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structure by the basic result that a set is computable if and only if the set and its complement are both computably enumerable. Infinite c.e. sets have always infinite computable subsets; but on the other hand, simple sets exist but do not always have a coinfinite computable superset. Post introduced already hypersimple and hyperhypersimple sets; later maximal sets were constructed which are c.e. sets such that every c.e. superset is either a finite variant of the given maximal set or is co-finite. Post's original motivation in the study of this lattice was to find a structural notion such that every set which satisfies this property is neither in the Turing degree of the computable sets nor in the Turing degree of the halting problem. Post did not find such a property and the solution to his problem applied priority methods instead; in 1991, Harrington and Soare found eventually such a property.
1237:(as defined in the previous paragraph) have the property that they cannot be automorphic to non-maximal sets, that is, if there is an automorphism of the computably enumerable sets under the structure just mentioned, then every maximal set is mapped to another maximal set. In 1974, Soare showed that also the converse holds, that is, every two maximal sets are automorphic. So the maximal sets form an orbit, that is, every automorphism preserves maximality and any two maximal sets are transformed into each other by some automorphism. Harrington gave a further example of an automorphic property: that of the creative sets, the sets which are many-one equivalent to the halting problem. 1195:, so that satisfying all the requirements will cause the set constructed to have the desired properties. Each requirement is assigned to a natural number representing the priority of the requirement; so 0 is assigned to the most important priority, 1 to the second most important, and so on. The set is then constructed in stages, each stage attempting to satisfy one of more of the requirements by either adding numbers to the set or banning numbers from the set so that the final set will satisfy the requirement. It may happen that satisfying one requirement will cause another to become unsatisfied; the priority order is used to decide what to do in such an event. 739:. After ten years, Kleene and Post showed in 1954 that there are intermediate Turing degrees between those of the computable sets and the halting problem, but they failed to show that any of these degrees contains a computably enumerable set. Very soon after this, Friedberg and Muchnik independently solved Post's problem by establishing the existence of computably enumerable sets of intermediate degree. This groundbreaking result opened a wide study of the Turing degrees of the computably enumerable sets which turned out to possess a very complicated and non-trivial structure. 6576: 1291:. This approach revolutionized earlier ways to determine when an infinite sequence (equivalently, characteristic function of a subset of the natural numbers) is random or not by invoking a notion of randomness for finite objects. Kolmogorov complexity became not only a subject of independent study but is also applied to other subjects as a tool for obtaining proofs. There are still many open problems in this area. 4798: 1752:, a prominent researcher in the field, has proposed that the field should be called "computability theory" instead. He argues that Turing's terminology using the word "computable" is more natural and more widely understood than the terminology using the word "recursive" introduced by Kleene. Many contemporary researchers have begun to use this alternate terminology. These researchers also use terminology such as 1169:(named after its discoverer) is a one-one numbering of all partial-computable functions; it is necessarily not an admissible numbering. Later research dealt also with numberings of other classes like classes of computably enumerable sets. Goncharov discovered for example a class of computably enumerable sets for which the numberings fall into exactly two classes with respect to computable isomorphisms. 4808: 4818: 979:, this is equivalent to saying that the reduction presents a single list of questions (depending only on the input) to the oracle simultaneously, and then having seen their answers is able to produce an output without asking additional questions regardless of the oracle's answer to the initial queries. Many variants of truth-table reducibility have also been studied. 1840: 1445:)-recursive. After a long phase of research by Russian scientists, this subject became repopularized in the west by Beigel's thesis on bounded queries, which linked frequency computation to the above-mentioned bounded reducibilities and other related notions. One of the major results was Kummer's Cardinality Theory which states that a set 1537:. Basic results are that all computably enumerable classes of functions are learnable while the class REC of all computable functions is not learnable. Many related models have been considered and also the learning of classes of computably enumerable sets from positive data is a topic studied from Gold's pioneering paper in 1967 onwards. 1804:
computable bijection, this proposal identifies all the infinite computable sets (the finite computable sets are viewed as trivial). According to Rogers, the sets of interest in computability theory are the noncomputable sets, partitioned into equivalence classes by computable bijections of the natural numbers.
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Beginning with the theory of computable sets and functions described above, the field of computability theory has grown to include the study of many closely related topics. These are not independent areas of research: each of these areas draws ideas and results from the others, and most computability
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Besides the lattice of computably enumerable sets, automorphisms are also studied for the structure of the Turing degrees of all sets as well as for the structure of the Turing degrees of c.e. sets. In both cases, Cooper claims to have constructed nontrivial automorphisms which map some degrees to
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The major research on strong reducibilities has been to compare their theories, both for the class of all computably enumerable sets as well as for the class of all subsets of the natural numbers. Furthermore, the relations between the reducibilities has been studied. For example, it is known that
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and hyperhypersimple sets. Post showed that these sets are strictly between the computable sets and the halting problem with respect to many-one reducibility. Post also showed that some of them are strictly intermediate under other reducibility notions stronger than Turing reducibility. But Post
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has stressed in his lecture (and I think justly) the great importance of the concept of general recursiveness (or Turing's computability). It seems to me that this importance is largely due to the fact that with this concept one has for the first time succeeded in giving an absolute notion to an
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has stressed in his lecture (and I think justly) the great importance of the concept of general recursiveness (or Turing's computability). It seems to me that this importance is largely due to the fact that with this concept one has for the first time succeeded in giving an absolute notion to an
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by permitting quantification over sets of natural numbers in addition to quantification over individual numbers. These areas are linked to the theories of well-orderings and trees; for example the set of all indices of computable (nonbinary) trees without infinite branches is complete for level
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Priority arguments have been employed to solve many problems in computability theory, and have been classified into a hierarchy based on their complexity. Because complex priority arguments can be technical and difficult to follow, it has traditionally been considered desirable to prove results
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When Post defined the notion of a simple set as a c.e. set with an infinite complement not containing any infinite c.e. set, he started to study the structure of the computably enumerable sets under inclusion. This lattice became a well-studied structure. Computable sets can be defined in this
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in geometry). The idea is that a computable bijection merely renames numbers in a set, rather than indicating any structure in the set, much as a rotation of the Euclidean plane does not change any geometric aspect of lines drawn on it. Since any two infinite computable sets are linked by a
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was developed during the 1960s and 1970s by Chaitin, Kolmogorov, Levin, Martin-Löf and Solomonoff (the names are given here in alphabetical order; much of the research was independent, and the unity of the concept of randomness was not understood at the time). The main idea is to consider a
713:. It can be shown that every computably enumerable set is many-one reducible to the halting problem, and thus the halting problem is the most complicated computably enumerable set with respect to many-one reducibility and with respect to Turing reducibility. In 1944, Post asked whether 742:
There are uncountably many sets that are not computably enumerable, and the investigation of the Turing degrees of all sets is as central in computability theory as the investigation of the computably enumerable Turing degrees. Many degrees with special properties were constructed:
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other degrees; this construction has, however, not been verified and some colleagues believe that the construction contains errors and that the question of whether there is a nontrivial automorphism of the Turing degrees is still one of the main unsolved questions in this area.
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Although there is considerable overlap in terms of knowledge and methods, mathematical computability theorists study the theory of relative computability, reducibility notions, and degree structures; those in the computer science field focus on the theory of
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Much recent research on Turing degrees has focused on the overall structure of the set of Turing degrees and the set of Turing degrees containing computably enumerable sets. A deep theorem of Shore and Slaman states that the function mapping a degree
1557:, as described by Sacks in 1990. These generalized notions include reducibilities that cannot be executed by Turing machines but are nevertheless natural generalizations of Turing reducibility. These studies include approaches to investigate the 537:
in the oracle set?". Each question will be immediately answered correctly, even if the oracle set is not computable. Thus an oracle machine with a noncomputable oracle will be able to compute sets that a Turing machine without an oracle cannot.
1701:, a formal theory of natural numbers and sets of natural numbers. The fact that certain sets are computable or relatively computable often implies that these sets can be defined in weak subsystems of second-order arithmetic. The program of 1199:
without priority arguments, or to see if results proved with priority arguments can also be proved without them. For example, Kummer published a paper on a proof for the existence of Friedberg numberings without using the priority method.
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as the correct formalization of the informal idea of effective calculation. In 1952, these results led Kleene to coin the two names "Church's thesis" and "Turing's thesis". Nowadays these are often considered as a single hypothesis, the
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Another important question is the existence of automorphisms in computability-theoretic structures. One of these structures is that one of computably enumerable sets under inclusion modulo finite difference; in this structure,
1191:. This method is primarily used to construct computably enumerable sets with particular properties. To use this method, the desired properties of the set to be constructed are broken up into an infinite list of goals, known as 1716:, as well as formal theories of the natural numbers weaker than Peano arithmetic. One method of classifying the strength of these weak systems is by characterizing which computable functions the system can prove to be 812:. The Turing jump of any set is always of higher Turing degree than the original set, and a theorem of Friedburg shows that any set that computes the Halting problem can be obtained as the Turing jump of another set. 1437: + 1. There are uncountably many of these sets and also some computably enumerable but noncomputable sets of this type. Later, Degtev established a hierarchy of computably enumerable sets that are (1,  465:, which is the set of (descriptions of) Turing machines that halt on input 0, is a well-known example of a noncomputable set. The existence of many noncomputable sets follows from the facts that there are only 480:
Although the halting problem is not computable, it is possible to simulate program execution and produce an infinite list of the programs that do halt. Thus the halting problem is an example of a
494:). Equivalently, a set is c.e. if and only if it is the range of some computable function. The c.e. sets, although not decidable in general, have been studied in detail in computability theory. 1705:
uses these subsystems to measure the non-computability inherent in well known mathematical theorems. In 1999, Simpson discussed many aspects of second-order arithmetic and reverse mathematics.
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to the degree of its Turing jump is definable in the partial order of the Turing degrees. A survey by Ambos-Spies and Fejer gives an overview of this research and its historical progression.
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contains the computably enumerable sets. The index sets given here are even complete for their levels, that is, all the sets in these levels can be many-one reduced to the given index sets.
846:, so named because they imply truth-table reducibility. A Turing machine implementing a strong reducibility will compute a total function regardless of which oracle it is presented with. 529:, introduced by Turing in 1939. An oracle Turing machine is a hypothetical device which, in addition to performing the actions of a regular Turing machine, is able to ask questions of an 458:
it is a total recursive (equivalently, general recursive) function. This article follows the second of these conventions. In 1996, Soare gave additional comments about the terminology.
1736:, which are not primitive recursive, are total. Not every total computable function is provably total in Peano arithmetic, however; an example of such a function is provided by 693:, but the converse does not always hold. Although the natural examples of noncomputable sets are all many-one equivalent, it is possible to construct computably enumerable sets 294:
is not effectively decidable. This result showed that there is no algorithmic procedure that can correctly decide whether arbitrary mathematical propositions are true or false.
