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NP vs PSPACE
[article]

2016
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arXiv
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pre-print

We present a proof of the conjecture NP = PSPACE by showing that arbitrary tautologies of Johansson's minimal propositional logic admit "small" polynomial-size dag-like natural deductions in Prawitz's system for minimal propositional logic. These "small" deductions arise from standard "large" tree-like inputs by horizontal dag-like compression that is obtained by merging distinct nodes labeled with identical formulas occurring in horizontal sections of deductions involved. The underlying

arXiv:1609.09562v1
fatcat:27ljismue5gfdn3ukdb7tvvqyy
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... ric" idea: if the height, h( ∂) , and the total number of distinct formulas, ϕ( ∂) , of a given tree-like deduction ∂ of a minimal tautology ρ are both polynomial in the length of ρ, | ρ|, then the size of the horizontal dag-like compression is at most h( ∂) ×ϕ( ∂) , and hence polynomial in | ρ|. The attached proof is due to the first author, but it was the second author who proposed an initial idea to attack a weaker conjecture NP= coNP by reductions in diverse natural deduction formalisms for propositional logic. That idea included interactive use of minimal, intuitionistic and classical formalisms, so its practical implementation was too involved. The attached proof of NP=PSPACE runs inside the natural deduction interpretation of Hudelmaier's cutfree sequent calculus for minimal logic.##
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Proof Compression and NP Versus PSPACE II

2020
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Bulletin of the Section of Logic
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We upgrade [3] to a complete proof of the conjecture NP = PSPACE that is known as one of the fundamental open problems in the mathematical theory of computational complexity; this proof is based on [2]. Since minimal propositional logic is known to be PSPACE complete, while PSPACE to include NP, it suffices to show that every valid purely implicational formula ρ has a proof whose weight (= total number of symbols) and time complexity of the provability involved are both polynomial in the weight

doi:10.18778/0138-0680.2020.16
fatcat:kgl5di3jdnd5tlboqackju2jeu
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... of ρ. As in [3], we use proof theoretic approach. Recall that in [3] we considered any valid ρ in question that had (by the definition of validity) a "short" tree-like proof π in the Hudelmaier-style cutfree sequent calculus for minimal logic. The "shortness" means that the height of π and the total weight of different formulas occurring in it are both polynomial in the weight of ρ. However, the size (= total number of nodes), and hence also the weight, of π could be exponential in that of ρ. To overcome this trouble we embedded π into Prawitz's proof system of natural deductions containing single formulas, instead of sequents. As in π, the height and the total weight of different formulas of the resulting tree-like natural deduction ∂1 were polynomial, although the size of ∂1 still could be exponential, in the weight of ρ. In our next, crucial move, ∂1 was deterministically compressed into a "small", although multipremise, dag-like deduction ∂ whose horizontal levels contained only mutually different formulas, which made the whole weight polynomial in that of ρ. However, ∂ required a more complicated verification of the underlying provability of ρ. In this paper we present a nondeterministic compression of ∂ into a desired standard dag-like deduction ∂0 that deterministically proves ρ in time and space polynomial in the weight of ρ. Together with [3] this completes the proof of NP = PSPACE. Natural deductions are essential for our proof. Tree-to-dag horizontal compression of π merging equal sequents, instead of formulas, is (possible but) not sufficient, since the total number of different sequents in π might be exponential in the weight of ρ − even assuming that all formulas occurring in sequents are subformulas of ρ. On the other hand, we need Hudelmaier's cutfree sequent calculus in order to control both the height and total weight of different formulas of the initial tree-like proof π, since standard Prawitz's normalization although providing natural deductions with the subformula property does not preserve polynomial heights. It is not clear yet if we can omit references to π even in the proof of the weaker result NP = coNP.##
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Proof Compression and NP Versus PSPACE II: Addendum

2022
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Bulletin of the Section of Logic
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In [3] we proved the conjecture NP = PSPACE by advanced proof theoretic methods that combined Hudelmaier's cut-free sequent calculus for minimal logic (HSC) [5] with the horizontal compressing in the corresponding minimal Prawitz-style natural deduction (ND) [6]. In this Addendum we show how to prove a weaker result NP = coNP without referring to HSC. The underlying idea (due to the second author) is to omit full minimal logic and compress only \naive" normal tree-like ND refutations of the

doi:10.18778/0138-0680.2022.01
fatcat:d734nbldjfb3baul2svn773b7e
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... tence of Hamiltonian cycles in given non-Hamiltonian graphs, since the Hamiltonian graph problem in NP-complete. Thus, loosely speaking, the proof of NP = coNP can be obtained by HSC-elimination from our proof of NP = PSPACE [3].##
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On Strong Normalization in Proof-Graphs for Propositional Logic

