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Sendov Conjecture


The Sendov conjecture asserts that if a polynomial f(z)=(z-r_1)(z-r_2)...(z-r_n) has polynomial degree n>=2 and all its roots in the closed unit disk, then every root r_k is within distance 1 of a critical point of f. It originated as an unpublished 1958 proposal by Blagovest Sendov (Sendov 2002), who communicated it to Marden in 1962 (Marden 1983). By Lucas's root theorem, the critical points, which are the roots of the derivative, also lie in the closed unit disk.

The conjecture was established for polynomial degrees at most 8 and, by Tao (2022), for all sufficiently large polynomial degrees. Tao (2026) described, checked, and reorganized an AI-generated proof obtained by L. Mazur with a Lean formalization, showing that it also proves the stronger Phelps-Rodriguez conjecture, and supplied a separate Lean formalization of his exposition.


See also

Critical Point, Lucas's Root Theorem, Phelps-Rodriguez Conjecture, Polynomial, Unit Disk

Portions of this entry contributed by Bruce Torrence

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References

Marden, M. "Conjectures on the Critical Points of a Polynomial." Amer. Math. Monthly 90, 267-276, 1983.Rahman, Q. I. and Schmeisser, G. Analytic Theory of Polynomials. Oxford, England: Oxford University Press, 2002.Schmeisser, G. "The Conjectures of Sendov and Smale." In Approximation Theory: A Volume Dedicated to Blagovest Sendov (Ed. B. Bojoanov). Sofia, Bulgaria: DARBA, pp. 353-369, 2002.Sendov, Bl. "Generalization of a Conjecture in the Geometry of Polynomials." Serdica Math. J. 28, 283-304, 2002.Tao, T. "Sendov's Conjecture for Sufficiently-High-Degree Polynomials." Acta Math. 229, 347-392, 2022. https://doi.org/10.4310/ACTA.2022.v229.n2.a3.Tao, T. "A Digestion of the Proof of Sendov's Conjecture." Aug. 12, 2026. https://terrytao.wordpress.com/2026/08/12/a-digestion-of-the-proof-of-sendovs-conjecture/.

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Sendov Conjecture

Cite this as:

Weisstein, Eric W., with contributions by Bruce Torrence. "Sendov Conjecture." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/SendovConjecture.html

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