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The terminology for computable functions and sets is not completely standardized. The definition in terms of μ-recursive functions as well as a different definition of
5630: 2224:(with commentary by Charles Parsons at pp. 144ff.). This 1990 edition has the cited footnote added by Gödel on p. 150 (which had also been added to Gödel's reprint in 2201:
To be more precise: a function of integers is computable in any formal system containing arithmetic if and only if it is computable in arithmetic, where a function
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Reducibilities weaker than Turing reducibility (that is, reducibilities that are implied by Turing reducibility) have also been studied. The most well known are
286:. In 1936, Church and Turing were inspired by techniques used by Gödel to prove his incompleteness theorems - in 1931, Gödel independently demonstrated that the 2619: 1481:'s model of learning in the limit from 1967 and has developed since then more and more models of learning. The general scenario is the following: Given a class 5713: 4854: 1129:
and others; in 1999, Simpson gave a detailed discussion of the program. The set-existence axioms in question correspond informally to axioms saying that the
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which was used in the original papers of Turing and others. In contemporary use, the term "computable function" has various definitions: according to
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for more detail). But, many of these index sets are even more complicated than the halting problem. These type of sets can be classified using the
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In 1967, Rogers has suggested that a key property of computability theory is that its results and structures should be invariant under computable
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The field of mathematical logic dealing with computability and its generalizations has been called "recursion theory" since its early days.
1393:)-recursive sets. The first major result in this branch of computability theory is Trakhtenbrot's result that a set is computable if it is ( 6040: 5363: 4427: 842:
An ongoing area of research in computability theory studies reducibility relations other than Turing reducibility. Post introduced several
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left open the main problem of the existence of computably enumerable sets of intermediate Turing degree; this problem became known as
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Further reducibilities (positive, disjunctive, conjunctive, linear and their weak and bounded versions) are discussed in the article
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to the halting problem, that is, whether there is no computably enumerable set with a Turing degree intermediate between those two.
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The study of arbitrary (not necessarily computably enumerable) Turing degrees involves the study of the Turing jump. Given a set
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The main form of computability studied in the field was introduced by Turing in 1936. A set of natural numbers is said to be a
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of the natural numbers is closed under various reducibility notions. The weakest such axiom studied in reverse mathematics is
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via an oracle Turing machine that computes a total function regardless of the oracle it is given. Because of compactness of
3544:(1958). "Three theorems on recursive enumeration: I. Decomposition, II. Maximal Set, III. Enumeration without repetition". 6600: 6534: 6317: 6234: 5947: 5878: 5755: 4997: 4642: 4619: 4349: 4339: 3703: 3546: 3155: 2778: 2021: 1126: 314: 5605: 6459: 6285: 5971: 5204: 4723: 4311: 4219: 4124: 3900: 3885: 2129: 1915: 1903: 1853: 1725: 1662:
There are close relationships between the Turing degree of a set of natural numbers and the difficulty (in terms of the
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of the analytical hierarchy. Both Turing reducibility and hyperarithmetical reducibility are important in the field of
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With a definition of effective calculation came the first proofs that there are problems in mathematics that cannot be
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of computable functions, is there a learner (that is, computable functional) which outputs for any input of the form (
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is a set of natural numbers encoding a solution to the halting problem for oracle Turing machines running with oracle
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Computability theory for digital computation is well developed. Computability theory is less well developed for
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sets (which were already known informally before Jockusch introduced them 1968) are examples of a set which is (
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The natural examples of sets that are not computable, including many different sets that encode variants of the
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where every function computable relative to that degree is majorized by a (unrelativized) computable function;
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asks which set-existence axioms are necessary to prove particular theorems of mathematics in subsystems of
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every Turing degree is either a truth-table degree or is the union of infinitely many truth-table degrees.
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are those where a reduction process may not terminate for all oracles; Turing reducibility is one example.
486:, which is a set that can be enumerated by a Turing machine (other terms for computably enumerable include 6519: 6246: 6224: 6191: 6084: 5930: 5915: 5888: 5839: 5723: 5658: 5483: 5449: 5444: 5318: 5149: 5126: 4778: 4609: 4490: 4257: 4247: 4242: 3473: 3322: 3061: 3009: 2810: 1737: 1663: 1562: 1554: 1260: 1061: 817: 623: 533:, which is a particular set of natural numbers. The oracle machine may only ask questions of the form "Is 345:
has no effective solution; this problem asked whether there is an effective procedure to decide whether a
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is not effectively solvable: there is no effective procedure that, given a word in a finitely presented
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How can noncomputable functions be classified into a hierarchy based on their level of noncomputability?
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The Undecidable: Basic Papers on Undecidable Propositions, Unsolvable Problems and Computable Functions
2731:. Handbook of the History of Logic. Vol. 9. Amsterdam: Elsevier/North-Holland. pp. 443–494. 6422: 6261: 6065: 5905: 5829: 5807: 5635: 5593: 5492: 5459: 5323: 5111: 5022: 4508: 4480: 4452: 4447: 4276: 4252: 4187: 4182: 4164: 4154: 4149: 4111: 4061: 4056: 3973: 3919: 3541: 3126: 2832: 2661: 2558: 2371: 2339: 1792:
fail to convey the fact that most of the objects studied in computability theory are not computable.
1558: 1162: 420: 346: 289: 3587: 1161:. Numberings can be partial-computable although some of its members are total computable functions. 1002:. These reducibilities are closely connected to definability over the standard model of arithmetic. 6551: 6442: 6427: 6407: 6364: 6251: 6201: 6127: 6072: 6009: 5802: 5797: 5745: 5513: 5502: 5174: 5074: 5002: 4993: 4989: 4924: 4919: 4773: 4698: 4614: 4599: 4364: 4144: 4101: 4096: 3993: 3983: 3955: 3660: 3014: 2922: 2878: 2814: 2503: 2468: 2094: 2048: 1858: 1702: 1686:. Gödel's proofs show that the set of logical consequences of an effective first-order theory is a 1166: 1113: 1106: 470: 398: 322: 266: 253: 57: 3803:
Webpage on Recursion Theory Course at Graduate Level with approximately 100 pages of lecture notes
3066: 1818:, which holds several research conferences each year. The interdisciplinary research Association 1569: 454:, it is a partial recursive function (which can be undefined for some inputs), while according to 6580: 6349: 6312: 6297: 6290: 6273: 6059: 5925: 5851: 5834: 5787: 5600: 5509: 5343: 5328: 5288: 5240: 5225: 5213: 5169: 5144: 4914: 4863: 4738: 4637: 4513: 4470: 4379: 4321: 4306: 4296: 4081: 3880: 3762: 3754: 3720: 3698: 3686: 3648: 3571: 3563: 3221: 2968: 2900: 2540: 2532: 2361: 2313: 2305: 2260: 1733: 1631: 1619: 1049: 906: 877: 857: 788: 630: 115:. The study of which mathematical constructions can be effectively performed is sometimes called 45: 6077: 5533: 3518:
Burgin, Mark; Klinger, Allen (2004). "Experience, Generations, and Limits in Machine Learning".
3493: 3477: 2758: 2507: 2052: 6515: 6322: 6132: 6122: 6014: 5895: 5730: 5706: 5487: 5471: 5376: 5353: 5230: 5199: 5164: 5059: 4894: 4758: 4688: 4667: 4629: 4437: 4404: 4384: 4076: 3988: 3862: 3497: 3452: 3426: 3396: 3373: 3352: 3342: 3300: 3274: 3270: 3233: 3192: 3159: 3106: 3090: 3027: 2984: 2860: 2790: 2740: 2691: 2480: 2445: 2190: 2143: 2106: 1992: 1980: 1845: 1671: 1667: 1057: 1010: 813: 735: 330: 302: 234: 2881:(1974). "Automorphisms of the lattice of recursively enumerable sets, Part I: Maximal sets". 6529: 6524: 6417: 6374: 6196: 6157: 6152: 6137: 5963: 5920: 5817: 5615: 5565: 5139: 5101: 4591: 4475: 4442: 4237: 4159: 4048: 4034: 4029: 3978: 3965: 3890: 3843: 3802: 3746: 3712: 3678: 3638: 3604: 3555: 3529: 3071: 3019: 2940: 2892: 2850: 2840: 2732: 2681: 2628: 2580: 2572: 2524: 2429: 2392: 2353: 2297: 2252: 2178: 2030: 1800: 1729: 1713: 1647: 547: 512: 451: 326: 49: 2954: 2754: 2703: 2642: 724:
As intermediate results, Post defined natural types of computably enumerable sets like the
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have been shown to be undecidable after these initial examples were established. In 1947,
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with respect to a previously agreed on acceptable numbering of all computable functions;
2836: 1469:; these choices must contain the true cardinality but leave out at least one false one. 6495: 6474: 6432: 6412: 6307: 6162: 5760: 5750: 5740: 5735: 5669: 5543: 5419: 5308: 5303: 5281: 4882: 4768: 4672: 4571: 4417: 4389: 3732: 3664: 3415: 3094: 2973: 2736: 2610: 2434: 2034: 1717: 1639: 376: 359: 334: 242: 92: 17: 3643: 3624: 3609: 2376:"On Computable Numbers, with an Application to the Entscheidungsproblem. A Correction" 1137:, which states that the powerset of the naturals is closed under Turing reducibility. 611:). The Turing degree of a set gives a precise measure of how uncomputable the set is. 6594: 6469: 6147: 5654: 5439: 5429: 5399: 5384: 5054: 4657: 3945: 3724: 3489: 3422: 3334: 3075: 2855: 2818: 2585: 2283: 2238: 2221: 2174: 2158: 2154: 2102: 2012: 1988: 1675: 1545:
Computability theory includes the study of generalized notions of this field such as
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interesting epistemological notion, i.e., one not depending on the formalism chosen."
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interesting epistemological notion, i.e., one not depending on the formalism chosen.
1690:, and that if the theory is strong enough this set will be uncomputable. Similarly, 469:
Turing machines, and thus only countably many computable sets, but according to the
6369: 6216: 6117: 6109: 5989: 5937: 5846: 5782: 5765: 5696: 5555: 5414: 5116: 4899: 4753: 4412: 3807: 3583: 2544: 2342:(1937) . "On computable numbers, with an application to the Entscheidungsproblem". 1709: 1478: 976: 73: 1064:. For example, the index set FIN of the class of all finite sets is on the level Σ 3023: 2365: 2133: 6479: 6359: 5538: 5528: 5475: 5159: 5079: 5064: 4944: 4889: 4743: 4369: 4281: 3481: 1976: 1694:
can be interpreted both in terms of definability and in terms of computability.
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This branch of computability theory analyzed the following question: For fixed
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This is the computability-theoretic branch of learning theory. It is based on
725: 269:. Although initially skeptical, by 1946 Gödel argued in favor of this thesis: 2945: 2926: 2845: 2695: 6561: 6464: 5517: 5434: 5394: 5358: 5294: 5106: 5096: 5069: 4268: 4229: 3338: 3296: 3229: 1796: 262: 246: 2864: 2053:"Computability Theory and Applications: The Art of Classical Computability" 2016: 1927:
A list of open problems is maintained by Joseph Miller and André Nies, the
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establishes a close relationship between the Turing jump operation and the
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if there is an oracle machine that correctly tells whether numbers are in
419:). The use of Turing machines here is not necessary; there are many other 6546: 6344: 5792: 5497: 5091: 4329: 3448: 3102: 3050:(1996). "Recursion theory on the reals and continuous-time computation". 3004:
Orponen, Pekka (1997). "A Survey of Continuous-Time Computation Theory".
