Multifractal analysis of the convergence exponents for the digits in $d$-decaying Gauss like dynamical systems
Kunkun Song, Mengjie Zhang
TL;DR
The paper addresses the multifractal analysis of convergence exponents for digits in $d$-decaying Gauss-like iIFS on $[0,1]$, introducing the convergence exponents $\tau_1(x)$ and $\tau_2(x)$ for digits and weighted products. It leverages conformal dynamics, pressure theory, and Cantor-type constructions to determine the Hausdorff dimension spectra of the corresponding level sets, showing that $\\dim_H E(\alpha)=\\dim_H E(\alpha,\{t_i\})=1/d$ for $0\le\alpha<\infty$, and revealing a piecewise spectrum for nondecreasing digits restricted to $\\Lambda$ with a threshold at $\\Sigma_t=\sum t_i$. Specifically, for $\\Lambda$, the spectrum is $0$ when $0\le\alpha<\\Sigma_t$, $(\\alpha-\\Sigma_t)/(d\\alpha)$ for $\\Sigma_t\le\alpha<\infty$, and $1/d$ at $\\alpha=\\infty$, with $F$ and $G$ sharing the same dimensional behavior. The work also connects these spectra to Lebesgue conformality and invariant measures, enriching the multifractal theory for infinite conformal systems and providing tools for analyzing digit-growth and restricted-growth sets in such systems.
Abstract
Let $\{a_n(x)\}_{n\geq1}$ be the sequence of digits of $x\in(0,1)$ in infinite iterated function systems with polynomial decay of the derivative. We first study the multifractal spectrum of the convergence exponent defined by the sequence of the digits $\{a_n(x)\}_{n\geq1}$ and the weighted products of distinct digits with finite numbers respectively, and then calculate the Hausdorff dimensions of the intersection of sets defined by the convergence exponent of the weighted product of distinct digits with finite numbers and sets of points whose digits are non-decreasing in such iterated function systems.
