Post correspondence problem
E679187
The Post correspondence problem is a classic undecidable decision problem in theoretical computer science and mathematical logic that plays a central role in demonstrating the limits of algorithmic computability.
All labels observed (1)
| Label | Occurrences |
|---|---|
| Post correspondence problem canonical | 2 |
How this entity was disambiguated
This entity first appeared as the object of triple T7666832 — resolving that mention is where its identity was fixed. The disambiguator weighed these candidate entities and picked the highlighted one (or “None”, minting a new entity). This is how homonymy is resolved: the same surface form can point to different entities.
Target entity: Post correspondence problem Context triple: [Computability Theory, fieldOfStudy, Post correspondence problem]
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A.
Entscheidungsproblem
The Entscheidungsproblem is a foundational decision problem in mathematical logic that asks whether there exists a general algorithm to determine the truth or falsity of any given first-order logical statement.
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B.
Halting problem
The halting problem is a fundamental decision problem in computability theory that asks whether a given program will eventually stop running or continue to run forever, and is famously proven to be undecidable.
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C.
Computability and Unsolvability
Computability and Unsolvability is a classic 1958 textbook by Martin Davis that systematically develops the theory of computable functions and undecidable problems, helping to shape modern computability theory.
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D.
Kleene’s recursion theorem
Kleene’s recursion theorem is a fundamental result in computability theory that guarantees the existence of self-referential programs, allowing a program to effectively obtain and use its own description.
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E.
Hilbert’s tenth problem
Hilbert’s tenth problem is a famous unsolved question in mathematics that asked for a general algorithm to determine whether any given Diophantine equation has an integer solution, and whose negative answer helped establish fundamental limits of computability.
- F. None of above. chosen
- G. Unsure - the case is ambiguous/there is not enough information to decide.
Target entity: Post correspondence problem Target entity description: The Post correspondence problem is a classic undecidable decision problem in theoretical computer science and mathematical logic that plays a central role in demonstrating the limits of algorithmic computability.
-
A.
Entscheidungsproblem
The Entscheidungsproblem is a foundational decision problem in mathematical logic that asks whether there exists a general algorithm to determine the truth or falsity of any given first-order logical statement.
-
B.
Halting problem
The halting problem is a fundamental decision problem in computability theory that asks whether a given program will eventually stop running or continue to run forever, and is famously proven to be undecidable.
-
C.
Computability and Unsolvability
Computability and Unsolvability is a classic 1958 textbook by Martin Davis that systematically develops the theory of computable functions and undecidable problems, helping to shape modern computability theory.
-
D.
Kleene’s recursion theorem
Kleene’s recursion theorem is a fundamental result in computability theory that guarantees the existence of self-referential programs, allowing a program to effectively obtain and use its own description.
-
E.
Hilbert’s tenth problem
Hilbert’s tenth problem is a famous unsolved question in mathematics that asked for a general algorithm to determine whether any given Diophantine equation has an integer solution, and whose negative answer helped establish fundamental limits of computability.
- F. None of above. chosen
Statements (48)
| Predicate | Object |
|---|---|
| instanceOf |
computability theory problem
ⓘ
decision problem ⓘ problem in theoretical computer science ⓘ undecidable problem ⓘ |
| alphabetSizeCondition | undecidable for alphabet of size at least 2 ⓘ |
| appearsIn |
formal languages and automata theory courses
ⓘ
introductory computability theory textbooks ⓘ |
| boundedVariant | NP-complete ⓘ |
| centralConcept |
Turing computability
ⓘ
algorithmic unsolvability ⓘ reduction ⓘ undecidability ⓘ |
| completeFor | recursively enumerable sets under many-one reductions ⓘ |
| complexityClass | RE-complete ⓘ |
| decisionQuestion | existence of a matching sequence of indices ⓘ |
| definedOver | finite alphabet ⓘ |
| dominoCountCondition | undecidable for sufficiently many dominoes ⓘ |
| field |
computability theory
ⓘ
mathematical logic ⓘ theoretical computer science ⓘ |
| hasInput |
finite list of pairs of strings
ⓘ
finite set of dominoes ⓘ |
| hasVariant |
bounded Post correspondence problem
ⓘ
modified Post correspondence problem NERFINISHED ⓘ |
| introducedBy | Emil Post NERFINISHED ⓘ |
| language | formal language theory ⓘ |
| namedAfter | Emil Post NERFINISHED ⓘ |
| output | yes or no ⓘ |
| property |
not decidable
ⓘ
recursively enumerable ⓘ semi-decidable ⓘ |
| publication | A variant of a recursively unsolvable problem ⓘ |
| question | whether there exists a sequence of dominoes forming equal top and bottom strings ⓘ |
| relatedTo |
Post normal systems
NERFINISHED
ⓘ
Turing machines NERFINISHED ⓘ context-free grammars ⓘ halting problem NERFINISHED ⓘ tiling problem ⓘ word problem for semi-Thue systems ⓘ |
| role |
canonical example of an undecidable problem
ⓘ
tool for proving undecidability of other problems ⓘ |
| typicalReductionFrom |
halting problem
ⓘ
word problem for Post normal systems ⓘ |
| usedToProve |
undecidability of Post normal system properties
ⓘ
undecidability of context-free grammar equivalence ⓘ undecidability of problems in formal language theory ⓘ undecidability of the halting problem variants ⓘ |
| yearIntroduced | 1946 ⓘ |
How these facts were elicited
The pipeline generated the facts above by prompting gpt-5.1 with this entity's name + description and the instruction below.
You are a knowledge base construction expert. Given a subject entity and a description of it, return factual statements that you know for the subject as a JSON list of dictionaries(triples), where keys must be "subject", "predicate" and "object". The number of facts may be very high, between 25 to 50 or more, for very popular subjects. For less popular subjects, the number of facts can be very low, like 5 or 10. # Requirements - If you don't know the subject at all, return an empty list. - If the subject is not a named entity, return an empty list. - Include at least one triple where predicate is "instanceOf". - Do not get too wordy. - Separate several objects into multiple triples with one object.
Subject: Post correspondence problem Description of subject: The Post correspondence problem is a classic undecidable decision problem in theoretical computer science and mathematical logic that plays a central role in demonstrating the limits of algorithmic computability.
Referenced by (2)
Full triples — surface form annotated when it differs from this entity's canonical label.