An extremal nonnegative sine polynomial
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Data
2003-09-01
Autores
Andreani, Roberto [UNESP]
Dimitrov, Dimitar K. [UNESP]
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Resumo
For any positive integer n, the sine polynomials that are nonnegative in [0, π] and which have the maximal derivative at the origin are determined in an explicit form. Associated cosine polynomials Kn (θ) are constructed in such a way that {Kn(θ)} is a summability kernel. Thus, for each Pi 1 ≤ P ≤ ∞ and for any 27π-periodic function f ∈ Lp [-π, π], the sequence of convolutions Kn * f is proved to converge to f in Lp[-ππ]. The pointwise and almost everywhere convergences are also consequences of our construction.
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Convergence, Extremal polynomial ultraspherical polynomials, Nonnegative sine polynomial, Positive summability kernel
Como citar
Rocky Mountain Journal of Mathematics, v. 33, n. 3, p. 759-774, 2003.