When James H. Simons celebrated his 60th birthday he did things a bit differently than private equity king Stephen Schwarzman. Instead of throwing a lavish gala and hiring Rod Stewart to serenade his guests, Mr Simons hosted a geometry symposium that featured chats on such topics as the Chern-Simons Invariants.

In fact, Mr Simons, president of $25bn (£12.5bn) hedge fund group Renaissance Technologies, does just about everything a little differently. The bearded 69-year-old is a prize-winning mathematician and former code-breaking cryptologist who spends little time on the Manhattan social circuit. He hires almost no one with a Wall Street pedigree, instead populating his 150-person group with PhDs in fields ranging from astrophysics to linguistics.