What is the relationship between first countable spaces and Hausdorff spaces?

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In summary, the conversation discusses how to show that a first countable space where no sequence has more than one limit must be Hausdorff. It is suggested to use the theorem stating that a Hausdorff space only allows sequences to have at most one limit. The conversation then looks at how to construct a sequence that converges to both x and y in a potentially non-Hausdorff space.
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Homework Statement


Let X be a first countable space where no sequence has more than one limit. Show that X must be Hausdorff.


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The Attempt at a Solution


Hi everyone,
Here's what I've done so far:

I used this thm: If X is a Hausdorff space, then sequences in X can have at most one limit. (but not necessarily the converse)

So X is potentially a Hausdorff space as all it's sequences have only one limit, if at all.

But then I'm completely stuck as to where to go from here. Obviously it's got something to do with being first countable, but I can't see what! Can anyone please give me a point in the right direction?

Thanks for any help!
 
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Assume that our space is not Hausdorff. Take x and y points where the Hausdorffness space (thus every neighbourhood of x intersects every neighbourhood of y)
Let the neighbourhood base of x be {B1,B2,...}, were [tex]...\subseteq B_3\subseteq B_2\subseteq B_1[/tex].
Likewise, let the neighbourhood base of y be {C1,C2,...}, were again [tex]...\subseteq C_3\subseteq C_2\subseteq C_1[/tex].

Try to construct a sequence that converges that converges to both x and y.
 

1. What is a Hausdorff space?

A Hausdorff space, also known as a T2 space, is a topological space in which any two distinct points have disjoint neighborhoods. In other words, for any two points in the space, there exist open sets that contain one point but not the other.

2. What is the significance of a Hausdorff space?

Hausdorff spaces are important in topology because they allow for the separation of points, which is a fundamental concept in understanding the structure of topological spaces. They also have many useful properties, such as being compact and being a limit of a sequence of points.

3. How is a Hausdorff space different from other topological spaces?

A Hausdorff space is more restrictive than other topological spaces, such as a T1 space, because it requires that any two distinct points have disjoint neighborhoods. This means that the space is not only separated by points, but also by open sets.

4. Can a Hausdorff space have infinitely many points?

Yes, a Hausdorff space can have infinitely many points. In fact, many commonly used topological spaces, such as the real numbers or Euclidean space, are Hausdorff spaces with infinitely many points.

5. How is the Hausdorff property useful in real-world applications?

The Hausdorff property has several practical applications, especially in the field of data analysis and pattern recognition. It allows for the comparison of different sets or shapes, and can be used to define metrics and distances between objects. It is also used in the study of fractals and self-similarity.

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