4 papers · 1 filter
Locales in presheaf toposes vs. presheaves of locales
Vasileios Aravantinos-Sotiropoulos, Panagis Karazeris, Joshua Wrigley
By a well-known characterisation, in a presheaf topos every internal suplattice is a presheaf of suplattices, but not every presheaf of suplattices is an internal suplattice (and s…
Filtral pretoposes and compact Hausdorff locales
Célia Borlido, Panagis Karazeris, Luca Reggio +1
The category of compact Hausdorff locales is a pretopos which is filtral, meaning that every object is covered by one whose subobject lattice is isomorphic to the lattice of filter…
Regular and effective regular categories of locales
Panagis Karazeris, Konstantinos Tsamis
We examine the analogues for the respective categories of locales of two well-known results about regularity and effectiveness of some categories of spaces. We show that the catego…
Final coalgebras in accessible categories
Panagis Karazeris, Apostolos Matzaris, Jiri Velebil
We give conditions on a finitary endofunctor of a finitely accessible category to admit a final coalgebra. Our conditions always apply to the case of a finitary endofunctor of a lo…