560 research outputs found

    Study of thin film large area photovoltaic solar energy converter Third quarterly report, 25 Apr. - 24 Jul. 1966

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    Cadmium sulfide-thin film large area photovoltaic solar energy converter - plastic substrate cell fabrication and stability testing under various conditions of temperature and humidit

    Development of cadmium sulfide thin film photovoltaic cells third quarterly report, apr. 15 - jul. 14, 1965

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    Cadmium sulfide thin film photovoltaic cells - cadmium sulfide film evaporation, cell testing, improvement, and stability, and plastic and metal substrate cell

    Pressure to order g8log(g)g^8*log(g) in ϕ4\phi^4-theory at weak coupling

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    We calculate the pressure of massless ϕ4\phi^4-theory to order g8log(g)g^8\log(g) at weak coupling. The contributions to the pressure arise from the hard momentum scale of order TT and the soft momentum scale of order gTgT. Effective field theory methods and dimensional reduction are used to separate the contributions from the two momentum scales: The hard contribution can be calculated as a power series in g2g^2 using naive perturbation theory with bare propagators. The soft contribution can be calculated using an effective theory in three dimensions, whose coefficients are power series in g2g^2. This contribution is a power series in gg starting at order g3g^3. The calculation of the hard part to order g6g^6 involves a complicated four-loop sum-integral that was recently calculated by Gynther, Laine, Schr\"oder, Torrero, and Vuorinen. The calculation of the soft part requires calculating the mass parameter in the effective theory to order g6g^6 and the evaluation of five-loop vacuum diagrams in three dimensions. This gives the free energy correct up to order g7g^7. The coefficients of the effective theory satisfy a set of renormalization group equations that can be used to sum up leading and subleading logarithms of T/gTT/gT. We use the solutions to these equations to obtain a result for the free energy which is correct to order g8log(g)g^8\log(g). Finally, we investigate the convergence of the perturbative series.Comment: 29 pages and 12 figs. New version: we have pushed the calculations to g^8*log(g) using the renormalization group to sum up log(g) from higher orders. Published in JHE

    Constraints on Conformal Windows from Holographic Duals

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    We analyze a beta function with the analytic form of Novikov-Shifman-Vainshtein-Zakharov result in the five dimensional gravity-dilaton environment. We show how dilaton inherits poles and fixed points of such beta function through the zeros and points of extremum in its potential. Super Yang-Mills and supersymmetric QCD are studied in detail and Seiberg's electric-magnetic duality in the dilaton potential is explicitly demonstrated. Non-supersymmetric proposals of similar functional form are tested and new insights into the conformal window as well as determinations of scheme-independent value of the anomalous dimension at the fixed point are presented.Comment: Fig. 5b is corrected to match the discussion in the tex

    Large-N spacetime reduction and the sign and silver-blaze problems of dense QCD

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    We study the spacetime-reduced (Eguchi-Kawai) version of large-N QCD with nonzero chemical potential. We explore a method to suppress the sign fluctuations of the Dirac determinant in the hadronic phase; the method employs a re-summation of gauge configurations that are related to each other by center transformations. We numerically test this method in two dimensions, and find that it successfully solves the silver-blaze problem. We analyze the system further, and measure its free energy F, the average phase theta of its Dirac determinant, and its chiral condensate . We show that F and are independent of mu in the hadronic phase but that, as chiral perturbation theory predicts, the quenched chiral condensate drops from its mu=0 value when mu~(pion mass)/2. Finally, we find that the distribution of theta qualitatively agrees with further, more recent, predictions from chiral perturbation theory.Comment: 43 pages, 17 figure
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