Jim Simons, a legendary mathematician who founded the most successful quantitative hedge fund Renaissance Technologies, passed away on Friday. : Jim Simons, a mathematician who founded the most successful quantitative hedge fund of all time, passed away on Friday in New York City, his foundation announced on its website. Pioneering mathematical models and algorithms to make investment decisions, Simons left behind an otherworldly track record at Renaissance Technologies, that bested legends such as Warren Buffett and George Soros.