Brian Randolph Greene (born February 9, 1963) is an American physicist known for his research on string theory. He is a professor of physics and mathematics at Columbia University and the chairman of the World Science Festival, which he co-founded in 2008. Greene has worked on mirror symmetry, relating two different Calabi–Yau manifolds (concretely relating the conifold to one of its orbifolds). He also described the flop transition, a mild form of topology change, showing that topology in string theory can change at the conifold point.
https://en.wikipedia.org/wiki/Brian_Greene