Infinite Hausdorff Spaces: Mutually Disjoint Open Subsets

In summary, an infinite Hausdorff space has an infinite collection of mutually disjoint open subsets, which can be proven by breaking each open set into smaller disjoint open sets and adding them to the collection. This shows that there is no maximum number of disjoint open sets in the space.
  • #1
mathboy
182
0
Prove that an infinite Hausdorff space has an infinite collection of mutually disjoint open subsets.
 
Last edited:
Physics news on Phys.org
  • #2
Each of the N disjoint open sets is itself an infinite Hausdorff space, so I can break each open set into smaller disjoint open sets, right?


Assume there are N disjoint open subsets {U1,...,Un} in X. Let x,y be in U1. Since X is Hausdorff there exists disjoint open subsets A and B containing x and y, respectively. Then (U1 intersect A) and (U1 intersect B) can replace U1 in the collection, giving us N+1 disjoint open subsets. Thus there is no maximum number of disjoint open sets in X.
 
Last edited:

1. What is an infinite Hausdorff space?

An infinite Hausdorff space is a topological space in which every two distinct points have disjoint neighborhoods. This means that there exists an open set containing one point but not the other, and vice versa. In other words, the space is "separated" by open sets.

2. What are mutually disjoint open subsets?

Mutually disjoint open subsets are open sets that do not share any points in common. In an infinite Hausdorff space, this means that every pair of open sets must have an empty intersection.

3. Why is it important for an infinite Hausdorff space to have mutually disjoint open subsets?

Having mutually disjoint open subsets is important in an infinite Hausdorff space because it allows us to separate points and neighborhoods. This leads to a more organized and structured space, making it easier to study and analyze.

4. How do you prove that a space is infinite Hausdorff?

To prove that a space is infinite Hausdorff, you must show that for every pair of distinct points in the space, there exists a pair of disjoint open sets containing each point. This can be done by using the definition of a Hausdorff space and the axioms of a topological space.

5. Can an infinite Hausdorff space have a finite number of mutually disjoint open subsets?

Yes, it is possible for an infinite Hausdorff space to have a finite number of mutually disjoint open subsets. For example, the real line with the standard topology has infinitely many points but only two disjoint open subsets (the empty set and the whole space).

Similar threads

  • Calculus and Beyond Homework Help
Replies
18
Views
1K
  • Calculus and Beyond Homework Help
Replies
1
Views
501
  • Calculus and Beyond Homework Help
Replies
1
Views
1K
  • Calculus and Beyond Homework Help
Replies
12
Views
1K
  • Calculus and Beyond Homework Help
Replies
4
Views
2K
  • Calculus and Beyond Homework Help
Replies
11
Views
1K
  • Set Theory, Logic, Probability, Statistics
Replies
22
Views
2K
  • Calculus and Beyond Homework Help
Replies
3
Views
4K
  • Calculus and Beyond Homework Help
Replies
1
Views
1K
  • Calculus and Beyond Homework Help
Replies
5
Views
825
Back
Top