Computing lebesgue number for an open covering

  • Context: Graduate 
  • Thread starter Thread starter Useful nucleus
  • Start date Start date
  • Tags Tags
    Computing
Click For Summary
SUMMARY

The discussion centers on the Lebesgue number lemma as presented in Munkres' work, which states that for a compact metric space X and an open covering A, there exists a δ>0 such that any subset of X with a diameter less than δ is contained in an element of A. Participants explore the computation of δ using a finite subcollection of A, noting that this δ is not necessarily the smallest Lebesgue number. The conversation also touches on the concept of the largest Lebesgue number and the implications of positive numbers smaller than a Lebesgue number being valid as well.

PREREQUISITES
  • Understanding of compact metric spaces
  • Familiarity with open coverings in topology
  • Knowledge of the Lebesgue number lemma
  • Basic concepts of metric space diameter
NEXT STEPS
  • Research the proof of the Lebesgue number lemma in Munkres' "Topology"
  • Explore methods for computing the smallest Lebesgue number
  • Investigate the properties of finite subcollections in open coverings
  • Learn about the implications of the largest Lebesgue number in topology
USEFUL FOR

Mathematicians, particularly those specializing in topology, students studying compact metric spaces, and researchers interested in the properties of open coverings and Lebesgue numbers.

Useful nucleus
Messages
374
Reaction score
62
Munkres proof for the Lebesgue number lemma which is
(If X is a compact metric space and A is an open covering then there exists δ>0 such that for each subset of X having diameter less than δ , then there exists an element of the covering A containing it)
gives a way to compute δ using a finite subcollection that covers the compact metric space. However, this is not necessarily the smallest Lebesgue number. I wonder if there is another proof that involves evaluating the smallest Lebesgue number, if the latter exists.
 
Physics news on Phys.org
Useful nucleus, do you mean the largest Lebesgue number? Any positive number smaller than a Lebesgue number for a covering is also a Lebesgue number for the covering.
 
lugita15, you are absolutely right, I meant largest Lebesgue number if exist. I did not have time to refelct on this question again, but will give it a try soon.
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
496
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 11 ·
Replies
11
Views
3K
  • · Replies 16 ·
Replies
16
Views
3K
  • · Replies 9 ·
Replies
9
Views
6K
  • · Replies 15 ·
Replies
15
Views
3K
  • · Replies 12 ·
Replies
12
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
Replies
16
Views
3K