Some remarks about Cantor sets

Exact Hausdorff and Packing measure of certain Cantor sets, not necessarily self-similar or homogeneous

We compute the exact Hausdorff and Packing measures of linear Cantor sets which might not be self similar or homogeneous . The calculation is based on the local behavior of the natural probability measure supported on the sets.

Classifying Cantor Sets by their Fractal Dimensions

In this article we study Cantor sets defined by monotone sequences, in the sense of Besicovitch and Taylor. We classify these Cantor sets in terms of their h-Hausdorff and h-Packing measures, for the family of dimension functions h, and characterize this classification in terms of the underlying sequences.

Some toy Furstenberg sets and projections of the four-corner Cantor set

We give lower bounds for the Hausdorff dimensions of some model Furstenberg sets.

特殊仿射康托集的代数差特征化

Characterization of the algebraic difference of special affine Cantor sets

本文研究了由参数l,r,p∈N生成的自相似康托集S-康托集，分析了其代数差的结构特征，揭示了其可能为区间、康托集、L-康托瓦尔、R-康托瓦尔或M-康托瓦尔等形式。

Packing and Hausdorff measures of Cantor sets associated with series

We study a generalization of Morán's sum sets, obtaining information about the $h$-Hausdorff and $h$-packing measures of these sets and certain of their subsets.

Almost-nowhere intersection of Cantor sets, and sufficient sampling of their cumulative distribution functions

Cantor sets are constructed from iteratively removing sections of intervals. This process yields a cumulative distribution function (CDF), constructed from the invariant measure associated with their iterated function systems. Under appropriate assumptions, we identify sampling schemes of such CDFs, meaning that the underlying Cantor set can be reconstructed from sufficiently many samples of its CDF. To this end, we prove that two Cantor sets have almost-nowhere (with respect to their respective invariant measures) intersection.

Distribution of random Cantor sets on Tubes

We show that there exist $(d-1)$ - Ahlfors regular compact sets $E \subset \mathbb{R}^{d}, d\geq 2$ such that for any $t< d-1$, we have \[ \sup_T \frac{\mathcal{H}^{d-1}(E\cap T)}{w(T)^t}<\infty \] where the supremum is over all tubes $T$ with width $w(T) >0$. This settles a question of T. Orponen. The sets we construct are random Cantor sets, and the method combines geometric and probabilistic estimates on the intersections of these random Cantor sets with affine subspaces.

Excursions on Cantor-like Sets

The ternary Cantor set $C$, constructed by George Cantor in 1883, is probably the best known example of a perfect nowhere-dense set in the real line, but as we will see later, it is not the only one. The present article we will explore the richness, the peculiarities and the generalities that has $C$ and explore some variants and generalizations of it. For a more systematic treatment the Cantor like sets we refer to our previous paper.

Sets of full measure avoiding Cantor sets

In relation to the Erd\H os similarity problem (show that for any infinite set $A$ of real numbers there exists a set of positive Lebesgue measure which contains no affine copy of $A$) we give some new examples of infinite sets which are not universal in measure, i.e. they satisfy the above conjecture. These are symmetric Cantor sets $C$ which can be quite thin: the length of the $n$-th generation intervals defining the Cantor set is decreasing almost doubly exponentially. Further, we achieve to construct a set, not just of positive measure, but of \textit{full measure} not containing any affi…

$L^2$-norm and estimates from below for Riesz transforms on Cantor sets

The aim of this paper is to estimate the $L^2$-norms of vector-valued Riesz transforms $R_ν^s$ and the norms of Riesz operators on Cantor sets in $\R^d$, as well as to study the distribution of values of $R_ν^s$. Namely, we show that this distribution is "uniform" in the following sense. The values of $|R_ν^s|^2$ which are comparable with its average value are attended on a "big" portion of a Cantor set. We apply these results to give examples demonstrating the sharpness of our previous estimates for the set of points where Riesz transform is large, and for the corresponding Riesz capacities. …

