Finite preorders and topological descent II: etale descent

[摘要] It is known that every effective (global-) descent morphism of topological spaces is an effective etale-descent morphism. On the other hand, in the predecessor of this paper we gave examples of: a descent morphism that is not an effective etale-descent morphism; an effective etale-descent morphism that is not a descent morphism. Both of the examples in fact involved only finite topological spaces, i.e. just finite preorders, and now we characterize the effective etale-descent morphisms of preorders/finite topological spaces completely. (C) 2002 Elsevier Science B.V. All rights reserved.

[发布日期] 2002-10-24