Proceedings of the International Geometry Center

ISSN-print: 2072-9812
ISSN-online: 2409-8906
ISO: 26324:2012
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On the Koebe Quarter Theorem for Polynomials

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Олександр Михайлович Стоколос
Jimmy Dillies
Dmitriy Dmitrishin
Andrey Smorodin

Abstract

The Koebe One Quarter Theorem states that the range of any Schlicht function contains the centered disc of radius 1/4 which is sharp due to the value of the Koebe function at −1. A natural question is finding polynomials that set the sharpness of the Koebe Quarter Theorem for polynomials. In particular, it was asked in [7] whether Suffridge polynomials [15] are optimal. For polynomials of degree 1 and 2 that is obviously true. It was demonstrated in [10] that Suffridge polynomials of degree 3 are not optimal and a promising alternative family of polynomials was introduced. These very polynomials were actually discovered earlier independently by M. Brandt [3] and D. Dimitrov [9]. In the current article we reintroduce these polynomials in a natural way and make a far-reaching conjecture that we verify for polynomials up to degree 6 and with computer aided proof up to degree 52. We then discuss the ensuing estimates for the value of the Koebe radius for polynomials of a specific degree.

Keywords:
Koebe one-quarter theorem, Koebe radius, univalent polynomial

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How to Cite
Стоколос, О., Dillies, J., Dmitrishin, D., & Smorodin, A. (2022). On the Koebe Quarter Theorem for Polynomials. Proceedings of the International Geometry Center, 14(3), 219-230. https://doi.org/10.15673/tmgc.v14i3.2057
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Papers