Intermediate logicIn mathematical logic, a superintuitionistic logic is a propositional logic extending intuitionistic logic. Classical logic is the strongest consistent superintuitionistic logic; thus, consistent superintuitionistic logics are called intermediate logics (the logics are intermediate between intuitionistic logic and classical logic). A superintuitionistic logic is a set L of propositional formulas in a countable set of variables pi satisfying the following properties: 1. all axioms of intuitionistic logic belong to L; 2.
Réseau de preuvesLes réseaux de preuves, inventés par le logicien Jean-Yves Girard en 1986 dans le cadre de la logique linéaire, sont un outil de démonstration formel pour cette même logique (c'est-à-dire une alternative aux séquents qui sont aussi employés en logique classique et intuitionniste). Grossièrement, il s'agit d'un équivalent de la déduction naturelle de la logique intuitionniste adaptée à la logique linéaire. Ils s'en différencient cependant par le caractère géométrique de cette approche : une preuve est formée par un hypergraphe et le critère de correction peut s'exprimer comme un parcours de graphe.
Admissible ruleIn logic, a rule of inference is admissible in a formal system if the set of theorems of the system does not change when that rule is added to the existing rules of the system. In other words, every formula that can be derived using that rule is already derivable without that rule, so, in a sense, it is redundant. The concept of an admissible rule was introduced by Paul Lorenzen (1955). Admissibility has been systematically studied only in the case of structural (i.e.
Extension conservatriceEn logique mathématique, une théorie logique T2 est une extension conservatrice (ou conservative) d'une théorie T1 si le langage de T2 étend le langage de T1, si chaque théorème de T1 est un théorème de T2 et si tout théorème de T2 qui est dans le langage de T1 est déjà un théorème de T1. Une extension propre est une extension non conservative. Informellement, cela veut dire que la nouvelle théorie peut éventuellement être plus commode pour prouver des théorèmes, mais qu’elle ne prouve pas de théorème nouveau concernant l'ancienne théorie.
MétathéorèmeIn logic, a metatheorem is a statement about a formal system proven in a metalanguage. Unlike theorems proved within a given formal system, a metatheorem is proved within a metatheory, and may reference concepts that are present in the metatheory but not the object theory. A formal system is determined by a formal language and a deductive system (axioms and rules of inference). The formal system can be used to prove particular sentences of the formal language with that system.
Logique de la prouvabilitéProvability logic is a modal logic, in which the box (or "necessity") operator is interpreted as 'it is provable that'. The point is to capture the notion of a proof predicate of a reasonably rich formal theory, such as Peano arithmetic. There are a number of provability logics, some of which are covered in the literature mentioned in . The basic system is generally referred to as GL (for Gödel–Löb) or L or K4W (W stands for well-foundedness). It can be obtained by adding the modal version of Löb's theorem to the logic K (or K4).
LudicsIn proof theory, ludics is an analysis of the principles governing inference rules of mathematical logic. Key features of ludics include notion of compound connectives, using a technique known as focusing or focalisation (invented by the computer scientist Jean-Marc Andreoli), and its use of locations or loci over a base instead of propositions. More precisely, ludics tries to retrieve known logical connectives and proof behaviours by following the paradigm of interactive computation, similarly to what is done in game semantics to which it is closely related.
