3,701 research outputs found

    L\'evy Processes on Uq(g)U_q(g) as Infinitely Divisible Representations

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    L\'evy processes on bialgebras are families of infinitely divisible representations. We classify the generators of L\'evy processes on the compact forms of the quantum algebras Uq(g)U_q(g), where gg is a simple Lie algebra. Then we show how the processes themselves can be reconstructed from their generators and study several classical stochastic processes that can be associated to these processes.Comment: 13 pages, LATEX file, ASI-TPA/13/99 (TU Clausthal); 6/99 (Preprint-Reihe Mathmatik, Univ. Greifswald)

    LEISURE UTILIZATION CONSTRAINTS AS PERCEIVED BY UNDERGRADUATE STUDENTS OF UNIVERSITY OF UYO, NIGERIA

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    The purpose of this study was to investigate leisure utilization constraints as perceived by undergraduate students of University of Uyo. Five indicators were adopted which were lack of self-skill, lack of time, anxiety, academic workload and religious activities. From these, five objectives were formulated with subsequent research questions and hypotheses. The study adopted a survey design with 278 respondents selected from six faculties using stratified and clustered sampling technique. A self-developed questionnaire validated by experts with a reliability co-efficient of .78 was used as the main instrument for data collection. The data generated were analyzed using percentages and mean to answer the research questions, while chi-square statistical tool was used to test the null hypotheses at .05 level of significance. The result of the study revealed that self-skill, lack of time, anxiety, academic workload and religious activities were perceived as significant constraints to leisure utilization among undergraduate students of the University of Uyo. This finding support earlier research work. It was recommended that the school directorate of sport should organized sensitization on available leisure activities requiring little or no special skills, proper scheduling of leisure activities compatible with the school time table, the school should provide a framework for emergency healthcare particularly for sport injuries and individuals should take responsibilities for their own health by enjoying the leisure time. Also, school authority should work in collaboration with various religious leaders within the campus to establish control and effective time management.  Article visualizations

    The liquid-glass transition of silica

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    We studied the liquid-glass transition of SiO2SiO_2 by means of replica theory, utilizing an effective pair potential which was proved to reproduce a few experimental features of silica. We found a finite critical temperature T0T_0, where the system undergoes a phase transition related to replica symmetry breaking, in a region where experiments do not show any transition. The possible sources of this discrepancy are discussed.Comment: 14 pages, 6 postscript figures. Revised version accepted for pubblication on J.Chem.Phy

    Quasispecies evolution in general mean-field landscapes

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    I consider a class of fitness landscapes, in which the fitness is a function of a finite number of phenotypic "traits", which are themselves linear functions of the genotype. I show that the stationary trait distribution in such a landscape can be explicitly evaluated in a suitably defined "thermodynamic limit", which is a combination of infinite-genome and strong selection limits. These considerations can be applied in particular to identify relevant features of the evolution of promoter binding sites, in spite of the shortness of the corresponding sequences.Comment: 6 pages, 2 figures, Europhysics Letters style (included) Finite-size scaling analysis sketched. To appear in Europhysics Letter

    Combination techniques and decision problems for disunification

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    Previous work on combination techniques considered the question of how to combine unification algorithms for disjoint equational theories E_{1} ,...,E_{n} in order to obtain a unification algorithm for the union E1 unified ... unified En of the theories. Here we want to show that variants of this method may be used to decide solvability and ground solvability of disunification problems in E_{1}cup...cup E_{n}. Our first result says that solvability of disunification problems in the free algebra of the combined theory E_{1}cup...cup E_{n} is decidable if solvability of disunification problems with linear constant restrictions in the free algebras of the theories E_{i}(i = 1,...,n) is decidable. In order to decide ground solvability (i.e., solvability in the initial algebra) of disunification problems in E_{1}cup...cup E_{n} we have to consider a new kind of subproblem for the particular theories Ei, namely solvability (in the free algebra) of disunification problems with linear constant restriction under the additional constraint that values of variables are not Ei-equivalent to variables. The correspondence between ground solvability and this new kind of solvability holds, (1) if one theory Ei is the free theory with at least one function symbol and one constant, or (2) if the initial algebras of all theories Ei are infinite. Our results can be used to show that the existential fragment of the theory of the (ground) term algebra modulo associativity of a finite number of function symbols is decidable; the same result follows for function symbols which are associative and commutative, or associative, commutative and idempotent

    Unification Theory - An Introduction

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    Aus der Einleitung: „Equational unification is a generalization of syntactic unification in which semantic properties of function symbols are taken into account. For example, assume that the function symbol '+' is known to be commutative. Given the unication problem x + y ≐ a + b (where x and y are variables, and a and b are constants), an algorithm for syntactic unification would return the substitution {x ↦ a; y ↦ b} as the only (and most general) unifier: to make x + y and a + b syntactically equal, one must replace the variable x by a and y by b. However, commutativity of '+' implies that {x ↦ b; y ↦ b} also is a unifier in the sense that the terms obtained by its application, namely b + a and a + b, are equal modulo commutativity of '+'. More generally, equational unification is concerned with the problem of how to make terms equal modulo a given equational theory, which specifies semantic properties of the function symbols that occur in the terms to be unified.

    Lennard-Jones binary mixture: a thermodynamical approach to glass transition

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    We study the liquid-glass transition of the Lennard-Jones binary mixture introduced by Kob and Andersen from a thermodynamic point of view. By means of the replica approach, translating the problem in the study of a molecular liquid, we study the phase transition due to the entropy crisis and we find that the Kauzmann's temperature \tk is 0.32\sim 0.32. At the end we compare analytical predictions with numerical results.Comment: 24 pages, 11 postscript figures. Revised version accepted for pubblication on J. Chem. Phys. Numerical precision of the computations improve

    Renormalized powers of quantum white noise

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    We prove some no-go theorems on the existence of a Fock representation of the *-Lie algebra. In particular we prove the nonexistence of such a representation for any *-Lie algebra containing . This drastic difference with the quadratic case proves the necessity of investigating different renormalization rules for the case of higher powers of white noise

    Squared white noise and other non-Gaussian noises as Levy processes on real Lie algebras

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    It is shown how the relations of the renormalized squared white noise defined by Accardi, Lu, and Volovich \cite{accardi+lu+volovich99} can be realized as factorizable current representations or L\'evy processes on the real Lie algebra \eufrak{sl}_2. This allows to obtain its It\^o table, which turns out to be infinite-dimensional. The linear white noise without or with number operator is shown to be a L\'evy process on the Heisenberg-Weyl Lie algebra or the oscillator Lie algebra. Furthermore, a joint realization of the linear and quadratic white noise relations is constructed, but it is proved that no such realizations exist with a vacuum that is an eigenvector of the central element and the annihilator. Classical L\'evy processes are shown to arise as components of L\'evy process on real Lie algebras and their distributions are characterized
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