The amount of debt tied to artificial intelligence has ballooned to $1.2 trillion, making it the largest segment in the investment-grade market, according to JPMorgan Chase & Co.AI companies now make up 14% of the high-grade market from 11.5% in 2020, surpassing US banks, the largest sector on the JPMorgan US Liquid Index (JULI) index at 11.7%, JPMorgan analysts including Nathaniel Rosenbaum and Erica Spear wrote in a note Monday....