While markets are on edge on a historic Federal Reserve decision day, another central bank could also have a massive impact on stocks this week. Investors will be hoping it doesn't raise interest rates again, after a surprise hike in July unwound the so-called carry trade and sparked a bout of market turbulence. The Japanese yen climbed as much as 0.8% against the dollar on Wednesday, reflecting investors' belief that the Fed and BoJ are at different stages of their monetary policy cycles.