1130: 3667:(1954). "The upper semi-lattice of degrees of recursive unsolvability". 1068:, the index set REC of the class of all recursive sets is on the level Σ 787:
degrees of 1-generic sets; and the degrees below the halting problem of
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Computability theory in mathematical logic has traditionally focused on
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that have the same computing power as Turing machines; for example the
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contains just all sets which are computably enumerable relative to Σ
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Many-one reductions are "stronger" than Turing reductions: if a set
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The main professional organization for computability theory is the
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A numbering is an enumeration of functions; it has two parameters,
64:. The field has since expanded to include the study of generalized 5686: 5032: 4877: 1799:
on the natural numbers (this suggestion draws on the ideas of the
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and the index set COMP of the class of all Turing-complete sets Σ
1072:, the index set COFIN of all cofinite sets is also on the level Σ 325:, will decide whether the element represented by the word is the 3356: 440:
for sets and functions computable by a Turing machine. The word
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Computability theory originated in the 1930s, with the work of
2241:(1936a). "An unsolvable problem of elementary number theory". 3226:
The Theory of Recursive Functions and Effective Computability
252:
The fundamental results the researchers obtained established
3785: 2819:"Post's Program and incomplete recursively enumerable sets" 2436:
Computability, An introduction to recursive function theory
1724:
any computable function that is provably total is actually
1658:
Relationships between definability, proof and computability
1179:
Turing degree § Post's problem and the priority method
83:
Basic questions addressed by computability theory include:
1017:(which contains some but not all c.e. sets) the index set 261:, which states that any function that is computable by an 219:
Hence, it is not computable; only a few values are known.
2715: 2713: 525:, a generalization of Turing computability defined using 3735:(1947). "Recursive unsolvability of a problem of Thue". 1461:
many possible choices of the cardinality of this set of
305:
and Post published independent papers showing that the
3701:(1956). "The lattice of recursively enumerable sets". 3331:
Systems that learn: an introduction to learning theory
1453:
such that some algorithm enumerates for each tuple of
1271:
and to measure the complexity of a number (or string)
1005: 427:
obtained from primitive recursion and the μ operator.
309:
cannot be effectively decided. Extending this result,
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are those into which all others can be translated. A
72:. In these areas, computability theory overlaps with 3808:
German language lecture notes on inductive inference
461:
Not every set of natural numbers is computable. The
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Proceedings of the National Academy of Sciences USA
1895:Many of these foundational papers are collected in 1183:Post's problem was solved with a method called the 1080:. These hierarchy levels are defined inductively, Σ 3414: 2972: 2433: 1712:includes the study of second-order arithmetic and 1590: 717:computably enumerable set is either computable or 503:theorists are familiar with the majority of them. 349:over the integers has a solution in the integers. 3630:Transactions of the American Mathematical Society 3006:Advances in Algorithms, Languages, and Complexity 2220:(NB. This volume also includes the 1946 paper by 1828:) also organizes a series of annual conferences. 1650:. For example, models of computation such as the 1654:model have formalized computation on the reals. 27:Study of computable functions and Turing degrees 2773: 2771: 2286:(1936b). "A note on the Entscheidungsproblem". 1886:covers many of the known results in this field. 436:functions by Gödel led to the traditional name 271: 56:that originated in the 1930s with the study of 3625:"Semirecursive sets and positive reducibility" 2564:Proceedings of the London Mathematical Society 2561:(1939). "Systems of logic based on ordinals". 2384:Proceedings of the London Mathematical Society 2345:Proceedings of the London Mathematical Society 2334: 2332: 4848: 3852:Note: This template roughly follows the 2012 3828: 3091:"Hierarchies of Provably Recursive Functions" 3089:Fairtlough, Matt; Wainer, Stanley S. (1998). 2620:Bulletin of the American Mathematical Society 2498: 2496: 2463: 2461: 2089: 2087: 1006:Rice's theorem and the arithmetical hierarchy 751:relative to which one can compute a function 507:Relative computability and the Turing degrees 395:from natural numbers to natural numbers is a 8: 2720:Ambos-Spies, Klaus; Fejer, Peter A. (2014). 2605: 2603: 2601: 2124: 2122: 1674:. A weaker relationship was demonstrated by 1509:if almost all hypotheses are the same index 1319:is it possible to compute for any different 629:Each can be translated into any other via a 445: 431: 407:if there is a Turing machine that, on input 287: 217:) grows faster than any computable function. 3131:"Is it Recursive, Computable or Decidable?" 2183:Kurt Gödel Publications 1938–1974 Volume II 1670:. One such relationship is made precise by 1441: + 1)-recursive but not (1,  1157:-th function in the numbering on the input 1044:or its complement is many-one reducible to 317:showed independently in the 1950s that the 5674: 5269: 5037: 4855: 4841: 4833: 3835: 3821: 3813: 755:which dominates every computable function 128: 3642: 3608: 3065: 3013: 2944: 2854: 2844: 2685: 2632: 2584: 1582: 1577: 1571: 1449:is computable if and only if there is an 1203:The lattice of computably enumerable sets 563:as the oracle set (in this case, the set 387:is in the set and halts with output 0 if 1187:; a proof using this method is called a 929:if there is a total computable function 601:then the sets are said to have the same 3786:Association for Symbolic Logic homepage 2473:Recursively Enumerable Sets and Degrees 1960: 1875: 1697:Computability theory is also linked to 1541:Generalizations of Turing computability 1013:showed that for every nontrivial class 641:, there is a total computable function 4552:Knowledge representation and reasoning 3588:"Language Identification in the Limit" 3368:. Perspectives in Mathematical Logic. 2475:. Perspectives in Mathematical Logic. 759:in the sense that there is a constant 30:For the concept of computability, see 4577:Philosophy of artificial intelligence 3772: 2783:Subsystems of Second Order Arithmetic 2648: 2592: 2416: 2323: 2270: 2225: 1896: 541:Informally, a set of natural numbers 7: 3896:Energy consumption (Green computing) 2927:"Definability in the Turing degrees" 1275:as the length of the shortest input 4582:Distributed artificial intelligence 3854:ACM Computing Classification System 1040:} has the property that either the 853:The strong reducibilities include: 4087:Integrated development environment 2737:10.1016/B978-0-444-51624-4.50010-1 2035:10.1002/j.1538-7305.1962.tb00480.x 1602:. The even more general notion of 1574: 1385:are true. Such sets are known as ( 1225:if and only if the set difference 25: 4562:Automated planning and scheduling 4092:Software configuration management 3644:10.1090/S0002-9947-1968-0220595-7 1985:Handbook of Recursive Mathematics 1884:Handbook of Recursive Mathematics 1048:, that is, can be mapped using a 618:, have two properties in common: 6574: 4816: 4806: 4797: 4796: 3791:Computability in Europe homepage 3289:Matiyasevich, Yuri Vladimirovich 1973:Goncharov, Sergei Savostyanovich 1838: 1600:effective descriptive set theory 1417:. On the other hand, Jockusch's 985:Reduction (computability theory) 483:computably enumerable (c.e.) set 78:effective descriptive set theory 4807: 4210:Computational complexity theory 3512:Research papers and collections 3203:from the original on 2022-03-01 3170:from the original on 2021-12-18 3160:"What is computability theory?" 3137:from the original on 2022-08-07 2932:Illinois Journal of Mathematics 2634:10.1090/S0002-9904-1944-08111-1 2406:from the original on 2022-07-18 2244:American Journal of Mathematics 2213:a computable term representing 2185:. Vol. II. New York, USA: 2099:Introduction to Metamathematics 2073:from the original on 2022-06-30 1732:proves that functions like the 1692:Tarski's indefinability theorem 1666:) of defining that set using a 1614:Continuous computability theory 876:if there is a total computable 681:is many-one reducible to a set 3994:Network performance evaluation 3486:Handbook of Mathematical Logic 3478:"Elements of Recursion Theory" 2727:. In Siekmann, Jörg H. (ed.). 