厚 Cantor 集乘积中的无限常数间隙长度树

Infinite constant gap length trees in products of thick Cantor sets

本文证明充分厚的 Cantor 集乘积可在平面上生成相邻顶点间距为常数的树，且该距离取值集合具有非空内部，并允许树为可数无限，扩展了分形集中的模式研究。

Visible and Invisible Cantor sets

In this article we study for which Cantor sets there exists a gauge-function h, such that the h-Hausdorff-measure is positive and finite. We show that the collection of sets for which this is true is dense in the set of all compact subsets of a Polish space X. More general, any generic Cantor set satisfies that there exists a translation-invariant measure mu for which the set has positive and finite mu-measure. In contrast, we generalize an example of Davies of dimensionless Cantor sets (i.e. a Cantor set for which any translation invariant measure is either zero or non-sigma-finite, that enab…

厚坎托集的非线性罗思定理

A non-linear Roth theorem for thick Cantor sets

本文提出了一种非线性罗思定理，用于厚坎托集中的三项等差数列存在性证明。

Kakeya-type sets over Cantor sets of directions in $\mathbb{R}^{d+1}$

Given a Cantor-type subset $Ω$ of a smooth curve in $\mathbb R^{d+1}$, we construct examples of sets that contain unit line segments with directions from $Ω$ and exhibit analytical features similar to those of classical Kakeya sets of arbitrarily small $(d+1)$-dimensional Lebesgue measure. The construction is based on probabilistic methods relying on the tree structure of $Ω$, and extends to higher dimensions an analogous planar result of Bateman and Katz. In particular, the existence of such sets implies that the directional maximal operator associated with the direction set $Ω$ is unbounded …

Calderon-Zygmund capacities and Wolff potentials on Cantor sets

We show that, for some Cantor sets in R^d, the capacity g_s associated to the s-dimensional Riesz kernel x/|x|^{s+1} is comparable to the capacity C_{2(d-s)/3,3/2} from non linear potential theory. It is an open problem to show that, when s is positive and non integer, they are comparable for all compact sets in R^d. We also discuss other open questions in the area.

Groups and Cantor sets

It is well known that n x n upper-triangular real matrices with 1's on the diagonal form a nilpotent Lie group with an interesting family of non-isotropic dilations and corresponding geometry, as in [9]. Here we look at p-adic versions of this, and related matters.

全测度普遍性对于康托集

Full measure universality for Cantor Sets

本文研究了康托集的全测度普遍性，证明在特定维度假设下，康托集不是全测度普遍的，并给出了相关结论。

Decoupling and near-optimal restriction estimates for Cantor sets

For any $α\in(0,d)$, we construct Cantor sets in $\mathbb{R}^d$ of Hausdorff dimension $α$ such that the associated natural measure $μ$ obeys the restriction estimate $\| \widehat{f dμ} \|_{p} \leq C_p \| f \|_{L^2(μ)}$ for all $p>2d/α$. This range is optimal except for the endpoint. This extends the earlier work of Chen-Seeger and Shmerkin-Suomala, where a similar result was obtained by different methods for $α=d/k$ with $k\in\mathbb{N}$. Our proof is based on the decoupling techniques of Bourgain-Demeter and a theorem of Bourgain on the existence of $Λ(p)$ sets.

非齐次随机圆盘型康托尔集的Favard长度

Favard length of non-homogeneous random disc-like Cantor sets

本文研究了非齐次随机四角康托尔集的Favard长度衰减，给出了尖锐估计，证明了Mattila下界的尖锐性，并构造了正解析容量但零Favard长度的新例子。

具有中心康托集值域的纯原子有限测度的唯一性刻画

A characterization of uniqueness of purely atomic finite measures with central Cantor set range

该研究刻画了值域为中心康托集的纯原子有限测度的唯一性，推广到对称康托集并对康托尔集值域测度的恢复做初步探讨。

When the algebraic difference of two central Cantor sets is an interval?

Let $C(a ),C(b)\subset \lbrack 0,1]$ be the central Cantor sets generated by sequences $ a,b \in (0,1)^{\mathbb{N}}$. The first main result of the paper gives a necessary and a sufficient condition for sequences $a$ and $b$ which inform when $C(a )-C(b)$ is equal to $[-1,1]$ or is a finite union of closed intervals. One of the corollaries following from this results shows that the product of thicknesses of two central Cantor sets which algebraic difference is an interval may be arbitrarily small. We also show that there are sets $C(a)$ and $C(b)$ with the Hausdorff dimension equal to $0$ such …

Exact Hausdorff Measure of Certain Non-Self-Similar Cantor Sets

We establish a formula yielding the Hausdorff measure for a class of non-self-similar Cantor sets in terms of the canonical covers of the Cantor set.

