My Ph.D. advisor Peter G. Bergmann has long been recognized as a co-inventor of a technique that lies at the core of modern attempts at unifying the fundamental laws of nature. The Dirac-Bergmann Hamiltonian constrained dynamics formalism is a method for reformulating, as so-called initial value problems, theories that enjoy a high degree of symmetry. In this form a conventional method exists for converting classical theories into quantum mechanical theories. Einstein’s general theory of relativity, his geometrical theory of gravity, is the supreme example a theory admitting this high degree of symmetry. His dynamical equations take the same form regardless of the choice of spatial and temporal coordinates. 

Following his tenure as Einstein’s young assistant at the Institute for Advanced Study in Princeton from 1936 through 1941, and work for the US Navy during World War II, Bergmann began at Syracuse University in 1948 an attempt to convert Einstein’s theory into a quantum theory of gravity. Although no one has yet succeeded in synthesizing general relativity with quantum theory, the Dirac-Bergmann technique is one of the mathematical foundations of all of today’s unified theories, including theories unifying weak and electromagnetic forces, grand unified theories, and even superstrings and branes.

I had since my graduate school days wondered what precisely were Bergmann’s own contributions in this domain and how had it happened that they were now largely ignored. After many years I have finally begun to investigate in depth the history of constrained Hamiltonian dynamics. 

My first published article dealing with Bergmann is a short piece appearing in Albert Einstein: Engineer of the Universe: One Hundred Authors for Einstein, Jürgen Renn ed. (Wiley-VCH, Weinheim, 2005) ISBN 10:3-527-40574-7. A gave a talk, "Peter Bergmann and the invention of constrained Hamiltonian dynamics", at the Seventh International Conference on the History of General Relativity in the Canary Islands in March, 2005. The published version appears in Einstein and the Changing Worldviews of Physics edited by C. Lehner, J. Renn and M. Schemmel.

This initial effort led me to begin to appreciate the earlier work of the Belgian physicist Léon Rosenfeld. I translated his groundbreaking 1930 article from the German, subsequently further polished with the assistance of Kurt Sundermeyer. It appeared in 2017 in the European Physical Journal H 42, 23-61.  An earlier preprint is available as a Max Planck for the History of Science preprint. Kurt and I published an extensive analysis of the work in the same issue in 2017, European Physical Journal H 42, 63-94.

In 2011 I partnered with the philosopher Dean Rickles of the University of Sydney, Australia, in a marathon cross-country journey in which we interviewed nine veteran relativity physicists. The trip was supported by a grant from the Center for History of Physics of the American Institute of Physics. The transcripts will eventually all appear on the Niels Bohr Library web site of the Center. We interviewed the following, with web links where available

Stanley Deser                        Californian Institute of Technology

Cécile DeWitt-Morette                    University of Texas at Austin

Ivor and Joanna Robinson                University of Texas at Dallas

Charles Misner                        University of Maryland

Dieter Brill                           University of Maryland

Louis Witten                         University of Cincinnati

James Anderson                      Stevens Institute of Technology

Joshua Goldberg                      Syracuse University

In 2013 I was a member of the local organizing committee for the 27^th Texas Symposium on Relativistic Astrophysics. I proposed and organized a plenary session of the meeting in which we brought together veterans of the first Texas Symposium held in Dallas in December,1963. The resulting Roundtable discussion was moderated by Jürgen Renn of the Max Planck Institute for the History of Science (MPIWG) in Berlin. I was successful in securing funding for this event from Austin College, MPIWG, and the Center for History of Physics of the American Institute of Physics. Participants included James Anderson, Dieter Brill, Cécile DeWitt-Morette, Joshua Goldberg, Roy Kerr, Charles Misner, Ezra Newman, Roger Penrose, Wolfgang Rindler and Louis Witten. We recorded separate interviews that will also eventually be deposited on the Center’s website.

I worked with the MPIWG in Berlin and a core group of philosophers and historians of science in helping to organize an anniversary of Einstein's 1915 publication in Berlin of his general theory of relativity meeting. The focus of A Century of General Relativity was on the so-called Golden Age of general relativity that followed the remarkable astrophysical and cosmological experimental discoveries of the 1960’s. My talk is available here. We followed up with a book on the Renaissance of General Relativity in which I have a contributed chapter discussing work by my dissertation advisor Peter Bergmann and his associates at Syracuse University in the period from 1949 to 1962. The preprint is available here.

In June, 2017 I traveled to England with Dean Rickles to interview Roger Penrose in Oxford and Chris Isham in London.  I also took this opportunity to interview my friend from graduate school days in Syracuse, Andrew Hodges. We covered both his research in twistor theory - begun under Penrose's direction - and his research on Alan Turing that led to his definitive prizewinning biography entitled Alan Turing: The Enigma. Dean and I returned to Oxford in October, 2018 to complete our interview with Penrose. All of these interviews will eventually be deposited on the AIP website.

I have devoted considerable effort in the period 2016 - 2019 in investigating the early work by Andrzej Trautman and Ivor Robinson on particle equations of motion and gravitational radiation. This began with a trip to Warsaw in the summer of 2016 to interview Trautman, with the support of the European Physical Journal H. Our coauthored interview will appear in the journal at the end of 2019, with the preprint available here. I ended up extensively investigating both the context and substance of the work that Trautman and Robinson undertook, and the resulting preprint is available here.

I should also mention that I was elected in 2015 to the executive committee of the American Institute of Physics Forum on the History of Physics, serving a three year term beginning in 2017. Partially as a consequence I chaired two historical sessions at annual April meetings of the APS, one on the 1957 Chapel Hill meeting in general relativity at the April meeting in Columbus, and another on Julian Schwinger at the April 2019 meeting in Denver. At each meeting I also gave short historical presentations, one on a history of Hamilton-Jacobi methods in general relativity and another on relativity research at Syracuse in the years 1960-61. I also gave a short talk on Rosenfeld at the March 2017 APS meeting in New Orleans.