075  Berichtsreihe des Mathematischen Seminars der Universität Kiel  
Michael Gnewuch, Henryk Wozniakowski:Generalized Tractability for Linear FunctionalsWe study approximation of continuous linear functionals I_{d} defined over reproducing kernel weighted Hilbert spaces of dvariate functions. Let n( ε, I_{d}) denote the minimal number of function values needed to solve the problem to within ε. There are many papers studying polynomial tractability for which n( ε, I_{d}) is to be bounded by a polynomial in ε^{1} and d. We study generalized tractability for which we want to guarantee that either n( ε, I_{d}) is not exponentially dependent on ε^{1} and d, which is called weak tractability, or is bounded by a power of T(ε^{1}, d) for (ε^{1},d) ∈ Ω ⊆ [1,∞) x N, which is called (T,Ω)tractability. Here, the tractability function T is nonincreasing in both arguments and does not depend exponentially on ε^{1} and d. We present necessary conditions on generalized tractability for arbitrary continuous linear functionals I_{d} defined on weighted Hilbert spaces whose kernel has a decomposable component, and sufficient conditions on generalized tractability for multivariate integration for general reproducing kernel Hilbert spaces. For some weighted Sobolev spaces these necessary and sufficient conditions coincide. They are expressed in terms of necessary and sufficient conditions on the weights of the underlying spaces. Mathematics Subject Classification (1991): 65D30, 68Q99 Bibliographical note: In: A. Keller, S. Heinrich, H. Niederreiter, Monte Carlo und QuasiMonte Carlo Methods 2006, 359381, Springer, BerlinHeidelberg, 2008. Keywords: tractability, worstcase setting, Multivariate Integration, Reproducing Kernel Hilbert Spaces

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