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Documents authored by Buss, Sam

Document
DOI: 10.4230/LIPIcs.ITCS.2023.30
TFNP Characterizations of Proof Systems and Monotone Circuits

Authors: Sam Buss, Noah Fleming, and Russell Impagliazzo

Published in: LIPIcs, Volume 251, 14th Innovations in Theoretical Computer Science Conference (ITCS 2023)

Abstract
Connections between proof complexity and circuit complexity have become major tools for obtaining lower bounds in both areas. These connections - which take the form of interpolation theorems and query-to-communication lifting theorems - translate efficient proofs into small circuits, and vice versa, allowing tools from one area to be applied to the other. Recently, the theory of TFNP has emerged as a unifying framework underlying these connections. For many of the proof systems which admit such a connection there is a TFNP problem which characterizes it: the class of problems which are reducible to this TFNP problem via query-efficient reductions is equivalent to the tautologies that can be efficiently proven in the system. Through this, proof complexity has become a major tool for proving separations in black-box TFNP. Similarly, for certain monotone circuit models, the class of functions that it can compute efficiently is equivalent to what can be reduced to a certain TFNP problem in a communication-efficient manner. When a TFNP problem has both a proof and circuit characterization, one can prove an interpolation theorem. Conversely, many lifting theorems can be viewed as relating the communication and query reductions to TFNP problems. This is exciting, as it suggests that TFNP provides a roadmap for the development of further interpolation theorems and lifting theorems. In this paper we begin to develop a more systematic understanding of when these connections to TFNP occur. We give exact conditions under which a proof system or circuit model admits a characterization by a TFNP problem. We show: - Every well-behaved proof system which can prove its own soundness (a reflection principle) is characterized by a TFNP problem. Conversely, every TFNP problem gives rise to a well-behaved proof system which proves its own soundness. - Every well-behaved monotone circuit model which admits a universal family of functions is characterized by a TFNP problem. Conversely, every TFNP problem gives rise to a well-behaved monotone circuit model with a universal problem. As an example, we provide a TFNP characterization of the Polynomial Calculus, answering a question from [Mika Göös et al., 2022], and show that it can prove its own soundness.
Cite as

Sam Buss, Noah Fleming, and Russell Impagliazzo. TFNP Characterizations of Proof Systems and Monotone Circuits. In 14th Innovations in Theoretical Computer Science Conference (ITCS 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 251, pp. 30:1-30:40, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{buss_et_al:LIPIcs.ITCS.2023.30,
  author =	{Buss, Sam and Fleming, Noah and Impagliazzo, Russell},
  title =	{{TFNP Characterizations of Proof Systems and Monotone Circuits}},
  booktitle =	{14th Innovations in Theoretical Computer Science Conference (ITCS 2023)},
  pages =	{30:1--30:40},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-263-1},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{251},
  editor =	{Tauman Kalai, Yael},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2023.30},
  URN =		{urn:nbn:de:0030-drops-175332},
  doi =		{10.4230/LIPIcs.ITCS.2023.30},
  annote =	{Keywords: Proof Complexity, Circuit Complexity, TFNP}
}
Document
DOI: 10.4230/LIPIcs.CSL.2020.12
Proof Complexity of Systems of (Non-Deterministic) Decision Trees and Branching Programs

Authors: Sam Buss, Anupam Das, and Alexander Knop

Published in: LIPIcs, Volume 152, 28th EACSL Annual Conference on Computer Science Logic (CSL 2020)

Abstract
This paper studies propositional proof systems in which lines are sequents of decision trees or branching programs, deterministic or non-deterministic. Decision trees (DTs) are represented by a natural term syntax, inducing the system LDT, and non-determinism is modelled by including disjunction, ∨, as primitive (system LNDT). Branching programs generalise DTs to dag-like structures and are duly handled by extension variables in our setting, as is common in proof complexity (systems eLDT and eLNDT). Deterministic and non-deterministic branching programs are natural nonuniform analogues of log-space (L) and nondeterministic log-space (NL), respectively. Thus eLDT and eLNDT serve as natural systems of reasoning corresponding to L and NL, respectively. The main results of the paper are simulation and non-simulation results for tree-like and dag-like proofs in LDT, LNDT, eLDT and eLNDT. We also compare them with Frege systems, constant-depth Frege systems and extended Frege systems.
Cite as

Sam Buss, Anupam Das, and Alexander Knop. Proof Complexity of Systems of (Non-Deterministic) Decision Trees and Branching Programs. In 28th EACSL Annual Conference on Computer Science Logic (CSL 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 152, pp. 12:1-12:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{buss_et_al:LIPIcs.CSL.2020.12,
  author =	{Buss, Sam and Das, Anupam and Knop, Alexander},
  title =	{{Proof Complexity of Systems of (Non-Deterministic) Decision Trees and Branching Programs}},
  booktitle =	{28th EACSL Annual Conference on Computer Science Logic (CSL 2020)},
  pages =	{12:1--12:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-132-0},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{152},
  editor =	{Fern\'{a}ndez, Maribel and Muscholl, Anca},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2020.12},
  URN =		{urn:nbn:de:0030-drops-116553},
  doi =		{10.4230/LIPIcs.CSL.2020.12},
  annote =	{Keywords: proof complexity, decision trees, branching programs, logspace, sequent calculus, non-determinism, low-depth complexity}
}
Document
DOI: 10.4230/LIPIcs.CCC.2018.16
Reordering Rule Makes OBDD Proof Systems Stronger

