# Main Page/doob

**William (Vilim) 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. In his school documentation, the small municipality of Donja Stubica in Zagorje is mentioned. This is where his father came from. His father, Eugen Victor Feller, was an apothecary and owner of company producing hygienic utensils and cosmetics.

William finished the 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 with his work *Über algebraisch rektifizierbare transzendente Kurven*.

## Work

Feller held a docent position at the University of Kiel beginning in 1928. He fled the Nazis and went to Denmark, (Copenhagen) in 1933. He also lectured in Sweden, (Stockholm and Lund). Finally, in 1939 he arrived in the USA 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.

He was the foremost probabilist outside of Russia. In the middle of the 20th century, probability was not generally viewed as a fruitful area of research in mathematics except in Russia, where Kolmogorov and others were influential. Feller contributed to the study of the relationship between Markov chains and differential equations. He wrote a two-volume treatise on probability that has since been universally regarded as one of the most important treatments of that subject.

## Results

Numerous topics relating to probability are named after him as Feller process, Feller explosion test, Feller-Brown movement, Feller property, Lindberg-Feller theorem. Books written by him and published as the textbooks are being considered invaluable in popularisation of the theory of probability and the best written during the 20th century.

Despite the fact that he spent the better part of his life out of Croatia where he was born and grew up, and where he started his education, he was in touch with relatives and the colleagues at University of Zagreb whom he often visited, and where he frequently lectured. He received numerous awards and was an honoured member of numerous educational institution (Boston, Zagreb, London, Copenhagen).

Feller initiated the publication of the now well-known review journal *Mathematical Reviews*.