Closure, interior and neighbourhood in a category
Abstract
The natural correspondences in topology between closure, interior
and neighbourhood no longer hold in an abstract categorical setting
where subobject lattices are not necessarily Boolean algebras. We
analyse three canonical correspondences between closure, interior and
neighbourhood operators in a category endowed with a subobject
structure. While these correspondences coincide in general topology,
the analysis highlights subtle di erences which distinguish di erent
approaches taken in the literature.