Freeman Dyson - Biography - Career in The United States

Career in The United States

In 1947 Dyson moved to the US, with a fellowship at Cornell University, where in 1951 he joined the faculty as a physics professor, although still lacking a doctorate. In 1953, he took up a post at the Institute for Advanced Study in Princeton, New Jersey.

In 1957, he became a naturalized citizen of the United States and renounced his British nationality. One reason stated for this is that his children born in the US had not been recognized as British subjects.

Dyson is best known for demonstrating in 1949 the equivalence of the formulations of quantum electrodynamics that existed by that time – Richard Feynman's diagrams, on the one hand, and, on the other, the operator method developed by Julian Schwinger and Sin-Itiro Tomonaga. He was the first person (besides Feynman) to appreciate the power of Feynman diagrams, and his paper written in 1948 and published in 1949 was the first to make use use of them. He said in that paper that Feynman diagrams were not just a computational tool, but a physical theory, and developed rules for the diagrams that completely solved the renormalization problem. Dyson's paper and also his lectures presented Feynman's theories of QED (quantum electrodynamics) in a form that other physicists could understand and undoubtedly facilitated the physics community's acceptance of Feynman's work. Robert Oppenheimer, in particular, was persuaded by Dyson that Feynman's new theory was as valid as Schwinger's and Tomonaga's. Oppenheimer rewarded Dyson with a lifetime appointment at the Institute for Advanced Study, "for proving me wrong", in Oppenheimer's words.

Also in 1949, in a related work, Dyson invented the Dyson series. It was this paper that inspired John Ward to derive his celebrated Ward identity.

Dyson also did work in a variety of topics in mathematics, such as topology, analysis, number theory and random matrices. There is an interesting story involving random matrices. In 1973 the number theorist Hugh Montgomery was visiting the Institute for Advanced Study and had just made his pair correlation conjecture concerning the distribution of the zeros of the Riemann zeta function. He showed his formula to the mathematician Atle Selberg who said it looked like something in mathematical physics and he should show it to Dyson, which he did. Dyson recognized the formula as the pair correlation function of the Gaussian unitary ensemble, which has been extensively studied by physicists. This suggested that there might be an unexpected connection between the distribution of primes 2,3,5,7,11,... and the energy levels in the nuclei of heavy elements such as uranium.

From 1957 to 1961 he worked on the Orion Project, which proposed the possibility of space-flight using nuclear pulse propulsion. A prototype was demonstrated using conventional explosives, but a treaty, which he was involved in and supported, banned the testing of nuclear weapons other than underground, and this caused the project to be abandoned.

In 1958 he led the design team for the TRIGA, a small, inherently safe nuclear reactor used throughout the world in hospitals and universities for the production of isotopes.

A seminal work by Dyson came in 1966 when, together with Andrew Lenard and independently of Elliott H. Lieb and Walter Thirring, he proved rigorously that the exclusion principle plays the main role in the stability of bulk matter. Hence, it is not the electromagnetic repulsion between electrons and nuclei that is responsible for two wood blocks that are left on top of each other not coalescing into a single piece, but rather it is the exclusion principle applied to electrons and protons that generates the classical macroscopic normal force. In condensed matter physics, Dyson also did studies in the phase transition of the Ising model in 1 dimension and spin waves.

Around 1979, Dyson worked with the Institute for Energy Analysis on climate studies. This group, under the direction of Alvin Weinberg, pioneered multidisciplinary climate studies, including a strong biology group. He is not an unqualified believer in the predictions being made by the believers in global warming (see below). Also during the 1970s, Dyson worked on climate studies conducted by the JASON defense advisory group.

He retired from the Institute for Advanced Study in 1994. In 1998, Dyson joined the board of the Solar Electric Light Fund. As of 2003, Dyson is the president of the Space Studies Institute, the space research organization founded by Gerard K. O'Neill. Dyson is a long-time member of the JASON defense advisory group.

Dyson is a regular contributor to the New York Review of Books.

Although Dyson has won numerous scientific awards, he has never won a Nobel Prize, which has led Nobel physics laureate Steven Weinberg to state that the Nobel committee has "fleeced" Dyson. Dyson has said that “I think it’s almost true without exception if you want to win a Nobel Prize, you should have a long attention span, get hold of some deep and important problem and stay with it for ten years. That wasn’t my style.”