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Munkres introduce the $T_1$ separation axiom and proves the following theorem:

Let $A \subset X$ where $X$ is $T_1$. Then $x$ is a limit point of $A$ iff every neighborhood of $x$ contains infinitely many points of $A$.

He does this in the context of discussing when sequences have unique limit points. He goes on to prove that if a space is Hausdorff then it does have a unique limit point. But he stops talking about $T_1$ spaces. This made me wonder:

  1. Do $T_1$ spaces have unique sequential limits?
  2. If they don't, what point is Munkres trying to make? -- That is, "$T_1$ spaces don't have unique limits but they have this other more general property XYZ that gets us part way there", where I'm failing to understand what XYZ is.
yoshi
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1 Answers1

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A very similar question (but not a real duplicate of the present one) is this: A separation axiom equivalent to uniqueness of limits of sequences . This should answer your second question: Uniqueness of sequential limits is a property stronger than $T_1$ but weaker than Hausdorff, and moreover that in general spaces it is more adequate to consider nets instead of sequences.

The reference provided by K. Y gives a negative answer to your first question.

Paul Frost
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