Equivalent Metrics: Convergent Sequences?

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In summary, equivalent metrics are two metrics that define the same topology on a set, meaning they have the same notions of open and closed sets and convergent sequences. To prove two metrics are equivalent, one must show that every open set in one metric is also open in the other metric and vice versa, by demonstrating that convergent sequences in one metric are also convergent in the other. Two metrics can be equivalent on one set but not on another, as the definition of equivalent metrics depends on the topology of the set. However, equivalent metrics do not affect the convergence of sequences, meaning that a sequence that is convergent in one metric will also be convergent in an equivalent metric. Therefore, all convergent sequences in one metric are also
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AxiomOfChoice
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Is it true that two metrics d_1 and d_2 on a set X are equivalent iff they have the same convergent sequences (i.e., a sequence that converges in d_1 converges in d_2 and vice versa)?
 
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Yes.

Engelking, "General Topology", Thm. 4.1.2

"Two metrics on X are equivalent iff they induce the same convergence."
 
  • #3
Yup, although the correct term is "topologically equivalent", since metrics can also be "uniformly equivalent" or "Lipschitz equivalent" and there might be more such equivalencies.
 

FAQ: Equivalent Metrics: Convergent Sequences?

What is the definition of equivalent metrics?

Equivalent metrics are two metrics that induce the same topology on a set. In other words, they define the same notions of open and closed sets, and therefore have the same convergent sequences.

How do you prove two metrics are equivalent?

To prove two metrics are equivalent, you must show that every open set in one metric is also an open set in the other metric, and vice versa. This can be done by showing that any sequence that is convergent in one metric is also convergent in the other metric.

Can two metrics be equivalent on one set but not on another?

Yes, it is possible for two metrics to be equivalent on one set but not on another. This is because the definition of equivalent metrics depends on the topology induced on the set, which can vary from set to set.

How do equivalent metrics affect the convergence of sequences?

Equivalent metrics do not affect the convergence of sequences. This means that if a sequence is convergent in one metric, it will also be convergent in an equivalent metric, and vice versa.

Are all convergent sequences in one metric also convergent in an equivalent metric?

Yes, all convergent sequences in one metric are also convergent in an equivalent metric. This is because equivalent metrics define the same notion of convergence, so any sequence that is convergent in one metric will also be convergent in the other.

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