Interpolating polynomial wavelets on [−1,1]

The present paper gives a contribution of wavelet aspects to classical algebraic polynomial approximation theory. As is so often the case in classical approximation, the authors follow the pattern provided by the trigonometric polynomial case. Algebraic polynomial interpolating scaling functions and wavelets are constructed by using the interpolation properties of de la Vallée Poussin kernels with respect to the four kinds of Chebyshev weights. For the decomposition and reconstruction of a given function the structure of the involved matrices is studied in order to reduce the computational effort by means of fast discrete cosine and sine transforms. Dedicated to Prof. Guiseppe Mastroianni on the occasion of his 65th birthday.AMS subject classification 65D05, 65T60     

Unconstrained and convex polynomial approximation inC[−1,1]

Some estimates for unconstrained and convex polynomial approximation in the uniform metric are obtained. These results are given in terms of the Ditzian-Totik moduli of smoothness , ≤1 with . The construction of the approximating polynomials does not depend on λ.     

Polynomials of best approximation inC[−1,1]

Equivalences between the condition |P _n ^(k) (x)|≦K(n ⁻¹√1−x ²+1/n ²) ^k n ^-a, whereP _n(x) is the bestn-th degree polynomial approximation tof(x), and the Peetre interpolation space betweenC[−1,1] and the space (1−x ²) ^k f ^(2k)(x)∈C[−1,1] is established. A similar result is shown forE _n(f)= ‖f−P _n‖ _C[−1,1]. Rates other thann ^-a are also discussed. Supported by NSERC grant A4816 of Canada.     

Shape-preserving bivariate polynomial approximation inC([−1,1]×[−1,1])

In this paper we construct bivariate polynomials attached to a bivariate function, that approximate with Jackson-type rate involving a bivariate Ditzian-Totik ω2-modulus of smoothness and preserve some natural kinds of bivariate monotonicity and convexity of function.The result extends that in univariate case-of D. Leviatan in [5-6], improves that in bivariate case of the author in [3] and in some special cases, that in bivariate case of G. Anastassiou in [1].     

Selfadjoint Schrödinger operators on the half-space with compactly supported Robin boundary conditions

Schrödinger differential operators on a half-space with compactly supported Robin boundary conditions are studied. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Convex polynomial and spline approximation in C[−1, 1]

We prove that a convex functionf C[–1, 1] can be approximated by convex polynomialsp _n of degreen at the rate of ₃(f, 1/n). We show this by proving that the error in approximatingf by C² convex cubic splines withn knots is bounded by ₃(f, 1/n) and that such a spline approximant has anL third derivative which is bounded by n³₃(f, 1/n). Also we prove that iff C²[–1, 1], then it is approximable at the rate ofn ^–2 (f, 1/n) and the two estimates yield the desired result.Communicated by Ronald A. DeVore.     

Approximation of Sondow’s generalized-Euler-constant function on the interval [−1, 1]

Using the Euler-Maclaurin (Boole/Hermite) summation formula, the generalized-Euler-Sondow-constant function γ(z),

$ \gamma(z):=\sum_{k=1}^{\infty}z^{k-1}\left(\frac{1}{k}-\ln\frac{k+1}{k}\right) \qquad (-1\le z\le 1),$

where \({\gamma(-1)=\ln\frac{4}{\pi}}\) and γ(1) is the Euler-Mascheroni constant, is estimated accurately.

     

Continuity and equicontinuity of semigroups on norming dual pairs

We study continuity and equicontinuity of semigroups on norming dual pairs with respect to topologies defined in terms of the duality. In particular, we address the question whether continuity of a semigroup already implies (local/quasi) equicontinuity. We apply our results to transition semigroups and show that, under suitable hypothesis on E, every transition semigroup on C _b (E) which is continuous with respect to the strict topology β ₀ is automatically quasi-equicontinuous with respect to that topology. We also give several characterizations of β ₀-continuous semigroups on C _b (E) and provide a convenient condition for the transition semigroup of a Banach space valued Markov process to be β ₀-continuous.     

