Quasisymmetrically minimal uniform Cantor sets

The uniform Cantor set E(n,c) of Hausdorff dimension 1, defined by a bounded sequence n of positive integers and a gap sequence c, is shown to be minimal for 1-dimensional quasisymmetric maps.     

Self-similar structure on intersections of triadic Cantor sets

Let C be the triadic Cantor set. We characterize the all real number α such that the intersection C∩(C+α) is a self-similar set, and investigate the form and structure of the all iterated function systems which generate the self-similar set.     

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).

     

华林问题及其变种

1770年,法国数学家拉格朗日(J.-L.Lagrange)证明了著名的4平方数定理,即定理(拉格朗日)任何正整数均能表成4个整数的平方和.但从古希腊最后一位数论学家丢番图(Diophantus,活跃于公元250年前后)的著作《算术》所举的例子来看,丢番图很可能已经知道这个结论了.而正式提出这个定理(猜想)的是法国数学家、诗人巴切特(C.Bachet,1581-1638),他也是《算术》拉丁文版(1621)的译者.     

Hausdorff dimension of perturbed Cantor sets without some boundedness condition

A perturbed Cantor set (without the uniform boundedness condition away from zero of contraction ratios) whose upper Cantor dimension and lower Cantor dimension coincide has its Hausdorff dimension of the same value of Cantor dimensions. We will show this using an energy theory instead of Frostman's density lemma which was used for the case of the perturbed Cantor set with the uniform boundedness condition. At the end, we will give a nontrivial example of such a perturbed Cantor set. This revised version was published online in August 2006 with corrections to the Cover Date.     

Intersections of homogeneous Cantor sets with their translations

We pursue the study on homogeneous Cantor sets with their translations. We get the fractal structure of intersection I（t）, and find that the Hausdorff measure of these sets forms a discrete spectrum whose non-zero values come only from shifting numbers with the coding of t. Concretely, a very brief calculation formula of the measure with the coding of t is given.     

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.

     

四分Cantor测度的谱性质

自仿测度μM,D谱性质的研究始于四分Cantor测度μ4(即M=4,D={0,2}的情形).在长期从事谱集研究的基础上,Jorgensen和Pedersen在1998年首次发现μ4是一个具有谱性质的分形测度,其谱Λ(M,S)与和谐对(M~(-1)D,S)密切相关,其中S={0,1}.近年来的研究表明,对于某些奇数l,数乘集合lΛ(M,S)也是测度μ4的谱.这使得测度μ4的一些谱具有较强的稀疏性.本文重点对具有上述性质的奇数l进行讨论.利用数论中同余关系和有限群中元素的阶的性质,得到当l分别为素数、素数幂和素数乘积时,lΛ(M,S)为谱的判别依据,改进推广Dutkay等人的工作.     

Rigidity for rational maps with Cantor Julia sets

In this paper, we prove that two rational maps with the Cantor Julia sets are quasicon- formally conjugate if they are topologically conjugate.     

Cantor集的性质及应用

Cantor集是实函数论中一类重要的集合.本文从定义、性质及应用三方面研究了Cantor集.目的是帮助初学者对Cantor集有一个较全面的认识.     

Random intersections of thick Cantor sets

Let , be Cantor sets embedded in the real line, and let , be their respective thicknesses. If , then it is well known that the difference set is a disjoint union of closed intervals. B. Williams showed that for some , it may be that is as small as a single point. However, the author previously showed that generically, the other extreme is true; contains a Cantor set for all in a generic subset of . This paper shows that small intersections of thick Cantor sets are also rare in the sense of Lebesgue measure; if , then contains a Cantor set for almost all in .

     

Projections of random Cantor sets

Recently Dekking and Grimmett have used the theories of branching processes in a random environment and of superbranching processes to find the almostsure box-counting dimension of certain orthogonal projections of random Cantor sets. This note gives a rather shorter and more direct calculation, and also shows that the Hausdorff dimension is almost surely equal to the box-counting dimension. We restrict attention to one-dimensional projections of a plane set—there is no difficulty in extending the proof to higher-dimensional cases.     

Dimension functions of Cantor sets

We estimate the packing measure of Cantor sets associated to non-increasing sequences through their decay. This result, dual to one obtained by Besicovitch and Taylor, allows us to characterize the dimension functions recently found by Cabrelli et al for these sets.

     

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.     

Sharp Lipschitz constant of bi-Lipschitz automorphism on Cantor set

Suppose C _r = (r C _r ) ∪ (r C _r + 1 − r) is a self-similar set with r ∈ (0, 1/2), and Aut(C _r ) is the set of all bi-Lipschitz automorphisms on C _r . This paper proves that there exists f* ∈ Aut(C _r ) such that

Fatness and thinness of uniform Cantor sets for doubling measures

Let E = E({nk},{ck}) be a fat uniform Cantor set. We prove that E is a minimally fat set for doubling measures if and only if (nkck)p = ∞ for all p < 1 and that E is a fairly fat set for doubling measures if and only if there are constants 0 < p < q < 1 such that (nkck)q < ∞ and (nkck)p = ∞. The classes of minimally thin uniform Cantor sets and of fairly thin uniform Cantor sets are also characterized.     

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.

     

Embeddings of self-similar ultrametric Cantor sets

We study self-similar ultrametric Cantor sets arising from stationary Bratteli diagrams. We prove that such a Cantor set C is bi-Lipschitz embeddable in R[Hdim(C)]+1, where [Hdim(C)] denotes the integer part of its Hausdorff dimension. We compute this Hausdorff dimension explicitly and show that it is the abscissa of convergence of a zeta-function associated with a natural sequence of refining coverings of C (given by the Bratteli diagram). As a corollary we prove that the transversal of a (primitive) substitution tiling of Rd is bi-Lipschitz embeddable in Rd+1.We also show that C is bi-Hölder embeddable in the real line. The image of C in R turns out to be the ω-spectrum (the limit points of the set of eigenvalues) of a Laplacian on C introduced by Pearson-Bellissard via noncommutative geometry.     

Good measures on Cantor space

While there is, up to homeomorphism, only one Cantor space, i.e. one zero-dimensional, perfect, compact, nonempty metric space, there are many measures on Cantor space which are not topologically equivalent. The clopen values set for a full, nonatomic measure is the countable dense subset is clopen of the unit interval. It is a topological invariant for the measure. For the class of good measures it is a complete invariant. A full, nonatomic measure is good if whenever are clopen sets with , there exists a clopen subset of such that . These measures have interesting dynamical properties. They are exactly the measures which arise from uniquely ergodic minimal systems on Cantor space. For some of them there is a unique generic measure-preserving homeomorphism. That is, within the Polish group of such homeomorphisms there is a dense, conjugacy class.