Diophantine approximation and Cantor sets

We provide an explicit construction of elements of the middle third Cantor set with any prescribed irrationality exponent. This answers a question posed by Kurt Mahler.     

Forbidden symmetries, Cantor sets and hypothetical graphite

Eight and twelve fold symmetries are discussed in connection with quasi-crystals and multiplicative multifractal-like n-dimensional Cantor sets.     

IFS attractors and Cantor sets

We build a metric space which is homeomorphic to a Cantor set but cannot be realized as the attractor of an iterated function system. We give also an example of a Cantor set K in R³ such that every homeomorphism f of R³ which preserves K coincides with the identity on K.     

Liouville numbers, Rajchman measures, and small Cantor sets

We show that the set of Liouville numbers carries a positive measure whose Fourier transform vanishes at infinity. The proof is based on a new construction of a Cantor set of Hausdorff dimension zero supporting such a measure.

     

On Cantor sets and doubling measures

For a large class of Cantor sets on the real-line, we find sufficient and necessary conditions implying that a set has positive (resp. null) measure for all doubling measures of the real-line. We also discuss same type of questions for atomic doubling measures defined on certain midpoint Cantor sets.     

Ultrametric Cantor sets and growth of measure

A class of ultrametric Cantor sets (C, d _u ) introduced recently (S. Raut and D. P. Datta, Fractals 17, 45–52 (2009)) is shown to enjoy some novel properties. The ultrametric d _u is defined using the concept of relative infinitesimals and an inversion rule. The associated (infinitesimal) valuation which turns out to be both scale and reparametrization invariant, is identified with the Cantor function associated with a Cantor set $ \tilde C $ \tilde C , where the relative infinitesimals are supposed to live in. These ultrametrics are both metrically as well as topologically inequivalent compared to the topology induced by the usual metric. Every point of the original Cantor set C is identified with the closure of the set of gaps of $ \tilde C $ \tilde C . The increments on such an ultrametric space is accomplished by following the inversion rule. As a consequence, Cantor functions are reinterpreted as locally constant functions on these extended ultrametric spaces. An interesting phenomenon, called growth of measure, is studied on such an ultrametric space. Using the reparametrization invariance of the valuation it is shown how the scale factors of a Lebesgue measure zero Cantor set might get deformed leading to a deformed Cantor set with a positive measure. The definition of a new valuated exponent is introduced which is shown to yield the fatness exponent in the case of a positive measure (fat) Cantor set. However, the valuated exponent can also be used to distinguish Cantor sets with identical Hausdorff dimension and thickness. A class of Cantor sets with Hausdorff dimension log₃ 2 and thickness 1 are constructed explicitly.     

Affine embeddings and intersections of Cantor sets

Let E,F⊂R^d$E,F\subset {\mathbb{R}}^d$ be two self-similar sets. Under mild conditions, we show that F   can be C¹$C^1$-embedded into E if and only if it can be affinely embedded into E; furthermore if F cannot be affinely embedded into E  , then the Hausdorff dimension of the intersection E∩f(F)$E\cap f(F)$ is strictly less than that of F   for any C¹$C^1$-diffeomorphism f   on R^d${\mathbb{R}}^d$. Under certain circumstances, we prove the logarithmic commensurability between the contraction ratios of E and F if F can be affinely embedded into E  . As an application, we show that _dimH?E∩f(F)<min?{_dimH?E,_dimH?F}${\dim }_H?E\cap f(F)<\min ?\{{\dim }_H?E,{\dim }_H?F\}$ when E is any Cantor-p set and F any Cantor-q   set, where p,q?2$p,q?2$ are two integers with log?p/log?q∉Q$\log ?p/\log ?q\notin \mathbb{Q}$. This is related to a conjecture of Furstenberg about the intersections of Cantor sets.     

广义Cantor集的自相似性

本文考虑一类广义Cantor集Γ_(β,の)={∞∑n=1dnβn:dn∈Dn,n≥1}的自相似性,其中0β1且对任意的n≥1,D_n为整数集Z的非空有限子集;并且给出Γ_(β,の)为齐次生成自相似集的充分必要条件.作为应用,本文考虑一类广义Cantor集交的自相似性,部分推广了Li,Yao和Zhang(2011)关于自相似性的结果.     

