What spaces can be obtained from $\mathbb{R}^{n}$ by taking quotient spaces and subspaces?

2011-03-08T10:25:05Z

Is there a good characterization of the smallest collection of topological spaces which contains $\mathbb{R}^{n}$ for each $n$, and is closed under taking subspaces and quotient spaces?

A bit of motivation: A friend of mine asked me to give an argument why the definition of a topological space is "right" or "natural", considered perhaps as a generalization of manifolds or cell complexes. While trying to answer him, I briefly wondered whether the collection of topological spaces is the closure of $\{ \mathbb{R}^{n} \}_{n \geq 0}$ under certain operations, say taking subspaces and quotient spaces. I quickly realized that this is false in general, though (there are counterexamples which have very large cardinality or don't satisfy first or second countability).

What spaces can be obtained from $\mathbb{R}^{n}$ by taking quotient spaces and subspaces? - MathOverflow

What spaces can be obtained from $\mathbb{R}^{n}$ by taking quotient spaces and subspaces?