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

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SUMMARY

The set of rational numbers, denoted as Q, with the relative topology inherited from the real numbers is not locally compact. A topological space X is defined as locally compact if for every point p in X, there exists an open set W containing p such that the closure of W, denoted as &overline;W, is compact. The discussion emphasizes the need to demonstrate that for any open set W containing a point p in Q, the closure &overline;W fails to be compact, thereby proving the non-local compactness of Q.

PREREQUISITES
  • Understanding of topological spaces and their properties
  • Familiarity with the concepts of open sets and closures in topology
  • Knowledge of compactness in the context of topological spaces
  • Basic understanding of rational numbers as a subset of real numbers
NEXT STEPS
  • Study the definition and properties of compact spaces in topology
  • Learn about the relative topology and its implications on subsets of topological spaces
  • Explore examples of locally compact and non-locally compact spaces
  • Investigate the implications of closure properties in topological spaces
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Mathematicians, students studying topology, and anyone interested in understanding the properties of rational numbers within the framework of real analysis.

bighadi
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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



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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.
 
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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 [tex]\in[/tex] X, there is an open set W such that p [tex]\in[/tex] W and [tex]\overline{W}[/tex], 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 [tex]\in[/tex] X such that for all open sets W and p [tex]\notin[/tex] W and [tex]\overline{W}[/tex] 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:

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