Johnson–Lindenstrauss lemma, a mathematical result concerning low-distortion embeddings of points from high-dimensional into low-dimensional Euclidean space contributed by Joram Lindenstrauss. Development of the measurement of rigidity by Elon Lindenstrauss in ergodic theory, and their applications to number theory.[2] Proof of Szemerédi's theorem solved by mathematician Hill Furstenberg. Expansion of axiomatic set theory and the ZF set theory by Abraham Fraenkel.