Siobhan Roberts writes:

Lunchtime in the cafeteria at the Institute for Advanced Study in Princeton, N.J. — sometimes called the Institute for Advanced Dining — is a heady scene, and Freeman Dyson, who died last week at 96, was a regular fixture, arriving with reading material tucked under his arm.

One day about 10 years ago, Dr. Dyson put down his tray of food at the physics table and joined the conversation. Nima Arkani-Hamed, a professor in the institute’s School of Natural Sciences, was talking about recent research that had brought him into contact with some beautiful, elementary, albeit ancient, results in projective geometry. He was asking around to see if people knew of any decent books on the subject, since everything he could find was too abstract and fancy.

“Freeman sat down next to me and immediately agreed that all the new books were too highfalutin and that he himself had learned projective geometry in school, from a great little practical book,” Dr. Arkani-Hamed said recently. When Dr. Arkani-Hamed lamented that such books no longer existed, Dr. Dyson happily offered to pass along his own, dotted with his youthful jottings.

“So that’s how I came into possession of Freeman’s book on projective geometry,” Dr. Arkani-Hamed said. “I learned a bunch of stuff that I now daily use in my work. It really brings me tremendous pleasure to have it.”

Dr. Dyson — math whiz turned physicist, humanist, author and cosmic visionary — was one of a kind, a polymath with a kaleidoscopic line of inquiry. Best known for his revolutionary calculations describing the interaction of light and matter, he produced valuable contributions to numerous fields, including solid state physics, ferromagnetism, astrophysics, biology and applied mathematics.

Often he sat along the eastern side of the institute’s dining room at a table for two, with a companion, or alone with his reading. Whenever I was there as a visitor, researching and writing, I sought him out. On one occasion in 2010, he suggested by email that we meet on the early side, at 12:15 p.m., “so as to be ahead of the mob of mathematicians.” He invariably arrived looking spiffy, in a tweedy sports jacket, shirt and tie. He usually got an entree, maybe roast beef with natural jus and braised carrots and mashed potato.

Over lunch on more than one occasion, I asked him about his 1983 paper “Unfashionable Pursuits.” Notoriously contrarian, he sought to identify unfashionable ideas that might later emerge as essential for 21st-century physics. “We ought to seek out and encourage the rare individualists who do not fit into the prevailing pattern,” he wrote. But he acknowledged that communal interest in fashionable problems served a purpose: The news and the rumors, “every petty success and every ephemeral triumph,” could be shared with friends at the lunch table.

Dr. Dyson was an anti-reductionist who liked to build bridges. His “Unfashionable Pursuits” paper surveyed the history of mathematics, and then, sixth-eighths of the way in, arrived at “the monster and the moral”: an entity that exists within the mathematical realm of symmetry, in the field of group theory. The “monster group” had been predicted to exist, and mathematicians hunted for verifying clues. Eventually, this creature was proved to live — or, technically, to act — in 196,883 dimensions, and to possess 808 sexdecillion or so symmetries. Dr. Dyson suggested that these symmetries might be connected to the symmetries of the universe. The monster and its ilk might seem like “a pleasant backwater in the history of mathematics,” he said. “But we should not be too sure that there is no connection.” [Continue reading…]