How does the definition of Mandelbrot set rely on the starting point of the iteration?

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Let $f_c(z)=z^2+c$. The Mandelbrot set is the subset of the complex plane given by



$$M=f_c^(n)(0),$$



where $f_c^(n)$ denotes the $n$-th iterate of $f_c$. Let



$$M_a=f_c^(n)(a).$$



How are these sets related?







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  • 2




    $c in M_a iff a in J_c$, the filled Julia set of $f_c$.
    – lhf
    Aug 6 at 10:21














up vote
8
down vote

favorite












Let $f_c(z)=z^2+c$. The Mandelbrot set is the subset of the complex plane given by



$$M=f_c^(n)(0),$$



where $f_c^(n)$ denotes the $n$-th iterate of $f_c$. Let



$$M_a=f_c^(n)(a).$$



How are these sets related?







share|cite|improve this question

















  • 2




    $c in M_a iff a in J_c$, the filled Julia set of $f_c$.
    – lhf
    Aug 6 at 10:21












up vote
8
down vote

favorite









up vote
8
down vote

favorite











Let $f_c(z)=z^2+c$. The Mandelbrot set is the subset of the complex plane given by



$$M=f_c^(n)(0),$$



where $f_c^(n)$ denotes the $n$-th iterate of $f_c$. Let



$$M_a=f_c^(n)(a).$$



How are these sets related?







share|cite|improve this question













Let $f_c(z)=z^2+c$. The Mandelbrot set is the subset of the complex plane given by



$$M=f_c^(n)(0),$$



where $f_c^(n)$ denotes the $n$-th iterate of $f_c$. Let



$$M_a=f_c^(n)(a).$$



How are these sets related?









share|cite|improve this question












share|cite|improve this question




share|cite|improve this question








edited Aug 6 at 12:20









Mark McClure

22.5k34069




22.5k34069









asked Aug 6 at 3:27









Nienz

1018




1018







  • 2




    $c in M_a iff a in J_c$, the filled Julia set of $f_c$.
    – lhf
    Aug 6 at 10:21












  • 2




    $c in M_a iff a in J_c$, the filled Julia set of $f_c$.
    – lhf
    Aug 6 at 10:21







2




2




$c in M_a iff a in J_c$, the filled Julia set of $f_c$.
– lhf
Aug 6 at 10:21




$c in M_a iff a in J_c$, the filled Julia set of $f_c$.
– lhf
Aug 6 at 10:21










2 Answers
2






active

oldest

votes

















up vote
5
down vote



accepted










The Mandelbrot set is interesting because the location of a complex number $c$ in the Mandelbrot set yields information about the dynamics of the function $f_c$ and about the geometry of the Julia set $J_c$. This is due to the strong influence of the critical orbit (i.e. the orbit of the critical point zero). Generally, the orbits of of arbitrary points have no such overwhelming influence, so there's really no reason to think the sets $M_a$ to be particularly interesting.



Nonetheless, we might expect some superficial relationships. Here are some hasty claims - hasty in the sense that I've only given these a few minutes of thought.



Similarities



  • Like $M$, the set $M_a$ is bounded by $max(2,|a|)$ for every $ainmathbb C$.

    • Should follow from the quadratic escape criterium.


  • Like $M$, the set $M_a$ is closed for every $ainmathbb C$.

    • By continuity of $f_c^n$, the complement of $M_a$ should be open.


  • Like $M$, the set $M_a$ is non-empty for every $ainmathbb C$.

    • I'm thinking that $a-a^2in M_a$ since, for $c=a-a^2$, we get $$f_c(a) = a^2 + a - a^2 = a.$$ That is, $a$ is a fixed point of $f_c$ so its orbit is certainly bounded.


A difference



  • Unlike $M$, the set $M_a$ need not be connected.

    • This is just a matter of experimentation. The set $M_1$, for example, is shown below.


enter image description here



Note that this image suggests a gap on the real axis around $c=-2.5$. Indeed, if you compute the orbit of $z=1$ under the iteration of $f_c(z)=z^2-2.5$, you'll find that the it diverges to $infty$. If, however, you compute the orbit of $z=1$ under the iteration of $f_c(z)=z^2-3$, you'll find that it is just the bounded two cycle $1to-2to1$. Of course, the orbit of $1$ is fixed under $f_c(z)=z^2$. This suggests that the gap is genuine.






