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arXiv · 1811.04308

Simultaneous zero-free approximation and universal optimal polynomial approximants

Catherine Bénéteau·Oleg Ivrii·Myrto Manolaki·Daniel Seco
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Abstract

Let $E$ be a closed subset of the unit circle of measure zero. Recently, Beise and Müller showed the existence of a function in the Hardy space $H^2$ for which the partial sums of its Taylor series approximate any continuous function on $E$. In this paper, we establish an analogue of this result in a non-linear setting where we consider optimal polynomial approximants of reciprocals of functions in $H^2$ instead of Taylor polynomials. The proof uses a new result on simultaneous zero-free approximation of independent interest. Our results extend to Dirichlet-type spaces $\mathcal{D}_α$ for $α\in [0,1]$.

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Catherine Bénéteau, Oleg Ivrii, Myrto Manolaki, Daniel Seco. 2019-05-19. Simultaneous zero-free approximation and universal optimal polynomial approximants. https://arxiv.org/abs/1811.04308

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