Renaissance Technologies, a quant hedge fund that oversees $84 billion, bought up $479.5 million worth of Facebook between April 1 and June 30, regulatory filings show. The hedge fund was apparently "buying the dip" after the social network's scandal-ridden spring caused shares to plunge by 20% at the end of March. Watch Facebook trade in real time here. Renaissance Technologies, the $80 billion hedge fund founded by Cold War code breaker James Simons, seems to think the worst for Facebook is over.