2005
DOI: 10.1093/logcom/exi022
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P ≠ NP ∩ co-NP for Infinite Time Turing Machines

Abstract: Abstract. Extending results of Schindler [Sch] and Hamkins and Welch [HW03], we establish in the context of infinite time Turing machines that P is properly contained in NP ∩ co-NP. Furthermore, NP ∩ co-NP is exactly the class of hyperarithmetic sets. For the more general classes, we establish that P + = NP + ∩ co-NP + = NP ∩ co-NP, though P ++ is properly contained in NP ++ ∩ co-NP ++ . Within any contiguous block of infinite clockable ordinals, we show that P α = NP α ∩ co-NP α , but if β begins a gap in th… Show more

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Cited by 23 publications
(18 citation statements)
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“…Schindler defined P + = P f 0 where f 0 (x) = ω x 1 ck + 1. [14] (Thm 4) shows directly P f 0 = P ω ck 1 . Underlying this is perhaps the following Bounding Lemma:…”
Section: Complexity Of Ittm-computationmentioning
confidence: 98%
See 1 more Smart Citation
“…Schindler defined P + = P f 0 where f 0 (x) = ω x 1 ck + 1. [14] (Thm 4) shows directly P f 0 = P ω ck 1 . Underlying this is perhaps the following Bounding Lemma:…”
Section: Complexity Of Ittm-computationmentioning
confidence: 98%
“…We refer the reader to this paper for the discussion and question of the P SP ACE f classes that arise. [28] showed that for almost all f , N P f = P f and later [14] showed that for many α P α = N P α ∩ co-N P α including those α that begin a gap in the clockable ordinals. (Such are admissible by [83] Thm.…”
Section: Complexity Of Ittm-computationmentioning
confidence: 99%
“…Schindler proved P = NP for infinite time Turing machines in [Sch03], using methods from descriptive set theory to analyze the complexity of the classes P and NP. This has now been generalized in joint work [DHS05] to the following, where the class co-NP consists of the complements of sets in NP. This proof appears in [DHS05].…”
Section: Some Applications and Extensionsmentioning
confidence: 99%
“…As the Web 2.0 age is dawning for mathematics, more and more mathematical development is moving online; not just publications. An example of this is the PolyMath site, where upon the recent announcement of a proof of P = N P , the mathematics community has organized itself in a WiKi and found a significant gap in the proof within two weeks; see [4]. The PlanetMath community which has collaborated on 8500 graduate-level encyclopedia articles over 10 years [20] is another, and also the Mizar community, who have formalized more than 60000 definitions, assertions, and proofs and have machine-checked them over the last 40 years.…”
Section: Introductionmentioning
confidence: 99%