What caused the Great Moderation? : some cross-country evidence

Over the last 20 years or so, the volatility of aggregate economic activity has fallen dramatically in most of the industrialized world. The timing and nature of the decline vary across countries, but the phenomenon has been so widespread and persistent that it has earned the label: “the Great Moderation.” A growing body of research has focused on the Great Moderation and its possible explanations, especially as it applies to the U.S. experience. The literature documents the international dimension of this volatility reduction, but so far little is known about the possible causes from a cross-country perspective. Summers shows why the Great Moderation has indeed been a common feature of much of the industrialized world. Specifically, he focuses on the reduction in the volatility of GDP growth that occurred in the G-7 countries (Canada, France, Germany, Italy, Japan, the United Kingdom, and the United States) and Australia. He uses international evidence to evaluate the merits of three likely explanations. He concludes that, from an international perspective, good luck in the form of smaller energy price shocks is not a compelling explanation for widespread moderation of GDP growth volatility. Rather, the Great Moderation is more likely due to better monetary policy outcomes and improved inventory management techniques.Gross domestic product ; Group of Seven countries ; Monetary policy

Local Operations and Completely Positive Maps in Algebraic Quantum Field Theory

Einstein introduced the locality principle which states that all physical effect in some finite space-time region does not influence its space-like separated finite region. Recently, in algebraic quantum field theory, R\'{e}dei captured the idea of the locality principle by the notion of operational separability. The operation in operational separability is performed in some finite space-time region, and leaves unchanged the state in its space-like separated finite space-time region. This operation is defined with a completely positive map. In the present paper, we justify using a completely positive map as a local operation in algebraic quantum field theory, and show that this local operation can be approximately written with Kraus operators under the funnel property

Self-Assembly of Infinite Structures

We review some recent results related to the self-assembly of infinite structures in the Tile Assembly Model. These results include impossibility results, as well as novel tile assembly systems in which shapes and patterns that represent various notions of computation self-assemble. Several open questions are also presented and motivated