share|cite|improve this answer



















  • 2




    Good answer. The figure for $M_1$ does not convince me that it is not connected. I would be tempted to try some larger constant, like $M_4$. It seems like it might be obvious from that plot.
    – Ross Millikan
    Aug 7 at 4:10










  • @RossMillikan Thanks. I added some more detail to the answer indicating that there is a genuine gap on the real axis around $c=-2.5$. Of course, the set might be connected but not simply connected but it doesn't look like it. :)
    – Mark McClure
    Aug 7 at 4:30










  • Is it known whether the Mandelbrot set is simply connected?
    – DanielWainfleet
    Aug 7 at 7:22






  • 1




    @DanielWainfleet Yes, it certainly is. Even simpler, it's quite easy to show that the intersection of the Mandelbrot set with the real axis is an interval, which is clearly not the case for $M_1$.
    – Mark McClure
    Aug 7 at 12:03

















up vote
0
down vote














How are these sets related?




They are related by $M = M_0$ :)



Sorry, I couldn't resist that answer. But you probably want to know how $M_a$ is related to $M$ more generally. Given $f_c$, define $g_c,a(x) := f_c(x+a) - a = (x+a)^2 + (c-a).$ Then we have
$$
f^n_c(a) = g_c,a^n(0).
$$



Therefore, $M_a$ is the equivalent of the Mandelbrot set for quadratic polynomials with a linear coefficient included (note nolinear coefficient is present in the quadratic polynomial $f_c$, but $g_c,a$ has linear coefficient $2a$).



One could define a four-dimensional version of the Mandelbrot set where we consider the behavior of all possible polynomials $boldsymbolz^2 + bx + c$ iterated starting from $z = 0$. This would be four-dimensional because there are now two complex variables, $a$ and $b$. Then $M_a$ would be the slice of this four-dimensional set where $b = 2a$, and $M$ would be the slice where $b = 0$.






share|cite|improve this answer





















  • I'm not sure that it makes any more sense to iterate $z^2+bx+c$ from 0 than it does to iterate $z^2+c$ from $a$.
    – Mark McClure
    Aug 7 at 11:40










  • @MarkMcClure I know, it's not a particularly illuminating observation, and of course does not compare to your answer :). I just thought it was worth pointing out the connection between starting from an arbitrary point $a$ and using a general quadratic rather than just $z^2 + c$.
    – 6005
    Aug 7 at 15:41










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2 Answers
2






active

oldest

votes








2 Answers
2






active

oldest

votes









active

oldest

votes






active

oldest

votes








up vote
5
down vote



accepted










The Mandelbrot set is interesting because the location of a complex number $c$ in the Mandelbrot set yields information about the dynamics of the function $f_c$ and about the geometry of the Julia set $J_c$. This is due to the strong influence of the critical orbit (i.e. the orbit of the critical point zero). Generally, the orbits of of arbitrary points have no such overwhelming influence, so there's really no reason to think the sets $M_a$ to be particularly interesting.



Nonetheless, we might expect some superficial relationships. Here are some hasty claims - hasty in the sense that I've only given these a few minutes of thought.



Similarities



  • Like $M$, the set $M_a$ is bounded by $max(2,|a|)$ for every $ainmathbb C$.

    • Should follow from the quadratic escape criterium.


  • Like $M$, the set $M_a$ is closed for every $ainmathbb C$.

    • By continuity of $f_c^n$, the complement of $M_a$ should be open.


  • Like $M$, the set $M_a$ is non-empty for every $ainmathbb C$.

    • I'm thinking that $a-a^2in M_a$ since, for $c=a-a^2$, we get $$f_c(a) = a^2 + a - a^2 = a.$$ That is, $a$ is a fixed point of $f_c$ so its orbit is certainly bounded.


A difference



  • Unlike $M$, the set $M_a$ need not be connected.

    • This is just a matter of experimentation. The set $M_1$, for example, is shown below.


enter image description here



Note that this image suggests a gap on the real axis around $c=-2.5$. Indeed, if you compute the orbit of $z=1$ under the iteration of $f_c(z)=z^2-2.5$, you'll find that the it diverges to $infty$. If, however, you compute the orbit of $z=1$ under the iteration of $f_c(z)=z^2-3$, you'll find that it is just the bounded two cycle $1to-2to1$. Of course, the orbit of $1$ is fixed under $f_c(z)=z^2$. This suggests that the gap is genuine.






share|cite|improve this answer



















  • 2




    Good answer. The figure for $M_1$ does not convince me that it is not connected. I would be tempted to try some larger constant, like $M_4$. It seems like it might be obvious from that plot.
    – Ross Millikan
    Aug 7 at 4:10










