### Recent Posts

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##### Kalles Fraktaler / Re: hybrid formulas
« Last post by FractalAlex on Yesterday at 02:50:14 PM »
I will try to make the Magnets and Nova fractals work in Kalles Fraktaler, if I was that good at coding and implementing fractals... But that doesn't prevent me from trying.
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##### Kalles Fraktaler / Re: Kalles Fraktaler 2.14
« Last post by FractalAlex on Yesterday at 02:47:10 PM »
Even if I disable series approximation, the vertical bands on the axis near -2±0i are still present, past e10. As I told earlier, the bands do not appear on Fractal eXtreme.
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##### Kalles Fraktaler / Re: Kalles Fraktaler 2.14
« Last post by claude on Yesterday at 02:39:22 PM »
I think the near-vertical bands at the left are a combination of low bailout radius and smooth colouring method - can choose linear (better for small radius) vs log (requires larger radius).  The final Z magnitude is taken into account for smooth colouring, which makes the outside of the escape disk not necessarily featureless.

Maybe worth checking, in case of a bug: do they change if you disable series approximation? Series approx is currently only used for Mandelbrot and Burning Ship (and that only to a limited extent).
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##### Fractal Mathematics And New Theories / Re: Parabolic Julia sets
« Last post by marcm200 on Yesterday at 01:26:33 PM »
(Please ignore this and see last post, wrong button)
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##### Fractal Mathematics And New Theories / Re: Parabolic Julia sets
« Last post by marcm200 on Yesterday at 01:25:50 PM »
"The king of parabolicty"

A constructed degree-7 polynomial to have 4 (ir)rationally indifferent fix points.

• a parabolic one at -1+0i (f'=+1)
• a Siegel fix-point with a critical point in its boundary at the origin ($$f=e^{2i\cdot \pi\cdot \alpha_{bounded}}$$, value defined below)
• a (probable) Siegel fix-point with rotation number of unbounded type at 1+0i ($$f=e^{2i\cdot \pi\cdot \alpha_{unbounded}}$$)
• a Cremer fix point in the upper right quadrant at 1+i ($$f=e^{2i\cdot \pi\cdot \alpha_{cremer}}$$)

following the description in https://fractalforums.org/fractal-mathematics-and-new-theories/28/julia-sets-true-shape-and-escape-time/2725/msg22939#msg22939. In short, a degree-7 polynomial with 8 coefficients was used to find a solution of the system consisting of 4 equations for the desired fixpoints and 4 for the derivates using maxima.

The approximative polynomial used:

$f(z)=(0.08742572471696199+0.9961710408648288 i)*z+ (-0.4544465364046477-2.345728439042568 i)*z^2 + (2.849251631498275-2.082596937337672 i)*z^3 + \\ (1.259747964272526+4.46270310026291 1)*z^4 + (-2.609925545684205+0.9479269742586326 i)*z^5 + (-0.8053014278678783-2.116974661220343 i)*z^6 + \\ (0.6732481894689685+0.1384989222142105 i)*z^7$

The image below is a rational impression, point-sampled (25000 max it) in the 4-square, cropped. non-rounding controlled with approximations to the derivatives (and hence neither truely a Cremer nor Siegel disc. The fix points are surrounded by the crossing of two vertical and two horizontal lines.

The picture displays the cusp-like shape of the parabolic basin, the two Siegel discs that look rather similar to me (bound/unbounded) and the Cremer-like impression with a tongue-like feature, which I suspect vanishes with higher iteration count, so might actually be a rational value for the derivative that lies outside the 8D parameter space for this type of combination of what the critical points do.

Values

$$\alpha_{bounded}$$: The value of the continued fraction 4+1/(4+1/(4+1/(... which is of bounded type and hence has a Siegel disc with a critical point in its boundary for any polynomial with that rotation number (Zhang-theorem in A Cheritat, P Roesch, Herman's condition and Siegel discs of bicritical polynomials). Here the first 100 fractions were computed, resulting in ~4.2360679774997898050514777.

$$\alpha_{unbounded}$$: The value of the continued fraction 1+1/(3+1/(4+1/(5+... I do not know whether this results in a Siegel disc or a Cremer point (I suspect the former, as the denominator are growing slowly), but it is a different arithmetic condition on the rotation number. Calculated were again the first 100 fractions, resulting in ~1.3160892412682212437857742.

$$\alpha_{cremer}$$: I used the value from post #39 above for the first 5 fractions, resulting in ~2.444468546637744044147-

Two consecutive continued fractions (lying on different sides of the true value) are closer than 10^-70 (arbitrarily chosen value).

The symbolic solution to the coefficients is (where m2,m3,m4 are the derivatives for the irrational fix points (bounded, unbounded, Cremer))::

Code: [Select]
A7 = -((-8*m4)+i*((-6*m4)+50*m2-44)+25*m3-17)/100A6 = ((-2*m4)+i*((-14*m4)+50*m3+100*m2-136)+25*m3-100*m2+77)/100A5 = ((-16*m4)+i*((-12*m4)+100*m2-88)+75*m3+100*m2-159)/100A4 = -((-4*m4)+i*((-28*m4)+100*m3+200*m2-272)+25*m3-200*m2+179)/100A3 = -((-4*m4)+i*((-3*m4)+25*m2-22)+25*m3+100*m2-121)/50A2 = ((-m4)+i*((-7*m4)+25*m3+50*m2-68)-50*m2+51)/50A1 = m2A0 = 0`
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##### Image Threads / Re: Twofold
« Last post by pauldelbrot on Yesterday at 06:27:35 AM »
Plasma Turbulence
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##### Kalles Fraktaler / Re: Kalles Fraktaler 2.14
« Last post by gerrit on Yesterday at 05:49:41 AM »
Claude, why do these bands appear even if we're on the real axis past e10, while being on a zoom point close to -2±0i? They do not appear on Fractal eXtreme... It occurs on fractals with low bailout values.
I think because of bailout value.
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##### Kalles Fraktaler / Re: hybrid formulas
« Last post by 3DickUlus on Yesterday at 05:34:03 AM »
...in that thread I offered up the 4 magnet fractal formulas that I had and that's the last post in the thread...

I have since regurgitated that old Amiga code as fragment code... you can find it at https://github.com/3Dickulus/My_Fragments/blob/master/Magnet.frag
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##### Kalles Fraktaler / Re: hybrid formulas
« Last post by FractalAlex on Yesterday at 01:57:29 AM »
I have no idea. All that I know so far is that the Magnet and Nova fractals use different bailout criteria. Perhaps you should check out more about Karl Runmo's attempt at including the Magnet here: http://www.fractalforums.com/programming/magnetic-mandelbrot/
Also, can you do some research to make it work?
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##### Kalles Fraktaler / Re: hybrid formulas
« Last post by 3DickUlus on Yesterday at 01:36:03 AM »
if a convergent fractal is inverted (mathematically) does that make it divergent?
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