1943:searches for the titles like " 1815:Association for Symbolic Logic 1722:primitive recursive arithmetic 1551:hyperarithmetical reducibility 1121:. This study was initiated by 1000:hyperarithmetical reducibility 709:but not many-one reducible to 391:is not in the set. A function 1: 6535:History of mathematical logic 4365:Multimedia information system 4350:Geographic information system 4340:Enterprise information system 3929:Computer systems organization 3704:The Journal of Symbolic Logic 3610:10.1016/s0019-9958(67)91165-5 3547:The Journal of Symbolic Logic 3467:Survey papers and collections 2674:Mathematical Research Letters 2508:"Computability and recursion" 2022:Bell System Technical Journal 2017:"On non-computable functions" 1153:and outputs the value of the 1125:and was studied in detail by 665:}. These sets are said to be 589:is Turing reducible to a set 6460:Primitive recursive function 4724:Computational social science 4312:Theoretical computer science 4125:Software development process 3901:Electronic design automation 3886:Very Large Scale Integration 3521:Theoretical Computer Science 3389:Computability and Randomness 3076:10.1016/0304-3975(95)00248-0 3053:Theoretical Computer Science 3024:10.1007/978-1-4613-3394-4_11 1916:list of undecidable problems 1854:Recursion (computer science) 1591:{\displaystyle \Pi _{1}^{1}} 1429:)-recursive if and only if 2 963:is truth-table reducible to 838:Reduction (recursion theory) 198: 192: 180: 175: 172: 169: 166: 4547:Natural language processing 4335:Information storage systems 3193:"Renaming recursion theory" 1754:partial computable function 1604:degrees of constructibility 1501:)) a hypothesis. A learner 781:algorithmically random sets 633:. That is, given such sets 444:stems from the German word 411:, halts and returns output 307:word problem for semigroups 151: 148: 6622: 5524:Schröder–Bernstein theorem 5251:Monadic predicate calculus 4910:Foundations of mathematics 4463:Human–computer interaction 4433:Intrusion detection system 4345:Social information systems 4330:Database management system 3445:Classical Recursion Theory 3417:Classical Recursion Theory 2722:"Degrees of unsolvability" 2687:10.4310/mrl.1999.v6.n6.a10 2670:"Defining the Turing Jump" 2516:Bulletin of Symbolic Logic 2442:Cambridge University Press 1918:gives additional examples. 1864:Transcomputational problem 1808:Professional organizations 1770:partial recursive function 1636:artificial neural networks 1248: 1176: 1104: 835: 510: 154: 145: 142: 139: 136: 29: 6570: 6557:Philosophy of mathematics 6506:Automated theorem proving 5677: 5631:Von Neumann–Bernays–Gödel 5272: 4792: 4729:Computational engineering 4704:Computational mathematics 3850: 3738:Journal of Symbolic Logic 3717:10.1017/S002248120008525X 3534:10.1016/j.tcs.2003.12.005 3256:Undergraduate level texts 2586:21.11116/0000-0001-91CE-3 2289:Journal of Symbolic Logic 2060:Department of Mathematics 1688:computably enumerable set 1465:numbers intersected with 996:arithmetical reducibility 477:sets of natural numbers. 383:, halts with output 1 if 333:proved (using results of 205: 4739:Computational healthcare 4734:Differentiable computing 4653:Graphics processing unit 4072:Domain-specific language 3941:Computational complexity 3621:Jockusch, Carl Groos Jr. 3366:Degrees of unsolvability 3099:Handbook of Proof Theory 2846:10.1073/pnas.88.22.10242 2577:10.1112/plms/s2-45.1.161 2397:10.1112/plms/s2-43.6.544 2358:10.1112/plms/s2-42.1.230 2205:is called computable in 2140:Dover Publications, Inc. 1969:Ershov, Yury Leonidovich 1628:analog signal processing 1457:different numbers up to 1266:universal Turing machine 957:Truth-table reducibility 745:hyperimmune-free degrees 105:subrecursive hierarchies 87:What does it mean for a 6207:Self-verifying theories 6028:Tarski's axiomatization 4979:Tarski's undefinability 4974:incompleteness theorems 4714:Computational chemistry 4648:Photograph manipulation 4539:Artificial intelligence 4355:Decision support system 3596:Information and Control 3474:Enderton, Herbert Bruce 3393:Oxford University Press 3364:Lerman, Manuel (1983). 3323:Osherson, Daniel Nathan 3293:Hilbert's Tenth Problem 3156:Simpson, Stephen George 2975:Higher Recursion Theory 2811:Harrington, Leo Anthony 2226:Davis' 1965 compilation 2187:Oxford University Press 1821:Computability in Europe 1774:recursively enumerable 1699:second-order arithmetic 1684:incompleteness theorems 1652:Blum–Shub–Smale machine 1561:which differs from the 1547:arithmetic reducibility 1135:recursive comprehension 1119:second-order arithmetic 971:is Turing reducible to 705:is Turing reducible to 689:is Turing reducible to 609:degree of unsolvability 597:is Turing reducible to 343:Hilbert's tenth problem 329:of the group. In 1970, 319:word problem for groups 18:Theory of computability 6581:Mathematics portal 6192:Proof of impossibility 5840:propositional variable 5150:Propositional calculus 4779:Educational technology 4610:Reinforcement learning 4360:Process control system 4258:Computational geometry 4248:Algorithmic efficiency 4243:Analysis of algorithms 3891:Systems on Chip (SoCs) 3441:Odifreddi, Piergiorgio 3411:Odifreddi, Piergiorgio 2946:10.1215/ijm/1256044641 2919:Slaman, Theodore Allen 2779:Simpson, Steven George 2666:Slaman, Theodore Allen 2181:; et al. (eds.). 1758:computably enumerable 1664:arithmetical hierarchy 1644:differential equations 1592: 1563:arithmetical hierarchy 1315:, for which functions 1307:with 0 <  1261:algorithmic randomness 1062:arithmetical hierarchy 818:arithmetical hierarchy 527:oracle Turing machines 523:relative computability 488:recursively enumerable 446: 432: 339:Matiyasevich's theorem 288: 280: 6450:Kolmogorov complexity 6403:Computably enumerable 6303:Model complete theory 6095:Principia Mathematica 5155:Propositional formula 4984:Banach–Tarski paradox 4749:Electronic publishing 4719:Computational biology 4709:Computational physics 4605:Unsupervised learning 4519:Distributed computing 4395:Information retrieval 4302:Mathematical analysis 4292:Mathematical software 4175:Theory of computation 4140:Software construction 4130:Requirements analysis 4008:Software organization 3936:Computer architecture 3906:Hardware acceleration 3871:Printed circuit board 3670:Annals of Mathematics 3542:Friedberg, Richard M. 3127:Fortnow, Lance Jeremy 2884:Annals of Mathematics 2662:Shore, Richard Arnold 2559:Turing, Alan Mathison 2372:Turing, Alan Mathison 2340:Turing, Alan Mathison 2105:. pp. 300, 376. 2064:University of Chicago 1945:computably enumerable 1929:André Nies's homepage 1678:in the proofs of his 1593: 1401:)-recursive for some 1295:Frequency computation 1257:Kolmogorov complexity 1251:Kolmogorov complexity 1245:Kolmogorov complexity 1212:Automorphism problems 1177:Further information: 1163:Admissible numberings 907:Many-one reducibility 844:strong reducibilities 624:computably enumerable 425:μ-recursive functions 421:models of computation 379:that, given a number 341:, which implies that 117:recursive mathematics 54:theory of computation 6601:Computability theory 6398:Church–Turing thesis 6385:Computability theory 5594:continuum hypothesis 5112:Square of opposition 4970:Gödel's completeness 4509:Concurrent computing 4481:Ubiquitous computing 4453:Application security 4448:Information security 4277:Discrete mathematics 4253:Randomized algorithm 4205:Computability theory 4183:Model of computation 4155:Software maintenance 4150:Software engineering 4112:Software development 4062:Programming language 4057:Programming paradigm 3974:Network architecture 3661:Kleene, Stephen Cole 3387:Nies, André (2009). 3267:Computability Theory 3105:. pp. 149–208. 3008:. pp. 209–224. 2923:Woodin, William Hugh 2879:Soare, Robert Irving 2815:Soare, Robert Irving 2504:Soare, Robert Irving 2469:Soare, Robert Irving 2095:Kleene, Stephen Cole 2049:Soare, Robert Irving 1790:computability theory 1680:completeness theorem 1638:and continuous-time 1570: 1559:analytical hierarchy 1493:(1), ...,  858:One-one reducibility 832:Other reducibilities 567:is also said to be ( 447:Entscheidungsproblem 353:Turing computability 347:Diophantine equation 290:Entscheidungsproblem 259:Church–Turing thesis 254:Turing computability 58:computable functions 38:Computability theory 6552:Mathematical object 6443:P versus NP problem 6408:Computable function 6202:Reverse mathematics 6128:Logical consequence 6005:primitive recursive 6000:elementary function 5773:Free/bound variable 5626:Tarski–Grothendieck 5145:Logical connectives 5075:Logical equivalence 4925:Logical consequence 4784:Document management 4774:Operations research 4699:Enterprise software 4615:Multi-task learning 4600:Supervised learning 4322:Information systems 4145:Software deployment 4102:Software repository 3956:Real-time computing 3699:Myhill, John R. Sr. 3325:; Royer, James S.; 3222:Rogers, Hartley Jr. 2969:Sacks, Gerald Enoch 2837:1991PNAS...8810242H 2831:(22): 10242–10246. 