Zipf distribution in top Chinese firms and an economic explanation

By analyzing the data of top 500 Chinese firms from the year 2002 to 2007, we reveal that their revenues and ranks obey the Zipf’s law with exponent of 1 for each year. This result confirms the universality of firm size character which has been presented in many other empirical works, since China possesses a unique ideological and political system. We offer an explanation of it based on a simple economic model which takes production and capital accumulation into account.     

Transient fluctuation of the prosperity of firms in a network economy

The transient fluctuation of the prosperity of firms in a network economy is investigated with an abstract stochastic model. The model describes the profit which firms make when they sell materials to a firm which produces a product and the fixed cost expense to the firms to produce those materials and product. The formulas for this model are parallel to those for population dynamics. The swinging changes in the fluctuation in the transient state from the initial growth to the final steady state are the consequence of a topology-dependent time trial competition between the profitable interactions and expense. The firm in a sparse random network economy is more likely to go bankrupt than expected from the value of the limit of the fluctuation in the steady state, and there is a risk of failing to reach by far the less fluctuating steady state.     

Response of firm agent network to exogenous shock

This paper describes an agent-based model of interacting firms, in which interacting firm agents rationally invest capital and labor in order to maximize payoff. Both transactions and production are taken into account in this model. First, the performance of individual firms on a real transaction network was simulated. The simulation quantitatively reproduced the cumulative probability distribution of revenue, material cost, capital, and labor. Then, the response of the firms to a given exogenous shock, defined as a sudden change of gross domestic product, is discussed. The longer tail in cumulative probability and skewed distribution of growth rate are observed for a high growth scenario.     

金融市场的宏观建模和微观建模——从金融海啸与市场风险谈起

金融市场是一个复杂系统,高风险大波动危象频仍,而传统经济金融理论对此无能为力.文章从复杂性科学视角出发,通过市场宏观建模,描绘出当前金融海啸一幅泡沫演化和湮灭的图像.文章进一步论述了一个基于市场微观模型的计算实验金融学框架,认为金融学应当重建唯象学框架,并指出金融物理学在经济学科学革命中的重要性.     

Effects of the turnover rate on the size distribution of firms: An application of the kinetic exchange models

We address the issue of the distribution of firm size. To this end we propose a model of firms in a closed, conserved economy populated with zero-intelligence agents who continuously move from one firm to another. We then analyze the size distribution and related statistics obtained from the model. There are three well known statistical features obtained from the panel study of the firms i.e., the power law in size (in terms of income and/or employment), the Laplace distribution in the growth rates and the slowly declining standard deviation of the growth rates conditional on the firm size. First, we show that the model generalizes the usual kinetic exchange models with binary interaction to interactions between an arbitrary number of agents. When the number of interacting agents is in the order of the system itself, it is possible to decouple the model. We provide exact results on the distributions which are not known yet for binary interactions. Our model easily reproduces the power law for the size distribution of firms (Zipf’s law). The fluctuations in the growth rate falls with increasing size following a power law (though the exponent does not match with the data). However, the distribution of the difference of the firm size in this model has Laplace distribution whereas the real data suggests that the difference of the log of sizes has the same distribution.     

Electric field dependent mobility edge and theory of the breakdown of the integer quantum Hall effect

We discuss the microscopic mechanism for the onset of dissipation in a quantum Hall system. Based on general results on the time dependence of the states in a disorder-broadened Landau band in the presence of a macroscopic electric field E, it is found that the mobility edges move from the band center towards the band tails when |E| is increased, in agreement with experiments. Since in real samples, |E| is space dependent, the mobility edges are also space dependent. Dissipation (i.e. breakdown of the quantum Hall effect) sets in at points (x, y), where |E(x, y)| has the value for which a mobility edge attains the Fermi energy. This value depends on the disorder potential and on the filling factor. Inside a sample, the conductivities depend on |E(x, y)| and hence on space. We discuss experimental applications, including dissipation in opposite corners of a Hall bar and related breakdown phenomena.     

