In this survey we present several results concerning various topologies that were introduced in recent years on spaces of valuation domains.
Spaces of valuation domainsThe motivations for studying from a topological point of view spaces of valuation domains come from various directions and, historically, mainly from Zariski's work on the reduction of singularities of an algebraic surface and a three-dimensional variety and, more generally, for establishing new foundations of algebraic geometry by algebraic means (see [45], [46], [47] and [48]). Other important applications with algebro-geometric flavour are due to Nagata [33] [34], Temkin [43], Temkin and Tyomkin [44]. Further motivations come from rigid algebraic geometry started by J. Tate [42] (see also the papers by Fresnel and van der Put [18], Huber and Knebusch [27], Fujiwara and Kato [19]), and from real algebraic geometry (see for instance Schwartz [39] and Huber [26]). For a deeper insight on these topics see [27].In the following, we want to present some recent results in the literature concerning various topologies on collections of valuation domains.Let K be a field, A an arbitrary subring of K and let qf(A) denote the quotient field of A. SetWhen A is the prime subring of K, we will simply denote by Zar(K) the space Zar(K|A). Recall that O. Zariski in [46] introduced a topological structure on the set Z := Zar(K|A) by taking, as a basis for the open sets, the subsets B F := B Z F := {V ∈ Z | V ⊇ F }, for F varying in the family of all finite subsets of K (see also [48, Chapter VI, §17, page 110]). When no confusion can arise, we will simply denote by B x the basic open set B {x} of Z. This topology is what that is now called the Zariski topology on Z Acknowledgments. During the preparation of this paper, the first two authors were partially supported by a research grant PRIN-MiUR.