"Brian Randolph Greene[1] (born February 9, 1963) is an American theoretical physicist and string theorist. He has been a professor at Columbia University since 1996 and chairman of the World Science Festival since co-founding it 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.Greene has become known to a wider audience