John Forbes Nash Jr.
![Nash in the 2000s](https://upload.wikimedia.org/wikipedia/commons/a/a9/John_Forbes_Nash%2C_Jr._by_Peter_Badge.jpg)
As a graduate student in the Princeton University Department of Mathematics, Nash introduced a number of concepts (including Nash equilibrium and the Nash bargaining solution) which are now considered central to game theory and its applications in various sciences. In the 1950s, Nash discovered and proved the Nash embedding theorems by solving a system of nonlinear partial differential equations arising in Riemannian geometry. This work, also introducing a preliminary form of the Nash–Moser theorem, was later recognized by the American Mathematical Society with the Leroy P. Steele Prize for Seminal Contribution to Research. Ennio De Giorgi and Nash found, with separate methods, a body of results paving the way for a systematic understanding of elliptic and parabolic partial differential equations. Their De Giorgi–Nash theorem on the smoothness of solutions of such equations resolved Hilbert's nineteenth problem on regularity in the calculus of variations, which had been a well-known open problem for almost sixty years.
In 1959, Nash began showing clear signs of mental illness, and spent several years at psychiatric hospitals being treated for schizophrenia. After 1970, his condition slowly improved, allowing him to return to academic work by the mid-1980s.
Nash's life was the subject of Sylvia Nasar's 1998 biographical book ''A Beautiful Mind'', and his struggles with his illness and his recovery became the basis for a film of the same name directed by Ron Howard, in which Nash was portrayed by Russell Crowe. Provided by Wikipedia