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We present some new findings concerning branched covers in topos theory. Our discussion involves a particular subtopos of a given topos that can be described as the smallest subtopos closed under small coproducts in the including topos. Our main result is a description of the covers of this subtopos as a category of fractions of branched covers, in the sense of Fox, of the including topos. We also have some new results concerning the general theory of KZ-doctrines, such as the closure under composition of discrete fibrations for a KZ-doctrine, in the sense of Bunge and Funk.
@article{TAC_2000_7_a0, author = {Jonathon Funk}, title = {On {Branched} {Covers} in {Topos} {Theory}}, journal = {Theory and applications of categories}, pages = {1--22}, publisher = {mathdoc}, volume = {7}, year = {2000}, language = {en}, url = {http://geodesic.mathdoc.fr/item/TAC_2000_7_a0/} }
Jonathon Funk. On Branched Covers in Topos Theory. Theory and applications of categories, Tome 7 (2000), pp. 1-22. http://geodesic.mathdoc.fr/item/TAC_2000_7_a0/