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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).

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) …
Qualcuno2's user avatar
2 votes

Fractal sets and dimensions

Suppose we construct sets $A,B,C$ with $A \subseteq [0,1]$, $\dim_\mathrm{H}(A) = 1/5$ and $\dim_\mathrm{P}(A) = 4/5$, $B \subseteq [2,3]$, $\dim_\mathrm{H}(B) = 1/5$ and $\dim_\mathrm{P}(B) = 2/5$, $ …
Gerald Edgar's user avatar
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9 votes
Accepted

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). …
Gerald Edgar's user avatar
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7 votes
Accepted

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 …
Gerald Edgar's user avatar
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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. …
Community's user avatar
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1 vote
Accepted

Hausdorff outer measure is finite if $\sum_{j = 1}^m |f(x_i)-f(x_{i-1})|^s \le c$

Take $s \ge 1$. We will use $(x+y)^s \le x^s+y^s$ for positive $x,y$. Let $C=2^{1+s/2}(1+c)$. I claim: $\mathcal H^s(G) \le C$. Let $N \in \mathbb N$. Let $\eta > 0$ be so small that $N2^s\et …
Gerald Edgar's user avatar
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1 vote

A calculus question related to quantization dimension

My response to the answer by fedja, Jun 5, 2011. This should be a comment, but won't fit. It didn't work. Taking values of $A,B,\epsilon$ that satisfy your conditions, then tracing back through u …
Gerald Edgar's user avatar
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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 $\sqrt{w-i}$ …
jeq'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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4 votes
Accepted

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 …
Gerald Edgar's user avatar
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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. …
Gerald Edgar's user avatar
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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 …
Gerald Edgar's user avatar
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3 votes

Reference for the iterated function system of the Koch snowflake

Aidan Burns, "78.13 Fractal tilings", Mathematical Gazette 78 (1994), 193–196 This article describes two remarkable tilings. The first is the Koch snowflake which will only tile the plane if tile …
Gerald Edgar's user avatar
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2 votes

Iterated function system on the plane

partial solution Something like this should work. We are given $r_1, r_2, r_3 > 0$ with $r_1^2+r_2^2+r_3^2<1$. Let $s$ be such that $r_1^s+r_2^s+r_3^s = 1$; this $s$ is the similarity dimension …
Gerald Edgar's user avatar
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3 votes

Fourier decay rate of Cantor measures

I would start looking here: MR1785620 (2001m:42020) Peres, Yuval; Schlag, Wilhelm; Solomyak, Boris, Sixty years of Bernoulli convolutions. Fractal geometry and stochastics, II (Greifswald/Koserow, 19 …
Gerald Edgar's user avatar
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