reducible preorder

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• Reduction (recursion theory) — In computability theory, many reducibility relations (also called reductions, reducibilities, and notions of reducibility) are studied. They are motivated by the question: given sets A and B of natural numbers, is it possible to effectively… …   Wikipedia

• Many-one reduction — In computability theory and computational complexity theory, a many one reduction is a reduction which converts instances of one decision problem into instances of a second decision problem. Reductions are thus used to measure the relative… …   Wikipedia

• Turing reduction — In computability theory, a Turing reduction from a problem A to a problem B, named after Alan Turing, is a reduction which solves A, assuming B is already known (Rogers 1967, Soare 1987). It can be understood as an algorithm that could be used to …   Wikipedia

• Wadge hierarchy — In descriptive set theory, Wadge degrees are levels of complexity for sets of reals and more comprehensively, subsets of any given topological space. Sets are compared by continuous reductions. The Wadge hierarchy is the structure of Wadge… …   Wikipedia

• PA degree — In recursion theory, a mathematical discipline, a PA degree is a Turing degree that computes a complete extension of Peano arithmetic (Jockusch 1987). These degrees are closely related to fixed point free (DNR) functions, and have been thoroughly …   Wikipedia

• Abstract rewriting system — In mathematical logic and theoretical computer science, an abstract rewriting system (also (abstract) reduction system or abstract rewrite system; abbreviation ARS) is a formalism that captures the quintessential notion and properties of… …   Wikipedia