Jankov Formula and Ternary Deductive Term
نویسنده
چکیده
Jankov (characteristic) formulas were introduced 50 years ago in [7] and proved to be a very useful tool for studying a broad range of logics, e.g. intermediate, modal, fuzzy, relevant, many-valued, etc. All these different logics have one thing in common: in one or the other form they admit the deduction theorem. From the standpoint of algebraic logic it means that their corresponding varieties have a ternary deductive (TD) term ([4]). It is natural to try to extend the notion of characteristic formula to such varieties and, thus, to apply this notion to an even broader class of logics, namely, to the logics whose algebraic semantic is a variety with a TD term. We give such a generalization below.
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