A few months ago, I was saddened to learn that Robert L. Mills had passed away. As a fellow graduate of Columbia College, I feel a special bond with Mills and am therefore submitting this memorial note.
Mills, who shared with C. N. Yang the 1980 Rumford Premium Prize from the American Academy of Arts and Sciences for “development of a generalized gauge invariant field theory,” died on 27 October 1999 from prostate cancer. His passing was a great loss to his family, friends, and the physics community.
Mills was born on 15 April 1927 in Englewood, New Jersey. He graduated from George School in Pennsylvania in early 1944 and, in March, entered Columbia College in New York. While there, he enlisted in the US Merchant Marines in the last year of World War II; he served until 1947.
On leave from the service, he attended classes at Columbia, where his father was an economics professor. In 1948, his senior year, Mills was a winner of the Putnam national college mathematics contest. The mathematical ability he displayed there was evident throughout his career as a theoretical physicist. He then studied at Cambridge University, where he received first-class honors in the mathematical tripos and a master’s degree. Mills returned to Columbia and got his PhD in 1955 under Norman Kroll for a thesis on radiative corrections in quantum electrodynamics.
From 1953 to 1955, Mills was a research associate at Brookhaven National Laboratory and shared an office with Yang. During that time, they developed what is now known as the Yang–Mills theory, 1 a non-abelian local gauge invariant theory that would become one of the pivotal concepts of physics. It formed the model for non-abelian gauge theories that followed and is thus one of the bases for the standard model of elementary particles and string theory. 2 Yang–Mills also has applications to mathematics.
From 1955 to 1956, Mills was a member of the Institute for Advanced Study in Princeton, New Jersey. He then joined the physics department of Ohio State University and became a full professor in 1962. He remained at OSU until his retirement in 1995. His research was in quantum field theory, the theory of alloys, and many-body theory. He worked with Andrew Sessler on many-body theory; later, Leon Cooper joined in the effort. That work, besides producing papers that appeared in Physical Review and Physical Review Letters, resulted in Mills’s writing a book, Propagators for Many-Particle Systems: An Elementary Treatment (Gordon and Breach, 1969). He later wrote Space, Time and Quanta: An Introduction to Contemporary Physics (W. H. Freeman, 1994). For his outstanding dedication to his students, Mills received OSU’s Rosalene Sedgwick Faculty Service Award. With his wife, Lee, he shared the OSU International Community Service Award. He was a visiting professor at many schools and a visiting scientist at CERN. After his retirement, he taught for a year as a Fulbright scholar at St. Patrick’s College in Ireland.
According to Sessler, “Robert was even-tempered and simply a joy to work with. His coworkers enjoyed interacting with him.” A memorial piece in the 2000 OSU Physics Department Magazine concludes with this statement: “A gentlemen of unfailing good humor and sincere and active concern for helping others, Robert Mills will be long remembered with great respect and affection.”
While preparing this letter, I couldn’t help but observe Mills’s devotion to his friends and their devotion to him, as exemplified by his interaction with Yang and Cooper, both Nobel laureates. The following comments were obtained via private communication.
In 1953–1954, I was visiting Brookhaven and Bob was my office mate. We discussed many things in physics, from the experimental results pouring out of the new Cosmotron, to theoretical topics like renormalization and the Ward identity. It was in that year that we found the very elegant and unique generalization of Maxwell’s equation. We were pleased by the beauty of the generalization, but neither of us had anticipated its great impact on physics 20 years later.
Bob spent one year, I think it was 1955–1956, at the Institute for Advanced Study in Princeton and we resumed our collaboration. One fruit of that was a paper on the overlapping divergence in the photon propagator which, however, was not written up for publication 3 until 1966, when he and his family visited us for the summer just after I had moved to [SUNY] Stony Brook.
Bob was an old-fashioned man. Among all the physicists that I know, he was certainly one of the most honest and the most sincere.
Bob had a brilliant mind. He was very quick at grasping new ideas. I shall treasure the memory of our intensive collaboration and of our many discussions on diverse topics ranging from accelerator theory to the theory of computability.
—C. N. Yang
Bob Mills and I, with Andy Sessler, wrote a paper 4 discussing possible superfluidity of helium-3. In it, we suggested that the electron pairing due to a phonon mediated electron–electron interaction could be duplicated among 3He atoms due to the atom–atom potential. Although the solution in 3He turned out to be somewhat more complicated, the basic idea was vindicated with the discovery, about ten years later, of the superfluidity of 3He.
Bob Mills was a talented, creative physicist. We miss him.
—Leon Cooper
I would be remiss in compiling this tribute to Mills if I didn’t mention the direct or indirect influence of Yang–Mills on some of the advances establishing the standard model. These advances, tours de force all, illustrate the wonderful synergy of theoretical and experimental physics and include the Glashow-Weinberg-Salam (GWS) theory, the Glashow-Iliopoulos-Maiani (GIM) model, the successful searches for neutral currents and for the gauge particles W± and Z0, the proof of the renormalization of Yang–Mills theories, and quantum chromodynamics encompassing asymptotic freedom and quark confinement. This is a splendid legacy indeed.
Many thanks to Lee Mills for so generously giving of her time to provide me with information on her husband’s career.
