Allyn Jackson Ronald Jensen receives a 2003 Steele Prize At the 109th Annual Meeting of the AMS in Baltimore in January 2003, a Steele Prize has been awarded to Ronald Jensen for a Seminal Contribution to Research. The text that follows presents the selection committee’s citation and a brief biographical sketch. (Allyn Jackson) Ronald Jensen’s paper,“The fine structure of the con- of an inner model, in this case G¨odel’s constructible structible hierarchy” (Annals of Mathematical Logic sets, that go far beyond G¨odel’s proof of the general- 4 (1972) 229–308), has been of seminal importance ized continuum hypothesis in this model. for two different directions of research in contempo- The second direction initiated by Jensen’s paper rary set theory: the inner model program and the use involves applying these combinatorial principles to of combinatorial principles of the sort that Jensen es- problems arising in other parts of mathematics. The tablished for the constructible universe. principle, which Jensen proved to hold in the con- The inner model program, one of the most active structible universe, has been particularly useful in parts of set theory nowadays, has as its goals the un- such applications. By now, it has become part of the derstanding of very large cardinals and their use to standard tool kit of several branches of mathematics, measure the consistency strength of assertions about ranging from general topology to module theory. much smaller sets. A central ingredient of this pro- Ronald Jensen received his Ph.D. in 1964 from the gram is to build, for a given large cardinal axiom, a University of Bonn. He continued his research at model of set theory that either is just barely large Bonn as a scientific assistant (1964–1969). From enough to contain that type of cardinal or is just 1969 until 1973 Jensen was a professor of mathemat- barely too small to contain it. The fine structure ics at the University of Oslo. During this period he techniques introduced in Jensen’s paper are the foun- held concurrent positions at Rockefeller University dation of the more recent work of Mitchell, Steel, (1969–1971) and the University of California, Berke- Jensen himself, and others constructing such models. ley (1971–1973). At the University of Bonn he was The paradigm, initiated by Jensen, for relating large awarded the Humboldt Prize (1974–1975) and served cardinals to combinatorial properties of smaller sets is as a professor of mathematics (1976–1978). He was first to show that the desired properties hold in these a visiting fellow at Oxford University’s Wolfson Col- inner models and then to show that, if they failed lege (1978–1979), a professor of mathematics at the to hold in the universe of all sets, then that universe University of Freiburg (1979–1981), and a senior re- and the inner model would differ so strongly that a search fellow at Oxford University’s All Souls Col- large cardinal that is barely missing from the inner lege (1981–1994). He moved to Humboldt University model would be present in the universe. The paper of Berlin, where he was a professor of mathematics cited here contains the first steps in this direction, es- (1994–2001). His areas of research interest include tablishing for the first time combinatorial properties set theory. Gottfried Wilhelm-Leibniz-Preistr¨ager 2003 Von den zehn Preisen gehen 3 + 2/2 an (im weiteren Wir freuen uns uber¨ diesen Erfolg und gratulieren. In Sinn) Mathematiker: H´el`ene Esnault/Eckhart Vieh- einem sp¨ateren Heft werden wir ausfuhrlicher¨ uber¨ weg, Gerhard Huisken, Rupert Klein und Hans-Peter die Preistr¨ager und die Preisverleihung berichten. Seidel. (FB) 40 DMV-Mitteilungen 1/2003.