Is there an interval of the form $[\sigma,\tau]$ in the lattice of topologies on some set $X$ such that $|[\sigma,\tau]| = \aleph_0$? In other words, do there exist two topologies $\sigma$ and $\tau$ on $X$ such that there are a countably infinite number of topologies on $X$ that are finer than $\sigma$ and coarser than $\tau$?
I can find intervals like this of size $n$ for every finite $n > 0$, and intervals of size $\mathfrak{c}$. But I don't see how to obtain closed intervals of any intermediate size. I have a proof (well, an idea for a proof) that if $|[\sigma,\tau]| = \aleph_0$, then $\sigma$ cannot be a Hausdorff topology. Other than this, though, I can't seem to say much of anything about this question.