  • @RossMillikan Thanks. I added some more detail to the answer indicating that there is a genuine gap on the real axis around $c=-2.5$. Of course, the set might be connected but not simply connected but it doesn't look like it. :)
    – Mark McClure
    Aug 7 at 4:30










  • Is it known whether the Mandelbrot set is simply connected?
    – DanielWainfleet
    Aug 7 at 7:22






  • 1




    @DanielWainfleet Yes, it certainly is. Even simpler, it's quite easy to show that the intersection of the Mandelbrot set with the real axis is an interval, which is clearly not the case for $M_1$.
    – Mark McClure
    Aug 7 at 12:03














up vote
5
down vote



accepted










The Mandelbrot set is interesting because the location of a complex number $c$ in the Mandelbrot set yields information about the dynamics of the function $f_c$ and about the geometry of the Julia set $J_c$. This is due to the strong influence of the critical orbit (i.e. the orbit of the critical point zero). Generally, the orbits of of arbitrary points have no such overwhelming influence, so there's really no reason to think the sets $M_a$ to be particularly interesting.



Nonetheless, we might expect some superficial relationships. Here are some hasty claims - hasty in the sense that I've only given these a few minutes of thought.



Similarities



  • Like $M$, the set $M_a$ is bounded by $max(2,|a|)$ for every $ainmathbb C$.

    • Should follow from the quadratic escape criterium.


  • Like $M$, the set $M_a$ is closed for every $ainmathbb C$.

    • By continuity of $f_c^n$, the complement of $M_a$ should be open.


  • Like $M$, the set $M_a$ is non-empty for every $ainmathbb C$.

    • I'm thinking that $a-a^2in M_a$ since, for $c=a-a^2$, we get $$f_c(a) = a^2 + a - a^2 = a.$$ That is, $a$ is a fixed point of $f_c$ so its orbit is certainly bounded.


A difference



  • Unlike $M$, the set $M_a$ need not be connected.

    • This is just a matter of experimentation. The set $M_1$, for example, is shown below.


enter image description here



Note that this image suggests a gap on the real axis around $c=-2.5$. Indeed, if you compute the orbit of $z=1$ under the iteration of $f_c(z)=z^2-2.5$, you'll find that the it diverges to $infty$. If, however, you compute the orbit of $z=1$ under the iteration of $f_c(z)=z^2-3$, you'll find that it is just the bounded two cycle $1to-2to1$. Of course, the orbit of $1$ is fixed under $f_c(z)=z^2$. This suggests that the gap is genuine.






share|cite|improve this answer



















  • 2




    Good answer. The figure for $M_1$ does not convince me that it is not connected. I would be tempted to try some larger constant, like $M_4$. It seems like it might be obvious from that plot.
    – Ross Millikan
    Aug 7 at 4:10










  • @RossMillikan Thanks. I added some more detail to the answer indicating that there is a genuine gap on the real axis around $c=-2.5$. Of course, the set might be connected but not simply connected but it doesn't look like it. :)
    – Mark McClure
    Aug 7 at 4:30










  • Is it known whether the Mandelbrot set is simply connected?
    – DanielWainfleet
    Aug 7 at 7:22






  • 1




    @DanielWainfleet Yes, it certainly is. Even simpler, it's quite easy to show that the intersection of the Mandelbrot set with the real axis is an interval, which is clearly not the case for $M_1$.
    – Mark McClure
    Aug 7 at 12:03












up vote
5
down vote



accepted







up vote
5
down vote



accepted






The Mandelbrot set is interesting because the location of a complex number $c$ in the Mandelbrot set yields information about the dynamics of the function $f_c$ and about the geometry of the Julia set $J_c$. This is due to the strong influence of the critical orbit (i.e. the orbit of the critical point zero). Generally, the orbits of of arbitrary points have no such overwhelming influence, so there's really no reason to think the sets $M_a$ to be particularly interesting.



Nonetheless, we might expect some superficial relationships. Here are some hasty claims - hasty in the sense that I've only given these a few minutes of thought.



Similarities



  • Like $M$, the set $M_a$ is bounded by $max(2,|a|)$ for every $ainmathbb C$.

    • Should follow from the quadratic escape criterium.


  • Like $M$, the set $M_a$ is closed for every $ainmathbb C$.

    • By continuity of $f_c^n$, the complement of $M_a$ should be open.


