Iteration with two analytic fixed points
#13
Okay, YES! I think I got it now. I only have part of it though, but the proof went something like this. This is only for the Schroder case, I can't remember what to do for the parabolic case--but that should take care of itself--if we stick to local iteration. There exists no local iteration about a neutral fixed points.

Assume that \(f\) is holomorphic on a domain \(H\) (not simply connected), and let's assume there are two fixed points \(p_0,p_1 \in H\), such that \(p_0\) is geometrically attracting. Let us additionally assume that \(f^{\circ t}(z)\) is holomorphic on all of \(H\), including the fixed point. Define \(\lambda = f'(p_0)\). We can define the domains:


\[
B(z) = \{q \in H\,|\,|\lambda^t| < 1,\,q = f^{\circ t}(z),\,\text{for some}\,z \in H\}\\
\]

This is a simply connected domain. And additionally, as \(t \to \infty\), we converge to \(p_0\), by the nature of the Schroder iteration. Now, we know that \(f:B(z) \to B(z)\) because \(f\) is a contraction mapping here. Therefore, for all \(z \in H\) and \(z \neq p_1\), \(p_1 \not\in B(z)\)--because it would be a simply connected domain with two fixed points. But the union of all \(B(z)\) is precisely \(H\), so \(f^{\circ t}(z)\) can't be holomorphic about all of \(H\).

Now, particularly, the assumption that might be troubling you is that we converge to \(p_0\) as \(t \to \infty\)--what if it converges somewhere else?

Well to play this out, we have to allow \(z \to J\) where \(J\) is the julia set of \(f\). The schroder coordinate change is no longer valid here, and if we could extend this value here, we've incidentally analytically continued \(\Psi^{-1}\) to a domain larger than its maximal domain; which is erroneous to say the least. I'm going to think about this more though, to further justify it for you. There should be something technical which will save me Smile

I'll keep working on polishing this, I know it's something close to this.

And again, this says nothing about your iteration, because \(B(z)\) is no longer a domain in your case (there are poles).



Also! for a bit more intuition. Every regular iteration that is a local iteration that is a schroder iteration is periodic. So say it has period \(\ell\), then the arc \(\gamma\) connecting \(\ell\) and \(0\), induces a simply connected domain through the jordan curve \(\mu = f^{\gamma}\) about any \(z\), so there can only be one fixed point contained within the center of this jordan curve. I can't see how we can move \(z\) to include neither fixed points/the other fixed points... I'll have to think about this more.
Reply


Messages In This Thread
RE: Iteration with two analytic fixed points - by JmsNxn - 08/04/2022, 09:33 PM

Possibly Related Threads…
Thread Author Replies Views Last Post
  Down with fixed points! Daniel 1 2,952 04/29/2023, 11:02 PM
Last Post: tommy1729
  double functional equation , continuum sum and analytic continuation tommy1729 6 10,388 03/05/2023, 12:36 AM
Last Post: tommy1729
  Qs on extension of continuous iterations from analytic functs to non-analytic Leo.W 18 26,719 09/18/2022, 09:37 PM
Last Post: tommy1729
Question The Different Fixed Points of Exponentials Catullus 22 26,316 07/24/2022, 12:22 PM
Last Post: bo198214
  Quick way to get the repelling fixed point from the attracting fixed point? JmsNxn 10 13,797 07/22/2022, 01:51 AM
Last Post: JmsNxn
  Constructing an analytic repelling Abel function JmsNxn 0 3,247 07/11/2022, 10:30 PM
Last Post: JmsNxn
  Is tetration analytic? Daniel 6 9,874 07/08/2022, 01:31 AM
Last Post: JmsNxn
Question Two Attracting Fixed Points Catullus 4 7,054 07/04/2022, 01:04 PM
Last Post: tommy1729
  Fractional iteration of x^2+1 at infinity and fractional iteration of exp bo198214 17 54,601 06/11/2022, 12:24 PM
Last Post: tommy1729
  Brute force tetration A_k(s) is analytic ! tommy1729 9 15,220 03/22/2021, 11:39 PM
Last Post: JmsNxn



Users browsing this thread: 1 Guest(s)