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Newton's method applied to rational functions: Fixed points and Julia sets

2025/03/11 by Tarakanta Nayak, Nayak, Tarakanta, Soumen Pal +3
Engineering · Mathematics · #37F10 #65H05 #Advanced Numerical Analysis Techniques #Dynamical Systems (math.DS) #FOS: Mathematics #Iterative Methods for Nonlinear Equations #Mathematical and Theoretical Analysis

paper · pdf · doi:10.48550/arxiv.2503.08498

openalex publication_date 2025/03/11 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28

Abstract

For a rational function R, let NR(z)=z-(R(z))/(R'(z)). Any such NR is referred to as a Newton map. We determine all the rational functions R for which NR has exactly two attracting fixed points, one of which is an exceptional point. Further, if all the repelling fixed points of any such Newton map are with multiplier 2, or the multiplier of the non-exceptional attracting fixed point is at most (4)/(5), then its Julia set is shown to be connected. If a polynomial p has exactly two roots, is unicritical but not a monomial, or p(z)=z(zn+a) for some a ∈ ℂ and n ≥ 1, then we have proved that the Julia set of N(1)/(p) is totally disconnected. For the McMullen map fλ(z)=zm - \fracλzn, λ∈ ℂ∖ \0\ and m,n ≥ 1, we have proved that the Julia set of Nfλ is connected and is invariant under rotations about the origin of order m+n. All the connected Julia sets mentioned above are found to be locally connected.

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