Two of the most remarkable trends in recent years have been the tremendous decline in violent crime and the comeback of once downtrodden and written-off cities. In his new book, Uneasy Peace: The Great Crime Decline, the Renewal of City Life and the New War on Violence, New York University sociologist Patrick Sharkey argues that these two trends are inextricably related. The decline in violent crime has paved the way for the urban revival, and the urban revival has in turn help to stabilize neig…