English

Intersections of Cantor sets with hyperbolas and continuous images

Number Theory 2026-01-28 v1

Abstract

Given λ(0,1/2)\lambda\in (0,1/2), let \begin{equation*} C_\lambda=\set{(1-\lambda)\sum_{i=1}^\infty d_i\lambda^{i-1}:d_i\in\set{0,1}} \end{equation*} be the middle Cantor sets with convex hull [0,1][0, 1]. We are interested in the set St={(x,y)Cλ×Cλ:xy=t}S_t=\set{(x,y)\in C_\lambda\times C_\lambda: xy=t}, where t[0,1]t\in[0,1]. Since the cases where t=0t=0 or t=1t=1 are trivial, we assume that t(0,1)t\in(0,1) in what follows. We show that there exists a λ0=0.4302\lambda_0=0.4302 such that for all λ\lambda satisfying λ0λ<1/2\lambda_0 \le \lambda < 1/2, the set StS_t has the cardinality of the continuum for every t(0,1)t \in (0,1). Besides, we further investigate the continuous image of Cλ×CλC_\lambda\times C_\lambda, that is, for any given 2k\nn2\le k\in \nn, we give a sufficient condition for set {xky:x,yCλ}\set{x^ky:x,y\in C_\lambda} to be the interval [0,1][0,1]. Our observations reveal that the behavior exhibited by the image of the function fk(x,y)=xkyf_k(x,y)=x^ky is complex and depends on the parameters kk and λ\lambda.

Cite

@article{arxiv.2601.19242,
  title  = {Intersections of Cantor sets with hyperbolas and continuous images},
  author = {Yi Cai and Xiu Chen and Lipeng Wang},
  journal= {arXiv preprint arXiv:2601.19242},
  year   = {2026}
}
R2 v1 2026-07-01T09:21:43.243Z