A note on Boiteux’ surplus function and dual Pareto efficiency

The purpose of this note is to study first a notion of a surplus function that originates in the work of [Boiteux, M., 1951. Le Revenu Distribuable et les Pertes Économiques. Econometrica 112–133] and to rely upon this notion to study dual Pareto efficiency in an exchange economy. This function, which we call the Boiteux’ surplus function, measures how many units of income an individual must be given to move from a reference utility level, to another utility level. We prove several properties of the Boiteux’ surplus function, and study in particular its links with the expenditure and the indirect utility functions. With regard to dual Pareto efficiency and the Boiteux’ surplus function our results are as follows. A feasible reference price–income pair is dual Pareto efficient if and only if it zero-maximizes the sum of individual Boiteux’ surplus functions among all feasible price–income pairs. We use these results to give a new proof (for the case of an exchange economy with positive prices) of the characterization by Luenberger of dual Pareto optima.     

A note on Faigle and Kern’s dual greedy polyhedra

U. Faigle and W. Kern have recently extended the work of their earlier paper and of M. Queyranne, F. Spieksma and F. Tardella and have shown that a dual greedy algorithm works for a system of linear inequalities with {:0,1}-coefficients defined in terms of antichains of an underlying poset and a submodular function on the set of ideals of the poset under some additional condition on the submodular function.?In this note we show that Faigle and Kern’s dual greedy polyhedra belong to a class of submodular flow polyhedra, i.e., Faigle and Kern’s problem is a special case of the submodular flow problem that can easily be solved by their greedy algorithm. Received: February 1999 / Accepted: December 1999?Published online February 23, 2000     

Asymptotics of Orthogonal Polynomials for a Weight with a Jump on [?1,1]

We consider the orthogonal polynomials on [−1,1] with respect to the weight

Polynomial inequalities and embedding theorems with exponential weights on (−1,1)

Letting 0<p≦∞, we prove Remez-, Bernstein–Markoff-, Schur- and Nikolskii-type inequalities for algebraic polynomials with exponential weights on (−1,1) multiplied by another weight function, which will satisfy the doubling or the A ^∗ condition at different occurrences. Moreover, we state embedding theorems between some function spaces related with exponential weights.     

Computer‐enhanced algebra resources: their effects on achievement and attitudes [1]

Findings from this study indicate that the use of computer-enhanced resources throughout an entire algebra course had no significant effect on algebra achievement, attitudes toward mathematics, and attitudes toward the instructional setting. Differences in ability did have a significant effect upon algebra achievement but did not significantly affect attitudes toward mathematics and the instructional setting. During the study, high- and average-ability students had a significant improvement in their attitudes toward computers. High-ability students were more reluctant to accept computers in the algebra course than average-ability students. An important finding of this study is that computer-related assignments can be given weekly throughout an entire course in second-year algebra without taking time and topics from the algebra content.     

Inverse spectral problem for singular AKNS and Schrödinger operators on [0,1]

We consider an inverse spectral problem for singular Sturm–Liouville equations on the unit interval with explicit singularity $a(a+1)/x^2$, $a\in \mathbb{N}$. This problem arises by splitting of the Schrödinger operator with radial potential acting on the unit ball of ${\mathbb{R}}^3$. Our goal is the global parametrization of potentials by spectral data noted by ${\lambda }^a$, and some norming constants noted by ${\kappa }^a$. For $a=0$ and 1, ${\lambda }^a\times {\kappa }^a$ was already known to be a global coordinate system on $L_{\mathbb{R}}^2(0,1)$. We extend this to any non-negative integer a. Similar result is obtained for singular AKNS operator. To cite this article: F. Serier, C. R. Acad. Sci. Paris, Ser. I 340 (2005).