  • Like $M$, the set $M_a$ is non-empty for every $ainmathbb C$.

    • I'm thinking that $a-a^2in M_a$ since, for $c=a-a^2$, we get $$f_c(a) = a^2 + a - a^2 = a.$$ That is, $a$ is a fixed point of $f_c$ so its orbit is certainly bounded.


A difference



  • Unlike $M$, the set $M_a$ need not be connected.

    • This is just a matter of experimentation. The set $M_1$, for example, is shown below.


enter image description here



Note that this image suggests a gap on the real axis around $c=-2.5$. Indeed, if you compute the orbit of $z=1$ under the iteration of $f_c(z)=z^2-2.5$, you'll find that the it diverges to $infty$. If, however, you compute the orbit of $z=1$ under the iteration of $f_c(z)=z^2-3$, you'll find that it is just the bounded two cycle $1to-2to1$. Of course, the orbit of $1$ is fixed under $f_c(z)=z^2$. This suggests that the gap is genuine.






share|cite|improve this answer















The Mandelbrot set is interesting because the location of a complex number $c$ in the Mandelbrot set yields information about the dynamics of the function $f_c$ and about the geometry of the Julia set $J_c$. This is due to the strong influence of the critical orbit (i.e. the orbit of the critical point zero). Generally, the orbits of of arbitrary points have no such overwhelming influence, so there's really no reason to think the sets $M_a$ to be particularly interesting.



Nonetheless, we might expect some superficial relationships. Here are some hasty claims - hasty in the sense that I've only given these a few minutes of thought.



Similarities



  • Like $M$, the set $M_a$ is bounded by $max(2,|a|)$ for every $ainmathbb C$.

    • Should follow from the quadratic escape criterium.


  • Like $M$, the set $M_a$ is closed for every $ainmathbb C$.

    • By continuity of $f_c^n$, the complement of $M_a$ should be open.


  • Like $M$, the set $M_a$ is non-empty for every $ainmathbb C$.

    • I'm thinking that $a-a^2in M_a$ since, for $c=a-a^2$, we get $$f_c(a) = a^2 + a - a^2 = a.$$ That is, $a$ is a fixed point of $f_c$ so its orbit is certainly bounded.


A difference



  • Unlike $M$, the set $M_a$ need not be connected.

    • This is just a matter of experimentation. The set $M_1$, for example, is shown below.


enter image description here



Note that this image suggests a gap on the real axis around $c=-2.5$. Indeed, if you compute the orbit of $z=1$ under the iteration of $f_c(z)=z^2-2.5$, you'll find that the it diverges to $infty$. If, however, you compute the orbit of $z=1$ under the iteration of $f_c(z)=z^2-3$, you'll find that it is just the bounded two cycle $1to-2to1$. Of course, the orbit of $1$ is fixed under $f_c(z)=z^2$. This suggests that the gap is genuine.







share|cite|improve this answer















share|cite|improve this answer



share|cite|improve this answer








edited Aug 7 at 4:29


























answered Aug 7 at 1:59









Mark McClure

22.5k34069




22.5k34069







  • 2




    Good answer. The figure for $M_1$ does not convince me that it is not connected. I would be tempted to try some larger constant, like $M_4$. It seems like it might be obvious from that plot.
    – Ross Millikan
    Aug 7 at 4:10










  • @RossMillikan Thanks. I added some more detail to the answer indicating that there is a genuine gap on the real axis around $c=-2.5$. Of course, the set might be connected but not simply connected but it doesn't look like it. :)
    – Mark McClure
    Aug 7 at 4:30










  • Is it known whether the Mandelbrot set is simply connected?
    – DanielWainfleet
    Aug 7 at 7:22






  • 1




    @DanielWainfleet Yes, it certainly is. Even simpler, it's quite easy to show that the intersection of the Mandelbrot set with the real axis is an interval, which is clearly not the case for $M_1$.
    – Mark McClure
    Aug 7 at 12:03












  • 2




    Good answer. The figure for $M_1$ does not convince me that it is not connected. I would be tempted to try some larger constant, like $M_4$. It seems like it might be obvious from that plot.
    – Ross Millikan
    Aug 7 at 4:10










  • @RossMillikan Thanks. I added some more detail to the answer indicating that there is a genuine gap on the real axis around $c=-2.5$. Of course, the set might be connected but not simply connected but it doesn't look like it. :)
    – Mark McClure
    Aug 7 at 4:30










