The Nikkei stock index briefly jumped more than 2 percent early Friday, tracking sharp gains on Wall Street overnight after lower-than-expected U.S. jobless claims eased fears about a recession in the world’s biggest economy. In the first 15 minutes of trading, the 225-issue Nikkei Stock Average rose 555.52 points, or 1.59 percent, from Thursday to 35,386.67. The broader Topix index was up 30.72 points, or 1.25 percent, at 2,492.42. On the top-tier Prime Market, gainers were led by nonferrous metal, mining and wholesale trade shares.