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https://hdl.handle.net/10316/4609
Título: | What is a first countable space? | Autor: | Gutierres, Gonçalo | Palavras-chave: | First countable space; Axiom of Choice | Data: | 2006 | Citação: | Topology and its Applications. 153:18 (2006) 3420-3429 | Resumo: | The definition of first countable space is standard and its meaning is very clear. But is that the case in the absence of the Axiom of Choice? The answer is negative because there are at least three choice-free versions of first countability. And, most likely, the usual definition does not correspond to what we want to be a first countable space. The three definitions as well as other characterizations of first countability are presented and it is discussed under which set-theoretic conditions they remain equivalent. | URI: | https://hdl.handle.net/10316/4609 | DOI: | 10.1016/j.topol.2006.03.003 | Direitos: | openAccess |
Aparece nas coleções: | FCTUC Matemática - Artigos em Revistas Internacionais |
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