization, through his membership on the executive committee, and by service to the journal’s editorial board. In 1963, Peter, with one of us (Schucking), Ivor Robinson, and Alfred Schild, helped organize the inaugural Texas Symposium on Relativistic Astrophysics.
Peter kept up an interest in thermodynamics and statistical mechanics and in epistemological questions, particularly the theory of measurement. He studied the measurement process in quantum theory and introduced the notion of an ensemble corresponding to time symmetry by selecting a sample using both initial and final states rather than just the fixing of the initial state. He extended to general relativity the Bohr—Rosenfeld argument on the measurement of field strengths. His result showed that the Riemann tensor is the measurable field and that its measurement with infinite precision requires a lattice of infinite rigidity. Peter carried out that work with one of his last students when he was a research professor at New York University.
Peter the teacher, research scientist, colleague, and friend touched and inspired a large number of physicists. During his 40 years at Syracuse, he guided 32 people through their dissertations and contributed actively to the research efforts of many more. In addition, a comparable number of postdocs spent up to two years at Syracuse, either as research associates or visiting professors. They were stimulated by his clear, sharp physical insights and by his personal warmth. His reputation as an outstanding teacher came from the thoughtful individual attention that he gave to students. He always had time for those who were serious in their study and research. His sensitivity to students and their need for support is demonstrated by the following anecdote. Once, during a faculty meeting, Peter was asked how he came to give an A grade to a student who was failing most of his other courses. Peter left the meeting, examined his grade book, returned, and responded, “It was a low A.”
At the end of September 2002, Peter, together with John Wheeler, was awarded the Einstein Prize by the American Physical Society for “pioneering investigations in general relativity, including gravitational radiation, black holes, spacetime singularities, and symmetries in Einstein’s equations, and for leadership and inspiration to generations of researchers in general relativity.” He learned about the award shortly before his death.
