Published online by Cambridge University Press: 26 September 2016
Let ${\mathcal{A}}$ be a locally noetherian Grothendieck category. We construct closure operators on the lattice of subcategories of
${\mathcal{A}}$ and the lattice of subsets of
$\text{ASpec}\,{\mathcal{A}}$ in terms of associated atoms. This establishes a one-to-one correspondence between hereditary torsion theories of
${\mathcal{A}}$ and closed subsets of
$\text{ASpec}\,{\mathcal{A}}$ . If
${\mathcal{A}}$ is locally stable, then the hereditary torsion theories can be studied locally. In this case, we show that the topological space
$\text{ASpec}\,{\mathcal{A}}$ is Alexandroff.