Intuitionistic logic and Muchnik degrees

Self-Contradiction Degrees in Intuitionistic Fuzzy Logic

This paper is an attempt to model to what extent an intuitionistic fuzzy set is self-contradictory, both in the case of selfcontradiction regarding a strong intuitionistic negation, and without depending on a specific negation. For this purpose, firstly, a geometrical study on self-contradiction regarding a negation is considered; afterwards some functions to measure degrees of self-contradicto...

Medvedev Degrees, Muchnik Degrees, Subsystems of Z2 and Reverse Mathematics

Turing Degrees and Muchnik Degrees of Recursively Bounded DNR Functions

Coding true arithmetic in the Medvedev and Muchnik degrees

We prove that the first-order theory of the Medvedev degrees, the first-order theory of the Muchnik degrees, and the third-order theory of true arithmetic are pairwise recursively isomorphic (obtained independently by Lewis, Nies, and Sorbi [7]). We then restrict our attention to the degrees of closed sets and prove that the following theories are pairwise recursively isomorphic: the first-orde...

Inside the Muchnik Degrees: Discontinuity, Learnability, and Constructivism

Every computable function has to be continuous. To develop computability theory of discontinuous functions, we study low levels of the arithmetical hierarchy of nonuniformly computable functions on Baire space. First, we classify nonuniformly computable functions on Baire space from the viewpoint of learning theory and piecewise computability. For instance, we show that mind-change-bounded-lear...