  • Is it known whether the Mandelbrot set is simply connected?
    – DanielWainfleet
    Aug 7 at 7:22






  • 1




    @DanielWainfleet Yes, it certainly is. Even simpler, it's quite easy to show that the intersection of the Mandelbrot set with the real axis is an interval, which is clearly not the case for $M_1$.
    – Mark McClure
    Aug 7 at 12:03







2




2




Good answer. The figure for $M_1$ does not convince me that it is not connected. I would be tempted to try some larger constant, like $M_4$. It seems like it might be obvious from that plot.
– Ross Millikan
Aug 7 at 4:10




Good answer. The figure for $M_1$ does not convince me that it is not connected. I would be tempted to try some larger constant, like $M_4$. It seems like it might be obvious from that plot.
– Ross Millikan
Aug 7 at 4:10












@RossMillikan Thanks. I added some more detail to the answer indicating that there is a genuine gap on the real axis around $c=-2.5$. Of course, the set might be connected but not simply connected but it doesn't look like it. :)
– Mark McClure
Aug 7 at 4:30




@RossMillikan Thanks. I added some more detail to the answer indicating that there is a genuine gap on the real axis around $c=-2.5$. Of course, the set might be connected but not simply connected but it doesn't look like it. :)
– Mark McClure
Aug 7 at 4:30












Is it known whether the Mandelbrot set is simply connected?
– DanielWainfleet
Aug 7 at 7:22




Is it known whether the Mandelbrot set is simply connected?
– DanielWainfleet
Aug 7 at 7:22




1




1




@DanielWainfleet Yes, it certainly is. Even simpler, it's quite easy to show that the intersection of the Mandelbrot set with the real axis is an interval, which is clearly not the case for $M_1$.
– Mark McClure
Aug 7 at 12:03




@DanielWainfleet Yes, it certainly is. Even simpler, it's quite easy to show that the intersection of the Mandelbrot set with the real axis is an interval, which is clearly not the case for $M_1$.
– Mark McClure
Aug 7 at 12:03










up vote
0
down vote














How are these sets related?




They are related by $M = M_0$ :)



Sorry, I couldn't resist that answer. But you probably want to know how $M_a$ is related to $M$ more generally. Given $f_c$, define $g_c,a(x) := f_c(x+a) - a = (x+a)^2 + (c-a).$ Then we have
$$
f^n_c(a) = g_c,a^n(0).
$$



Therefore, $M_a$ is the equivalent of the Mandelbrot set for quadratic polynomials with a linear coefficient included (note nolinear coefficient is present in the quadratic polynomial $f_c$, but $g_c,a$ has linear coefficient $2a$).



One could define a four-dimensional version of the Mandelbrot set where we consider the behavior of all possible polynomials $boldsymbolz^2 + bx + c$ iterated starting from $z = 0$. This would be four-dimensional because there are now two complex variables, $a$ and $b$. Then $M_a$ would be the slice of this four-dimensional set where $b = 2a$, and $M$ would be the slice where $b = 0$.






share|cite|improve this answer





















  • I'm not sure that it makes any more sense to iterate $z^2+bx+c$ from 0 than it does to iterate $z^2+c$ from $a$.
    – Mark McClure
    Aug 7 at 11:40










  • @MarkMcClure I know, it's not a particularly illuminating observation, and of course does not compare to your answer :). I just thought it was worth pointing out the connection between starting from an arbitrary point $a$ and using a general quadratic rather than just $z^2 + c$.
    – 6005
    Aug 7 at 15:41














up vote
0
down vote














How are these sets related?




They are related by $M = M_0$ :)



Sorry, I couldn't resist that answer. But you probably want to know how $M_a$ is related to $M$ more generally. Given $f_c$, define $g_c,a(x) := f_c(x+a) - a = (x+a)^2 + (c-a).$ Then we have
$$
f^n_c(a) = g_c,a^n(0).
$$



Therefore, $M_a$ is the equivalent of the Mandelbrot set for quadratic polynomials with a linear coefficient included (note nolinear coefficient is present in the quadratic polynomial $f_c$, but $g_c,a$ has linear coefficient $2a$).