整数康托集：算术组合性质

Integer Cantor Sets: Arithmetic Combinatorial Properties

本文研究整数康托集的算术组合性质，探讨了交集性质、均匀分布、多项式均值遍历定理及度量对称相关性等核心问题。

On Intersections of Cantor Sets: Hausdorff Measure

We establish formulas for bounds on the Haudorff measure of the intersection of certain Cantor sets with their translates. As a consequence we obtain a formula for the Hausdorff dimensions of these intersections.

Cantor集上某些奇异积分主值的存在性与Hausdorff维数

Existence of principal values of some singular integrals on Cantor sets, and Hausdorff dimension

本文研究了Cantor集上奇异积分主值的存在性，证明了在测度线性密度消失时主值存在点集的Hausdorff维数等于集合维数，并推广至高维Riesz奇异积分，同时引入鞅辅助证明。

The Favard length of product Cantor sets

Nazarov, Peres and Volberg proved recently that the Favard length of the $n$-th iteration of the four-corner Cantor set is bounded from above by $n^{-c}$ for an appropriate $c$. We generalize this result to all product Cantor sets whose projection in some direction has positive 1-dimensional measure.

Hausdorff and harmonic measures on non-homogeneous Cantor sets

We consider (not self-similar) Cantor sets defined by a sequence of piecewise linear functions. We prove that the dimension of the harmonic measure on such a set is strictly smaller than its Hausdorff dimension. Some Hausdorff measure estimates for these sets are also provided.

Subsum Sets: Intervals, Cantor Sets, and Cantorvals

Given a sequence converging to zero, we consider the set of numbers which are sums of (infinite, finite, or empty) subsequences. When the original sequence is not absolutely summable, the subsum set is an unbounded closed interval which includes zero. When it is absolutely summable the subsum set is one of the following: a finite union of (nontrivial) compact intervals, a Cantor set, or a "symmetric Cantorval".

Two Measures on Cantor Sets

We give an example of Cantor type set for which its equilibrium measure and the corresponding Hausdorff measure are mutually absolutely continuous. Also we show that these two measures are regular in Stahl-Totik sense.

Intrinsic Approximation on Cantor-like Sets, a Problem of Mahler

In 1984, Kurt Mahler posed the following fundamental question: How well can irrationals in the Cantor set be approximated by rationals in the Cantor set? Towards development of such a theory, we prove a Dirichlet-type theorem for this intrinsic diophantine approximation on Cantor-like sets, and discuss related possible theorems/conjectures. The resulting approximation function is analogous to that for R^d, but with d being the Hausdorff dimension of the set, and logarithmic dependence on the denominator instead.

Diffusion on middle-$ξ$ Cantor sets

In this paper, we study $C^ζ$-calculus on generalized Cantor sets, which have self-similar properties and fractional dimensions that exceed their topological dimensions. Functions with fractal support are not differentiable or integrable in terms of standard calculus, so we must involve local fractional derivatives. We have generalized the $C^ζ$-calculus on the generalized Cantor sets known as middle-$ξ$ Cantor sets. We have suggested a calculus on the middle-$ξ$ Cantor sets for different values of $ξ$ with $0<ξ<1$. Differential equations on the middle-$ξ$ Cantor sets have been solved, and we …

康托集之和与积中的开区间

Open intervals in sums and products of Cantor sets

本文通过新论证证明足够多个任意中心康托集的和与积可产生大的开区间，并将讨论推广到其 $C^1$ 像，为 Astels 的厚度结果提供新视角，同时处理康托集幂的和与积问题。

On the self similarity of generalized Cantor sets

We consider the self-similar structure of the class of generalized Cantor sets $$Γ_{\mathcal{D}}=\Big\{\sum_{n=1}^\infty d_nβ^{n}: d_n\in D_n, n\ge 1\Big\},$$ where $0<β<1$ and $D_n, n\ge 1,$ are nonempty and finite subsets of $\mathbb{Z}$. We give a necessary and sufficient condition for $Γ_{\mathcal{D}}$ to be a homogeneously generated self similar set. An application to the self-similarity of intersections of generalized Cantor sets will be given.

Recent progress on Favard length estimates for planar Cantor sets

This is an expository paper detailing some of the recent advances on the problem, with emphasis on the number-theoretic method developed in my paper with Bond and Volberg for rational product sets (arXiv:1109.1031).