2729:Computational Logic 1859:Computability logic 1738:Goodstein's theorem 1726:primitive recursive 1703:reverse mathematics 1668:first-order formula 1587: 1473:Inductive inference 1363:such that at least 1229: −  1173:The priority method 1167:Friedberg numbering 1114:reverse mathematics 1107:Reverse mathematics 1101:Reverse mathematics 848:Weak reducibilities 667:many-one equivalent 375:set) if there is a 284:effectively decided 267:computable function 6606:Mathematical logic 6350:Transfer principle 6313:Semantics of logic 6298:Categorical theory 6274:Non-standard model 5788:Logical connective 4915:Information theory 4864:Mathematical logic 4567:Search methodology 4514:Parallel computing 4471:Interaction design 4380:Computing platform 4307:Numerical analysis 4297:Information theory 4082:Software framework 4045:Software notations 3984:Network components 3881:Integrated circuit 3796:2011-02-17 at the 3271:Chapman & Hall 2189:. pp. 144ff. 1981:Remmel, Jeffrey B. 1734:Ackermann function 1720:. For example, in 1632:analog electronics 1620:analog computation 1588: 1573: 1555:α-recursion theory 1505:learns a function 1358:, ..., y 1050:many-one reduction 919:many-one reducible 878:injective function 631:many-one reduction 405:recursive function 46:mathematical logic 6588: 6587: 6520:Abstract category 6323:Theories of truth 6133:Rule of inference 6123:Natural deduction 6104: 6103: 5649: 5648: 5354:Cartesian product 5259: 5258: 5165:Many-valued logic 5140:Boolean functions 5023:Russell's paradox 4998:diagonal argument 4895:First-order logic 4830: 4829: 4759:Electronic voting 4689:Quantum Computing 4682:Applied computing 4668:Image compression 4438:Hardware security 4428:Security services 4385:Digital marketing 4165:Open-source model 4077:Modeling language 3989:Network scheduler 3402:978-0-19-923076-1 3112:978-0-08-053318-6 3033:978-1-4613-3396-8 2746:978-0-444-51624-4 2430:Cutland, Nigel J. 2196:978-0-19-514721-6 2179:Feferman, Solomon 2149:978-0-486-43228-1 1931:has it published. 1846:Philosophy portal 1648:dynamical systems 1367:of the equations 1337:, ...,  1189:priority argument 866:one-one reducible 719:Turing equivalent 498:Areas of research 373:Turing computable 331:Yuri Matiyasevich 297:Many problems in 223: 222: 95:to be computable? 44:, is a branch of 16:(Redirected from 6613: 6579: 6578: 6530:History of logic 6525:Category of sets 6418:Decision problem 6197:Ordinal analysis 6138:Sequent calculus 6036:Boolean algebras 5976: 5975: 5950: 5921:logical/constant 5675: 5661: 5584:Zermelo–Fraenkel 5335:Set operations: 5270: 5207: 5038: 5018:Löwenheim–Skolem 4905:Formal semantics 4857: 4850: 4843: 4834: 4820: 4819: 4810: 4809: 4800: 4799: 4620:Cross-validation 4592:Machine learning 4476:Social computing 4443:Network security 4238:Algorithm design 4160:Programming team 4120:Control variable 4097:Software library 4035:Software quality 4030:Operating system 3979:Network protocol 3844:Computer science 3837: 3830: 3823: 3814: 3770: 3728: 3694: 3656: 3646: 3614: 3612: 3592: 3579: 3537: 3507: 3462: 3447:. Vol. II. 3436: 3420: 3406: 3383: 3360: 3333:(2nd ed.). 3310: 3284: 3263:Cooper, S. Barry 3244: 3243: 3228:(2nd ed.). 3218: 3212: 3211: 3209: 3208: 3189:Friedman, Harvey 3185: 3179: 3178: 3176: 3175: 3152: 3146: 3145: 3143: 3142: 3123: 3117: 3116: 3086: 3080: 3079: 3069: 3044: 3038: 3037: 3017: 3001: 2995: 2994: 2978: 2965: 2959: 2958: 2948: 2915: 2909: 2908: 2875: 2869: 2868: 2858: 2848: 2807: 2801: 2800: 2775: 2766: 2765: 2763: 2757:. Archived from 2726: 2717: 2708: 2707: 2689: 2658: 2652: 2646: 2636: 2607: 2596: 2590: 2588: 2555: 2549: 2548: 2512: 2500: 2491: 2490: 2465: 2456: 2455: 2439: 2426: 2420: 2414: 2412: 2411: 2405: 2380: 2369: 2336: 2327: 2321: 2280: 2274: 2268: 2235: 2229: 2219: 2171: 2165: 2164: 2126: 2117: 2116: 2091: 2082: 2081: 2079: 2078: 2072: 2057: 2045: 2039: 2038: 2009: 2003: 2002: 1965: 1948: 1938: 1932: 1925: 1919: 1912: 1906: 1893: 1887: 1880: 1848: 1843: 1842: 1841: 1801:Erlangen program 1786:recursion theory 1730:Peano arithmetic 1714:Peano arithmetic 1624:analog computers 1597: 1595: 1594: 1589: 1586: 1581: 1433: <  1413: >  1311: <  789:limit-computable 548:Turing reducible 513:Turing reduction 475:uncountably many 471:Cantor's theorem 452:Nigel J. Cutland 449: 435: 327:identity element 293: 208: 201: 195: 190: 188: 183: 178: 129: 113:formal languages 50:computer science 42:recursion theory 40:, also known as 21: 6621: 6620: 6616: 6615: 6614: 6612: 6611: 6610: 6591: 6590: 6589: 6584: 6573: 6566: 6511:Category theory 6501:Algebraic logic 6484: 6455:Lambda calculus 6393:Church encoding 6379: 6355:Truth predicate 6211: 6177:Complete theory 6100: 5969: 5965: 5961: 5956: 5948: 5668: and  5664: 5659: 5645: 5621:New Foundations 5589:axiom of choice 5572: 5534:Gödel numbering 5474: and  5466: 5370: 5255: 5205: 5186: 5135:Boolean algebra 5121: 5085:Equiconsistency 5050:Classical logic 5027: 5008:Halting problem 4996: and  4972: and  4960: and  4959: 4954:Theorems ( 4949: 4866: 4861: 4831: 4826: 4817: 4788: 4769:Word processing 4677: 4663:Virtual reality 4624: 4586: 4557:Computer vision 4533: 4529:Multiprocessing 4495: 4457: 4423:Security hacker 4399: 4375:Digital library 4316: 4267:Mathematics of 4262: 4224: 4200:Automata theory 4195:Formal language 4169: 4135:Software design 4106: 4039: 4025:Virtual machine 4003: 3999:Network service 3960: 3951:Embedded system 3924: 3857: 3846: 3841: 3798:Wayback Machine 3782: 3751:10.2307/2267170 3733:Post, Emil Leon 3731: 3697: 3683:10.2307/1969708 3665:Post, Emil Leon 3659: 3619: 3590: 3582: 3560:10.2307/2964290 3540: 3517: 3504: 3472: 3459: 3439: 3433: 3409: 3403: 3386: 3380: 3370:Springer-Verlag 3363: 3349: 3320: 3307: 3287: 3281: 3261: 3253: 3251:Further reading 3248: 3247: 3240: 3220: 3219: 3215: 3206: 3204: 3187: 3186: 3182: 3173: 3171: 3154: 3153: 3149: 3140: 3138: 3125: 3124: 3120: 3113: 3095:Buss, Samuel R. 3088: 3087: 3083: 3046: 3045: 3041: 3034: 3003: 3002: 2998: 2991: 2981:Springer-Verlag 2967: 2966: 2962: 2917: 2916: 2912: 2897:10.2307/1970842 2877: 2876: 2872: 2809: 2808: 2804: 2797: 2787:Springer-Verlag 2777: 2776: 2769: 2761: 2747: 2724: 2719: 2718: 2711: 2660: 2659: 2655: 2611:Post, Emil Leon 2609: 2608: 2599: 2557: 2556: 2552: 2510: 2502: 2501: 2494: 2487: 2477:Springer-Verlag 2467: 2466: 2459: 2452: 2428: 2427: 2423: 2409: 2407: 2403: 2378: 2370: 2338: 2337: 2330: 2302:10.2307/2269326 2282: 2281: 2277: 2257:10.2307/2371045 2237: 2236: 2232: 2209:if there is in 2199:. p. 150: 2197: 2177:(1990). "". In 2173: 2172: 2168: 2150: 2132:, ed. (2004) . 2128: 2127: 2120: 2113: 2093: 2092: 2085: 2076: 2074: 2070: 2055: 2047: 2046: 2042: 2011: 2010: 2006: 1999: 1967: 1966: 1962: 1957: 1952: 1951: 1939: 1935: 1926: 1922: 1913: 1909: 1898:The Undecidable 1894: 1890: 1881: 1877: 1872: 1844: 1839: 1837: 1834: 1810: 1750:Robert I. Soare 1746: 1660: 1646:and continuous 1622:that occurs in 1616: 1568: 1567: 1543: 1475: 1383: 1376: 1361: 1357: 1353: 1342: 1336: 1329: 1297: 1253: 1247: 1214: 1205: 1185:priority method 1181: 1175: 1143: 1127:Stephen Simpson 1123:Harvey Friedman 1111:The program of 1109: 1103: 1096: 1092: 1086: 1079: 1075: 1071: 1067: 1042:halting problem 1034: 1008: 941:if and only if 933:such that each 891:if and only if 883:such that each 840: 834: 616:halting problem 573:computable from 519: 511:Main articles: 509: 500: 463:halting problem 456:Robert I. Soare 363:(also called a 355: 218: 207:Does not appear 206: 199: 193: 186: 184: 181: 176: 125: 93:natural numbers 35: 28: 23: 22: 15: 12: 11: 5: 6619: 6617: 6609: 6608: 6603: 6593: 6592: 6586: 6585: 6571: 6568: 6567: 6565: 6564: 6559: 6554: 6549: 6544: 6543: 6542: 6532: 6527: 6522: 6513: 6508: 6503: 6498: 6496:Abstract logic 6492: 6490: 6486: 6485: 6483: 6482: 6477: 6475:Turing machine 6472: 6467: 6462: 6457: 6452: 6447: 6446: 6445: 6440: 6435: 6430: 6425: 6415: 6413:Computable set 6410: 6405: 6400: 6395: 6389: 6387: 6381: 6380: 6378: 6377: 6372: 6367: 6362: 6357: 6352: 6347: 6342: 6341: 6340: 6335: 6330: 6320: 6315: 6310: 6308:Satisfiability 6305: 6300: 6295: 6294: 6293: 6283: 6282: 6281: 6271: 6270: 6269: 6264: 6259: 6254: 6249: 6239: 6238: 6237: 6232: 6225:Interpretation 6221: 6219: 6213: 6212: 6210: 6209: 6204: 6199: 6194: 6189: 6179: 6174: 6173: 6172: 6171: 6170: 6160: 6155: 6145: 6140: 6135: 6130: 6125: 6120: 6114: 6112: 6106: 6105: 6102: 6101: 6099: 6098: 6090: 