Let $\mathcal{A}$ be a Banach algebra, the map $\sigma$ maps each element $a\in\mathcal{A}$ to its spectrum $\sigma(a)$, which is a compact subset of $\mathbb{C}$.
The collection of compact subsets of $\mathbb{C}$ has a natural topology, the one given by Hausdorff distance. Then a natural question is: what are the points of continuity of $\sigma$ ?
When $\mathcal{A}=B(\mathcal{H})$ for some Hilbert space $\mathcal{H}$, the problem is solved by Conway and his colleagues, but I don't know whether it is solved for general Banach algebras.
After thinking about this for quite a while, I thought a reversed way might also be interesting (although much harder it seems). That is, what is the initial topology on $\mathcal{A}$ with respect to $\sigma$ ?
I do not know where to start so any suggestion is welcome. Thanks!
