کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
4657879 | 1633072 | 2016 | 13 صفحه PDF | دانلود رایگان |

Given a Tychonoff space X , let F(X)F(X) and A(X)A(X) be respectively the free topological group and the free Abelian topological group over X in the sense of Markov. For every n∈Nn∈N, let Fn(X)Fn(X) (resp. An(X)An(X)) denote the subspace of F(X)F(X) (resp. A(X)A(X)) that consists of words of reduced length at most n with respect to the free basis X . In this paper, we discuss two weak forms of countability axioms in F(X)F(X) or A(X)A(X), namely the csf-countability and snf-countability. We provide some characterizations of the csf-countability and snf -countability of F(X)F(X) and A(X)A(X) for various classes of spaces X. In addition, we also study the csf-countability and snf -countability of Fn(X)Fn(X) or An(X)An(X), for n=2,3,4n=2,3,4. Some results of Arhangel'skiı̌ in [1] and Yamada in [20] are generalized. An affirmative answer to an open question posed by Li et al. in [11] is provided.
Journal: Topology and its Applications - Volume 207, 1 July 2016, Pages 96–108