# Which topological spaces are metrizable?

Which topological spaces are metrizable?

## Which topological spaces are metrizable?

It states that a topological space is metrizable if and only if it is regular, Hausdorff and has a σ-locally finite base. A σ-locally finite base is a base which is a union of countably many locally finite collections of open sets. For a closely related theorem see the Bing metrization theorem.

### How can you prove that a topological space is metrizable?

Let (X, T ) be a topological space. Let d : X ×X → R be a metric. If the topology generated by d is T , then we say T is metrizable.

Are topological spaces vector spaces?

A topological vector space is a vector space which is also a topological space, and where the vector space operations are continuous functions. This implies that the space has a uniform topological structure, allowing a notion of uniform convergence. Some authors also require that the space is a Hausdorff space.

Is a metrizable space a metric space?

There is no difference between a metrizable space and a metric space (proof included). Bookmark this question.

## Are topological manifolds metrizable?

A manifold is metrizable if and only if it is paracompact. Since metrizability is such a desirable property for a topological space, it is common to add paracompactness to the definition of a manifold. In any case, non-paracompact manifolds are generally regarded as pathological.

### Is every normal space metrizable?

Every second countable regular space is metrizable. While every metrizable space is normal (and regular) such spaces do not need to be second countable. For example, any discrete space X is metrizable, but if X consists of uncountably many points it does not have a countable basis (Exercise 4.10).

Under what conditions does a metrizable space have a metrizable compactification?

Under what conditions does a metrizable space have a metrizable compactification? SOLUTION. If A is a dense subset of a compact metric space, then A must be second countable because a compact metric space is second countable and a subspace of a second countable space is also second countable.

Is every smooth manifold metrizable?

It is known that every smooth manifold possess a complete Riemannian metric, hence in particular it is completely metrizable, however there are non smoothable manifolds.

## Is the discrete topology metrizable?

Therefore, the basis consists of all singleton sets as well as X itself, giving rise to a topology that contains all possible unions of elements in X – precisely the discrete topology. So, we see that a set under the discrete topology is always metrizable by way of the trivial metric.

### Is every metrizable space is normal?

Any metrizable space, i.e., any space realized as the topological space for a metric space, is a perfectly normal space — it is a normal space and every closed subset of it is a G-delta subset (it is a countable intersection of open subsets).

What is a topological vector space?