Questions About Single Element Set X={0} in Euclidean Metric

  • Context: Graduate 
  • Thread starter Thread starter anjana.rafta
  • Start date Start date
  • Tags Tags
    Element Set
Click For Summary

Discussion Overview

The discussion revolves around the properties of the single element set X={0} within the context of different metric spaces, particularly the Euclidean metric. Participants explore concepts of openness and closedness of sets, the relevance of metric spaces, and the implications of discrete metrics.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions the relevance of the metric space in defining properties of the set X={0}.
  • Another participant explains that the openness or closedness of the set depends on whether it is considered as a metric space itself or as a subset of a larger metric space, specifically mentioning that {0} is both open and closed in its own metric space but closed in the context of the real numbers.
  • There is a discussion about the discrete metric, where it is stated that every set in a discrete metric is both open and closed, including the elements {0} and {1} in the interval [0,1].
  • A participant expresses confusion about the definitions and requests further resources for understanding the concepts better.
  • Another participant notes that sets can exist without a metric but can still have a topology, emphasizing the definitions and rules associated with open sets.

Areas of Agreement / Disagreement

Participants express differing views on the relevance of metric spaces and the definitions of open and closed sets, indicating that the discussion remains unresolved with multiple competing perspectives.

Contextual Notes

There is a lack of consensus on the foundational concepts of metric spaces and their implications for the set X={0}. Participants have varying levels of understanding, and some foundational assumptions about metric spaces and topologies are not fully articulated.

anjana.rafta
Messages
8
Reaction score
0
i have few doubt regarding a single element set. let X={0}, in euclidiean metric. my questions are:

1. does matric space even matters? or matric space is defined?
2. is this set open/closed/none of them?
3. for a discrete matric on [0,1], [0,1]= {0}+(0,1] = {0}+(0,1)+{1}, then {0},{1} are open or closed?
how do we say that every element in dicrete matric space is open??


Thanks
 
Physics news on Phys.org
anjana.rafta said:
i have few doubt regarding a single element set. let X={0}, in euclidiean metric. my questions are:

1. does matric space even matters? or matric space is defined?

I have a hard time figuring out what you mean with this. Why would a metric not matter?

2. is this set open/closed/none of them?

If you consider {0} as a metric space, then this is open and closed. However, if you conside {0} as a subset of the metric space [tex](\mathbb{R},d)[/tex], then the set is closed and not open. As you see, open and closedness are relative depending on what the underlying set is.

3. for a discrete matric on [0,1], [0,1]= {0}+(0,1] = {0}+(0,1)+{1}, then {0},{1} are open or closed?

If you consider [0,1] with the discrete metric, then {0} and {1} are both open and closed. In fact, EVERY set in the discrete metric is both open and closed.

Hope that helped!

PS: it's metric, and not matric :smile:
 
thanks for that quick reply. but am still confused.

1.does metric space even matters? or metric space is defined? this is wrt X={0}. this set be defined with any metric space.. does it matter?
2.If you consider {0} as a metric space, then this is open and closed. However, if you conside {0} as a subset of the metric space LaTeX Code: (\\mathbb{R},d) , then the set is closed and not open. As you see, open and closedness are relative depending on what the underlying set is.
am not able understand what tou stated in above comment
i think i havn't got the concept correctly. could you please point me to some place/book that talks about it. am a beginner with the course.

thanks for the PS :)
 
I am not sure where the confusion lies. However for starters, you can have sets with no metric but with a topology. You can also have sets with no topology.

Note: having a topology means open sets are defined and obey standard rules. All unions of open sets are open, all intersections of a finite number of open sets are open, the whole set and the empty set are open.
 

Similar threads

  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 12 ·
Replies
12
Views
2K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 32 ·
2
Replies
32
Views
3K
  • · Replies 14 ·
Replies
14
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 3 ·
Replies
3
Views
3K