Cantor sets with absolutely continuous harmonic measure

We construct Ahlfors regular Cantor sets $K$ of small dimension in the plane, such that the Hausdorff measure on $K$ is equivalent to the harmonic measure associated to its complement. In particular the Green function in $R^2 \backslash K$ satisfies $G^p (x) \simeq \mathrm{dist} (x, K)^δ$ whenever $\mathrm{dist} (x, K) \le 1$ and $p$ is far from $K$.

Fourier transform and expanding maps on Cantor sets

We study the Fourier transforms $\widehatμ(ξ)$ of non-atomic Gibbs measures $μ$ for uniformly expanding maps $T$ of bounded distortions on $[0,1]$ or Cantor sets with strong separation. When $T$ is totally non-linear, then $\widehatμ(ξ) \to 0$ at a polynomial rate as $|ξ| \to \infty$.

高维Cantor集I：稳定相交的判据

Cantor sets in higher dimension I: Criterion for stable intersections

本文在高维空间中研究Cantor集的稳定相交判据，并提出构造显式稳定相交Cantor集的方法，适用于Hausdorff维度极小的复杂情形。

On Sums of Nearly Affine Cantor Sets

For a compact set $K\subset \mathbb{R}^1$ and a family $\{C_λ\}_{λ\in J}$ of dynamically defined Cantor sets sufficiently close to affine with $\text{dim}_H\, K+\text{dim}_H\, C_λ>1$ for all $λ\in J$, under natural technical conditions we prove that the sum $K+C_λ$ has positive Lebesgue measure for almost all values of the parameter $λ$. As a corollary, we show that generically the sum of two affine Cantor sets has positive Lebesgue measure provided the sum of their Hausdorff dimensions is greater than one.

Moreira's Theorem on the arithmetic sum of dynamically defined Cantor sets

We present a complete proof of a theorem of C.G. Moreira. Under mild checkable conditions, the theorem asserts that the Hausdorff dimension of the arithmetic sum of two dynamically defined Cantor subsets of the real line, equals either the sum of the dimensions or 1, whichever is smaller.

康托集的描述：集合论综述与开放问题

Descriptions of Cantor Sets: A Set-Theoretic Survey and Open Problems

本文综述了实数上确定性康托集的集合论视角，探讨了四种层次递进的描述方法，并提出开放问题以促进进一步研究。

On Intersections of Cantor Sets: Self-Similarity

Let C be a Cantor set. For a real number t let C+t be the translate of C by t, We say two real numbers s,t are equivalent if the intersection of C and C+s is a translate of the intersection of C and C+t. We consider a class of Cantor sets determined by similarities with one fixed positive contraction ratio. For this class of Cantor set, we show that an "initial segment" of the intersection of C and C+t is a self-similar set with contraction ratios that are powers of the contraction ratio used to describe C as a self- similar set if and only if t is equivalent to a rational number. Our results …

On Sums of Semibounded Cantor Sets

Motivated by questions arising in the study of the spectral theory of models of aperiodic order, we investigate sums of functions of semibounded closed subsets of the real line. We show that under suitable thickness assumptions on the sets and growth assumptions on the functions, the sums of such sets contain half-lines. We also give examples to show our criteria are sharp in suitable regimes.

Cantor sets and cyclicity in weighted Dirichlet spaces

We treat the problem of characterizing the cyclic vectors in the weighted Dirichlet spaces, extending some of our earlier results in the classical Dirichlet space. The absence of a Carleson-type formula for weighted Dirichlet integrals necessitates the introduction of new techniques.

分形不确定性原理对于随机康托集

Fractal uncertainty principle for random Cantor sets

本文研究了随机康托集的分形不确定性原理，通过不同的随机方法构建了维度在(0,2/3)内的随机康托集，并证明了在高概率下该原理成立。

Orthogonal polynomials on Cantor sets of zero Lebesgue measure

In this survey article, we review some results and conjectures related to orthogonal polynomials on Cantor sets. The main purpose of this paper is to emphasize the role of equilibrium measures in order to have a general theory of sufficiently good measures (measures that behave similarly to measures which are in the Szegő class and the isospectral torus in the finite gap case) supported on totally disconnected subsets of $\mathbb{R}$. We present some open problems a number of which can be studied numerically.

