Quarterly 13F filings show that two of the world’s best-known quantitative investment firms made notable shifts in the June quarter. Renaissance Technologies, the $75 billion hedge fund founded by mathematician Jim Simons, kept Palantir Technologies as its largest holding but trimmed the stake to roughly 13.5 million shares. The firm opened a $421 million position in UnitedHealth Group—its biggest new equity bet—and disclosed a separate $7 million allocation to Bitcoin, marking a rare move into the cryptocurrency by the secretive quant shop. Ray Dalio’s Bridgewater Associates, which manages about $25 billion in reportable U.S. equity holdings, initiated a $63 million stake in chip designer Arm Holdings and exited its position in Alibaba Group. The filings provide the first public look at the funds’ equity books since the end of June and highlight a tilt toward U.S. healthcare and semiconductor names, alongside a modest foray into digital assets, as managers reposition for the second half of 2025.