Countable fan-tightness versus countable tightness
Countable fan-tightness versus countable tightness
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发表时间：
1996
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通讯作者：
A. Arhangel'skii;A. Bella
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作者：
A. Arhangel'skii;A. Bella
可数紧性与更强的可数扇紧性概念相比较。特别地，我们证明了在可数紧正则空间中可数紧性等价于可数扇紧性，并且可数扇紧性被伪开紧映射保持。讨论了乘积运算下的可数紧度和可数扇紧度的性质。
Countable tightness is compared to the stronger notion of countable fan-tight\-ness. In particular, we prove that countable tightness is equivalent to countable fan-tightness in countably compact regular spaces, and that countable fan-tightness is preserved by pseudo-open compact mappings. We also discuss the behaviour of countable tightness and of countable fan-tightness under the product operation.