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Fractals deal with special sets that exhibit complicated patterns in every scale. Fractal sets usually have a Hausdorff dimension different from its topological dimension. Examples include Julia sets, the Sierpinski triangle, the Cantor set. Fractals naturally appear in dynamical system, such as iterations in the complex plane, or as strange attractors to continuous dynamical systems, (see Lorentz attractor).

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Parametrization of the boundary of the Mandelbrot set

Lasse's answer expanded: Let $\psi$ be the map of the exterior of the unit disk onto the exterior of the Mandelbrot set, with Laurent series $$ \psi(w) = w + \sum_{n=0}^\infty b_n w^{-n} = w - \frac{1 …
Gerald Edgar's user avatar
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17 votes

Fractal questions: Weierstraß-Mandelbrot

My question is whether there are nowhere differentiable continuous functions (between real numbers) whose graph are not fractals? Of course this depends on your definition of fractal. … Added: Kiesswetter function, two figures from Classics on Fractals Figure 18.2 (source: Wayback Machine)      Figure 18.3 (source: Wayback Machine) …
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11 votes
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Is there an intrinsic definition of fractal (i.e. not embedded in euclidean space)?

Topological dimension (say, covering dimension) $\dim_\mathrm{T}$ and Hausdorff dimension $\dim_\mathrm{H}$ both make sense for metric spaces. Benoit Mandelbrot defined $A$ to be a fractal iff $\dim_ …
Gerald Edgar's user avatar
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10 votes

Fractals of dimension zero

One example: the set of Liouville numbers has Hausdorff dimension zero. In number theory, a Liouville number is an irrational number $x$ with the property that, for every positive integer $n$, the …
Gerald Edgar's user avatar
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9 votes
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Why in the Sierpiński Triangle is this set being used as the example for the OSC and not a m...

I guess that illustration relates to the paper Bandt, Christoph; Nguyen Viet Hung; Rao, Hui, On the open set condition for self-similar fractals, Proc. Am. Math. Soc. 134, No. 5, 1369-1374 (2006). …
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8 votes

Dimensions of self-affine sets

Falconer, "The Hausdorff dimension of self-affine fractals" Math. Proc. Cambr. Phil. Soc. 103 (1988) 339-350 [2] G. A. …
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7 votes
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Does finite Hausdorff dimension imply finite packing dimension?

A construction used (repeatedy) in the paper Edgar, G. A., Centered densities and fractal measures, New York J. Math. 13, 33-87 (2007). ZBL1112.28004. For more information, see that paper. We constru …
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7 votes

How can we not know the $s$-measure of the Sierpiński triangle?

The latest I could find is Móra, Péter, Estimate of the Hausdorff measure of the Sierpinski triangle, Fractals 17, No. 2, 137-148 (2009). ZBL1178.28007. …
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6 votes
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Hausdorff dimension: subset of $\mathbb{R}^n$ vs. boundary of this subset

"Smaller" in the sense of $\le$ ... If $S$ is closed and has Hausdorff dimension $< n$, then $S$ has empty interior, so (as noted by Joel) $S$ is its own boundary, and thus we have equality for the tw …
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6 votes

How to define a differential form on a fractal?

There is an example of Hassler Whitney that is a lot of fun. Whitney, Hassler, "A function not constant on a connected set of critical points." Duke Math. J. 1 (1935), no. 4, 514–517. He con …
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5 votes

Measure 0 sets on the line with Hausdorff dimension 1

Perhaps Hausdorff's original paper? He uses gauge functions other than powers of x. And constructs Cantor sets corresponding to them. For example if you take $x |\log x|$ then you get a set of Haus …
Gerald Edgar's user avatar
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4 votes

Hausdorff dimension for invariant measure?

Hausdorff dimension of a measure is studied, yes. The mathematical texts should treat this. Falconer, Fractal Geometry 2nd edition p. 209 Edgar, Integral, Probability, and Fractal Measures p. 123
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Hausdorff dimension of inverse images.

Indeed, more is true: (1) The topological dimension is $\ge d-1$. And (2) the Hausdorff dimension is $\ge$ the topological dimension. For (1) note that $C$ is a closed set that separates $\mathbb …
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4 votes

Self-similarity of a dendrite fractal

OK, as hinted in my comment. Here is the fractal $J$: Now choose a branch of the squareroot so that $\sqrt{w-i}$ is continuous on this set. Here is the image of $J$ under the map $\sqrt{w-i}$ …
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4 votes
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Angles and proportions occurring in L-system fractals

In your first example, I think the ratio is $$ \arctan\frac{\sqrt{127+96\sqrt{2}\;}}{7} \approx 66.643774 \text{ degrees} $$ There is no reason to think this is a rational number of degrees. And: the …
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