LONDON — European markets are expected to open lower on Friday, as U.S. tech stock volatility spills over the Atlantic once again. Futures tied to London's FTSE 100 were last seen trading 1% lower, while those tied to Germany's DAX and the French CAC 40 were down 1.3% and 1.1%, respectively. Global stocks have fluctuated wildly this week, as concerns about AI valuations hang over equity markets. Some respite from a four-day sell-off followed Nvidia 's earnings release on Wednesday, but its own