English

NTP2 topological structures

Logic 2026-05-20 v1

Abstract

A subset of a topological space is constructible if it is a finite Boolean combination of closed sets. We prove that every NTP2_2 expansion of (R,<,+)(\mathbb{R},<,+) by constructible sets defines only constructible sets, and that definable functions are generically piecewise continuous. The result also holds for all NTP2_2 expansions of (Qp,+,)(\mathbb{Q}_p,+,\cdot), and all NTP2_2 definably complete expansions of ordered groups. In the latter case, the structure is generically locally o-minimal, has definable choice, and carries a well-behaved notion of naive topological dimension. For NIP uniform topological structures, constructibility of definable sets is preserved in the Shelah expansion. We classify strong expansions of (R,<,+)(\mathbb{R},<,+) by constructible sets, and obtain results on NTP2_2 d-minimal structures.

Keywords

Cite

@article{arxiv.2604.24522,
  title  = {NTP2 topological structures},
  author = {Pablo Andújar Guerrero},
  journal= {arXiv preprint arXiv:2604.24522},
  year   = {2026}
}