Yitang Zhang

Yitang Zhang is a Chinese-American mathematician who in 2013, after more than a decade working largely outside mainstream academic mathematics, achieved a breakthrough on one of number theory's long-standing open problems, the question of gaps between prime numbers. The twin prime conjecture proposes that there are infinitely many pairs of prime numbers that differ by exactly two, but no one had ever proven that there are infinitely many prime pairs separated by any fixed, bounded distance at all. Zhang proved that there exist infinitely many pairs of primes that differ by less than 70 million, the first time any finite bound on the gap between infinitely many prime pairs had ever been established, a result that represented decisive progress toward, though not a full proof of, the twin prime conjecture itself. His paper, titled Bounded Gaps Between Primes, was accepted by the prestigious journal Annals of Mathematics within about three weeks of submission, an unusually fast review for a major result, and the announcement caused considerable excitement in the mathematical community both for the mathematics itself and for the unlikely circumstances of its discovery by a previously little-known researcher. Following Zhang's breakthrough, other mathematicians rapidly improved on his numerical bound through a large collaborative online project, reducing the proven gap from 70 million down to a few hundred within about a year, building directly on the techniques Zhang had introduced.