World stocks fall before crunch weekend for Greece; Nifty ends below 8400: Markets have closed the session on a lower note tracking weakness among banks, capital goods and metal shares. Further, global markets are also witnessing weak trend as Greece and its international creditors yet again failed to sign a truce. The Sensex ended down 84 points at 27,812 and Nifty closed 17 points down at 8,381. On the currency front, the rupee continued to trade flat against the US dollar at 63.60 as gains in the US currency overseas capped upside gains. Meanwhile, RBI Governor Raghuram Rajan has asked central banks from across the world to define "new rules of the game" as he warned that the global economy may be slipping into problems similar to the Great Depression of the 1930s.