# Saharon Shelah

Wolf Prize Laureate in Mathematics 2001

**Saharon Shelah**

#### Affiliation at the time of the award:

**Hebrew University of Jerusalem****, Israel**

#### Award citation:

**“for his many fundamental contributions to mathematical logic and set theory, and their applications within other parts of mathematics”.**

#### Prize share:

**Saharon Shelah **

**Vladimir I. Arnold**

Professor Saharon Shelah is a leading mathematician in the foundations of mathematics and mathematical logic. His staggering output, of 700 papers and half a dozen monographs, includes the creation of several entirely new theories that changed the course of model theory and modern set theory, as well as providing the tools to settle old problems from many other branches of mathematics, including group theory, topology, measure theory, Banach spaces, and combinatorics.

Shelah created a number of subfields of set theory, most notably the theory of proper forcing and the theory of possible cofinalities, a remarkable refinement of the notion of cardinality, which led to the proofs of definite statements in areas previously considered far beyond the limits of undecidability. Shelah’s work on set theoretic algebra and its applications showed that dozens of areas of algebra involve phenomena that are not controlled by universally-recognized axioms of set theory (independence phenomena). In model theory he carried through a monumental program of deep structural analysis known as “stability theory” which now dominates a large part of the field.