In this paper we introduce stable topology and F-topology on the set of all prime filters of a BL-algebra A and show that the set of all prime filters of A, namely Spec(A) with the stable topology is a compact space but not T0. Then by means of stable topology, we define and study pure filters of a BL-algebra A and obtain a one to one correspondence between pure filters of A and closed subsets of Max(A), the set of all maximal filters of A, as a subspace of Spec(A). We also show that for any filter F of BL-algebra A if σ(F)=F then U(F) is stable and F is a pure filter of A, where σ(F)= { a\in A | y\wedge z=0 for some z\in F and y \in a\perp } and U(F) = { P \in Spec(A) \vert F \nsubseteq P }.
Keywords: BL-algebra; prime filters; maximal filters; pure filters; stable topology; F-topology;
AMS: 03G25; 06F99; 08A72;
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