Philip Hartman

Philip Hartman, who lived from 16 May 1915 to 28 August 2015, was an American mathematician at Johns Hopkins University who worked on differential equations and introduced the Hartman-Grobman theorem. He served as chairman of the mathematics department at Johns Hopkins for several years and died in August 2015 at the age of one hundred. His book Ordinary Differential Equations, first published in 1964 and reissued by the Society for Industrial and Applied Mathematics in 2002 as volume 38 of Classics in Applied Mathematics, gives a necessary and sufficient condition for solutions of ordinary initial value problems to be unique and to depend in a C1 manner on the initial conditions. The Hartman-Watson distribution is named after him and Geoffrey S. Watson. He has an Erdos number of two. Among his students was Charles C. Pugh, who took his doctorate under him at Johns Hopkins in 1965.