Skip to main content
13 events
when toggle format what by license comment
Jan 17, 2023 at 2:09 vote accept Iosif Pinelis
Jan 17, 2023 at 0:37 answer added fedja timeline score: 1
May 31, 2021 at 16:22 comment added Iosif Pinelis @AbdelmalekAbdesselam : Thank you for these further ideas. Meanwhile, i have done some simple rewriting of the iteration equation, now almost in a convolution form.
May 31, 2021 at 16:18 history edited Iosif Pinelis CC BY-SA 4.0
added 447 characters in body
May 31, 2021 at 16:05 comment added Abdelmalek Abdesselam ...in the near Gaussian case. Given that the situation is simpler than for the RG, I would expect it would not require as much ingenuity to find a Lyapunov functions that would allow a proof in the global (far from Gaussian) case. BTW a better link than above is mathoverflow.net/questions/182752/…
May 31, 2021 at 16:05 comment added Abdelmalek Abdesselam I just did a quick computation which gives support to your conjecture. Functions $h_k(r)=r^k$ are eigenfunctions of the linearization (no need for orthogonal polynomials like Hermite etc.) with eigenvalues $c_k=(4/\pi)\times W_k$ in terms of Wallis integrals in the notations of en.wikipedia.org/wiki/Wallis%27_integrals The only expanding/relevant directions are for $k=0,1$, while $k=2$ is neutral/marginal. Finally for $k>2$ , the corresponding directions are contracting. This is exactly the same as in the RG link I mentioned. One can mimick Koralov-Sinai and make this into a proof...
May 31, 2021 at 15:50 comment added Iosif Pinelis @AbdelmalekAbdesselam : Thank you for your suggestions. I see your point better now, and will have these suggestions in mind.
May 31, 2021 at 15:11 comment added Abdelmalek Abdesselam Of course the iterations are different, but the methods used for one might work for the other. It would take me some time to work it out, but the renormalization group inspired strategy I would use for your questions is: 1) write $g$ as the Gaussian times $(1+h)$ and write the iteration for the function $h$, 2) write the linearization of the transformation at the fixed point $h=0$, 3) see if you can diagonalize it explicitly using suitable orthogonal polynomials for the integral over $t$. Ultimately, one would need a Lyapunov function like some kind of entropy. Does Stein's method help?
May 31, 2021 at 15:03 comment added Iosif Pinelis @AbdelmalekAbdesselam : Thank you for this reference. Both settings indeed involve iterations. I think that other setting is a case of the central limit theorem for iid summands and $2^k$ summands, for natural $k$. Here the setting involves a different kind of iterations. But presumably/hopefully in this setting too one has normality in the limit.
May 31, 2021 at 14:46 comment added Abdelmalek Abdesselam Related mathoverflow.net/questions/191791/…
May 31, 2021 at 13:19 history edited Iosif Pinelis CC BY-SA 4.0
added 814 characters in body
May 31, 2021 at 0:54 history edited Iosif Pinelis CC BY-SA 4.0
added 12 characters in body
May 31, 2021 at 0:49 history asked Iosif Pinelis CC BY-SA 4.0