Evaluating departures from fair representation

Computer–intensive estimates are introduced to evaluate departures from proportionality between the numbers of electors in a partition of a voting population and the numbers of representatives in the corresponding partition of the elected representation. At the first stage a pair of indices is proposed, one to evaluate the total strength of the departures and the other to indicate to what extent they are due to over–representation increasing (or decreasing) with the number of electors in a group. The properties of the indices are examined in suitably defined stochastic models which describe this type of over–representation. Since the values of the indices are strongly influenced by the distribution of electors in the given partition, a second stage of estimation is performed in order to get some [partition–free] information on the existence of a monotone size representation, and, if it exists, on its strength. The relevant transformation is based on intensive computer simulation in the introduced models. The methods proposed are applied to the results of the 1991 election of the Polish Scientific Research Council, which distributes funds among universities, scientific institutions and individual groups of researchers.     

Diffusion of directed polymers in a strong random environment

We consider a system of random walks or directed polymers interacting with an environment which is random in space and time. It was shown by Imbrie and Spencer that in spatial dimensions three or above the behavior is diffusive if the directed polymer interacts weakly with the environment and if the random environment follows the Bernoulli distribution. Under the same assumption on the random environment as that of Imbrie and Spencer, we establish that in spatial dimensions four or above the behavior is still diffusive even when the directed polymer interacts strongly with the environment. More generally, we can prove that, if the random environment is bounded and if the supremum of the support of the distribution has a positive mass, then there is an integerd ₀ such that in dimensions higher thand ₀ the behavior of the random polymer is always diffusive.     

Module Homomorphisms on Random Normed Modules

ＭｏｄｕｌｅＨｏｍｏｍｏｒｐｈｉｓｍｓｏｎＲａｎｄｏｍＮｏｒｍｅｄＭｏｄｕｌｅｓＧｕｏＴｉｅｘｉｎ（郭铁信）（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｈｅｍａｔｉｃｓ，ＸｉａｍｅｎＵｎｉｖｅｒｓｉｔｙ，Ｘｉａｍｅｎ，Ｆｕｊｉａｎ，３６１００５）Ａｂｓｔｒａｃｔ...     

Inhomogeneous random sequential adsorption on a lattice

We study idealized random sequential adsorption on a lattice, with adsorption probabilities inhomogeneous both in space and in time, and including the possibility of cooperativity. Attention is directed to the mean occupancy of a given site as a function of time, which is represented by a weighted random walk on the lattice. In the special case of nearest neighbor exclusion, the walk is transformed to one in which only neighbors of occupied sites can be occupied, but with a renormalized probability. Reduction theorems are presented, with which the general case of a tree lattice is completely solved in inverse form.     

n-ary fragmentation model with nearest point flaw and maximal net force fracture

Through the distinction between “real” and “virtual” links between the nodes of a graph, we develop a set of simple rules leading to scale-free networks with a tunable degree distribution exponent. Albeit sharing some similarities with preferential attachment, our procedure is both faster than a naïve implementation of the Barabási and Albert model and exhibits different clustering properties. The model is thoroughly studied numerically and suggests that reducing the set of partners a node can connect to is important in seizing the diversity of scale-free structures.     

Crystallization of Random Trigonometric Polynomials

We give a precise measure of the rate at which repeated differentiation of a random trigonometric polynomial causes the roots of the function to approach equal spacing. This can be viewed as a toy model of crystallization in one dimension. In particular we determine the asymptotics of the distribution of the roots around the crystalline configuration and find that the distribution is not Gaussian.     

Occupation measure for random walk on the circle

We give bounds on the probability of deviation of the occupation measure of an interval on the circle for random walk.     

Analytic study of the effect of persistence on a one-dimensional biased random walk

An analytic study of a one-dimensional biased random walk with correlations between nearest-neighbour steps is presented, both in a lattice model and in its continuous version. First, the treatment of the unbiased problem is recalled and the effect of correlations on the diffusion coefficient is discussed. Then the study is extended to the biased case. The problem is then completely determined by two independent parameters, the degree of correlations in the motion on the one hand and the value of the bias on the other. Both the velocity of the particle and its diffusion coefficient are computed. As a result, the velocity as well as the diffusion coefficient are enhanced when there are positive correlations (qualified as persistence) in the motion, and reduced in the opposite case.     

Mirrorless lasers

Experimental realization of mirrorless lasers in the last decade have resulted in hectic activity in this field, due to their novelty, simplicity and ruggedness and their great potential for application. In this article, I will review the various developments in this field in roughly chronological order, and discuss some possible applications of this exciting phenomenon, also termed as ‘random lasing’.     

模糊数据的线性回归模型

研究观测数据为模糊数据的统计线性回归模型 ,由该模型所得回归系数非模糊 ,易于应用。对于对称三角模糊数据一元线性回归给出最优解的解析表达式 ;将对称三角模糊数多元线性回归问题给出转化为一类二次规划问题的方法 ;证明了最优解的存在性和估计量的无偏性。