Gerald Sacks

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Gerald Enoch Sacks (born 1933, Brooklyn) is a logician whose most important contributions have been in recursion theory. Named after him is Sacks forcing, a forcing notion based on perfect sets[1] and the Sacks Density Theorem, which asserts that the partial order of the recursively enumerable Turing degrees is dense.[2] Sacks had a joint appointment as a professor at the Massachusetts Institute of Technology and at Harvard University starting in 1972 and became emeritus at M.I.T. in 2006 and at Harvard in 2012.[3][4][5]

Sacks earned his Ph.D. in 1961 from Cornell University under the direction of J. Barkley Rosser, with a dissertation entitled On Suborderings of Degrees of Recursive Insolvability. Among his notable students are Lenore Blum, Harvey Friedman, Sy Friedman, Leo Harrington, Richard Shore, Steve Simpson and Theodore Slaman.[6]

Selected publications[edit]

  • Degrees of unsolvability, Princeton University Press 1963, 1966[7]
  • Saturated Model Theory, Benjamin 1972; 2nd edition, World Scientific 2010[8]
  • Higher Recursion theory, Springer 1990[9]
  • Selected Logic Papers, World Scientific 1999[10]
  • Mathematical Logic in the 20th Century, World Scientific 2003


  1. ^ Halbeisen, Lorenz J. (2011), Combinatorial Set Theory: With a Gentle Introduction to Forcing, Springer Monographs in Mathematics, Springer, pp. 380–381, ISBN 9781447121732.
  2. ^ Soare, Robert I. (1987), Recursively Enumerable Sets and Degrees: A Study of Computable Functions and Computably Generated Sets, Perspectives in Mathematical Logic, Springer, p. 245, ISBN 9783540152996.
  3. ^ Short CV, retrieved 2015-06-26.
  4. ^ "Professor Gerald Sacks Retires from MIT" (PDF), Integral: News from the Mathematics Department at MIT, 1: 6, Autumn 2006.
  5. ^ Chi Tat Chong, Yue Yang, "An interview with Gerald E. Sacks", Recursion Theory: Computational Aspects of Definability, ISBN 3110275643, 2015, p. 275
  6. ^ Gerald Sacks at the Mathematics Genealogy Project
  7. ^ Review of Degrees of unsolvability by Kenneth Appel, MR0186554
  8. ^ Review of Saturated model theory by P. Stepanek, MR0398817
  9. ^ Review of Higher recursion theory by Dag Normann, MR1080970
  10. ^ Review of Selected logic papers by Dag Normann, MR1783306