John Forbes Nash , Jr. ( June 13 , 1928 -- May 23 , 2015 ) was an American mathematician with fundamental contributions in game theory , differential geometry , and partial differential equations .
< indicator name = `` top-icon '' > </indicator> John Forbes Nash Jr. ( June 13 , 1928 -- May 23 , 2015 ) was an American mathematician who worked in game theory and differential geometry .