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JOURNALS // Trudy Instituta Matematiki i Mekhaniki UrO RAN // Archive

Trudy Inst. Mat. i Mekh. UrO RAN, 2009 Volume 15, Number 1, Pages 66–78 (Mi timm205)

This article is cited in 3 papers

Pointwise estimates of polynomials orthogonal on a circle with respect to a weight not belonging to the spaces $L^r$ ($r>1$).

V. M. Badkov

Institute of Mathematics and Mechanics, Ural Branch of the Russian Academy of Sciences

Abstract: Two-sided pointwise estimates are established for polynomials that are orthogonal on the circle $|z|=1$ with the weight $\varphi(\tau):=h(\tau)|\sin(\tau/2)|^{-1}g(|\sin(\tau/2)|)$ ($\tau\in\mathbb R$), where $g(t)$ is a concave modulus of continuity slowly changing at zero such that $t^{-1}g(t)\in L^1[0,1]$ and $h(\tau)$ is a positive function from the class $C_{2\pi}$ with a modulus of continuity satisfying the integral Dini condition. The obtained estimates are applied to find the order of the distance from the point $t=1$ to the greatest zero of a polynomial orthogonal on the segment [-1,1].

Keywords: orthogonal polynomials, pointwise estimates, the Szegő function.

UDC: 517.5

Received: 20.02.2009


 English version:
Proceedings of the Steklov Institute of Mathematics (Supplement Issues), 2009, 265, suppl. 1, S64–S77

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