3 papers
math.LO2026
On the complexity of extensions of non-archimedean Polish groups admitting a compatible complete left-invariant metric
Longyun Ding, Xu Wang
In this article, motivated by a problem asked by Allison and Panagiotopoulos, we study a problem concerning the complexity of group extensions within a hierarchy (denoted by -C…
math.LO2026
Complete orbit equivalence relation and non-universal Polish groups
Longyun Ding, Ruiwen Li, Bo Peng
We show that a non-universal Polish group can induce a complete orbit equivalence relation, which answers a question of Sabok from \cite{OPENPROBLEMS}.
math.LO2024
On equivalence relations induced by Polish groups
Longyun Ding, Yang Zheng
The motivation of this article is to introduce a kind of orbit equivalence relations which can well describe structures and properties of Polish groups from the perspective of Bore…