Undecidability of intuitionistic theories formulated with the apartness relation
Hypersequents and fuzzy logic.
Fuzzy logics based on t-norms and their residua have been investigated extensively from a semantic perspective but a unifying proof theory for these logics has, until recently, been lacking. In this paper we survey results of the authors and others which show that a suitable proof-theoretic framework for fuzzy logics is provided by hypersequents, a natural generalization of Gentzen-style sequents. In particular we present hypersequent calculi for the logic of left-continuous t-norms MTL and related...
On 2nd order intuitionistic propositional calculus with full comprehension.
How to make your logic fuzzy.
The aim of this paper is to provide a methodology for turning a known crisp logic into a fuzzy system. We require of the methodology that it be meaningful in general terms, using processes which are independent of the notion of fuzziness, and that it yield a considerable number of known fuzzy systems.
Information frames, implication systems and modalities.
We investigate the logical systems which result from introducing the modalities L and M into the family of substructural implication logics (including relevant, linear and intuitionistic implication). Our results lead to the formulation of a uniform labelled refutation system for these logics.
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