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Register a new userSelf-similar sets with super-exponential close cylinders
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Changhao Chen
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S. Baker (2019), B. Barany and A. K{a}enm{a}ki (2019) independently showed that there exist iterated function systems without exact overlaps and there are super-exponentially close cylinders at all small levels. We adapt the method of S. Baker and obtain further examples of this type. We prove that for any algebraic number $betage 2$ there exist real numbers $s, t$ such that the iterated function system $$ left {frac{x}{beta}, frac{x+1}{beta}, frac{x+s}{beta}, frac{x+t}{beta}right } $$ satisfies the above property.
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We study random walks on a $d$-dimensional torus by affine expanding maps whose linear parts commute. Assuming an irrationality condition on their translation parts, we prove that the Haar measure is the unique stationary measure. We deduce that if $K subset mathbb{R}^d$ is an attractor of a finite iterated function system of $ngeq 2$ maps of the form $x mapsto D^{-r_i} x + t_i (i=1, ldots, n)$, where $D$ is an expanding $dtimes d$ integer matrix, and is the same for all the maps, and $r_{i} inmathbb{N}$, under an irrationality condition on the translation parts $t_i$, almost every point in $K$ (w.r.t. any Bernoulli measure) has an equidistributed orbit under the map $xmapsto Dx$ (multiplication mod $mathbb{Z}^{d}$). In the one-dimensional case, this conclusion amounts to normality to base $D$. Thus for example, almost every point in an irrational dilation of the middle-thirds Cantor set is normal to base 3.
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It is known that the heuristic principle, referred to as the multifractal formalism, need not hold for self-similar measures with overlap, such as the $3$-fold convolution of the Cantor measure and certain Bernoulli convolutions. In this paper we study an important function in the multifractal theory, the $L^{q}$-spectrum, $tau (q)$, for measures of finite type, a class of self-similar measures that includes these examples. Corresponding to each measure, we introduce finitely many variants on the $% L^{q}$-spectrum which arise naturally from the finite type structure and are often easier to understand than $tau $. We show that $tau$ is always bounded by the minimum of these variants and is equal to the minimum variant for $qgeq 0$. This particular variant coincides with the $L^{q}$-spectrum of the measure $mu$ restricted to appropriate subsets of its support. If the IFS satisfies particular structural properties, which do hold for the above examples, then $tau$ is shown to be the minimum of these variants for all $q$. Under certain assumptions on the local dimensions of $mu$, we prove that the minimum variant for $q ll 0$ coincides with the straight line having slope equal to the maximum local dimension of $mu $. Again, this is the case with the examples above. More generally, bounds are given for $tau$ and its variants in terms of notions closely related to the local dimensions of $mu $.
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