Gerald Sacks is a logician who holds a joint appointment at Harvard University

Harvard University

Harvard University is a private Ivy League university located in Cambridge, Massachusetts, United States, established in 1636 by the Massachusetts legislature. Harvard is the oldest institution of higher learning in the United States and the first corporation chartered in the country...

 as a Professor of Mathematical Logic

Mathematical logic

Mathematical logic is a subfield of mathematics with close connections to foundations of mathematics, theoretical computer science and philosophical logic. The field includes both the mathematical study of logic and the applications of formal logic to other areas of mathematics...

 and the Massachusetts Institute of Technology

Massachusetts Institute of Technology

The Massachusetts Institute of Technology is a private research university located in Cambridge, Massachusetts. MIT has five schools and one college, containing a total of 32 academic departments, with a strong emphasis on scientific and technological education and research.Founded in 1861 in...

 as a Professor Emeritus. His most important contributions have been in recursion theory

Recursion theory

Computability theory, also called recursion theory, is a branch of mathematical logic that originated in the 1930s with the study of computable functions and Turing degrees. The field has grown to include the study of generalized computability and definability...

. Named after him is Sacks forcing, a forcing

Forcing (mathematics)

In the mathematical discipline of set theory, forcing is a technique invented by Paul Cohen for proving consistency and independence results. It was first used, in 1963, to prove the independence of the axiom of choice and the continuum hypothesis from Zermelo–Fraenkel set theory...

 notion based on perfect sets and the Sacks Density Theorem, which asserts that the partial order of the recursively enumerable Turing degrees is dense.

Sacks earned his Ph.D.

Doctor of Philosophy

Doctor of Philosophy, abbreviated as Ph.D., PhD, D.Phil., or DPhil , in English-speaking countries, is a postgraduate academic degree awarded by universities...

 in 1961 from Cornell University

Cornell University

Cornell University is an Ivy League university located in Ithaca, New York, United States. It is a private land-grant university, receiving annual funding from the State of New York for certain educational missions...

 under the direction of J. Barkley Rosser, with a dissertation entitled On Suborderings of Degrees of Recursive Insolvability. Among his notable students are Harvey Friedman

Harvey Friedman

Harvey Friedman is a mathematical logician at Ohio State University in Columbus, Ohio. He is noted especially for his work on reverse mathematics, a project intended to derive the axioms of mathematics from the theorems considered to be necessary...

, Leo Harrington

Leo Harrington

Leo Anthony Harrington is a professor of mathematics at the University of California, Berkeley who works inrecursion theory, model theory, and set theory.* Harrington and Jeff Paris proved the Paris–Harrington theorem....

, Richard Shore, and Theodore Slaman

Theodore Slaman

Theodore Allen Slaman is a professor of mathematics at the University of California, Berkeley who works in recursion theory.Slaman and W. Hugh Woodin formulated the Bi-interpretability Conjecture for the Turing degrees, which conjectures that the partial order of the Turing degrees is logically...

. A distinctive characteristic of his logic classes was that in the middle of each
class, a previously selected student would have to get up and tell a joke. The joke had to be short, funny, and inoffensive to receive credit.

External links