Degree spectra of homeomorphism types of Polish spaces


Abstract in English

A Polish space is not always homeomorphic to a computably presented Polish space. In this article, we examine degrees of non-computability of presenting homeomorphic copies of Polish spaces. We show that there exists a $0$-computable low$_3$ Polish space which is not homeomorphic to a computable one, and that, for any natural number $n$, there exists a Polish space $X_n$ such that exactly the high$_{2n+3}$-degrees are required to present the homeomorphism type of $X_n$. We also show that no compact Polish space has an easiest presentation with respect to Turing reducibility.

Download