Jim Simons. AP Images / Jason Decrow Several world-class investors piled into Nvidia stock last quarter, SEC filings revealed this week. Firms tied to Jim Simons, Paul Tudor Jones, Stanley Druckenmiller, and George Soros all bought in. Nvidia stock has tripled this year as investors bet the AI boom will fuel demand for microchips. Several of the world's best investors loaded up on Nvidia stock last quarter, signaling they expect the microchip maker to play a pivotal role in the artificial-intelligence revolution. For example, David Tepper's Appaloosa Management boosted its stake in the chipmaker by nearly 600% to just over...