How to show simplicial complex is Hausdorff?

In summary, for any simplicial complex S, it can be shown to be Hausdorff by proving that for any two distinct points p and q in S, there exist neighbourhoods U and V of p and q respectively such that U∩V=∅. This can be done by considering a simplex T in S containing p and q and taking the open stars of p and q in T, which are disjoint by construction. Therefore, S is Hausdorff.
  • #1
KennethK
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0

Homework Statement


Prove that any simplicial complex is Hausdorff.

Homework Equations

The Attempt at a Solution


I have proved that for any finite simplicial complex, it is metrizable and hence Hausdorff.

How to show the statement for infinite case?
 
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  • #2
Let S be a simplicial complex. We need to show that for any two distinct points p, q in S there exist neighbourhoods U and V of p and q respectively such that U∩V=∅.Let p and q be two distinct points in S. Since S is a simplicial complex, there exists a simplex T in S containing p and q. Let U and V be the open stars of p and q respectively in T. Then U and V are disjoint by construction, and they are neighbourhoods of p and q respectively. Thus U∩V=∅, which shows that S is Hausdorff.
 

1. How do you define a Hausdorff simplicial complex?

A Hausdorff simplicial complex is a type of topological space in which every two distinct points have disjoint neighborhoods. In other words, for any two points in the complex, there exists open sets containing each point that do not overlap.

2. What is the significance of a simplicial complex being Hausdorff?

A Hausdorff simplicial complex is important because it ensures that the complex is well-behaved and has a well-defined topology. This is especially useful in applications such as algebraic topology, where the structure of the complex is crucial for understanding its properties.

3. How can you show that a simplicial complex is Hausdorff?

To show that a simplicial complex is Hausdorff, you must demonstrate that for any two distinct points in the complex, there exists open sets containing each point that do not intersect. This can be done by considering the definition of the complex and its topology, and using logical reasoning to show that the condition is satisfied.

4. Are there any conditions that guarantee a simplicial complex is Hausdorff?

Yes, there are certain conditions that guarantee a simplicial complex is Hausdorff. For example, if the complex is finite or locally finite, meaning that each point has a finite number of neighboring simplices, then it is automatically Hausdorff. Additionally, if the complex is constructed from a finite or countable set of points, it will also be Hausdorff.

5. Can a simplicial complex be both Hausdorff and non-Hausdorff?

No, a simplicial complex cannot be both Hausdorff and non-Hausdorff. By definition, a space is either Hausdorff or non-Hausdorff, so a simplicial complex must fall into one of these categories. However, it is possible for different subspaces of a simplicial complex to have different topologies, meaning that some subspaces may be Hausdorff while others are not.

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