From Natural History to the Nuclear Shell Model: Chemical Thinking in the Work of Mayer,Haxel, Jensen,and Suess

In 1949 the nuclear shell model was discovered simultaneously in the United States and Germany. Both discoveries were the result of a nuclear scientist looking at geochemical and nuclear data with the eyes of a chemist. Maria Goeppert Mayer in the United States and Hans Suess in Germany both brought a chemists perspective to the problem; the theoretical solution was subsequently supplied independently by Mayer and Hans Jensen.Karen E. Johnson is Priest Associate Professor at St.Lawrence University, where she teaches physics and history of science. She is currently writing a dual biography of Maria Goeppert Mayer and Joseph E.Mayer.     

A Transnational and Transregional Study of the Impact and Effectiveness of Social Distancing for COVID-19 Mitigation

We present an analysis of the relationship between SARS-CoV-2 infection rates and a social distancing metric from data for all the states and most populous cities in the United States and Brazil, all the 22 European Economic Community countries and the United Kingdom. We discuss why the infection rate, instead of the effective reproduction number or growth rate of cases, is a proper choice to perform this analysis when considering a wide span of time. We obtain a strong Spearman’s rank order correlation between the social distancing metric and the infection rate in each locality. We show that mask mandates increase the values of Spearman’s correlation in the United States, where a mandate was adopted. We also obtain an explicit numerical relation between the infection rate and the social distancing metric defined in the present work.     

The princeton years and beyond: 1930–1945

Summary A personal view of the development of solid-state physics in United States between 1930 and 1945 is presented. It will describe the basis for the world into which Fausto Fumi stepped when he arrived in the United States in 1948. In honour of Prof. Fausto Fumi on the occasion of his retirement from teaching.     

Editorial: Winds of Change

When compared to developments occurring at synchrotron radiation facilities, the neutron scattering world often gives the impression of moving in slow motion. This was perhaps true a decade ago, but is certainly not the case anymore. Such positive dynamics could be clearly felt during the recent American Conference on Neutron Scattering (see page 4) where approximately 500 scientists from all over the world gathered in the Washington, D.C. area. Aside from a very exciting science program, the future of neutron scattering worldwide was discussed as well. While third generation sources are being built in the United States and Japan, major upgrades are being made at almost all running facilities.     

Correspondence principle for the quantum net

Finkelstein's suggestion for a flexible logic is taken up in the context of his causal net theory. We interpret on the net certain concepts that are first expressed in terms of the canonical flexible logic of the macroscopic world, namely, the logic of sheaves over the manifold model, here taken to be flat. From this we infer a correspondence principle in the form of a simple (model-dependent) semantics which translates certain concepts between the purely quantum world of the net and the familiar classical-quantum hybridized world of the macroscopic model. As an application, we derive and solve the reticular version of the massless Dirac equation by analyzing the Dirac operator on the net, where its behavior is easily apprehended.     

Innovation flow through social networks: productivity distribution in France and Italy

From a detailed empirical analysis of the productivity of non financial firms across several countries and years we show that productivity follows a non-Gaussian distribution with `fat tails' in the large productivity region which are well mimicked by power law behaviors. We discuss how these empirical findings can be linked to a mechanism of exchanges in a social network where firms improve their productivity by direct innovation and/or by imitation of other firm's technological and organizational solutions. The type of network-connectivity determines how fast and how efficiently information can diffuse and how quickly innovation will permeate or behaviors will be imitated. From a model for innovation flow through a complex network we show that the expectation values of the productivity of each firm are proportional to its connectivity in the network of links between firms. The comparison with the empirical distributions in France and Italy reveals that in this model, such a network must be of a scale-free type with a power-law degree distribution in the large connectivity range.     

An analogy of the size distribution of business firms with Bose-Einstein statistics

We approach the size distribution of business firms by proposing an analogy of the firms’ ranking with a boson gas, identifying the annual revenue of the firms with energy. We found that Bose-Einstein statistics fits very well to the empirical cumulative distribution function for the firms’ ranking for different countries. The fitted values for the temperature-like parameter are compared between countries and with an index of economic development, and we found that our results support the hypothesis that the temperature of the economy can be associated with the level of economic development of a country. Moreover, for most of the countries the value obtained for the fugacity-like parameter is close to 1, suggesting that the analogy could correspond to a photon gas in which the number of particles is not conserved; this is indeed the case for real-world firms’ dynamics, where new firms arrive in the economy and other firms disappear, either by merging with others or through bankruptcy.     

