Abstract
Adendroid is an arcwise connected hereditarily unicoherent continuum. Ashore set in a dendroidX is a subsetA ofX such that, for each ε>0, there exists a subdendroidB ofX such that the Hausdorff distance fromB toX is less then ε andB∩A=θ.
Answering a question by I. Puga, in this paper we prove that the finite union of pairwise disjoint shore subdendroids of a dendroidX is a shore set. We also show that the hypothesis that the shore subdendroids are disjoint is necessary. It is still unknown if the union of two closed disjoint shore subsets of a dendroidX is also shore set.
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Illanes, A. Finite unions of shore sets. Rend. Circ. Mat. Palermo 50, 483–498 (2001). https://doi.org/10.1007/BF02844427
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DOI: https://doi.org/10.1007/BF02844427