Metric spaces - is my answer right?

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In summary, a metric space is a mathematical concept that uses a distance function to describe the distance between points in a set. To determine if a set is a metric space, you need to check if it satisfies the three properties of a metric. Metric spaces are important in mathematics as they provide a framework for studying distance and convergence in a general setting. They are different from other types of spaces, such as topological spaces or vector spaces, because they are specifically defined by a metric. It is possible for two different metrics to define the same metric space, as long as the three properties of a metric are satisfied.
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Homework Statement


Give an example of two metric spaces (X1, d1) and (X2, d2) which are topologically equivalent and for which (X1, d1) is complete and (X2, d2) is not.


2. The attempt at a solution
The open unit disc and R2. They are homeomorphic, but there are Cauchy sequences in the disc which will converge to limits outside of the disc, so it's not complete.
 
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  • #2
I can't argue with your reasoning.
 
  • #3
Thanks - I was pretty sure, but wanted to check.
 

1. What is a metric space?

A metric space is a mathematical concept used to describe the distance between points in a set. It is defined by a distance function called a metric, which assigns a non-negative real number to pairs of points in the set, satisfying certain properties.

2. How do I know if a set is a metric space?

To determine if a set is a metric space, you need to check if it satisfies the three properties of a metric: non-negativity, identity of indiscernibles, and the triangle inequality. If all three properties are satisfied, then the set is a metric space.

3. What is the importance of metric spaces in mathematics?

Metric spaces are important in mathematics because they provide a framework for studying the concept of distance and convergence in a general setting. They are used in various fields such as topology, analysis, and geometry, and have applications in areas such as computer science, physics, and engineering.

4. How are metric spaces different from other types of spaces?

Metric spaces are different from other types of spaces, such as topological spaces or vector spaces, because they are specifically defined by a metric or distance function. This metric allows for the concept of distance and convergence, which is not present in other types of spaces.

5. Can two different metrics define the same metric space?

Yes, it is possible for two different metrics to define the same metric space. This is because the properties of the metric that define a metric space are independent of the specific metric chosen. As long as the three properties of a metric are satisfied, the resulting space will be the same.

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