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Partial Orders of Bijectively Related or Homeomorphic Topologies

General Topology 2024-12-12 v1

Abstract

Topologies τ,σTopX\tau , \sigma \in \mathop{{\mathrm{Top}}}\nolimits _X are bijectively related, in notation τσ\tau \sim \sigma, if there are continuous bijections f:(X,τ)(X,σ)f: (X, \tau )\rightarrow (X, \sigma ) and g:(X,σ)(X,τ)g: (X, \sigma)\rightarrow (X, \tau). Defining [τ]={σTopX:στ}[\tau ]_{\cong}=\{ \sigma \in \mathop{{\mathrm{Top}}}\nolimits _X : \sigma \cong \tau\} and [τ]={σTopX:στ}[\tau ]_{\sim }=\{ \sigma \in \mathop{{\mathrm{Top}}}\nolimits _X : \sigma \sim \tau\} we show that for each infinite 1-homogeneous linear order L{\mathbb L} there is a topology τTopL\tau \in \mathop{{\mathrm{Top}}}\nolimits _{|L|} such that: (a) [τ],˙2LL\langle [\tau ]_{\cong}, \subset \rangle \cong \dot{\bigcup}_{2^{|L|}}{\mathbb L} (the disjoint union of 2L2^{|L|}-many copies of L{\mathbb L}); so, each maximal chain in [τ][\tau ]_{\cong} is isomorphic to L{\mathbb L}; (b) [τ],˙2LL~\langle [\tau ]_{\sim}, \subset \rangle\cong \dot{\bigcup}_{2^{|L|}}\widetilde{{\mathbb L}}, where L~\widetilde{{\mathbb L}} is the Dedekind completion of L{\mathbb L}; thus, each maximal chain in [τ][\tau ]_{\sim} is isomorphic to L~\widetilde{{\mathbb L}}. If, in addition, the linear order L{\mathbb L} is Dedekind complete, then the topology τ\tau is weakly reversible, non-reversible and [τ],=[τ],˙2LL\langle [\tau ]_{\sim}, \subset \rangle=\langle [\tau ]_{\cong}, \subset \rangle\cong \dot{\bigcup}_{2^{|L|}}{\mathbb L}.

Keywords

Cite

@article{arxiv.2412.08319,
  title  = {Partial Orders of Bijectively Related or Homeomorphic Topologies},
  author = {Aleksandar Janjoš and Miloš S. Kurilić},
  journal= {arXiv preprint arXiv:2412.08319},
  year   = {2024}
}

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15 pages