English

Limit points of subsequences

General Topology 2019-06-13 v2 Functional Analysis Probability

Abstract

Let xx be a sequence taking values in a separable metric space and I\mathcal{I} be a generalized density ideal or an FσF_\sigma-ideal on the positive integers (in particular, I\mathcal{I} can be any Erd{\H o}s--Ulam ideal or any summable ideal). It is shown that the collection of subsequences of xx which preserve the set of I\mathcal{I}-cluster points of xx [respectively, I\mathcal{I}-limit points] is of second category if and only if the set of I\mathcal{I}-cluster points of xx [resp., I\mathcal{I}-limit points] coincides with the set of ordinary limit points of xx; moreover, in this case, it is comeager. In particular, it follows that the collection of subsequences of xx which preserve the set of ordinary limit points of xx is comeager.

Keywords

Cite

@article{arxiv.1801.00343,
  title  = {Limit points of subsequences},
  author = {Paolo Leonetti},
  journal= {arXiv preprint arXiv:1801.00343},
  year   = {2019}
}

Comments

To appear in Topology Appl. arXiv admin note: substantial text overlap with arXiv:1711.04265

R2 v1 2026-06-22T23:33:28.233Z