English

Bounds on Scott Ranks of Some Polish Metric Spaces

Logic 2019-06-12 v1

Abstract

If N\mathcal{N} is a proper Polish metric space and M\mathcal{M} is any countable dense submetric space of N\mathcal{N}, then the Scott rank of N\mathcal{N} in the natural first order language of metric spaces is countable and in fact at most ω1M+1\omega_1^{\mathcal{M}} + 1, where ω1M\omega_1^{\mathcal{M}} is the Church-Kleene ordinal of M\mathcal{M} (construed as a subset of ω\omega) which is the least ordinal with no presentation on ω\omega computable from M\mathcal{M}. If N\mathcal{N} is a rigid Polish metric space and M\mathcal{M} is any countable dense submetric space, then the Scott rank of N\mathcal{N} is countable and in fact less than ω1M\omega_1^{\mathcal{M}}.

Keywords

Cite

@article{arxiv.1906.04351,
  title  = {Bounds on Scott Ranks of Some Polish Metric Spaces},
  author = {William Chan},
  journal= {arXiv preprint arXiv:1906.04351},
  year   = {2019}
}