The fate of the type I non-BPS D7-brane

We describe the fate of the Type I non-BPS D7-brane, which is tachyonic but carries a non-trivial K-theory \IZ_2 charge. It decays to topologically non-trivial gauge field configurations on the background D9-branes. In the uncompactified theory the decay proceeds to infinity, while with a transverse torus the decay reaches a final state, a toron gauge configuration with vanishing Chern classes but non-trivial \IZ_2 charge. A similar behaviour is obtained for the type I non-BPS D8-brane, and other related systems. We construct explicit examples of type IIB orientifolds with non-BPS D7-branes, which are hence non-supersymmetric, but for which supersymmetry is restored upon condensation of the tachyon. We also report on the interesting structure of non-BPS states of type IIA theory in the presence of an O6-plane, their M-theory lifts, the relation between string theory K-theory and M-theory cohomology, and its interplay with NS-NS charged objects. We discuss several new effects, including: i) transmutation between NS-NS and RR torsion charges, ii) non-BPS states classified by K-theory but not by cohomology in string theory, but whose lift to M-theory is cohomological.Comment: 26 pages, latex, 4 eps figures. v2. Footnote concerning the non-existence of certain 1-brane charges in Section

Research on Relationship between Export Trade，RMB Exchange Rate and Export Rebate

出口退税政策是一个国家或地区对出口货物免征国内生产、流通环节的间接税，或退还已报关离境的出口货物在国内生产、流通环节已缴纳的间接税的一种税收政策制度。作为国家调控出口贸易发展重要的政策工具，出口退税政策自1985年正式在我国开始实行，这对于鼓励外贸出口、扩大创汇起到了积极作用。人民币汇率政策也是调控我国对外贸易活动的重要经济杠杆，它的调整会影响对外贸易的平衡与国内经济活动。出口退税和人民币汇率政策在调控出口贸易领域相似的政策效果，让我们有必要去研究和分析两者之间存在的内在联系。概括而言，人民币汇率是一种货币政策工具，它通过多种效应共同作用于出口贸易，会产生连续影响的作用，并波及到整个经济层面；...Export rebate is an important party of tax system, which means that government should refund the value-added tax and consumption tax to the export enterprises in order to make them take part in a fair competition in the international market. As an important policy tool to regulate the export trade, export rebate began to be implemented formally by our government in 1985, which has achieved remarka...学位：经济学硕士院系专业：经济学院国际贸易系_国际贸易学学号：1572006115116

Increasing returns to scale and the arms race: The end of the Richardson paradigm?

Considered here is an arms race in which weapons production exhibits increasing returns to scale technology that stems from the increasing importance of information, electronics, computers, software, etc. in modern weapons systems. Just as in general equilibrium theory, increasing returns to scale in an arms race leads to very different results than constant or decreasing returns to scale. As one implication, increasing returns can lead to multiple stable equilibria, which can be ranked such that both parties are better off at a lower equilibrium. In this case, both parties could be made better off through arms control agreements that lead to a lower equilibrium. Another implication is that increasing returns can create the possibility of specialization and trade in weapons between the participants in an arms race. Yet another implication is that a third nation may sell weapons to both sides in a conflict. Overall, both the behavior of the participants in an arms race and the implied research agenda are very different for the alternative paradigm of an increasing returns to scale technology in arms production, as compared to the dominant paradigm, the Richardson model of the arms race. The latter assumes a constant or diminishing returns to scale technology, but it cannot account for some modern arms race phenomena. The Richardson model should be replaced by this new paradigm that takes explicit account of the increasing returns technology resulting from the nature of new types of weapons systems.Arms control, Arms races, Increasing returns to scale, Information, Richardson model of the arms race,