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arXiv · 2004.06955

Total disconnectedness of Julia sets of random quadratic polynomials

Krzysztof Lech·Anna Zdunik
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Abstract

For a sequence of complex parameters $\{c_n\}$ we consider the compositions of functions $f_{c_n} (z) = z^2 + c_n$, which is the non-autonomous version of the classical quadratic dynamical system. The definitions of Julia and Fatou sets are naturally generalized to this setting. We answer a question posed by Br\"uck, B\"uger and Reitz, whether the Julia set for such a sequence is almost always totally disconnected, if the values $c_n$ are chosen randomly from a large disk. Our proof is easily generalized to answer a lot of other related questions regarding typical connectivity of the random Julia set. In fact we prove the statement for a much larger family of sets than just disks, in particular if one picks $c_n$ randomly from the main cardioid of the Mandelbrot set, then the Julia set is still almost always totally disconnected.

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Krzysztof Lech, Anna Zdunik. 2020-04-15. Total disconnectedness of Julia sets of random quadratic polynomials. https://doi.org/10.1017/etds.2020.148

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