Tokyo stocks opened lower Thursday on concerns over the world economy a day after the heads of some top central banks warned about the risks of high and persistent inflation. In the first 15 minutes of trading, the 225-issue Nikkei Stock Average fell 137.45 points, or 0.51 percent, from Wednesday to 26,667.15. The broader Topix index was down 8.87 points, or 0.47 percent, at 1,884.70. On the top-tier Prime Market, decliners were led by mining, oil and coal product, and consumer credit issues. At 9 a.m., the dollar fetched 136.60-61 yen compared with 136.55-65 yen in New York and 136.02-04 yen …