2016
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Electronical Notes in Theoretical Computer Science
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Traditional proof theory of Propositional Logic deals with proofs whose size can be huge. Proof theoretical studies discovered exponential gaps between normal or cut free proofs and their respective non-normal proofs. The use of proof-graphs, instead of trees or lists, for representing proofs is getting popular among proof-theoreticians. Proof-graphs serve as a way to study complexity of propositional proofs and to provide more efficient theorem provers, concerning size of propositional proofs.

doi:10.1016/j.entcs.2016.06.012
fatcat:f4wwpgry4fc5rmowu6ew2a2hlu
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... Fpl-graphs were initially developed for minimal implicational logic representing proofs through references rather than copy. Thus, formulas and sub-deductions preserved in the graph structure, can be shared deleting unnecessary sub-deductions resulting in the reduced proof. In this work, we consider full minimal propositional logic and show how to reduce (eliminating maximal formulas) these representations such that strong normalization theorem can be proved by simply counting the number of maximal formulas in the original derivation. In proof-graphs, the main reason for obtaining the strong normalization property using such simple complexity measure is a direct consequence of the fact that each formula occurs only once in the proof-graph and the case of the hidden maximum formula that usually occurs in the tree-form derivation is already represented in the fpl-graph.##
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Proof-graphs for Minimal Implicational Logic

2014
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Electronic Proceedings in Theoretical Computer Science
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It is well-known that the size of propositional classical proofs can be huge. Proof theoretical studies discovered exponential gaps between normal or cut free proofs and their respective non-normal proofs. The aim of this work is to study how to reduce the weight of propositional deductions. We present the formalism of proof-graphs for purely implicational logic, which are graphs of a specific shape that are intended to capture the logical structure of a deduction. The advantage of this

doi:10.4204/eptcs.144.2
fatcat:stbdnq2enneoliegqxe3dokhey
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... m is that formulas can be shared in the reduced proof. In the present paper we give a precise definition of proof-graphs for the minimal implicational logic, together with a normalization procedure for these proof-graphs. In contrast to standard tree-like formalisms, our normalization does not increase the number of nodes, when applied to the corresponding minimal proof-graph representations.##
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Page 7553 of Mathematical Reviews Vol. , Issue 2000j
[page]

2000
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Mathematical Reviews
*

*Gordeev*, Lev

*Gordeev*,

*Lew*............ See

*Gordeev*, Lev Gordillo Ardila, Jorge Enrique .... * 11001 Gordon, Cameron McA. $7012,57036 Gordon, E. ...

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Page 416 of National Union Catalog Vol. 17, Issue
[page]

1958
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National Union Catalog
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Tolstol, Lev ,

*Lew*Ni laevich, grat. voina | mir. PG3365. V65G6 NjP MH InU NNC VtMiM NIC L. N. Tolstogo. 59-26265 t Gordeichuk, Nikolai Maksi sch see Hordiichuk, Mykola Maksymovych. ... TS1490.G65 °59-38829 t*Gordeev*, V A Yerpoficrso m oGcayaAusanne antoMaTMYeCcKAX TKAWKUX ctanxos, Mocxsa, W3,-s0 mayyno-texn. aut-ps:) PCOCP, 1960. 182 p._ illus. 28cm. ...##
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Page 214 of SMPTE Motion Imaging Journal Vol. 110, Issue Supplement
[page]

2001
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SMPTE Motion Imaging Journal
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*GORDEEV*, M.G. GORDON, V.N. GOROKHOV, A.P. GRECHISHNIKOV, V. GRIBOV, G. GRINEVETSKY, G. INSHIN, E.|. IVANOV, V.I. IVANOV, V.P. IVANOVSKY, V.Z. KHAIMOV, V.1. KHLEBNIKOV, I.D. KHOLIN, |.A.l. ...

*LEW*, J.M. REDOVIAN SANTA CLARA: T.F. BURCHILL, M. CHULANI, R.G. GREEN, J.C. KUO, M.D. LANDA, R.P. MANFREDO, C.A. PRESSLER, H.K. REGNIER JR, G. SADOWSKI, J. SHIKE, D.K. TAO, J.P. WADDELL, G.L. ...

