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+--- Thread: On to C^\infty--and attempts at C^\infty hyper-operations (/showthread.php?tid=1297)
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RE: On to C^\infty--and attempts at C^\infty hyper-operations - sheldonison - 03/02/2021
(03/01/2021, 11:22 PM)MphLee Wrote: I'm probably missing some key piece of the puzzle (terminology). Are you talking about a kind of inverse Schroeder-like function right? A confortable abuse of name similar to how we can call \( \phi_{n+1} \) inverse Abel-like function of \( \phi_{n} \)?
In a strict sense, I don't see how \( \psi_{n} \) is a Schroeder function of \( \phi_{n} \) or of \( \phi_{n-1} \).
Sorry for the confusion; yes you are correct. The Schroeder like function is Schroeder like only in that it has a formal power series beginning with x+a2x^2 ... and a multiplier at zero, with the multiplier=e. Since it is a formal series, we can get the formal inverse and generate a \( \Psi(x) \) function and then it turns out the function we're iterating is actually
\( f(x)=e^{(x+1)}\cdot\Psi(x);\;\; \) This is the function James is actually iterating when he generates \( \phi \)
\( \Psi(f(x))=e\cdot\Psi(x);\;\;\; \) Schroeder function and inverse formal definition using f(x)
\( \Psi^{-1}(e\cdot~x)=f(\Psi^{-1}(x)) \)
\( \phi(x)=\Psi^{-1}(e^x);\;\;\;\phi_n(x)=\Psi_n^{-1}(e^x);\;\; \) this works for n=2,3,4 ....
The FPS (formal power series) approach is another intriguing approach to understanding \( \phi \), and the iterated \( \phi_n \) functions. The FPS approach would need more effort to make it rigorous; and the effort to make the FPS rigorous might become increasingly daunting for the iterated phi series for n>2. Even though \( \phi \) is entire, f has singularities where the derivative of \( \Psi^{-1} \) is equal to zero. Here is the Taylor series for f; the function we are actually iterating to generate \( \phi \), which has a fixed point of \( f(0)=0;\;f^{'}(0)=e \)
Code:
{f=
x^ 1* 2.71828182845905
+x^ 2* 1.71828182845905
+x^ 3* 0.775624792750073
+x^ 4* 0.191889268327428
+x^ 5* 0.0520249429156080
+x^ 6* 0.00599242247026314
+x^ 7* 0.00182349994116415
+x^ 8* 9.81807721872041 E-5
+x^ 9* -5.19018256906951 E-5
+x^10* 7.84647429007181 E-5
+x^11* -5.26096655278693 E-5
+x^12* 3.02110037576056 E-5
+x^13* -1.51896837385654 E-5
+x^14* 6.77204817742090 E-6
+x^15* -2.59325526178607 E-6 ...Here are the first few Taylor series coefficients of the \( \Psi^{-1}(x) \) function which is entire. We can generate the individual terms with a closed form in terms of "e", but I don't have a generic equation for the closed form. The higher order pentation, and hexation \( \Psi_3^{-1};\;\Psi_4^{-1} \) also have similar formal series representations, which I have also generated.
Code:
x
+x^ 2* 0.367879441171442
+x^ 3* 0.117454709986170
+x^ 4* 0.0324612092929206
+x^ 5* 0.00811730704942829
+x^ 6* 0.00188547471967479
+x^ 7* 0.000413224905195451
+x^ 8* 8.63482541739982 E-5
+x^ 9* 1.73333585608164 E-5
+x^10* 3.36137276288664 E-6
+x^11* 6.32477784106711 E-7
+x^12* 1.15869533017107 E-7
+x^13* 2.07255547935482 E-8
+x^14* 3.62795192280962 E-9
+x^15* 6.22699185709248 E-10 + ...Finally, for completeness here are the first few Taylor series terms of the formal series for \( \Psi(x) \)
Code:
x
+x^ 2* -0.367879441171442
+x^ 3* 0.153215856487055
+x^ 4* -0.0653506857689096
+x^ 5* 0.0275282379807258
+x^ 6* -0.0111894054323465
+x^ 7* 0.00428067464337933
+x^ 8* -0.00147921549686095
+x^ 9* 0.000417655162777504
+x^10* -5.90712473237761 E-5
+x^11* -3.60198809495273 E-5
+x^12* 4.43758017488974 E-5
+x^13* -3.14471384470661 E-5
+x^14* 1.81562489170478 E-5
+x^15* -9.15769831156020 E-6RE: On to C^\infty--and attempts at C^\infty hyper-operations - JmsNxn - 03/02/2021
Hey Everyone. Haven't been on for a while, been a little busy. I thought I'd post the modified form of the paper.
It details how to construct \( C^\infty \) hyper-operations; minus maybe a few details. But I'm confident I got everything down. In fact, I'm confident that if we do it in the manner Sheldon describes, using a sequence of infinite compositions,
\(
\phi_n(s) = \Omega_{j=1}^\infty \phi_{n-1}(s-j+z)\bullet z\\
\)
Not much really changes. I chose to use the exponential convergents rather than the \( \phi_n \) convergents, simply because it generalizes well to the construction of arbitrary super-functions. All we need really is an exponential convergents. In fact, \( \phi_n \) will look pretty much similarly, because of its exponential nature. The better form of Sheldon's method is that we retain holomorphy. Since I'm only trying to show \( C^\infty \), I figure holomorphy isn't really needed.
I do believe we could definitely use \( \phi_n(s) \) to construct \( e \uparrow^n x \). I believe it's more of an aesthetic issue, and I find it a bit more natural to just use,
\(
\Phi_n(s) = \Omega_{j=1}^\infty e^{s-j}e \uparrow^{n-1} z\bullet z\\
\)
And do away with \( \phi \). Also because this satisfies the more natural equation,
\(
\Phi_n(s+1) = e^s e \uparrow^{n-1} \Phi_n(s)\\
\)
And it removes a bit of the untangling if we were to use \( \phi_n \).
Anyway, here's what I have so far. The proof of \( C^\infty \) hyper-operators is surprisingly copy/paste from the proof of \( C^\infty \) tetration, so long as you pay attention to the generalization, it should be fine.
Any questions, comments or the what have you are greatly appreciated. I spent a lot of time restructuring the paper, but a lot of it is similar to what I wrote before.
Thanks, James