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Interior of sums of planar sets and curves
Published online by Cambridge University Press: 05 September 2018
Abstract
Recently, considerable attention has been given to the study of the arithmetic sum of two planar sets. We focus on understanding the interior (A + Γ)°, when Γ is a piecewise ${\mathcal C}^2$ curve and A ⊂ ℝ2. To begin, we give an example of a very large (full-measure, dense, Gδ) set A such that (A + S1)° = ∅, where S1 denotes the unit circle. This suggests that merely the size of A does not guarantee that (A + S1)° ≠ ∅. If, however, we assume that A is a kind of generalised product of two reasonably large sets, then (A + Γ)° ≠ ∅ whenever Γ has non-vanishing curvature. As a byproduct of our method, we prove that the pinned distance set of C := Cγ × Cγ, γ ⩾ 1/3, pinned at any point of C has non-empty interior, where Cγ (see (1.1)) is the middle 1 − 2γ Cantor set (including the usual middle-third Cantor set, C1/3). Our proof for the middle-third Cantor set requires a separate method. We also prove that C + S1 has non-empty interior.
- Type
- Research Article
- Information
- Mathematical Proceedings of the Cambridge Philosophical Society , Volume 168 , Issue 1 , January 2020 , pp. 119 - 148
- Copyright
- Copyright © Cambridge Philosophical Society 2018
Footnotes
† This work came out of a collaboration that started at ICERM at Brown University, Rhode Island. This research was supported by the Mathematics Research Institute of the Ohio State University.
Partially supported by the grant OTKA 123782, by MTA-BME Stochastics Research Group and by ICERM, by supporting his participation on one of their a semester programs in 2016.
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