Ronald Jensen
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Ronald Björn Jensen (born April 1, 1936) is a mathematician working in logic and set theory. He studied economics at American University and mathematics at the University of Bonn getting a PhD in mathematics in 1964 (supervised by Gisbert Hasenjäger). Jensen spent most of his academic career in Europe at the University of Bonn, the University of Oslo, the University of Freiburg, Oxford University and the Humboldt-Universität zu Berlin with shorter stays at Rockefeller University (1969-1971) and UC Berkeley (1971-1973). In 2001, he retired from the Humboldt-Universität zu Berlin and is currently living in Berlin. Jensen is the recipient of the 2003 Leroy P. Steele Prize for Seminal Contribution to Research of the American Mathematical Society for his 1972 paper entitled "The fine structure of the constructible hierarchy" in which he invented fine structure theory.
Jensen contributed to many fields of mathematical logic, more specifically set theory. Among his most known results are
- the consistency of NFU,
- the fine structure theory of the constructible universe L, including the definitions and proofs of various combinatorial principles in L: diamond
, square, and morasses. - the Jensen Covering Lemma for L,
- the construction of the Dodd-Jensen core model, including the general theory of Core Models,
- the technique of coding the universe in a real.
