lingo.lol is one of the many independent Mastodon servers you can use to participate in the fediverse.
A place for linguists, philologists, and other lovers of languages.

Server stats:

55
active users

#mathart

3 posts3 participants0 posts today

Another visualization of Costa's original surface (torus with three punctures).

The parametrization is as attributed to Alfred Gray:

mathworld.wolfram.com/CostaMin

The \(\wp\)-function is evaluated numerically using Wikipedia's expression in terms of \(\vartheta\)-functions, summing cosines over \(1 \leq n \leq 4\):
en.wikipedia.org/wiki/Theta_fu

en.wikipedia.org/wiki/Weierstr

My code to evaluate complex line integrals is fairly simple-minded; line segments and parabolic sums ("Simpson's rule") with 16 pieces (subintervals) sufficed.

With these conventions, the unit square \([0, 1] + i[0, 1]\) is a fundamental domain. The points \(1/2\) and \(i/2\) are the catenoid ends; \((1+i)/2\) is the planar end. I split the domain into four squares of side length \(1/2\), three centered at the punctures, the fourth centered at \(0\). The colors correspond to these squares.

To parametrize these squares "nicely" I used the inverse elliptic function
\[
f(z) := \int_{0}^{z} \frac{dw}{\sqrt{1 + w^{4}}},
\]
which maps the unit disk conformally to a square with sides parallel to the coordinate axes. Scaling, translating, and precomposing with polar coordinates (for the center) or with the exponential map (to avoid the punctures), and a bit of ad hoc fiddling to shrink the disks (avoiding the singularities of the integrand/corners of the image of \(f\)), gives the image/animation shown.

#FractalFriday (It's already Saturday)

Elephant valley of the Mobius Mandelbrot set.

Formula: \(z_{n+1}=f(z_n^2+c,1)\)

where \(f(z, a)\) is defined as (C-like pseudocode):

Complex f(Complex z, Real a) {
Real dist = abs(re(z)) - a;
if (re(z) > a) {
re(z) = -a + dist;
im(z) = -im(z);
} else if (re(z) < -a) {
re(z) = a - dist;
im(z) = -im(z);
}
return z;
}

Coloring is done by using three very similar colormaps, mapped to triangle inequality average values.
The final color is produced by interpolating between these three colors using the so called "atom domains".

Generated using my GLSL Shadertoy fractal generator: shadertoy.com/view/33sSRf