Questions tagged [complex-dynamics]

This tag is for questions relating to complex dynamics, study of dynamical systems defined by iteration of functions on complex number spaces. It was an area of research established by Fatou and Julia towards the beginning of the last century.

Complex dynamics concerns the iteration of analytic functions of one complex variable. Such iteration arises, for example, when solving complex equations by Newton’s method. For each function, the complex plane is divided into two fundamentally different parts – the Fatou set, where the behavior of the iterates is stable under local variation, and the Julia set, where it is chaotic. The subject of complex dynamics experienced a huge resurgence of interest in the 1980s, with the advent of computer graphics illustrating the highly intricate nature of most Julia sets, and the introduction of powerful new techniques from complex analysis leading to much profound new work.

References:

https://en.wikipedia.org/wiki/Complex_dynamics

371 questions
55
votes
1 answer

Has this chaotic map been studied?

I have recently been playing around with the discrete map $$z_{n+1} = z_n - \frac{1}{z_n}$$ That is, repeatedly mapping each number to the difference between itself and its reciprocal. It shows some interesting behaviour. This map seems so…
45
votes
3 answers

Why does the Mandelbrot set appear when I use Newton's method to find the inverse of $\tan(z)$?

Why does the Mandelbrot set appear when I use Newton's method to find the inverse of $\tan(z)$ Specifically for the equation $y = \tan(z)$ I use Newton's method ($20$ iterations) to solve $0 = \tan(y) - z$ for $y$, where $y_0 = \tan(z)$ ($y_0$…
33
votes
1 answer

Does complex dynamics offer any insights into real dynamics?

One of the most fascinating things about complex analysis is that it provides insights into real analysis. Here are two pictures from Needham's book Visual Complex Analysis (p. 65): Picture 1 (real). Consider the following two functions. Both…
27
votes
3 answers

Mandelbrot set and prime numbers

I have written a simple program in C to generate Mandelbrot set. Wherever I zoom in, it seems to me that I see prime numbers, most often 11, 17, 19. For example the object on the attached image has 11 branches. Is there some deeper explanation, or…
25
votes
3 answers

Supremum of all y-coordinates of the Mandelbrot set

Let $M\subset \mathbb R^2$ be the Mandelbrot set. What is $\sup\{ y : (x,y) \in M \}$? Is this known? To be more descriptive: What is the supremum of all y-coordinates of all black points in the following picture: Picture File:Mandel zoom 00…
21
votes
11 answers

half iterate of $x^2+c$

I'm looking for literature on fractional iterates of $x^2+c$, where c>0. For c=0, generating the half iterate is trivial. $$h(h(x))=x^2$$ $$h(x)=x^{\sqrt{2}}$$ The question is, for $c>0,$ and $x>1$, when is the half iterate of $x^2+c$ smaller than…
19
votes
0 answers

When does $x^{x^{x^{...^x}}}$ diverge but $x^{x^{x^{...^c}}}$ converge?

Let us define these two sequences as follows: $a_0=1$, $b_0=c$ $a_{n+1}=x^{a_n}$, $b_{n+1}=x^{b_n}$ $b_{n+1}\ne b_n$ for any $n$. $x,c\in\mathbb C$ Is it possible for $a_n$ to diverge but $b_n$ to converge under these conditions? For example, if…
17
votes
3 answers

Finding the all roots of a polynomial by using Newton-Raphson method.

Is there a general formulation for finding all roots of a polynomial, especially the complex ones, by using the Newton-Raphson Method?
E.H.E
  • 23,590
16
votes
2 answers

Integral over filled Julia sets

Defining the usual quadratic Julia set iteration $f_c(z)=z^2+c$ for complex $c$, and its $n$th iteration $f^n_c(z)=f_c(f_c(\cdots f_c(z)\cdots))$, you can define a function of 4 variables $$c_{x,y,z,w}=\begin{cases} 1 & f_{x+iy}^\infty(z+iw)\text{…
15
votes
2 answers

Is $\frac{1}{\exp(z)} - \frac{1}{\exp(\exp(z))} + \frac{1}{\exp(\exp(\exp(z)))} -\ldots$ entire?

Let $z$ be a complex number. Is the alternating infinite series $$ f(z) = \frac{1}{\exp(z)} - \frac{1}{\exp(\exp(z))} + \frac{1}{\exp(\exp(\exp(z)))} -\dotsb $$ an entire function ? Does it even converge everywhere ? Additional questions (added dec…
15
votes
0 answers

is the Buddhabrot well-defined?

Define the Mandelbrot set $M = \{ c \in \mathbb{C} : P_c^n(0) \not\to \infty \text{ as } n \to \infty \}$ where $P_c(z) = z^2 + c$. Define the complement of the Mandelbrot set $\overline{M} = \mathbb{C} - M$. Define the escape time $N : \overline{M}…
Claude
  • 5,852
14
votes
3 answers

Quadratic Julia sets and periodic cycles

Consider the function $f_c(z) = z^2 + c$. Applying this function repeatedly, we get the familiar quadratic Julia sets that fractal enthusiasts burn compute cycles plotting. Infinity is always one attractor of the system. Depending on the choice of…
13
votes
2 answers

Is there an entire function with domains for which $f(A)=B$ and $f(B)=A$?

Let $f$ be an entire function. Suppose that there exist two nonempty disjoint, open, connected non-empty sets $A,B$ in the plane such that $f(A)=B$ and $f(B)=A$. Does it follow that $f$ is linear? Equivalently, if a meromorphic function satisfies…
Emolga
  • 3,587
13
votes
1 answer

Perfect circles in the Mandelbrot set?

It is known that the boundary of the period 2 hyperbolic component of the Mandelbrot set is a perfect circle of radius $\frac{1}{4}$ centered at $-1$. Moreover it is known that the boundaries of the circle-like period 3 hyperbolic components are…
Claude
  • 5,852
12
votes
2 answers

Help locating mini mandelbrots

I would like to be able to list the coordinates of all the first level minibrots. Here is a picture of the mandelbrot set generated by fraqtive: zooming in to the circled area we see a slightly distorted copy of the original fractal the julia set…
albatross
  • 443
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