English

Locales as spaces in outer models

Logic 2024-11-12 v1

Abstract

Let M be a transitive model of set theory and X be a space in the sense of M. Is there a reasonable way to interpret X as a space in V? A general theory due to Zapletal provides a natural candidate which behaves well on sufficiently complete spaces (for instance \v{C}ech complete spaces) but behaves poorly on more general spaces - for instance, the Zapletal interpretation does not commute with products. We extend Zapletal's framework to instead interpret locales, a generalization of topological spaces which focuses on the structure of open sets. Our extension has a number of desirable properties; for instance, localic products always interpret as spatial products. We show that a number of localic notions coincide exactly with properties of their interpretations; for instance, we show a locale is TUT_U if and only if all its interpretations are T1T_1, a locale is II-Hausdorff if and only if all its interpretations are T2T_2, a locale is regular if and only if all its interpretations are T3T_3, and a locale is compact if and only if all its interpretations are compact.

Keywords

Cite

@article{arxiv.2411.05967,
  title  = {Locales as spaces in outer models},
  author = {Nathaniel Bannister},
  journal= {arXiv preprint arXiv:2411.05967},
  year   = {2024}
}
R2 v1 2026-06-28T19:53:50.380Z