
For a sequence of points \(\alpha_k\) in a compact subset of the open unit disk, the authors consider the orthogonal rational functions (with prescribed poles) obtained by orthogonalizing the sequence \(1,z/\pi_1(z), z^2/\pi_2(z),\ldots,z^n/\pi_n(z)\), where \(\pi_n(z) = \prod_{j=1}^n(1-\bar{\alpha}_j z)\), with respect to a positive measure \(\mu\) on the unit circle. The main result (Theorem 1.1) is the asymptotic behaviour of these orthogonal rational functions on the closed unit disk, with a rate of convergence. The condition on the measure \(\mu\) is that it is absolutely continuous with a weight \(w\) which is bounded away from 0 and \(\infty\), and this weight satisfies a Lipschitz-Dini condition. Furthermore, the counting measures \(\nu_n\) for the points \(\{\alpha_1,\ldots,\alpha_n\}\) are supposed to converge weakly to a measure on a compact subset of the open unit disk. The proof is along the lines of Bernstein-Szegő, and consists of approximating \(1/w\) by trigonometric rational functions with prescribed poles (Theorem 2.1) and by obtaining a rational equivalent of the Bernstein-Szegő polynomials (Theorem 3.1).
Science & Technology, General Mathematics, Trigonometric approximation, Mathematics, Applied, orthogonal rational functions, 0101 Pure Mathematics, asymptotics, 0102 Applied Mathematics, Physical Sciences, 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics, 4904 Pure mathematics, 4901 Applied mathematics, Orthogonal functions and polynomials, general theory of nontrigonometric harmonic analysis, Mathematics
Science & Technology, General Mathematics, Trigonometric approximation, Mathematics, Applied, orthogonal rational functions, 0101 Pure Mathematics, asymptotics, 0102 Applied Mathematics, Physical Sciences, 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics, 4904 Pure mathematics, 4901 Applied mathematics, Orthogonal functions and polynomials, general theory of nontrigonometric harmonic analysis, Mathematics
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