William Feller

William Feller
Vilim "Willy" Feller (1906-1970)
Born	July 7, 1906 (1906-07-07) Zagreb, Austria-Hungary
Died	January 14, 1970 (1970-01-15) New York, USA
Citizenship	American
Nationality	Croatian
Fields	Mathematician
Institutions	University of Kiel University of Copenhagen University of Stockholm University of Lund Brown University Cornell University Princeton University
Alma mater	University of Zagreb University of Göttingen
Doctoral advisor	Richard Courant
Doctoral students	George Forsythe Lawrence Shepp George Seifert
Known for	Feller process Feller's coin-tossing constants Feller-continuous process Proof by intimidation Feller transition function Feller semigroup Feller's property Feller Brownian motions Feller's test for explosions Lindeberg-Feller condition Feller operator Feller potential Feller measures Krein-Feller differential operators Kolmogorov-Feller equation
Influences	Stanko Vlögel
Notable awards	National Medal of Science (USA) in Mathematical, Statistical, and Computational Sciences (1969)
Signature

William (Vilim) Feller born Vilibald Srećko Feller (July 7, 1906 – January 14, 1970), was a Croatian-American mathematician specializing in probability theory.

Early life and education

Feller was born in Zagreb to Ida Oemichen-Perc, a Croatian-Austrian Catholic, and Eugen Victor Feller, who was born to a Polish Jew named David Feller and an Austrian Catholic named Elsa Holzer. Eugen was a famous chemist and created Elsa fluid named after his mother. According to Gian-Carlo Rota, Feller's father's surname was a "Slavic tongue twister", which William changed at the age of twenty—but as can be seen, this claim was false. His christened name, Vilibald, was chosen by his Catholic mother for the saint day of his birthday. In his school documentation, the small municipality of Donja Stubica in Zagorje is mentioned. This is the birthplace of his father, who was an apothecary and owner of a company producing hygienic utensils and cosmetics.

William finished his elementary and middle education in Zagreb, as well as two years of his math study. From 1925, he continued his study in Göttingen, Germany where he gained the doctoral degree in 1926 under the supervision of Richard Courant, with his work Über algebraisch rektifizierbare transzendente Kurven.

Work

Feller held a docent position at the University of Kiel beginning in 1928. Because he refused to sign a Nazi oath, he fled the Nazis and went to Copenhagen, Denmark in 1933. He also lectured in Sweden (Stockholm and Lund). Finally, in 1939 he arrived in the U.S. where he became a citizen in 1944 and was on the faculty at Brown and Cornell. In 1950 he became a professor at Princeton University.

The works of Feller are contained in 104 papers and two books on a variety of topics such as mathematical analysis, theory of measurement, functional analysis, geometry, and differential equations.

Feller was one of the greatest probabilists of the twentieth century, who is remembered for his championing of probability theory as a branch of mathematical analysis in Sweden and the United States. In the middle of the 20th century, probability theory was popular in France and Russia, while mathematical statistics was more popular in the United Kingdom and the United States, according to the Swedish statistician, Harald Cramér. His two-volume textbook on probability theory and its applications was called "the most successful treatise on probability ever written" by Gian-Carlo Rota. By stimulating his colleagues and students in Sweden and then in the United States, Feller helped establish research groups studying the analytic theory of probability. In his research, Feller contributed to the study of the relationship between Markov chains and differential equations, where his theory of generators of one-parameter semigroups of stochastic processes gave rise to the theory of "Feller operators".

Results

Numerous topics relating to probability are named after him, including Feller processes, Feller's explosion test, Feller–Brown movement, and the Lindberg–Feller theorem. Feller made fundamental contributions to renewal theory, Tauberian theorems, random walks, diffusion processes, and the law of the iterated logarithm. Feller was among those early editors who launched the journal Mathematical Reviews.

Feller was born, raised, and educated in Croatia. After he emigrated, Feller continued to write and when possible to visit his Croatian relatives. He visited and lectured at the University of Zagreb. He held academic posts in Boston, Zagreb, London, Copenhagen, and Cornell University. Fleeing from Nazi persecution, Feller spent much of the 1930s and World War II in Sweden, where he taught at Lund University and Stockholm University.

External links

• William Feller at the Mathematics Genealogy Project.
• A biographical memoir by Murray Rosenblatt
• Croatian Giants of Science - in Croatian
• O'Connor, John J.; Robertson, Edmund F., "William Feller", MacTutor History of Mathematics archive, University of St Andrews, http://www-history.mcs.st-andrews.ac.uk/Biographies/Feller.html .
• "Fine Hall in its golden age: Remembrances of Princeton in the early fifties" by Gian-Carlo Rota. Contains a section on Feller at Princeton.
• Feller Matriculation Form giving personal details