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The Effective Topos

. The L. E. J. Brouwer Centenary Symposium Proceedings of the Conference held in Noordwijkerhout, volume 110 of Studies in Logic and the Foundations of Mathematics, Elsevier, (1982)
DOI: http://dx.doi.org/10.1016/S0049-237X(09)70129-6

Abstract

Publisher Summary This chapter describes the most accessible of the series of toposes that can be constructed from notions of realizability: it is that based on the original notion of recursive realizability and presents the abstract approach to recursive realizability in some detail. The chapter introduces effective topos and discusses the notion of a negative formula that arises naturally in the theory of sheaves. The chapter presents features of effective topos, where the power-set matters: uniformity principles and properties of j-operators. The chapter recommends that while constructing a topos from a tripos, one must add new subobjects of the sets one has started with to represent the nonstandard predicates and take quotients of these by the nonstandard equivalence relations.

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The Effective Topos

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