The zero sets of (D + a)g(t) with D = d/dt in the (t, a)plane are investigated for g(t) = te(e−1) and g(t) = e(e+1). The results are used to determine entire interpolations to functions xn+e , which give representations for the best approximation and best one-sided approximation from the class of functions of exponential type η > 0 to xn+e .

As usual, p∗ is called a best approximation (b.a.) to f in (or, by elements of) IPγ,n. To give some examples, let X = Lp[0, 1] and set γ(t) = G(·, t), where G(s, t) is defined on [0, 1] × T . With G Green’s function for a k–th order ordinary linear initial value problem on (0, 1] and T = [0, 1), one has approximation by generalized splines. With G(s, t) = e and T = IR, one has approximation by ...

We consider radial complex scaling/perfectly matched layer methods for scalar resonance problems in homogeneous exterior domains. introduce a new abstract framework to analyze the convergence of domain truncations and discretizations. Our theory requires rather minimal assumptions on scaling profile includes affine, smooth, unbounded profiles. report swift technique more technical one approxima...

Comon’s well-known scheme for independent component analysis (ICA) is based on the maximal diagonalization, in a least-squares sense, of a higher-order cumulant tensor. In a previous papr, we proved that for fourth-order cumulants, the computation of an elementary Jacobi rotation is equivalent to the computation of the best rank-1 approximation of a fourth-order tensor. In this paper, we show t...

Tree approximation is a form of nonlinear wavelet approximation that appears naturally in applications such as image compression and entropy encoding. The distinction between tree approximation and the more familiar n-term wavelet approximation is that the wavelets appearing in the approximant are required to align themselves in a certain connected tree sturcture. This makes their positions eas...

The hp-adaptive approximation is formulated as an approximation problem on a full binary tree T , where for each of the leaves ∆ an order p(∆) ≥ 1 is assigned in such a way that the sum of all such p(∆) does not exceed N , called complexity of the approximation. The leaves ∆ correspond to the cells of the partition, while p(∆) is the order of the polynomial used for the local approximation on ∆...

We present a method for hierarchical data approximation using quadratic simplicial elements for domain decomposition and field approximation. Higher-order simplicial elements can approximate data better than linear elements. Thus, fewer quadratic elements are required to achieve similar approximation quality. We use quadratic basis functions and compute best quadratic simplicial spline approxim...

In this article, by using Chebyshev’s polynomials and Chebyshev’s expansion, we obtain the best uniform polynomial approximation out of P2n to a class of rational functions of the form (ax2+c)-1 on any non symmetric interval [d,e]. Using the obtained approximation, we provide the best uniform polynomial approximation to a class of rational functions of the form (ax2+bx+c)-1 for both cases b2-4a...

This paper studies properties of the likelihood ratio (LR) tests associated with the limited information maximum likelihood (LIML) estimators in a structural form estimation when the number of instrumental variables is large. Two types of asymptotic theories are developed to approximate the distribution of the likelihood ratio (LR) statistic under the null hypothesis H0 : β = β0: a (large sampl...