脱氧核糖核酸柔性的分子动力学模拟:Amber bsc1和bsc0力场的对比研究

脱氧核糖核酸(DNA)的结构柔性对DNA生物功能的实现具有重要作用,全原子分子动力学模拟是一种研究DNA结构柔性的重要方法.DNA的分子动力学力场在Amber bsc0基础上有了进一步的发展,即Amber bsc1.本文采用基于最新bsc1力场和先前bsc0力场的分子动力学模拟对DNA的宏观柔性和微观柔性进行对比研究,发现力场的改进对DNA宏观柔性参量的预测有一定改善,即所预测的拉伸模量和扭转-伸缩耦合比与实验值更为接近,而弯曲持久长度和扭转持久长度两种力场结果皆与实验值一致.微观分析发现,除了滑移量稍变大,bsc1力场得到的微观结构参量如扭转角和倾斜角与实验值更为接近,且新力场下DNA宏观柔性的改善与DNA的微观结构参量及其涨落紧密相关.     

Recent developments in fiber optics in the United States

This paper reviews recent developments of fiber optics technology and applications in the United States. The major application of fiber optics in the world is in telecommunications, and the United States represents 40% of this world market. In 1986, U.S. telecommunications companies, mainly telephone companies, will invest $24 billion dollars in new telephone plants. Of this, approximately 4% will be invested in fiber optics. These telephony applications represent approximately 80–90% of the total fiber optics equipment market. The remaining market is divided among a number of applications such as local area networks (LAN), military data links, CATV, and process control. Each of these applications is discussed and factors affecting the use of fiber optics are analyzed.     

Recent developments in fiber optics in the United States

This paper reviews recent developments of fiber optics technology and applications in the United States. The major application of fiber optics in the world is in telecommunications, and the United States represents 40% of this world market. In 1986, U.S. telecommunications companies, mainly telephone companies, will invest $24 billion dollars in new telephone plants. Of this, approximately 4% will be invested in fiber optics. These telephony applications represent approximately 80-90% of the total fiber optics equipment market. The remaining market is divided among a number of applications such as local area networks (LAN), military data links, CATV, and process control. Each of these applications is discussed and factors affecting the use of fiber optics are analyzed.     

宇宙演化与热寂说

在已成熟的宇宙演化理论的基础上,文章作者重新讨论了Clausius提出的热寂问题.宇宙演化指其组分和宏观面貌的变化.主要是微观结团和宏观结团.从物理原理上讲,这些结团过程是力学的,而不是热力学的.力学过程一定程度上破坏了原有的热平衡,热力学则倾向于恢复热平衡.所有已知的物理规律,包括热力学在内,都在宇宙演化中起着它应起的作用.作为后果,宇宙的熵在演化中一直是增加的.克劳修斯把热力学第二定律用于宇宙是正确的.可是他认为宇宙的熵会极大化并不正确.这是因为在演化过程中会出现组分粒子的退耦.     

Will the leading firm continue to dominate the market in the Taiwan notebook industry?

This study investigates whether the market share leader in the notebook industry in Taiwan is likely to maintain its dominant position. Market share data are used to investigate the intensity of competitiveness in the industry, and data on the gap in market shares are employed to elucidate the dominance of the leading firm in Taiwan's notebook industry during the 1998-2004 period. The newly developed Panel SURADF tests advanced by Breuer et al. [Misleading inferences from panel unit root tests with an illustration from purchasing power parity, Rev. Int. Econ. 9 (3) (2001) 482-493] are employed to determine whether the market share gap is stationary or not. Unlike other panel-based unit root tests which are joint tests of a unit root for all members of a panel and are incapable of determining the mix of I(0) and I(1) series in a panel setting, the Panel SURADF tests have the advantage of being able to investigate a separate unit root null hypothesis for each individual panel member and are, therefore, able to identify how many and which series in a panel are stationary processes. The empirical results from several panel-based unit root tests substantiate that the market shares of the firms studied here are non-stationary, indicating that Taiwan's notebook industry is highly competitive; however, Breuer et al.'s [12] Panel SURADF tests unequivocally show that only Compal is stationary with respect to market share gap. In terms of sales volume, Compal is the second largest firm in the notebook industry in Taiwan, and the results indicate that it alone has the opportunity to become the market share leader in the notebook industry.