undecidability
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Post correspondence problem — The Post correspondence problem is an undecidable decision problem that was introduced by Emil Post in 1946.[1] Because it is simpler than the halting problem and the Entscheidungsproblem it is often used in proofs of undecidability. Contents 1… … Wikipedia
Proof of impossibility — A proof of impossibility, sometimes called a negative proof or negative result , is a proof demonstrating that a particular problem cannot be solved, or cannot be solved in general. Often proofs of impossibility have put to rest decades or… … Wikipedia
Halting problem — In computability theory, the halting problem can be stated as follows: Given a description of a computer program, decide whether the program finishes running or continues to run forever. This is equivalent to the problem of deciding, given a… … Wikipedia
Aperiodic tiling — are an aperiodic set of tiles, since they admit only non periodic tilings of the plane:] Any of the infinitely many tilings by the Penrose tiles is non periodic. More informally, many refer to the Penrose tilings as being aperiodic tilings , but… … Wikipedia
metalogic — /met euh loj ik/, n. the logical analysis of the fundamental concepts of logic. [1835 45; META + LOGIC] * * * Study of the syntax and the semantics of formal languages and formal systems. It is related to, but does not include, the formal… … Universalium
Combinatory logic — Not to be confused with combinational logic, a topic in digital electronics. Combinatory logic is a notation introduced by Moses Schönfinkel and Haskell Curry to eliminate the need for variables in mathematical logic. It has more recently been… … Wikipedia
Raphael M. Robinson — Raphael Mitchel Robinson (November 2 1911, National City California January 27 1995. Berkeley California) was an American mathematician.Born in National City, California, Robinson was the youngest of four children of a lawyer and a teacher. He… … Wikipedia
Simply typed lambda calculus — The simply typed lambda calculus (lambda^ o) is a typed interpretation of the lambda calculus with only one type combinator: o (function type). It is the canonical and simplest example of a typed lambda calculus. The simply typed lambda calculus… … Wikipedia
Description number — Description numbers are numbers that arise in the theory of Turing machines. They are very similar to Gödel numbers, and are also occasionally called Gödel numbers in the literature. Given some universal Turing machine, every Turing machine can,… … Wikipedia
Undecidable problem — In computability theory and computational complexity theory, an undecidable problem is a decision problem for which it is impossible to construct an algorithm that leads to a yes or no answer the problem is not decidable.A decision problem is any … Wikipedia