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Page 591 of Journal of the Electrochemical Society Vol. 108, Issue 6
[page]

1961
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Journal of the Electrochemical Society
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*Gordeev*, G. V., “Ionization by collision at n-p junctions,” Fiz. Tverdogo Tela, 1, 851 (1959). Handbuch der Physik, ... ., “Internal field emission and

*lew*temperature thermionic emission into vacuum,” Proc. IRE, 48, 1644 (1960) . Goetzberger, A., and W. Shockley, “Metal precipitates in silicon p-n junctions,” J. ...

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Page 152 of SMPTE Motion Imaging Journal Vol. 104, Issue 5
[page]

1995
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SMPTE Motion Imaging Journal
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*LEW*, R. A. MIZER, S. QUINN, R. J. STEWART, M. |. ZIEGLER SANTA CLARA: N. R. BAKER, F. W. BARLING, R. J. BEST, A. T. BOURKE, D. T. CHANG, A. EAGLE, M. A. ELSTON, R. L. GOODWIN, H. GRAY, C. A. ... FROLOV, ~

*GORDEEV*, M. G. GORDON, V. N. GOROKHOV, . GRECHISHNIKOV, G. GRINEVETSKY, IVANOV, V. |. IVANOV, V. P. IVANOVSKY, KHLEBNIKOV, |. D. KHOLIN, C. Z. KOCHUASHVILI, . KRIVOVIAZ, L. G. LISHIN, E. G. ...

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Page 160 of SMPTE Motion Imaging Journal Vol. 101, Issue 5
[page]

1992
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SMPTE Motion Imaging Journal
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*Gordeev*, M. G. Gordon, V. N. Gorokhov, A. P. Grechishnikov, G. Grinevetsky, V. I. Ivanov, E. I. Ivanov, V. P. Ivanovsky, V. I. Khlebnikov, I. D. Kholin, C. Z. Kochuashvili, V. A. Kontorovitch, V. F. ...

*Lew*, S. S. Mirzad, R. A. Mizer, R. J. Stewart Sanger: R. C. Vaughn Santa Clara: F. W. Barling, A. J. Benedetti, R. J. Best, D. T. Chang, A. Chopra, G. W. Cintas, C. Fields, H. Gray, C. A. Hardman, H. ...

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Kozakoznawstwo jako nurt naukowy – perspektywy, stan i możliwości

2021
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Acta Universitatis Lodziensis. Folia Litteraria Polonica
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*Gordeev*, Istoriâ kazačestva, Veče, Moskva 2006, s. 8, 13. 36 R. ... pochodzić m.in. od rosyjskich zbiegów (władimir Broniewski 18 , siergiej sołowjow 19 , wasilij kluczewski i siergiej Płatonow 20 , Aleksandr szennikow 21 , nikołaj Mininkow 22 ), ple- mion chazarskich (

*Lew*...

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Yet another argument in favour of NP=CoNP
[article]

2020
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arXiv
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pre-print

We would like very much to thank professor

arXiv:2101.00003v1
fatcat:p3na5hk4grcevpoesvjx7stli4
*Lew**Gordeev*for the work we have done together and the inspiration to follow this alternative approach. ...##
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Page 633 of Mathematical Reviews Vol. , Issue Index
[page]

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Mathematical Reviews
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(with

*Gordeev*, E. N.) Qualitative investigation of trajectory problems. (Russian. English summary) Kibernetika (Kiev) 1986, no. 5, 82-89, 105, 135. ...*Lew*) 88g:41028 §41A60 (42A38, 44A15, 65R10) (with Gabutti, Bruno) The numerical performance of Tricomi’s formula for inverting the Laplace transform. Numer. Math. 51 (1987), no. 3, 369-380. (P. M. ...##
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Can We Model the Effect of Observed Sea Level Rise on Tides?

2018
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Journal of Geophysical Research - Oceans
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Negative amplitude responses to SLR at the mouth of the Delaware Bay are additionally worked out by a regression of annual M 2 changes (ΔH) against sea level changes (Δs) at station

doi:10.1029/2018jc013959
fatcat:3gmqwcwdunbppfhadqpfxz4hya
*Lewes*(1957*Lewes*... .,*Gordeev*et al., 1977; Ray, 1998 ) but non-trivial in practice; a complete treatment in forward models requires either global convolution integrals (Farrell, 1973; Stepanov & Hughes, 2004) or spherical ...
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