The polar-set characterization for strongly incomplete polynomial approximation

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Let K⊂C∖{0}K\subset {\mathbb{C}}\setminus \{0\} be a compact set. A polynomial of the indicated form is ∑k=n/τnnakzk\sum_{k=n/\tau_n}^{n}a_kz^k, where τn→1\tau_n\to 1. Polar-set characterization conjecture. Any function continuous on KK (or equivalently, any polynomial) can be uniformly approximated on KK by polynomials of the form

∑k=n/τnnakzk\sum_{k=n/\tau_n}^{n}a_kz^k

with τn→1\tau_n\to 1, if and only if KK is polar. This conjecture seeks to characterize exactly the compact sets supporting approximation by strongly incomplete polynomials; the supplied context gives no resolution.

References

Primary source

Stéphane Charpentier and Konstantinos Maronikolakis, “Quantitative incomplete polynomial approximation and frequently universal Taylor series”, arXiv:2504.20240 (2025).

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