Hausdorff dimension of Cantor sets and polynomial hulls

We give examples of Cantor sets in of Hausdorff dimension 1 whose polynomial hulls have non-empty interior.

     

Multiplicatively badly approximable numbers and generalised Cantor sets

Let p be a prime number. The p-adic case of the Mixed Littlewood Conjecture states that for all α∈R. We show that with the additional factor of the statement is false. Indeed, our main result implies that the set of α for which is of full dimension. The result is obtained as an application of a general framework for Cantor sets developed in this paper.     

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.     

On the geometry of random Cantor sets and fractal percolation

Random Cantor sets are constructions which generalize the classical Cantor set, middle third deletion being replaced by a random substitution in an arbitrary number of dimensions. Two results are presented here. (a) We establish a necessary and sufficient condition for the projection of ad-dimensional random Cantor set in [0,1]^d onto ane-dimensional coordinate subspace to contain ane-dimensional ball with positive probability. The same condition applies to the event that the projection is the entiree-dimensional unit cube [0,1] ^e . This answers a question of Dekking and Meester,⁽⁹⁾ (b) The special case of fractal percolation arises when the substitution is as follows: The cube [0,1] ^d is divided intoM ^d subcubes of side-lengthM ^–, and each such cube is retained with probabilityp independently of all other subcubes. We show that the critical valuep _c(M, d) ofp, marking the existence of crossings of [0,1] ^d contained in the limit set, satisfiesp _c(M, d)p _c(d) asM, wherep _c(d) is the critical probability of site percolation on a latticeL ^d obtained by adding certain edges to the hypercubic lattice ^d . This result generalizes in an unexpected way a finding of Chayes and Chayes,⁽⁴⁾ who studied the special case whend=2.     

Superbranching processes and projections of random Cantor sets

We study sequences (X ₀, X ₁, ...) of random variables, taking values in the positive integers, which grow faster than branching processes in the sense that , for m, n0, where the X _n (m, i) are distributed as X _n and have certain properties of independence. We prove that, under appropriate conditions, X _n ^1/n almost surely and in L ¹, where =sup E(X _n )^1/n . Our principal application of this result is to study the Lebesgue measure and (Hausdorff) dimension of certain projections of sets in a class of random Cantor sets, being those obtained by repeated random subdivisions of the M-adic subcubes of [0, 1] ^d . We establish a necessary and sufficient condition for the Lebesgue measure of a projection of such a random set to be non-zero, and determine the box dimension of this projection.Work done partly whilst visiting Cornell University with the aid of a Fulbright travel grant     

Doubling measures on Cantor sets and their extensions

We study the doubling property of binomial measures on the middle interval Cantor set. We obtain a necessary and sufficient condition that enables a binomial measure to be doubling. Then we determine those doubling binomial measures which can be extended to be doubling on [0,1]. Finally, we construct a compact set X in [0,1] and a doubling measure μ on X, such that [`(F)]_X=X\overline{F}_{X}=X and m|_EX{\mu|}_{E_{X}} is doubling on E _X , where E _X is the set of accumulation points of X and F _X is the set of isolated points of X.     

Sum of Cantor sets: Self-similarity and measure

In this note it is shown that the sum of two homogeneous Cantor sets is often a uniformly contracting self-similar set and it is given a sufficient condition for such a set to be of Lebesgue measure zero (in fact, of Hausdorff dimension less than one and positive Hausdorff measure at this dimension).

     

Cantor sets and numbers with restricted partial quotients

For let be a Cantor set constructed from the interval , and let . We derive conditions under which

When these conditions do not hold, we derive a lower bound for the Hausdorff dimension of the above sum and product. We use these results to make corresponding statements about the sum and product of sets , where is a set of positive integers and is the set of real numbers such that all partial quotients of , except possibly the first, are members of .

     

About C 1-minimality of the hyperbolic Cantor sets

In this work we prove that a C ^1+α -hyperbolic Cantor set contained in S ¹ that is close to an affine Cantor set is not C ¹-minimal.     

The Hausdorff Centred measure of the symmetry Cantor sets

Let 0＜λ≤1/3,K (λ) be the attractor of an iterated function system { ψ1,ψ2 } on the line, where ψ1 (x ) =λx, ψ2(x)=1-λ+λx, x∈ [0,1]. We call K (λ) the symmetry Cantor sets. In this paper, we obtained the exact Hausdorff Centred measure of K (λ).