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William Feller (Vilim, Willy, Willi, 1906-1970) is a well known name among mathematicians dealing with probability theory. He was born and educated in Zagreb as Vilim Feller, where he studied mathematics for two years (completing 4 semesters out of 8), and then in 1926 continued his studies at the University of Göttingen. By the end of the same year, at the age of 20, he defended his doctoral degree in mathematics. Göttingen at that time the strongest mathematical center in the world besides Paris. He was a professor at the Universities of Kiel, Copenhagen, Stockholm, Lund, Providence, Princeton etc., a member of many scientific organizations. More than 150 mathematical notions bear his name, and here are just a few of them: Feller’s process, Feller’s transition function, Feller’s semigroup, Feller’s property. He is best known for his monograph “An Introduction to Probability Theory and its Applications”, Volumes I and II, on 1153 pp., translated into Russian, Chinese, Castilian, Japanese, Hungarian and Polish. They are considered among the best mathematical textbooks written in the 20th century. At the International Congress of Mathematicians held in 1958 in Edinburgh, William Feller gave a plenary talk “Some new connections between probability and classical analysis.”

For more information see William Feller (photo by Paul Halmos).

Feller was among those who initiated issuing the important Mathematical Reviews journal, and was its first executive editor (1944-1945). He worked with von Neumann, one of the creators of modern computers. Feller was awarded the National Medal of Science of the USA in 1969. He was in touch with his relatives in Zagreb, as well as with his colleagues at the University of Zagreb.

Joseph Doob, a renowned American mathematician, wrote about Feller the following:

Those who knew him personally remember Feller best for his gusto, the pleasure with which he met life, and the excitement with which he drew on his endless fund of anecdotes about life and its absurdities, particularly the absurdities involving mathematics and mathematicians. To listen to his lecture was a unique experience, for no one else could lecture with such intense excitement. No one could generated in himself as well as in his auditors so much intense excitement. In losing him, the world of mathematics has lost one of its strongest personalities as well as one of its strongest researchers.

Vilim Feller, extensive biography, with emphasis on his life in Zagreb, Croatia

Ferdinand Feller, the eldest brother of Vilim (William) Feller (1906-1970), is the author of the graphic sign of the Croatian optical industry Ghetaldus, named after Marinus Ghetaldus, that is, after Marin Getaldić. Photo by D.Ž. in the city of Rijeka. See also Elsa fluid.