Max-min compact-set conjecture for Tschebyshev–Padé approximants

Let FFfF\in\mathcal F_f be an admissible compact set for ff, and let {Ωn}\{\Omega_n\} be an interpolation table disjoint from FF. Assume that the limiting density ω\omega in the interpolation-table limit exists and that its support is disjoint from ee. For the denominators QnQ_n, write ν(Qn)\nu(Q_n) for their zero-counting measure, and let λΓ~\lambda_{\widetilde\Gamma} denote the equilibrium measure associated with a compact set Γ~\widetilde\Gamma. Max-min compact-set conjecture. There exists a unique compact set Γ~\widetilde\Gamma having the max-min property, such that

1nν(Qn)λΓ~as n.\frac{1}{n}\nu(Q_n)\overset{*}{\to}\lambda_{\widetilde\Gamma}\qquad\text{as }n\to\infty.

The theorem preceding this conjecture proves the claim under more restrictive assumptions through the max-min energy and GRS methods; the authors state that extending it to general limiting densities requires modifications whose validity is not yet formally established, and they note that further restrictions on ω\omega may be necessary.

Sources & referencesView supporting material

Primary source

Evguenii A. Rakhmanov and Sergey P. Suetin, “Tschebyshev-Padé approximations for multivalued functions”, arXiv:2106.01047 (2021).

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