John Forbes Nash Jr. (June 13, 1928 – May 23, 2015), known and published as John Nash, was an American mathematician who made fundamental contributions to game theory, real algebraic geometry, differential geometry, and partial differential equations. Nash and fellow game theorists John Harsanyi and Reinhard Selten were awarded the 1994 Nobel Prize in Economics. In 2015, he and Louis Nirenberg were awarded the Abel Prize for their contributions to the field of partial differential equations. As a graduate student in the Princeton University Department of Mathematics, Nash introduced a number of concepts (including the 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 60 years. In 1959, Nash began showing 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 2001 film of the same name directed by Ron Howard, in which Nash was portrayed by Russell Crowe.
Early life and education John Forbes Nash Jr. was born on June 13, 1928, in Bluefield, West Virginia. His father, John Forbes Nash Sr., was an electrical engineer for the Appalachian Electric Power Company. His mother, Margaret Virginia (née Martin) Nash, had been a schoolteacher before she was married. He was baptized in the Episcopal Church. His younger sister Martha was born in 1930. Nash attended kindergarten and public school, and he learned from books provided by his parents and grandparents. Nash's parents pursued opportunities to supplement their son's education, and arranged for him to take advanced mathematics courses at nearby Bluefield College (now Bluefield University) during his final year of high school. He attended Carnegie Institute of Technology (which later became Carnegie Mellon University) through a full benefit of the George Westinghouse Scholarship, initially majoring in chemical engineering. He switched to a chemistry major and eventually, at the advice of his teacher John Lighton Synge, to mathematics. After graduating in 1948, with both bachelor of science and master of science degrees in mathematics, Nash accepted a fellowship to Princeton University, where he pursued further graduate studies in mathematics and sciences. Nash's adviser and former Carnegie Tech professor Richard Duffin wrote a letter of recommendation for Nash's entrance to Princeton, stating, "He is a mathematical genius." Nash was also accepted at Harvard University, the University of Chicago, and the University of Michigan. However, the chairman of the mathematics department at Princeton, Solomon Lefschetz, offered him the John S. Kennedy fellowship, convincing Nash that Princeton valued him more. Further, he considered Princeton more favorably because of its proximity to his family in Bluefield. At Princeton, he began work on his equilibrium theory, later known as the Nash equilibrium.
Research contributions
Nash did not publish extensively, although many of his papers are considered landmarks in their fields. As a graduate student at Princeton, he made foundational contributions to game theory and real algebraic geometry. As a postdoctoral fellow at MIT, Nash turned to differential geometry. Although the results of Nash's work on differential geometry are phrased in a geometrical language, the work is almost entirely to do with the mathematical analysis of partial differential equations. After proving his two isometric embedding theorems, Nash turned to research dealing directly with partial differential equations, where he discovered and proved the De Giorgi–Nash theorem, thereby resolving one form of Hilbert's nineteenth problem. In 2011, the National Security Agency declassified letters written by Nash in the 1950s, in which he had proposed a new encryption–decryption machine. The letters show that Nash had anticipated many concepts of modern cryptography, which are based on computational hardness.
Game theory Nash earned a PhD in 1950 with a 28-page dissertation on noncooperative games. The thesis, written under the supervision of doctoral advisor Albert W. Tucker, contained the definition and properties of the Nash equilibrium, a crucial concept in noncooperative games. A version of his thesis was published a year later in the Annals of Mathematics. In the early 1950s, Nash carried out research on a number of related concepts in game theory, including the theory of cooperative games. For his work, Nash was one of the recipients of the Nobel Memorial Prize in Economic Sciences in 1994.
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