Ronald Jensen

Ronald Björn Jensen ( born April 1, 1936) is an American mathematician who deals with axiomatic set theory and mathematical logic.

Jensen studied 1954-1959 Economics at the American University in Washington, DC and thereafter until 1964 Mathematics at the University of Bonn, where he received his doctorate in 1964 at Gisbert rabbits Jaeger. After that he was in Bonn, where he habilitated in 1967 to 1969 assistant. 1969 to 1975 he was professor at the University of Oslo and taught simultaneously at the Rockefeller University in New York ( until 1971 ) and the University of California, Berkeley ( until 1973 ). 1974 to 1975 he was a Humboldt Prize winner at the University of Bonn, where he was professor from 1976 to 1978. 1978/79 he was a visiting scholar at Oxford University, 1979-1981 Professor at the University of Freiburg im Breisgau. 1981-1994 he was a Senior Research Fellow at All Souls College, Oxford University. 1994 until his retirement in 2001 he was professor of mathematical logic at the Humboldt University in Berlin. He lives in Berlin.

Jensen did research in axiomatic set theory, especially the theory of large cardinals and inner models such as Kurt Gödel constructive universe. For The fine structure of the constructible hierarchy, ( Annals of Mathematical Logic, Volume 4, 1972, p.229 -308 ), he received the 2003 Leroy P. Steele Prize. The work was seminal for the development of internal models for which Jensen depending on assumptions about the existence of large cardinals provided new constructions. His covering theorem states that if the number Zero Sharp ( ) does not exist, not countable infinite sets of ordinals constructible by the same amounts thickness can be covered. Jensen showed the existence of various nuclear models (core models ), so the Dodd -Jensen Core Model for non- existence of a measurable cardinal. Next he found various combinatorial principles (diamonds, Square, Morass ) in internal models that have been applied in other areas of mathematics. He is also known for his coding theorem ( proved in Coding the Universe, 1982).

In 1990, he was the first Gödel Lecturer. In 2001 he held the Tarski Lectures.

Writings

• Models of set theory. Consistency and independence of the continuum hypothesis and the axiom of choice. ( Lecture Notes in Mathematics, Vol 37). Springer, Berlin 1967.
• Coding the Universe. Cambridge University Press, Cambridge 1982, ISBN 0-521-28040-0 (along with Aaron Beller and Philip Welch).