William Feller

William Feller, born Vilibald Srecko Feller in Zagreb on 7 July 1906 and died on 14 January 1970, was a Croatian-American mathematician who specialized in probability theory. He left Europe after refusing to sign a Nazi oath, working in Copenhagen and Sweden before joining Brown University in 1939, then Cornell in 1945 and Princeton in 1950, where he held the Eugene Higgins chair in mathematics until his death. His papers and two books ranged across analysis, measure theory, functional analysis, geometry and differential equations as well as statistics, but he is remembered above all for treating probability as a branch of mathematical analysis. His work linking Markov chains with differential equations gave rise to the theory of Feller operators, and his two-volume textbook on probability and its applications became a standard treatise. Feller processes and the Lindeberg-Feller theorem carry his name.