Nvidia on Wednesday denied reports it received a subpoena from the Department of Justice over antitrust concerns. "We have inquired with the U.S. Department of Justice and have not been subpoenaed," an Nvidia representative told CNBC. "Nonetheless, we are happy to answer any questions regulators may have about our business."Bloomberg reported Tuesday that Nvidia had received a subpoena, causing the stock to slip in after-hours trading. The chipmaker's shares had already given up nearly 10% during regular tr ...