English

Kuratowski monoids of $n$-topological spaces

General Topology 2021-11-01 v4 Combinatorics Rings and Algebras

Abstract

Generalizing the famous 14-set closure-complement Theorem of Kuratowski from 1922, we prove that for a set XX endowed with nn pairwise comparable topologies τ1τn\tau_1\subset\dots\subset\tau_n, by repeated application of the operations of complement and closure in the topologies τ1,,τn\tau_1,\dots,\tau_n to a subset AXA\subset X we can obtains at most 2K(n)=2i,j=0n(i+ji)(i+jj)2K(n)=2\sum_{i,j=0}^n\binom{i+j}{i}\binom{i+j}{j} distinct sets.

Keywords

Cite

@article{arxiv.1508.07703,
  title  = {Kuratowski monoids of $n$-topological spaces},
  author = {T. Banakh and O. Chervak and T. Martynyuk and M. Pylypovych and A. Ravsky and M. Simkiv},
  journal= {arXiv preprint arXiv:1508.07703},
  year   = {2021}
}

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20 pages