"The research under this proposal aims at a better understanding of monetary policy in light of the recent events following the financial crisis. There are three main objectives. The first is to study monetary policy in models where financial securities have different liquidity properties which could vary over time and be subject to sudden changes. The new framework will address the mechanisms at the root of the financial crisis and its propagation to real economic activity and at the same time study the appropriate policy responses and the forthcoming exit strategies. The second objective aims at extending the analyses of optimal monetary policy to abnormal times where deleveraging or liquidity shocks bring the nominal interest rate to the zero lower bound and more unconventional policies are needed. The third objective is directed to study open-economy models where the liquidity properties of financial securities affect the conduct of monetary policy, as in a currency area in which sovereign debt of some countries loses its safe-asset status or in small open economies challenged by imperfect credibility in the domestic fiat-money system."