6089: 6088: 6087: 6082: 6081: 6080: 6075: 6070: 6050: 6049: 6048: 6046:minimal axioms 6043: 6032: 6031: 6030: 6019: 6018: 6017: 6012: 6007: 6002: 5997: 5992: 5979: 5977: 5958: 5957: 5955: 5954: 5953: 5952: 5940: 5935: 5934: 5933: 5928: 5923: 5918: 5908: 5903: 5898: 5893: 5892: 5891: 5886: 5876: 5875: 5874: 5869: 5864: 5859: 5849: 5844: 5843: 5842: 5837: 5832: 5822: 5821: 5820: 5815: 5810: 5805: 5800: 5795: 5785: 5780: 5775: 5770: 5769: 5768: 5763: 5758: 5753: 5743: 5738: 5736:Formation rule 5733: 5728: 5727: 5726: 5721: 5711: 5710: 5709: 5699: 5694: 5689: 5684: 5678: 5672: 5655:Formal systems 5651: 5650: 5647: 5646: 5644: 5643: 5638: 5633: 5628: 5623: 5618: 5613: 5608: 5603: 5598: 5597: 5596: 5591: 5580: 5578: 5574: 5573: 5571: 5570: 5569: 5568: 5558: 5553: 5552: 5551: 5544:Large cardinal 5541: 5536: 5531: 5526: 5521: 5507: 5506: 5505: 5500: 5495: 5480: 5478: 5468: 5467: 5465: 5464: 5463: 5462: 5457: 5452: 5442: 5437: 5432: 5427: 5422: 5417: 5412: 5407: 5402: 5397: 5392: 5387: 5381: 5379: 5372: 5371: 5369: 5368: 5367: 5366: 5361: 5356: 5351: 5346: 5341: 5333: 5332: 5331: 5326: 5316: 5311: 5309:Extensionality 5306: 5304:Ordinal number 5301: 5291: 5286: 5285: 5284: 5273: 5267: 5261: 5260: 5257: 5256: 5254: 5253: 5248: 5243: 5238: 5233: 5228: 5223: 5222: 5221: 5211: 5210: 5209: 5196: 5194: 5188: 5187: 5185: 5184: 5183: 5182: 5177: 5172: 5162: 5157: 5152: 5147: 5142: 5137: 5131: 5129: 5123: 5122: 5120: 5119: 5114: 5109: 5104: 5099: 5094: 5089: 5088: 5087: 5077: 5072: 5067: 5062: 5057: 5052: 5046: 5044: 5035: 5029: 5028: 5026: 5025: 5020: 5015: 5010: 5005: 5000: 4988:Cantor's  4986: 4981: 4976: 4966: 4964: 4951: 4950: 4948: 4947: 4942: 4937: 4932: 4927: 4922: 4917: 4912: 4907: 4902: 4897: 4892: 4887: 4886: 4885: 4874: 4872: 4868: 4867: 4862: 4860: 4859: 4852: 4845: 4837: 4828: 4827: 4825: 4824: 4814: 4804: 4793: 4790: 4789: 4787: 4786: 4781: 4776: 4771: 4766: 4761: 4756: 4751: 4746: 4741: 4736: 4731: 4726: 4721: 4716: 4711: 4706: 4701: 4696: 4691: 4685: 4683: 4679: 4678: 4676: 4675: 4673:Solid modeling 4670: 4665: 4660: 4655: 4650: 4645: 4640: 4634: 4632: 4626: 4625: 4623: 4622: 4617: 4612: 4607: 4602: 4596: 4594: 4588: 4587: 4585: 4584: 4579: 4574: 4572:Control method 4569: 4564: 4559: 4554: 4549: 4543: 4541: 4535: 4534: 4532: 4531: 4526: 4524:Multithreading 4521: 4516: 4511: 4505: 4503: 4497: 4496: 4494: 4493: 4488: 4483: 4478: 4473: 4467: 4465: 4459: 4458: 4456: 4455: 4450: 4445: 4440: 4435: 4430: 4425: 4420: 4418:Formal methods 4415: 4409: 4407: 4401: 4400: 4398: 4397: 4392: 4390:World Wide Web 4387: 4382: 4377: 4372: 4367: 4362: 4357: 4352: 4347: 4342: 4337: 4332: 4326: 4324: 4318: 4317: 4315: 4314: 4309: 4304: 4299: 4294: 4289: 4284: 4279: 4273: 4271: 4264: 4263: 4261: 4260: 4255: 4250: 4245: 4240: 4234: 4232: 4226: 4225: 4223: 4222: 4217: 4212: 4207: 4202: 4197: 4192: 4191: 4190: 4179: 4177: 4171: 4170: 4168: 4167: 4162: 4157: 4152: 4147: 4142: 4137: 4132: 4127: 4122: 4116: 4114: 4108: 4107: 4105: 4104: 4099: 4094: 4089: 4084: 4079: 4074: 4069: 4064: 4059: 4053: 4051: 4041: 4040: 4038: 4037: 4032: 4027: 4022: 4017: 4011: 4009: 4005: 4004: 4002: 4001: 3996: 3991: 3986: 3981: 3976: 3970: 3968: 3962: 3961: 3959: 3958: 3953: 3948: 3943: 3938: 3932: 3930: 3926: 3925: 3923: 3922: 3913: 3908: 3903: 3898: 3893: 3888: 3883: 3878: 3873: 3867: 3865: 3859: 3858: 3851: 3848: 3847: 3842: 3840: 3839: 3832: 3825: 3817: 3811: 3810: 3805: 3800: 3788: 3781: 3780:External links 3778: 3777: 3776: 3729: 3695: 3677:(3): 379–407. 3657: 3637:(2): 420–436. 3617: 3603:(5): 447–474. 3580: 3554:(3): 309–316. 3538: 3528:(1–3): 71–91. 3514: 3513: 3509: 3508: 3502: 3469: 3468: 3464: 3463: 3457: 3437: 3431: 3407: 3401: 3384: 3378: 3361: 3347: 3321:Jain, Sanjay; 3317: 3316: 3315:Advanced texts 3312: 3311: 3305: 3285: 3279: 3258: 3257: 3252: 3249: 3246: 3245: 3238: 3213: 3197:FOM email list 3191:(1998-08-28). 3180: 3164:FOM email list 3158:(1998-08-24). 3147: 3129:(2004-02-15). 3118: 3111: 3081: 3039: 3032: 3015:10.1.1.53.1991 2996: 2989: 2960: 2939:(2): 320–334. 2910: 2870: 2802: 2795: 2767: 2764:on 2013-04-20. 2745: 2709: 2680:(6): 711–722. 2653: 2627:(5): 284–316. 2597: 2571:(1): 161–228. 2550: 2529:10.2307/420992 2523:(3): 284–321. 2492: 2485: 2457: 2450: 2421: 2391:(1): 544–546. 2352:(1): 230–265. 2328: 2284:Church, Alonzo 2275: 2251:(2): 345–363. 2239:Church, Alonzo 2230: 2195: 2166: 2152:. p. 84: 2148: 2118: 2111: 2083: 2051:(2011-12-22). 2040: 2029:(3): 877–884. 2004: 1997: 1959: 1958: 1956: 1953: 1950: 1949: 1933: 1920: 1907: 1888: 1874: 1873: 1871: 1868: 1867: 1866: 1861: 1856: 1850: 1849: 1833: 1830: 1809: 1806: 1745: 1742: 1672:Post's theorem 1659: 1656: 1642:, modelled by 1640:control theory 1615: 1612: 1606:is studied in 1585: 1580: 1576: 1542: 1539: 1474: 1471: 1381: 1374: 1359: 1355: 1351: 1340: 1334: 1327: 1296: 1293: 1249:Main article: 1246: 1243: 1213: 1210: 1204: 1201: 1174: 1171: 1142: 1139: 1105:Main article: 1102: 1099: 1094: 1088: 1081: 1077: 1073: 1069: 1065: 1058:Rice's theorem 1032: 1007: 1004: 981: 980: 954: 913:be injective. 904: 836:Main article: 833: 830: 814:Post's theorem 777:random degrees 769:g(x) < f(x) 736:Post's problem 675: 674: 627: 559:when run with 508: 505: 499: 496: 467:countably many 377:Turing machine 360:computable set 354: 351: 335:Julia Robinson 243:Stephen Kleene 221: 220: 203: 202: 197: 191: 179: 174: 171: 168: 165: 157: 156: 153: 150: 147: 144: 141: 138: 135: 124: 121: 109:formal methods 100: 99: 96: 62:Turing degrees 26: 24: 14: 13: 10: 9: 6: 4: 3: 2: 6618: 6607: 6604: 6602: 6599: 6598: 6596: 6583: 6582: 6577: 6569: 6563: 6560: 6558: 6555: 6553: 6550: 6548: 6545: 6541: 6538: 6537: 6536: 6533: 6531: 6528: 6526: 6523: 6521: 6517: 6514: 6512: 6509: 6507: 6504: 6502: 6499: 6497: 6494: 6493: 6491: 6487: 6481: 6478: 6476: 6473: 6471: 6470:Recursive set 6468: 6466: 6463: 6461: 6458: 6456: 6453: 6451: 6448: 6444: 6441: 6439: 6436: 6434: 6431: 6429: 6426: 6424: 6421: 6420: 6419: 6416: 6414: 6411: 6409: 6406: 6404: 6401: 6399: 6396: 6394: 6391: 6390: 6388: 6386: 6382: 6376: 6373: 6371: 6368: 6366: 6363: 6361: 6358: 6356: 6353: 6351: 6348: 6346: 6343: 6339: 6336: 6334: 6331: 6329: 6326: 6325: 6324: 6321: 6319: 6316: 6314: 6311: 6309: 6306: 6304: 6301: 6299: 6296: 6292: 6289: 6288: 6287: 6284: 6280: 6279:of arithmetic 6277: 6276: 6275: 6272: 6268: 6265: 6263: 6260: 6258: 6255: 6253: 6250: 6248: 6245: 6244: 6243: 6240: 6236: 6233: 6231: 6228: 6227: 6226: 6223: 6222: 6220: 6218: 6214: 6208: 6205: 6203: 6200: 6198: 6195: 6193: 6190: 6187: 6186:from ZFC 6183: 6180: 6178: 6175: 6169: 6166: 6165: 6164: 6161: 6159: 6156: 6154: 6151: 6150: 6149: 6146: 6144: 6141: 6139: 6136: 6134: 6131: 6129: 6126: 6124: 6121: 6119: 6116: 6115: 6113: 6111: 6107: 6097: 6096: 6092: 6091: 6086: 6085:non-Euclidean 6083: 6079: 6076: 6074: 6071: 6069: 6068: 6064: 6063: 6061: 6058: 6057: 6055: 6051: 6047: 6044: 6042: 6039: 6038: 6037: 6033: 6029: 6026: 6025: 6024: 6020: 6016: 6013: 6011: 6008: 6006: 6003: 6001: 5998: 5996: 5993: 5991: 5988: 5987: 5985: 5981: 5980: 5978: 5973: 5967: 5962:Example  5959: 5951: 5946: 5945: 5944: 5941: 5939: 5936: 5932: 5929: 5927: 5924: 5922: 5919: 5917: 5914: 5913: 5912: 5909: 5907: 5904: 5902: 5899: 5897: 5894: 5890: 5887: 5885: 5882: 5881: 5880: 5877: 5873: 5870: 5868: 5865: 5863: 5860: 5858: 5855: 5854: 5853: 5850: 5848: 5845: 5841: 5838: 5836: 5833: 5831: 5828: 5827: 5826: 5823: 5819: 5816: 5814: 5811: 5809: 5806: 5804: 5801: 5799: 5796: 5794: 5791: 5790: 5789: 5786: 5784: 5781: 5779: 5776: 5774: 5771: 5767: 5764: 5762: 5759: 5757: 5754: 5752: 5749: 5748: 5747: 5744: 5742: 5739: 5737: 5734: 5732: 5729: 5725: 5722: 5720: 5719:by definition 5717: 5716: 5715: 5712: 5708: 5705: 5704: 5703: 5700: 5698: 5695: 5693: 5690: 5688: 5685: 5683: 5680: 5679: 5676: 5673: 5671: 5667: 5662: 5656: 5652: 5642: 5639: 5637: 5634: 5632: 5629: 5627: 5624: 5622: 5619: 5617: 5614: 5612: 5609: 5607: 5606:Kripke–Platek 5604: 5602: 5599: 5595: 5592: 5590: 5587: 5586: 5585: 5582: 5581: 5579: 5575: 5567: 5564: 5563: 5562: 5559: 5557: 5554: 5550: 5547: 5546: 5545: 5542: 5540: 5537: 5535: 5532: 5530: 5527: 5525: 5522: 5519: 5515: 5511: 5508: 5504: 5501: 5499: 5496: 5494: 5491: 5490: 5489: 5485: 5482: 5481: 5479: 5477: 5473: 5469: 5461: 5458: 5456: 5453: 5451: 5450:constructible 5448: 5447: 5446: 5443: 5441: 5438: 5436: 5433: 5431: 5428: 5426: 5423: 5421: 5418: 5416: 5413: 5411: 5408: 5406: 5403: 5401: 5398: 5396: 5393: 5391: 5388: 5386: 5383: 5382: 5380: 5378: 5373: 5365: 5362: 5360: 5357: 5355: 5352: 5350: 5347: 5345: 5342: 5340: 5337: 5336: 5334: 5330: 5327: 5325: 5322: 5321: 5320: 5317: 5315: 5312: 5310: 5307: 5305: 5302: 5300: 5296: 5292: 5290: 5287: 5283: 5280: 5279: 5278: 5275: 5274: 5271: 5268: 5266: 5262: 5252: 5249: 5247: 5244: 5242: 5239: 5237: 5234: 5232: 5229: 5227: 5224: 5220: 5217: 5216: 5215: 5212: 5208: 