English

Tychonoff Expansions with Prescribed Resolvability Properties

General Topology 2023-11-21 v1

Abstract

The recent literature offers examples, specific and hand-crafted, of Tychonoff spaces (in ZFC) which respond negatively to these questions, due respectively to Ceder and Pearson (1967) and to Comfort and Garc\'ia-Ferreira (2001): (1) Is every ω\omega-resolvable space maximally resolvable? (2) Is every maximally resolvable space extraresolvable? Now using the method of KID{\mathcal{KID}} expansion, the authors show that {\it every} suitably restricted Tychonoff topological space (X,\sT)(X,\sT) admits a larger Tychonoff topology (that is, an "expansion") witnessing such failure. Specifically the authors show in ZFC that if (X,\sT)(X,\sT) is a maximally resolvable Tychonoff space with S(X,\sT)Δ(X,\sT)=κS(X,\sT)\leq\Delta(X,\sT)=\kappa, then (X,\sT)(X,\sT) has Tychonoff expansions \sU=\sUi\sU=\sU_i (1i51\leq i\leq5), with Δ(X,\sUi)=Δ(X,\sT)\Delta(X,\sU_i)=\Delta(X,\sT) and S(X,\sUi)Δ(X,\sUi)S(X,\sU_i)\leq\Delta(X,\sU_i), such that (X,\sUi)(X,\sU_i) is: (i=1i=1) ω\omega-resolvable but not maximally resolvable; (i=2i=2) [if κ\kappa' is regular, with S(X,\sT)κκS(X,\sT)\leq\kappa'\leq\kappa] τ\tau-resolvable for all τ<κ\tau<\kappa', but not κ\kappa'-resolvable; (i=3i=3) maximally resolvable, but not extraresolvable; (i=4i=4) extraresolvable, but not maximally resolvable; (i=5i=5) maximally resolvable and extraresolvable, but not strongly extraresolvable.

Keywords

Cite

@article{arxiv.0910.0439,
  title  = {Tychonoff Expansions with Prescribed Resolvability Properties},
  author = {W. W. Comfort and Wanjun Hu},
  journal= {arXiv preprint arXiv:0910.0439},
  year   = {2023}
}

Comments

25 pages, 0 figures

R2 v1 2026-06-21T13:53:31.480Z