Uniform continuity in top. spaces

Click For Summary

Discussion Overview

The discussion revolves around the concept of uniform continuity within the context of topological spaces versus metric spaces. Participants explore the definitions and implications of uniform continuity, its relationship to continuity in general topological spaces, and the role of uniform spaces in this context.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that uniform continuity is primarily a metric space concept due to the absence of a distance function in general topological spaces, but questions whether a generalization could exist.
  • Another participant explains the definition of continuity in topological spaces and how it relates to the epsilon-delta definition in metric spaces, proposing that uniform continuity would require additional structure, specifically the concept of uniform spaces.
  • A participant introduces the idea of uniform spaces, indicating that they generalize the notion of uniform continuity beyond metric spaces.
  • It is noted that if a space is metrizable, the metric will coincide with its uniformity.
  • One participant points out that multiple metrics can yield the same uniformity, providing an example involving different distance functions on the real line.
  • A later reply acknowledges the previous point about equivalent metrics, indicating a correction to the earlier statement.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of uniform continuity in topological spaces, with some supporting the idea of extending the concept and others emphasizing its metric origins. The discussion remains unresolved regarding the feasibility of defining uniform continuity in general topological spaces.

Contextual Notes

Participants highlight the need for additional structure in topological spaces to define uniform continuity, which may depend on specific properties of the spaces being discussed.

Bleys
Messages
74
Reaction score
0
So my teacher said that uniform continuity was a metric space notion, not a topological space one. At first it seemed obvious, since there is no "distance" function in general topological spaces. But then I remembered that you can generalize point-wise continuity in general topologies, so why not uniform continuity? I'm probably wrong; I wouldn't know the details to construct such a definition, but I know that Hausdorff spaces behave similarly to metric spaces (being Hausdorff themselves) in some respects, so maybe it would be possible?
 
Physics news on Phys.org
The definition of a continuous function from a topological space X to a topological space Y is that the inverse image of an open set in Y is an open set in X. This agrees with the epsilon delta definition of continuity for a metric space.

In a metric space, the idea of uniform continuity is that for a given epsilon, for any point in the domain you can pick the same size delta ball and the function will map into an epsilon ball around the image of that point. So if you wanted to extend this idea to a general topological space, you would need some notion of open sets around different points being of a comparable size. To do this you need some additional structure, and this is the idea of a uniform space: http://en.wikipedia.org/wiki/Uniform_space
 
There is a more general type of space, called uniform space ... As with the metric case, a single toplogical space may correspond to many different uniform spaces.
 
Just to add the side statement that if the space is metrizable, then the
metric coincides with its uniformity.
 
To contradict Bacle, two different metrics may yield the same uniformity.
For example, in the real line, take distance |x-y| in one case, and distance 2|x-y| in the other case.
 
Right, my bad. Up to equivalent metrics.
 

Similar threads

  • · Replies 11 ·
Replies
11
Views
4K
  • · Replies 24 ·
Replies
24
Views
6K
  • · Replies 18 ·
Replies
18
Views
12K
  • · Replies 42 ·
2
Replies
42
Views
11K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 14 ·
Replies
14
Views
3K
  • · Replies 1 ·
Replies
1
Views
4K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K