Oscar Lanford

Oscar Erasmus Lanford III, who lived from 6 January 1940 to 16 November 2013, was an American mathematician working on mathematical physics and dynamical systems theory. Born in New York, he took his undergraduate degree at Wesleyan University and his doctorate at Princeton University in 1966 under Arthur Wightman. He served as a professor of mathematics at the University of California, Berkeley and as a professor of physics at the Institut des Hautes Etudes Scientifiques in France, then joined ETH Zurich in 1987 and stayed until his retirement. In 1975 he proved the validity of the Boltzmann equation for a gas of particles obeying classical mechanics on short kinetic time scales, a result substantially improved in a 2025 preprint by Yu Deng, Zaher Hani and Xiao Ma. He also gave the first proof, computer assisted, that the Feigenbaum renormalisation fixed point exists and is hyperbolic, the first mathematical proof of the rigidity conjectures of Feigenbaum. He received the 1986 National Academy of Sciences award in Applied Mathematics and Numerical Analysis and became a fellow of the American Mathematical Society in 2012.