6,187 research outputs found

    The chiral transition of N_f=2 QCD with fundamental and adjoint fermions

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    We study QCD with two staggered Dirac fermions both in the fundamental (QCD) and the adjoint representation (aQCD) near the chiral transition. The aim is to find the universality class of the chiral transition and to verify Goldstone effects below the transition. We investigate aQCD, because in that theory the deconfinement and the chiral transitions occur at different temperatures T_d<T_c. Here, we show that the scaling behaviour of the chiral condensate in the vicinity of \beta_c is in full agreeement with that of the 3d O(2) universality class. In the region T_d<T<T_c we confirm the quark mass dependence of the chiral condensate which is expected due to the existence of Goldstone modes like in 3d O(N) spin models. For fundamental QCD we use the p4-action. Here, we find Goldstone effects below T_c like in aQCD and the 3d O(N) spin models, however no O(2)/O(4) scaling near the chiral transition point. The result for QCD may be a consequence of the coincidence of the deconfinement transition with the chiral transition.Comment: 6 pages, 5 figures, poster contribution to Lattice 2005 (Nonzero temperature and density), one reference added, figure 2 change

    Specific heat and energy for the three-dimensional O(2) model

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    We investigate the three-dimensional O(2) model on lattices of size 8^3 to 160^3 close to the critical point at zero magnetic field. We confirm explicitly the value of the critical coupling J_c found by Ballesteros et al. and estimate there the universal values of g_r and xi/L. At the critical point we study the finite size dependencies of the energy density epsilon and the specific heat C. We find that the nonsingular part of the specific heat C_{ns} is linearly dependent on 1/alpha. From the critical behaviour of the specific heat for T not T_c on the largest lattices we determine the universal amplitude ratio A+/A-. The alpha- dependence of this ratio is close to the phenomenological relation A+/A- = 1-4alpha.Comment: Lattice2001(spin), 3 pages, 4 figure

    Testing the meson cloud in the nucleon in Drell-Yan processes

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    We discuss the present status of the \bar u-\bar d asymmetry in the nucleon and analize the quantities which are best suited to verify the asymmetry. We find that the Drell-Yan asymmetry is the quantity insensitive to the valence quark distributions and very sensitive to the flavour asymmetry of the sea. We compare the prediction of the meson cloud model with different experimental data including the Fermilab E772 data and recent data of the NA51 Collaboration at CERN and make predictions for the planned Drell-Yan experiments.Comment: written in ReVTeX, 26 pages + 10 PS-figure

    Technical Guide for the Analysis of Microenterprise Financial Institutions

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    The purpose of this technical guide is to provide a standard format for the analysis of institutions that provide financial services to the microenterprise sector. The technical guide outlines the appropriate techniques and scope of analysis for evaluating and designing programs of support to specialized financial institutions. The analytical techniques presented in this guide are structured to facilitate the process of institutional analysis and project design represented in the diagram below. The analytical framework applied in this technical guide is comprised of two basic components. The first part of the analysis, described in chapters 1 through 5, is dedicated to deriving a series of quantitative performance indicators that measure the performance of the institution. The investigation begins with an analysis of financial performance in order to derive general indicators regarding the sustainability of the institution. Credit operations are then analyzed in order to identify sources of inefficiency. The investigation concludes with an assessment of the impact of the credit services on the institution's clients.Social Development, Financial Sector, Microbusinesses & Microfinance, Microenterprise Finance Institutions

    Critical behaviour and Scaling functions for the three-dimensional O(6) spin model with external field

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    We numerically investigate the three-dimensional O(6) model on 12^3 to 120^3 lattices. From Binder's cumulant at vanishing magnetic field we obtain the critical coupling J_c=1.42865(5) and verify this value with the \chi^2-method. The universal value of Binder's cumulant at this point is g_r(J_c)=-1.94456(10). At the critical coupling we find the critical exponents \nu=0.818(5), \beta=0.425(2) and \gamma=1.604(6) from a finite size scaling analysis. We also determine the finite-size-scaling function on the critical line and the equation of state. Our O(6)-result for the equation of state is compared to the Ising, O(2) and O(4) results.Comment: 5 pages, 4 figures, To appear in the proceedings of Workshop on Strong and Electroweak Matter (SEWM 2002), Heidelberg, Germany, 2-5 Oct 200

    Small Angular Scale Simulations of the Microwave Sky

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    We describe and compare two types of microwave sky simulations which are good for small angular scales. The first type uses expansions in spherical harmonics, and the second one is based on plane waves and the Fast Fourier Transform. The angular power spectrum is extracted from maps corresponding to both types of simulations, and the resulting spectra are appropriately compared. In this way, the features and usefulness of Fourier simulations are pointed out. For 100\ell \geq 100, all the simulations lead to similar accuracies; however, the CPU cost of Fourier simulations is 10\sim 10 times smaller than that for spherical harmonic simulations. For 100\ell \leq 100, the simulations based on spherical harmonics seem to be preferable.Comment: 16 pages (LATEX), 2 postcript figures. Accepted in Ap

    Electrochemical detection of the microbial activity of heterotrophic and autotrophic activated sludge organisms

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    The microbial activity of microorganisms in biological waste water treatment was determined by means of an electrochemical bioactivity sensor (BAS). The signal of the sensor system is proportional to the substrate degradation and thus to the decisive target value in sewage treatment. By using physiologically active substances the aptitude of the sensor for detecting inhibition of microorganisms in active sludge was investigated. The signals of the BAS were correlated with an established method for determining microbial activity. For this purpose the total dehydrogenase activity as the key enzyme of metabolism was investigated. A good agreement was found between the measuring results. The BAS delivers values online and thus these values are available for automation and control tasks. The electrochemical bioactivity sensor provides a novel measuring system for determining the activity of both heterotrophic and autotrophic microorganisms in biological waste water treatment

    Degrees of Lookahead in Regular Infinite Games

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    We study variants of regular infinite games where the strict alternation of moves between the two players is subject to modifications. The second player may postpone a move for a finite number of steps, or, in other words, exploit in his strategy some lookahead on the moves of the opponent. This captures situations in distributed systems, e.g. when buffers are present in communication or when signal transmission between components is deferred. We distinguish strategies with different degrees of lookahead, among them being the continuous and the bounded lookahead strategies. In the first case the lookahead is of finite possibly unbounded size, whereas in the second case it is of bounded size. We show that for regular infinite games the solvability by continuous strategies is decidable, and that a continuous strategy can always be reduced to one of bounded lookahead. Moreover, this lookahead is at most doubly exponential in the size of a given parity automaton recognizing the winning condition. We also show that the result fails for non-regular gamesxwhere the winning condition is given by a context-free omega-language.Comment: LMCS submissio
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