5203: 5202: 5201: 5198: 5197: 5195: 5193: 5189: 5181: 5178: 5176: 5173: 5171: 5168: 5167: 5166: 5163: 5161: 5158: 5156: 5153: 5151: 5148: 5146: 5143: 5141: 5138: 5136: 5133: 5132: 5130: 5128: 5127:Propositional 5124: 5118: 5115: 5113: 5110: 5108: 5105: 5103: 5100: 5098: 5095: 5093: 5090: 5086: 5083: 5082: 5081: 5078: 5076: 5073: 5071: 5068: 5066: 5063: 5061: 5058: 5056: 5055:Logical truth 5053: 5051: 5048: 5047: 5045: 5043: 5039: 5036: 5034: 5030: 5024: 5021: 5019: 5016: 5014: 5011: 5009: 5006: 5004: 5001: 4999: 4995: 4991: 4987: 4985: 4982: 4980: 4977: 4975: 4971: 4968: 4967: 4965: 4963: 4957: 4952: 4946: 4943: 4941: 4938: 4936: 4933: 4931: 4928: 4926: 4923: 4921: 4918: 4916: 4913: 4911: 4908: 4906: 4903: 4901: 4898: 4896: 4893: 4891: 4888: 4884: 4881: 4880: 4879: 4876: 4875: 4873: 4869: 4865: 4858: 4853: 4851: 4846: 4844: 4839: 4838: 4835: 4823: 4815: 4813: 4805: 4803: 4795: 4794: 4791: 4785: 4782: 4780: 4777: 4775: 4772: 4770: 4767: 4765: 4762: 4760: 4757: 4755: 4752: 4750: 4747: 4745: 4742: 4740: 4737: 4735: 4732: 4730: 4727: 4725: 4722: 4720: 4717: 4715: 4712: 4710: 4707: 4705: 4702: 4700: 4697: 4695: 4692: 4690: 4687: 4686: 4684: 4680: 4674: 4671: 4669: 4666: 4664: 4661: 4659: 4658:Mixed reality 4656: 4654: 4651: 4649: 4646: 4644: 4641: 4639: 4636: 4635: 4633: 4631: 4627: 4621: 4618: 4616: 4613: 4611: 4608: 4606: 4603: 4601: 4598: 4597: 4595: 4593: 4589: 4583: 4580: 4578: 4575: 4573: 4570: 4568: 4565: 4563: 4560: 4558: 4555: 4553: 4550: 4548: 4545: 4544: 4542: 4540: 4536: 4530: 4527: 4525: 4522: 4520: 4517: 4515: 4512: 4510: 4507: 4506: 4504: 4502: 4498: 4492: 4491:Accessibility 4489: 4487: 4486:Visualization 4484: 4482: 4479: 4477: 4474: 4472: 4469: 4468: 4466: 4464: 4460: 4454: 4451: 4449: 4446: 4444: 4441: 4439: 4436: 4434: 4431: 4429: 4426: 4424: 4421: 4419: 4416: 4414: 4411: 4410: 4408: 4406: 4402: 4396: 4393: 4391: 4388: 4386: 4383: 4381: 4378: 4376: 4373: 4371: 4368: 4366: 4363: 4361: 4358: 4356: 4353: 4351: 4348: 4346: 4343: 4341: 4338: 4336: 4333: 4331: 4328: 4327: 4325: 4323: 4319: 4313: 4310: 4308: 4305: 4303: 4300: 4298: 4295: 4293: 4290: 4288: 4285: 4283: 4280: 4278: 4275: 4274: 4272: 4270: 4265: 4259: 4256: 4254: 4251: 4249: 4246: 4244: 4241: 4239: 4236: 4235: 4233: 4231: 4227: 4221: 4218: 4216: 4213: 4211: 4208: 4206: 4203: 4201: 4198: 4196: 4193: 4189: 4186: 4185: 4184: 4181: 4180: 4178: 4176: 4172: 4166: 4163: 4161: 4158: 4156: 4153: 4151: 4148: 4146: 4143: 4141: 4138: 4136: 4133: 4131: 4128: 4126: 4123: 4121: 4118: 4117: 4115: 4113: 4109: 4103: 4100: 4098: 4095: 4093: 4090: 4088: 4085: 4083: 4080: 4078: 4075: 4073: 4070: 4068: 4065: 4063: 4060: 4058: 4055: 4054: 4052: 4050: 4046: 4042: 4036: 4033: 4031: 4028: 4026: 4023: 4021: 4018: 4016: 4013: 4012: 4010: 4006: 4000: 3997: 3995: 3992: 3990: 3987: 3985: 3982: 3980: 3977: 3975: 3972: 3971: 3969: 3967: 3963: 3957: 3954: 3952: 3949: 3947: 3946:Dependability 3944: 3942: 3939: 3937: 3934: 3933: 3931: 3927: 3921: 3917: 3914: 3912: 3909: 3907: 3904: 3902: 3899: 3897: 3894: 3892: 3889: 3887: 3884: 3882: 3879: 3877: 3874: 3872: 3869: 3868: 3866: 3864: 3860: 3855: 3849: 3845: 3838: 3833: 3831: 3826: 3824: 3819: 3818: 3815: 3809: 3806: 3804: 3801: 3799: 3795: 3792: 3789: 3787: 3784: 3783: 3779: 3774: 3771:Reprinted in 3768: 3764: 3760: 3756: 3752: 3748: 3744: 3740: 3739: 3734: 3730: 3726: 3722: 3718: 3714: 3710: 3706: 3705: 3700: 3696: 3692: 3688: 3684: 3680: 3676: 3672: 3671: 3666: 3662: 3658: 3654: 3650: 3645: 3640: 3636: 3632: 3631: 3626: 3622: 3618: 3616: 3611: 3606: 3602: 3598: 3597: 3589: 3585: 3584:Gold, E. Mark 3581: 3577: 3573: 3569: 3565: 3561: 3557: 3553: 3549: 3548: 3543: 3539: 3535: 3531: 3527: 3523: 3522: 3516: 3515: 3511: 3510: 3505: 3503:0-7204-2285-X 3499: 3495: 3491: 3490:North-Holland 3487: 3483: 3479: 3475: 3471: 3470: 3466: 3465: 3460: 3458:0-444-50205-X 3454: 3450: 3446: 3442: 3438: 3434: 3432:0-444-87295-7 3428: 3424: 3423:North-Holland 3419: 3418: 3412: 3408: 3404: 3398: 3394: 3390: 3385: 3381: 3379:3-540-12155-2 3375: 3371: 3367: 3362: 3358: 3354: 3350: 3348:0-262-10077-0 3344: 3340: 3336: 3335:Bradford Book 3332: 3328: 3324: 3319: 3318: 3314: 3313: 3308: 3306:0-262-13295-8 3302: 3298: 3294: 3290: 3286: 3282: 3280:1-58488-237-9 3276: 3272: 3268: 3264: 3260: 3259: 3255: 3254: 3250: 3241: 3239:0-262-68052-1 3235: 3231: 3227: 3223: 3217: 3214: 3202: 3198: 3194: 3190: 3184: 3181: 3169: 3165: 3161: 3157: 3151: 3148: 3136: 3132: 3128: 3122: 3119: 3114: 3108: 3104: 3100: 3096: 3092: 3085: 3082: 3077: 3073: 3068: 3067:10.1.1.6.5519 3063: 3059: 3055: 3054: 3049: 3043: 3040: 3035: 3029: 3025: 3021: 3016: 3011: 3007: 3000: 2997: 2992: 2990:3-540-19305-7 2986: 2982: 2977: 2976: 2970: 2964: 2961: 2956: 2952: 2947: 2942: 2938: 2934: 2933: 2928: 2924: 2920: 2914: 2911: 2906: 2902: 2898: 2894: 2891:(1): 80–120. 2890: 2886: 2885: 2880: 2874: 2871: 2866: 2862: 2857: 2852: 2847: 2842: 2838: 2834: 2830: 2826: 2825: 2820: 2816: 2812: 2806: 2803: 2798: 2796:3-540-64882-8 2792: 2788: 2784: 2780: 2774: 2772: 2768: 2760: 2756: 2752: 2748: 2742: 2738: 2734: 2730: 2723: 2716: 2714: 2710: 2705: 2701: 2697: 2693: 2688: 2683: 2679: 2675: 2671: 2667: 2663: 2657: 2654: 2650: 2647:Reprinted in 2644: 2640: 2635: 2630: 2626: 2622: 2621: 2616: 2612: 2606: 2604: 2602: 2598: 2594: 2591:Reprinted in 2587: 2582: 2578: 2574: 2570: 2566: 2565: 2560: 2554: 2551: 2546: 2542: 2538: 2534: 2530: 2526: 2522: 2518: 2517: 2509: 2505: 2499: 2497: 2493: 2488: 2486:0-387-15299-7 2482: 2478: 2474: 2470: 2464: 2462: 2458: 2453: 2451:0-521-29465-7 2447: 2443: 2438: 2437: 2431: 2425: 2422: 2418: 2415:Reprinted in 2402: 2398: 2394: 2390: 2386: 2385: 2377: 2373: 2367: 2363: 2359: 2355: 2351: 2347: 2346: 2341: 2335: 2333: 2329: 2325: 2322:Reprinted in 2319: 2315: 2311: 2307: 2303: 2299: 2295: 2291: 2290: 2285: 2279: 2276: 2272: 2269:Reprinted in 2266: 2262: 2258: 2254: 2250: 2246: 2245: 2240: 2234: 2231: 2227: 2223: 2218: 2216: 2212: 2208: 2204: 2198: 2192: 2188: 2184: 2180: 2176: 2170: 2167: 2163: 2160: 2156: 2151: 2145: 2141: 2137: 2136: 2131: 2130:Davis, Martin 2125: 2123: 2119: 2114: 2112:0-7204-2103-9 2108: 2104: 2103:North-Holland 2100: 2096: 2090: 2088: 2084: 2069: 2065: 2061: 2054: 2050: 2044: 2041: 2036: 2032: 2028: 2024: 2023: 2018: 2014: 2008: 2005: 2000: 1998:0-7204-2285-X 1994: 1990: 1989:North-Holland 1986: 1982: 1978: 1974: 1970: 1964: 1961: 1954: 1946: 1942: 1937: 1934: 1930: 1924: 1921: 1917: 1911: 1908: 1905: 1901: 1899: 1892: 1889: 1885: 1879: 1876: 1869: 1865: 1862: 1860: 1857: 1855: 1852: 1851: 1847: 1836: 1831: 1829: 1827: 1823: 1822: 1817: 1816: 1807: 1805: 1802: 1798: 1793: 1791: 1787: 1783: 1779: 1775: 1771: 1767: 1763: 1759: 1755: 1751: 1743: 1741: 1739: 1735: 1731: 1727: 1723: 1719: 1715: 1711: 1708:The field of 1706: 1704: 1700: 1695: 1693: 1689: 1685: 1681: 1677: 1673: 1669: 1665: 1657: 1655: 1653: 1649: 1645: 1641: 1637: 1633: 1629: 1625: 1621: 1613: 1611: 1609: 1605: 1601: 1583: 1578: 1564: 1560: 1556: 1552: 1548: 1540: 1538: 1536: 1532: 1529:learns every 1528: 1524: 1520: 1516: 1512: 1508: 1504: 1500: 1496: 1492: 1488: 1484: 1480: 1472: 1470: 1468: 1464: 1460: 1456: 1452: 1448: 1444: 1440: 1436: 1432: 1428: 1424: 1420: 1419:semirecursive 1416: 1412: 1408: 1404: 1400: 1396: 1392: 1388: 1384: 1377: 1370: 1366: 1362: 1347: 1343: 1333: 1326: 1322: 1318: 1314: 1310: 1306: 1302: 1294: 1292: 1290: 1286: 1282: 1278: 1274: 1270: 1267: 1262: 1258: 1255:The field of 1252: 1244: 1242: 1238: 1236: 1232: 1228: 1224: 1220: 1211: 1209: 1202: 1200: 1196: 1194: 1190: 1186: 1180: 1172: 1170: 1168: 1164: 1160: 1156: 1152: 1148: 1140: 1138: 1136: 1132: 1128: 1124: 1120: 1116: 1115: 1108: 1100: 1098: 1091: 1084: 1063: 1059: 1055: 1051: 1047: 1043: 1039: 1035: 1028: 1024: 1020: 1016: 1012: 1003: 1001: 997: 992: 988: 986: 978: 974: 970: 966: 962: 958: 955: 952: 948: 944: 940: 936: 932: 928: 924: 920: 916: 912: 908: 905: 902: 898: 894: 890: 886: 882: 879: 875: 871: 867: 863: 859: 856: 855: 854: 851: 849: 845: 839: 831: 829: 827: 821: 819: 815: 811: 807: 803: 802: 797: 792: 790: 786: 782: 778: 774: 770: 766: 763:depending on 762: 758: 754: 750: 746: 740: 738: 737: 731: 727: 722: 720: 716: 712: 708: 704: 700: 696: 692: 688: 684: 680: 672: 668: 664: 660: 656: 652: 648: 644: 640: 636: 632: 628: 625: 621: 620: 619: 617: 612: 610: 607:(also called 606: 605: 604:Turing degree 600: 596: 592: 588: 584: 581: 577: 574: 570: 566: 562: 558: 554: 550: 549: 544: 539: 536: 532: 528: 524: 518: 517:Turing degree 514: 506: 504: 497: 495: 493: 492:semidecidable 489: 485: 484: 478: 476: 472: 468: 464: 459: 457: 453: 448: 443: 439: 434: 428: 426: 422: 418: 414: 410: 406: 402: 400: 394: 390: 386: 382: 378: 374: 370: 366: 362: 361: 352: 350: 348: 344: 340: 336: 332: 328: 324: 320: 316: 315:William Boone 312: 311:Pyotr Novikov 308: 304: 300: 295: 292: 291: 285: 279: 276: 270: 268: 264: 260: 255: 250: 248: 244: 240: 236: 232: 231:Alonzo Church 228: 216: 212: 204: 163: 159: 158: 134: 131: 130: 127: 122: 120: 118: 114: 110: 106: 97: 94: 90: 86: 85: 84: 81: 79: 75: 71: 67: 66:computability 63: 59: 55: 51: 47: 43: 39: 33: 32:Computability 19: 6572: 6384: 6370:Ultraproduct 6217:Model theory 6182:Independence 6118:Formal proof 6110:Proof theory 6093: 6066: 6023:real numbers 5995:second-order 5906:Substitution 5783:Metalanguage 5724:conservative 5697:Axiom schema 5641:Constructive 5611:Morse–Kelley 5577:Set theories 5556:Aleph number 5549:inaccessible 5455:Grothendieck 5339:intersection 5226:Higher-order 5214:Second-order 5160:Truth tables 5117:Venn diagram 4900:Formal proof 4754:Cyberwarfare 4413:Cryptography 4204: 3742: 3736: 3708: 3702: 3674: 3673:. Series 2. 