Ultrametric Cantor Sets and Growth of Measure

A class of ultrametric Cantor sets $(C, d_{u})$ introduced recently in literature (Raut, S and Datta, D P (2009), Fractals, 17, 45-52) is shown to enjoy some novel properties. The ultrametric $d_{u}$ is defined using the concept of {\em relative infinitesimals} and an {\em inversion} rule. The associated (infinitesimal) valuation which turns out to be both scale and reparametrisation invariant, is identified with the Cantor function associated with a Cantor set $\tilde C$ where the relative infinitesimals are supposed to live in. These ultrametrics are both metrically as well as topologically …

Affine embeddings of Cantor sets and dimension of $αβ$-sets

Let $E, F\subset {\Bbb R}^d$ be two self-similar sets, and suppose that $F$ can be affinely embedded into $E$. Under the assumption that $E$ is dust-like and has a small Hausdorff dimension, we prove the logarithmic commensurability between the contraction ratios of $E$ and $F$. This gives a partial affirmative answer to Conjecture 1.2 in \cite{FHR14}. The proof is based on our study of the box-counting dimension of a class of multi-rotation invariant sets on the unit circle, including the $αβ$-sets initially studied by Engelking and Katznelson.

离散康托集的分形不确定性原理何时最具不确定性？

When is the fractal uncertainty principle for discrete Cantor sets most uncertain?

该研究给出离散康托集分形不确定性原理达到最不确定指数的充要条件，研究分布式谱对并完成循环群中的分类，还探讨了连续情形下的对应情况。

Fractal uncertainty principle for discrete Cantor sets with random alphabets

In this paper, we investigate the fractal uncertainty principle (FUP) for discrete Cantor sets, which are determined by an alphabet from a base of digits. Consider the base of M digits and the alphabets of cardinality A such that all the corresponding Cantor sets have a fixed dimension 0<log A/log M<2/3. We prove that the FUP with an improved exponent over Dyatlov-Jin (arXiv:1608.02238) holds for almost all alphabets, asymptotically as M tends to infinity. Our result provides the best possible exponent when the Cantor sets enjoy either the strongest Fourier decay assumption or strongest additi…

On the arithmetic sums of Cantor sets

Let $C_\la$ and $C_\ga$ be two affine Cantor sets in $\mathbb{R}$ with similarity dimensions $d_\la$ and $d_\ga$, respectively. We define an analog of the Bandt-Graf condition for self-similar systems and use it to give necessary and sufficient conditions for having $\Ha^{d_\la+d_\ga}(C_\la + C_\ga)>0$ where $C_\la + C_\ga$ denotes the arithmetic sum of the sets. We use this result to analyze the orthogonal projection properties of sets of the form $C_\la \times C_\ga$. We prove that for Lebesgue almost all directions $θ$ for which the projection is not one-to-one, the projection has zero $(d_…

Kakeya Sets in Cantor directions

We construct a union of N parallelograms of dimensions approximately 1/N x 1 in the plane, with the slope of their long sides in the standard Cantor set. The union has area 1/log N but the union of the doubles has area log log N/ log N. In particular, this implies unbounded of the associated maximal operator in L^p for any p different from infinity. The construction is by randomizing an earlier construction of the second author for the L^2 case. The proof that the construction satisfies the desired conditions is by elementary estimates in the theory of percolation on trees as developed by R. L…

离散二维Cantor集的分形不确定性

Fractal uncertainty for discrete 2D Cantor sets

本文证明了离散二维Cantor集具有分形不确定性原理当且仅当其不含正交直线，关键运用了Lang猜想的定量形式，回答了Dyatlov的问题并应用于开放量子映射。

随机平面圆盘状 Cantor 集的 Buffon 投针问题

The Buffon's needle problem for random planar disk-like Cantor sets

本文研究了有限正1-Hausdorff测度自相似Cantor集的第三种随机模型，证明了Buffon针落在其δ-邻域的概率衰减率为c/log(1/δ)，印证了任何合理的正有限长度随机Cantor集均具有该衰减阶的直觉。

二维Cantor集II：稳定交集的最优维度约束

Cantor sets in higher dimensions II: Optimal dimension constraint for stable intersections

本文证明了对于正则Cantor集，上盒维数之和小于d时可被小变形分离，且此约束是最佳的。通过构造具有任意小厚度的正则Cantor集对，展示了C^{1+α}稳定交集的条件。