Journal of Pure and Applied Algebra ( IF 0.7 ) Pub Date : 2021-02-15 , DOI: 10.1016/j.jpaa.2021.106712 Paul Gartside
For a Tychonoff space X the free Abelian topological group over X, denoted , is the free Abelian group on the set X with the coarsest topology so that for any continuous map of X into an Abelian topological group its canonical extension to a homomorphism on is continuous.
We show there is a family of maximal size, , consisting of separable metrizable spaces, such that if M and N are distinct members of then and are not topologically isomorphic (moreover, neither embeds topologically in nor is an open image of ). We show there is a chain , of maximal size, of separable metrizable spaces such that if then embeds as a closed subgroup of but no subspace of is homeomorphic to .
We show that the character (minimal size of a local base at 0) of is (minimal size of a cofinal set in ) for every non-discrete, analytic M, but consistently there is a co-analytic M such that the character of is strictly above .
The main tool used for these results is the Tukey order on the neighborhood filter at 0 in an , and a connection with the family of compact subsets of an auxiliary space.
中文翻译:
Tukey阶和自由阿贝尔拓扑群的多样性
对于吉洪诺夫空间X的游离阿贝尔拓扑群超过X,表示为,是集合X上具有最粗糙拓扑的自由Abelian群,因此对于X到Abelian拓扑群的任何连续映射,其正规扩展为 是连续的。
我们证明有一个家庭 最大尺寸 ,由可分离的可量化空间组成,因此,如果M和N是 然后 和 不是拓扑同构的(此外, 都没有拓扑嵌入 也不是 )。我们显示有一个链,最大大小,可分离的可量化空间,例如 然后 嵌入为的封闭子组 但没有子空间 是同胚的 。
我们证明了该字符(本地底数的最小大小为0) 是 (在 )对于每个非离散分析M,但始终存在一个协分析M,使得 严格以上 。
这些结果使用的主要工具是在 ,以及与辅助空间的紧凑子集族的连接。