3668: 3634: 3628: 3600: 3594: 3551: 3545: 3525: 3519: 3485: 3482:Barwise, Jon 3444: 3416: 3388: 3365: 3330: 3327:Sharma, Arun 3292: 3266: 3225: 3216: 3205:. Retrieved 3196: 3183: 3172:. Retrieved 3163: 3150: 3139:. Retrieved 3121: 3098: 3084: 3060:(1): 23–44. 3057: 3051: 3042: 3005: 2999: 2974: 2963: 2936: 2930: 2913: 2888: 2882: 2873: 2828: 2822: 2805: 2782: 2759:the original 2728: 2677: 2673: 2656: 2624: 2618: 2568: 2562: 2553: 2520: 2514: 2472: 2435: 2424: 2408:. Retrieved 2388: 2382: 2349: 2343: 2296:(1): 40–41. 2293: 2287: 2278: 2248: 2242: 2233: 2214: 2210: 2206: 2202: 2200: 2182: 2169: 2153: 2142:p. 84. 2134: 2098: 2075:. Retrieved 2059: 2043: 2026: 2020: 2015:(May 1962). 2007: 1984: 1977:Nerode, Anil 1963: 1936: 1923: 1910: 1904:Martin Davis 1897: 1891: 1883: 1878: 1825: 1819: 1813: 1811: 1794: 1789: 1785: 1781: 1777: 1773: 1769: 1765: 1761: 1757: 1753: 1747: 1710:proof theory 1707: 1696: 1661: 1617: 1544: 1534: 1530: 1526: 1522: 1518: 1514: 1510: 1506: 1502: 1498: 1494: 1490: 1486: 1482: 1479:E. Mark Gold 1476: 1466: 1462: 1458: 1454: 1450: 1446: 1442: 1438: 1434: 1430: 1426: 1422: 1414: 1410: 1406: 1402: 1398: 1394: 1390: 1386: 1379: 1372: 1368: 1364: 1349: 1345: 1338: 1331: 1324: 1320: 1316: 1312: 1308: 1304: 1300: 1298: 1288: 1284: 1280: 1276: 1272: 1268: 1254: 1239: 1235:Maximal sets 1230: 1226: 1222: 1218: 1215: 1206: 1197: 1193:requirements 1192: 1188: 1184: 1182: 1158: 1154: 1150: 1146: 1144: 1134: 1112: 1110: 1089: 1082: 1053: 1045: 1037: 1030: 1029:th c.e. set 1026: 1022: 1018: 1014: 1009: 993: 989: 982: 977:Cantor space 972: 968: 964: 960: 950: 946: 942: 938: 934: 930: 926: 922: 918: 914: 910: 900: 896: 892: 888: 884: 880: 873: 869: 865: 861: 852: 847: 843: 841: 825: 822: 809: 805: 799: 795: 793: 784: 776: 772: 768: 764: 760: 756: 752: 749:high degrees 748: 744: 741: 734: 723: 714: 710: 706: 702: 698: 694: 690: 686: 682: 678: 676: 671:m-equivalent 670: 666: 662: 658: 654: 650: 646: 642: 638: 634: 613: 608: 602: 598: 594: 590: 586: 585:). If a set 582: 580:recursive in 579: 575: 572: 568: 564: 560: 556: 552: 546: 542: 540: 534: 530: 522: 520: 501: 491: 487: 481: 479: 473:, there are 460: 441: 437: 429: 416: 412: 408: 404: 396: 392: 388: 384: 380: 372: 368: 364: 358: 356: 296: 281: 272: 251: 224: 214: 161: 132: 126: 123:Introduction 116: 101: 82: 74:proof theory 70:definability 41: 37: 36: 6480:Type theory 6428:undecidable 6360:Truth value 6247:equivalence 5926:non-logical 5539:Enumeration 5529:Isomorphism 5476:cardinality 5460:Von Neumann 5425:Ultrafilter 5390:Uncountable 5324:equivalence 5241:Quantifiers 5231:Fixed-point 5200:First-order 5080:Consistency 5065:Proposition 5042:Traditional 5013:Lindström's 5003:Compactness 4945:Type theory 4890:Cardinality 4764:Video games 4744:Digital art 4501:Concurrency 4370:Data mining 4282:Probability 4015:Interpreter 3745:(1): 1–11. 3711:: 215–220. 3492:. pp.  3048:Moore, Cris 2175:Gödel, Kurt 2013:Radó, Tibor 1768:instead of 1344:a tuple of 1233:is finite. 923:m-reducible 870:1-reducible 801:Turing jump 779:containing 730:hypersimple 299:mathematics 239:Alan Turing 235:Rózsa Péter 213:function Σ( 211:Busy Beaver 6595:Categories 6291:elementary 5984:arithmetic 5852:Quantifier 5830:functional 5702:Expression 5420:Transitive 5364:identities 5349:complement 5282:hereditary 5265:Set theory 4822:Glossaries 4694:E-commerce 4287:Statistics 4230:Algorithms 4188:Stochastic 4020:Middleware 3876:Peripheral 3773:Davis 1965 3207:2006-01-09 3174:2006-01-09 3141:2018-03-22 2649:Davis 1965 2593:Davis 1965 2417:Davis 1965 2410:2022-08-08 2324:Davis 1965 2271:Davis 1965 2222:Kurt Gödel 2155:Kurt Gödel 2077:2017-08-23 1955:References 1941:MathSciNet 1902:edited by 1797:bijections 1676:Kurt Gödel 1608:set theory 1489:(0),  1287:) outputs 1279:such that 1141:Numberings 767:such that 701:such that 645:such that 569:relatively 399:computable 227:Kurt Gödel 52:, and the 6562:Supertask 6465:Recursion 6423:decidable 6257:saturated 6235:of models 6158:deductive 6153:axiomatic 6073:Hilbert's 6060:Euclidean 6041:canonical 5964:axiomatic 5896:Signature 5825:Predicate 5714:Extension 5636:Ackermann 5561:Operation 5440:Universal 5430:Recursive 5405:Singleton 5400:Inhabited 5385:Countable 5375:Types of 5359:power set 5329:partition 5246:Predicate 5192:Predicate 5107:Syllogism 5097:Soundness 5070:Inference 5060:Tautology 4962:paradoxes 4643:Rendering 4638:Animation 4269:computing 4220:Semantics 3911:Processor 3725:123260425 3339:MIT Press 3297:MIT Press 3230:MIT Press 3062:CiteSeerX 3010:CiteSeerX 2696:1073-2780 1575:Π 1378:) = 1221:is below 785:1-generic 622:They are 551:to a set 442:decidable 438:recursive 397:(Turing) 369:recursive 365:decidable 263:algorithm 247:Emil Post 6547:Logicism 6540:timeline 6516:Concrete 6375:Validity 6345:T-schema 6338:Kripke's 6333:Tarski's 6328:semantic 6318:Strength 6267:submodel 6262:spectrum 6230:function 6078:Tarski's 6067:Elements 6054:geometry 6010:Robinson 5931:variable 5916:function 5889:spectrum 5879:Sentence 5835:variable 5778:Language 5731:Relation 5692:Automata 5682:Alphabet 5666:language 5520:-jection 5498:codomain 5484:Function 5445:Universe 5415:Infinite 5319:Relation 5102:Validity 5092:Argument 4990:theorem, 4802:Category 4630:Graphics 4405:Security 4067:Compiler 3966:Networks 3863:Hardware 3794:Archived 3767:30320278 3623:(1968). 3586:(1967). 3576:25834814 3476:(1977). 3449:Elsevier 3443:(1999). 3413:(1989). 3357:98-34861 3329:(1999). 3291:(1993). 3265:(2004). 3224:(1987). 3201:Archived 3168:Archived 3135:Archived 3103:Elsevier 2971:(1990). 2925:(1986). 2865:11607241 2817:(1991). 2781:(1999). 2668:(1999). 2613:(1944). 2506:(1996). 2471:(1987). 2432:(1980). 2401:Archived 2374:(1938). 2318:42323521 2157:(1946): 2097:(1952). 2068:Archived 1983:(1998). 1832:See also 1728:, while 1354:, y 1348:numbers 1131:powerset 949:) is in 899:) is in 773:x > c 771:for all 653: : 433:rekursiv 89:function 6489:Related 6286:Diagram 6184: ( 6163:Hilbert 6148:Systems 6143:Theorem 6021:of the 5966:systems 5746:Formula 5741:Grammar 5657: ( 5601:General 5314:Forcing 5299:Element 5219:Monadic 4994:paradox 4935:Theorem 4871:General 4812:Outline 3759:2267170 3691:1969708 3653:1994957 3568:2964290 3494:527–566 3484:(ed.). 3097:(ed.). 2955:0840131 2905:1970842 2833:Bibcode 2755:3362163 2704:1739227 2643:0010514 2545:5894394 2310:2269326 2265:2371045 1521:learns 1425:,  1405:,  1397:,  1389:,  1330:,  1323:inputs 685:, then 91:on the 6252:finite 6015:Skolem 5968:  5943:Theory 5911:Symbol 5901:String 5884:atomic 5761:ground 5756:closed 5751:atomic 5707:ground 5670:syntax 5566:binary 5493:domain 5410:Finite 5175:finite 5033:Logics 4992:  4940:Theory 3765:  3757:  3723:  3689:  3651:  3574:  3566:  3500:  3455:  3429:  3399:  3376:  3355:  3345:  3303:  3277:  3273:/CRC. 3236:  3109:  3064:  3030:  3012:  2987:  2953:  2903:  2863:  2853:  2793:  2753:  2743:  2702:  2694:  2641:  2543:  2537:420992 2535:  2483:  2448:  2364:  2316:  2308:  2263:  2193:  2159:Tarski 2146:  2109:  1995:  1900:(1965) 1409:with 2 1036:is in 1025:: the 937:is in 887:is in 798:, the 791:sets. 726:simple 531:oracle 303:Markov 275:Tarski 245:, and 111:, and 6242:Model 5990:Peano 5847:Proof 5687:Arity 5616:Naive 5503:image 5435:Fuzzy 5395:Empty 5344:union 5289:Class 4930:Model 4920:Lemma 4878:Axiom 4215:Logic 4049:tools 3763:S2CID 3755:JSTOR 3721:S2CID 3687:JSTOR 3649:JSTOR 3591:(PDF) 3572:S2CID 3564:JSTOR 3480:. In 3093:. 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Index

Theory of computability
Computability
mathematical logic
computer science
theory of computation
computable functions
Turing degrees
computability
definability
proof theory
effective descriptive set theory
function
natural numbers
subrecursive hierarchies
formal methods
formal languages
Busy Beaver
Kurt Gödel
Alonzo Church
Rózsa Péter
Alan Turing
Stephen Kleene
Emil Post
Turing computability
Church–Turing thesis
algorithm
computable function
Tarski
effectively decided
Entscheidungsproblem

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