One could define a four-dimensional version of the Mandelbrot set where we consider the behavior of all possible polynomials $boldsymbolz^2 + bx + c$ iterated starting from $z = 0$. This would be four-dimensional because there are now two complex variables, $a$ and $b$. Then $M_a$ would be the slice of this four-dimensional set where $b = 2a$, and $M$ would be the slice where $b = 0$.






share|cite|improve this answer





















  • I'm not sure that it makes any more sense to iterate $z^2+bx+c$ from 0 than it does to iterate $z^2+c$ from $a$.
    – Mark McClure
    Aug 7 at 11:40










  • @MarkMcClure I know, it's not a particularly illuminating observation, and of course does not compare to your answer :). I just thought it was worth pointing out the connection between starting from an arbitrary point $a$ and using a general quadratic rather than just $z^2 + c$.
    – 6005
    Aug 7 at 15:41












up vote
0
down vote










up vote
0
down vote










How are these sets related?




They are related by $M = M_0$ :)



Sorry, I couldn't resist that answer. But you probably want to know how $M_a$ is related to $M$ more generally. Given $f_c$, define $g_c,a(x) := f_c(x+a) - a = (x+a)^2 + (c-a).$ Then we have
$$
f^n_c(a) = g_c,a^n(0).
$$



Therefore, $M_a$ is the equivalent of the Mandelbrot set for quadratic polynomials with a linear coefficient included (note nolinear coefficient is present in the quadratic polynomial $f_c$, but $g_c,a$ has linear coefficient $2a$).



One could define a four-dimensional version of the Mandelbrot set where we consider the behavior of all possible polynomials $boldsymbolz^2 + bx + c$ iterated starting from $z = 0$. This would be four-dimensional because there are now two complex variables, $a$ and $b$. Then $M_a$ would be the slice of this four-dimensional set where $b = 2a$, and $M$ would be the slice where $b = 0$.






share|cite|improve this answer














How are these sets related?




They are related by $M = M_0$ :)



Sorry, I couldn't resist that answer. But you probably want to know how $M_a$ is related to $M$ more generally. Given $f_c$, define $g_c,a(x) := f_c(x+a) - a = (x+a)^2 + (c-a).$ Then we have
$$
f^n_c(a) = g_c,a^n(0).
$$



Therefore, $M_a$ is the equivalent of the Mandelbrot set for quadratic polynomials with a linear coefficient included (note nolinear coefficient is present in the quadratic polynomial $f_c$, but $g_c,a$ has linear coefficient $2a$).



One could define a four-dimensional version of the Mandelbrot set where we consider the behavior of all possible polynomials $boldsymbolz^2 + bx + c$ iterated starting from $z = 0$. This would be four-dimensional because there are now two complex variables, $a$ and $b$. Then $M_a$ would be the slice of this four-dimensional set where $b = 2a$, and $M$ would be the slice where $b = 0$.







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answered Aug 7 at 5:15









6005

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  • I'm not sure that it makes any more sense to iterate $z^2+bx+c$ from 0 than it does to iterate $z^2+c$ from $a$.
    – Mark McClure
    Aug 7 at 11:40










  • @MarkMcClure I know, it's not a particularly illuminating observation, and of course does not compare to your answer :). I just thought it was worth pointing out the connection between starting from an arbitrary point $a$ and using a general quadratic rather than just $z^2 + c$.
    – 6005
    Aug 7 at 15:41
















  • I'm not sure that it makes any more sense to iterate $z^2+bx+c$ from 0 than it does to iterate $z^2+c$ from $a$.
    – Mark McClure
    Aug 7 at 11:40










  • @MarkMcClure I know, it's not a particularly illuminating observation, and of course does not compare to your answer :). I just thought it was worth pointing out the connection between starting from an arbitrary point $a$ and using a general quadratic rather than just $z^2 + c$.
    – 6005
    Aug 7 at 15:41















I'm not sure that it makes any more sense to iterate $z^2+bx+c$ from 0 than it does to iterate $z^2+c$ from $a$.
– Mark McClure
Aug 7 at 11:40




I'm not sure that it makes any more sense to iterate $z^2+bx+c$ from 0 than it does to iterate $z^2+c$ from $a$.
– Mark McClure
Aug 7 at 11:40












@MarkMcClure I know, it's not a particularly illuminating observation, and of course does not compare to your answer :). I just thought it was worth pointing out the connection between starting from an arbitrary point $a$ and using a general quadratic rather than just $z^2 + c$.
– 6005
Aug 7 at 15:41




@MarkMcClure I know, it's not a particularly illuminating observation, and of course does not compare to your answer :). I just thought it was worth pointing out the connection between starting from an arbitrary point $a$ and using a general quadratic rather than just $z^2 + c$.
– 6005
Aug 7 at 15:41












 

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