Rising volatility in momentum-heavy markets, highlighted by recent swings in Korean memory stocks, adds to the case that positioning has become stretched. ---Earlier:JPMorgan says today's AI-fuelled momentum rally is one of the fastest on record, and is starting to show the same warning signs that preceded past busts. JPMorgan's systematic research desk flagged a growing disconnect between momentum and other traditional investment factors such as valuation and quality. The bank said these warning signs extend beyond the technology sector into industrials, and are visible geographically in both Japan and emerging markets. Stripping out those paper gains, the bank said, underlying earnings growth would still be strong at around 19%.