No CrossRef data available.
Published online by Cambridge University Press: 20 November 2018
We consider two generalizations R 0w and R 0 of the usual symmetry axiom for topological spaces to arbitrary closure spaces and convergence spaces. It is known that the two properties coincide on Top and define a non-simple subcategory. We show that R0W defines a simple subcategory of closure spaces and R0 a non-simple one. The last negative result follows from the stronger statement that every epireflective subcategory of R0 Conv containing all T 1 regular topological spaces is not simple. Similar theorems are shown for the topological categories Fil and Mer.