After teaching at Princeton University and the University of Wisconsin , he was made an assistant professor at the University of Michigan in 1958. The following year he moved to Bell Telephone Laboratories . He was also visiting professor at Yale , Columbia and Rutgers .
In 1960 he proved a theorem named after him about the order properties of an infinite sequence of finite trees. The theorem says that in an infinite set of finite trees there exists a tree that is part of another tree in the set. In 1981, Harvey Friedman showed that a variant of the sentence in Peano arithmetic is undecidable. In order to be able to formulate the theorem in Peano arithmetic, Friedman had to formulate a finite version of Kruskal's theorem, but with a very rapidly growing finite set.
- Recent alumni deaths paw.princeton.edu, accessed February 17, 2011
- Joseph Bernard Kruskal in the Mathematics Genealogy Project (English)
- Thomas Koshy: Discrete mathematics with applications. Elsevier 2004, ISBN 0-12-421180-1 . (Chapter 9: Trees, p. 616)
- Kruskal, Well-quasi-ordering, the tree theorem, and Vazsonyi's conjecture, Transactions of the American Mathematical Society, Volume 95, 1960, pp. 210-225. A simpler proof was Crispin Nash-Williams , Proc. Cambridge Phil. Soc., Vol. 59, 1963, pp. 833-835.
- Marianne Freiberger, Picking Holes in Mathematics, Plus Magazine
|ALTERNATIVE NAMES||Kruskal, Joseph Bernard (full name)|
|BRIEF DESCRIPTION||American mathematician and statistician|
|DATE OF BIRTH||January 29, 1928|
|PLACE OF BIRTH||New York City|
|DATE OF DEATH||September 19, 2010|
|Place of death||Princeton, New Jersey|