Is the Set of Rational Numbers with the Relative Topology Not Locally Compact?

AI Thread Summary
The discussion centers on proving that the set of rational numbers with the relative topology is not locally compact. A topological space is defined as locally compact if, for every point, there exists an open set containing that point whose closure is compact. The original poster expresses confusion and requests a proof, but is reminded that homework helpers require evidence of personal effort before providing assistance. The conversation also includes a humorous comment about wanting a Saleen S7, indicating a light-hearted tone amidst the academic inquiry. Ultimately, the focus remains on the need to demonstrate the non-local compactness of the rational numbers.
bighadi
Messages
2
Reaction score
0

Homework Statement



Prove that the set of rational numbers with the relative topology as a subset of the real numbers is not locally compact

Homework Equations



none

The Attempt at a Solution



I am totally confused and want someone to give me a proof. I have looked at some stuff online but nothing made sense.
 
Physics news on Phys.org


You would like someone to give you a proof? I would like someone to give me a Saleen S7. Neither is going to happen in the immediate future. Note this from the guidelines.

1) Did you show your work? Homework helpers will not assist with any questions until you've shown your own effort on the problem. Remember, we help with homework, we don't do your homework.
 


Okay, let's start with a definition:

A topological space X is locally compact if for each p \in X, there is an open set W such that p \in W and \overline{W}, the closure of W, is compact.

So, since we are trying to show that Q is not locally compact, we need to show that there exists p \in X such that for all open sets W and p \notin W and \overline{W} is not compact.

Assuming I wrote the negation of being locally compact correctly, how do I show the the above statement?

[By the way, I would also love getting a Saleen S7.]

I think I posted this under the wrong section. I meant to put it under "Calculus and beyond".
 
Last edited:
I picked up this problem from the Schaum's series book titled "College Mathematics" by Ayres/Schmidt. It is a solved problem in the book. But what surprised me was that the solution to this problem was given in one line without any explanation. I could, therefore, not understand how the given one-line solution was reached. The one-line solution in the book says: The equation is ##x \cos{\omega} +y \sin{\omega} - 5 = 0##, ##\omega## being the parameter. From my side, the only thing I could...
Back
Top