The paper discusses new cubature formulas for classical integral operators of mathematical physics based on the «approximate approximation» of the density with Gaussian and related functions. We derive formulas for the cubature of harmonic, elastic and diffraction potentials approximating with high order in some range relevant for numerical computations. We prove error estimates and provide numerical results for the Newton potential.
We study smoothness spaces generated by maximal functions related to the local approximation errors of integral operators. It turns out that in certain cases these smoothness classes coincide with the spaces , 0 < p≤∞, introduced by DeVore and Sharpley [DS] by means of the so-called sharp maximal functions of Calderón and Scott. As an application we characterize the spaces in terms of the coefficients of wavelet decompositions.
The asymptotic behaviour of ε-entropy of classes of Lipschitz functions in is obtained. Moreover, the asymptotics of ε-entropy of classes of Lipschitz functions in whose tail function decreases as is obtained. In case p = 1 the relation between the ε-entropy of a given class of probability densities on and the minimax risk for that class is discussed.