U.S. stocks are down, with the S&P 500's decline led by a significant sell-off in the technology sector. Investors are showing concerns over the high cost of debt for companies in the artificial intelligence (AI) space, leading to a rotation out of growth-oriented tech stocks and into defensive sectors like financials and energy. Several major technology companies, including chipmakers, are experiencing notable declines, which is weighing on the tech-heavy Nasdaq and the broader S&P 500.