Authors: Sam Buss, Dmitry Itsykson, Alexander Knop, and Dmitry Sokolov

Published in: LIPIcs, Volume 102, 33rd Computational Complexity Conference (CCC 2018)

Abstract
Atserias, Kolaitis, and Vardi showed that the proof system of Ordered Binary Decision Diagrams with conjunction and weakening, OBDD(^, weakening), simulates CP^* (Cutting Planes with unary coefficients). We show that OBDD(^, weakening) can give exponentially shorter proofs than dag-like cutting planes. This is proved by showing that the Clique-Coloring tautologies have polynomial size proofs in the OBDD(^, weakening) system. The reordering rule allows changing the variable order for OBDDs. We show that OBDD(^, weakening, reordering) is strictly stronger than OBDD(^, weakening). This is proved using the Clique-Coloring tautologies, and by transforming tautologies using coded permutations and orification. We also give CNF formulas which have polynomial size OBDD(^) proofs but require superpolynomial (actually, quasipolynomial size) resolution proofs, and thus we partially resolve an open question proposed by Groote and Zantema. Applying dag-like and tree-like lifting techniques to the mentioned results, we completely analyze which of the systems among CP^*, OBDD(^), OBDD(^, reordering), OBDD(^, weakening) and OBDD(^, weakening, reordering) polynomially simulate each other. For dag-like proof systems, some of our separations are quasipolynomial and some are exponential; for tree-like systems, all of our separations are exponential.
Cite as

Sam Buss, Dmitry Itsykson, Alexander Knop, and Dmitry Sokolov. Reordering Rule Makes OBDD Proof Systems Stronger. In 33rd Computational Complexity Conference (CCC 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 102, pp. 16:1-16:24, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{buss_et_al:LIPIcs.CCC.2018.16,
  author =	{Buss, Sam and Itsykson, Dmitry and Knop, Alexander and Sokolov, Dmitry},
  title =	{{Reordering Rule Makes OBDD Proof Systems Stronger}},
  booktitle =	{33rd Computational Complexity Conference (CCC 2018)},
  pages =	{16:1--16:24},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-069-9},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{102},
  editor =	{Servedio, Rocco A.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CCC.2018.16},
  URN =		{urn:nbn:de:0030-drops-88720},
  doi =		{10.4230/LIPIcs.CCC.2018.16},
  annote =	{Keywords: Proof complexity, OBDD, Tseitin formulas, the Clique-Coloring principle, lifting theorems}
}
Document
DOI: 10.4230/LIPIcs.ITCS.2017.31
Expander Construction in VNC1

Authors: Sam Buss, Valentine Kabanets, Antonina Kolokolova, and Michal Koucky

Published in: LIPIcs, Volume 67, 8th Innovations in Theoretical Computer Science Conference (ITCS 2017)

Abstract
We give a combinatorial analysis (using edge expansion) of a variant of the iterative expander construction due to Reingold, Vadhan, and Wigderson (2002), and show that this analysis can be formalized in the bounded arithmetic system VNC^1 (corresponding to the "NC^1 reasoning"). As a corollary, we prove the assumption made by Jerabek (2011) that a construction of certain bipartite expander graphs can be formalized in VNC^1. This in turn implies that every proof in Gentzen's sequent calculus LK of a monotone sequent can be simulated in the monotone version of LK (MLK) with only polynomial blowup in proof size, strengthening the quasipolynomial simulation result of Atserias, Galesi, and Pudlak (2002).
Cite as

Sam Buss, Valentine Kabanets, Antonina Kolokolova, and Michal Koucky. Expander Construction in VNC1. In 8th Innovations in Theoretical Computer Science Conference (ITCS 2017). Leibniz International Proceedings in Informatics (LIPIcs), Volume 67, pp. 31:1-31:26, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

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@InProceedings{buss_et_al:LIPIcs.ITCS.2017.31,
  author =	{Buss, Sam and Kabanets, Valentine and Kolokolova, Antonina and Koucky, Michal},
  title =	{{Expander Construction in VNC1}},
  booktitle =	{8th Innovations in Theoretical Computer Science Conference (ITCS 2017)},
  pages =	{31:1--31:26},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-029-3},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{67},
  editor =	{Papadimitriou, Christos H.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2017.31},
  URN =		{urn:nbn:de:0030-drops-81871},
  doi =		{10.4230/LIPIcs.ITCS.2017.31},
  annote =	{Keywords: expander graphs, bounded arithmetic, alternating log time, sequent calculus, monotone propositional logic}
}
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