Annals of Pure and Applied Logic ( IF 0.8 ) Pub Date : 2020-06-25 , DOI: 10.1016/j.apal.2020.102854 Longyun Ding , Kai Gu
Let be the set of all metrics on ω, and let be the set of all metrics r on ω such that the completion of is compact. We define the Cauchy sequence equivalence relation on as: iff the set of Cauchy sequences in is same as in . We also denote .
We show that is a -complete equivalence relation, while is a equivalence relation. We also show that is Borel bireducible to an orbit equivalence relation. Furthermore, we investigate the Borel reducibility between and some benchmark equivalence relations. For instance, we show that and are Borel reducible to , and is not. Restrictions of on some special invariant subsets of are also considered.
中文翻译:
关于可数度量空间中柯西序列产生的等价关系
让 是ω上所有度量的集合,并令是集合所有指标[R对ω使得完成紧凑。我们定义柯西序列等价关系 上 如: 如果在其中的柯西序列集 与中相同 。我们也表示。
我们证明 是一个 -完全等价关系,而 是一个 等价关系。我们还表明Borel可归约为一个轨道等价关系。此外,我们研究了以及一些基准等效关系。例如,我们表明 和 Borel可还原为 和 不是。的限制 在...的一些特殊不变子集上 也被考虑。