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URN: urn:nbn:de:0030-drops-50736
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Tight Size-Degree Bounds for Sums-of-Squares Proofs

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Abstract

We exhibit families of 4-CNF formulas over n variables that have sums-of-squares (SOS) proofs of unsatisfiability of degree (a.k.a. rank) d but require SOS proofs of size n^Omega(d) for values of d = d(n) from constant all the way up to n^delta for some universal constant delta. This shows that the n^O(d) running time obtained by using the Lasserre semidefinite programming relaxations to find degree-d SOS proofs is optimal up to constant factors in the exponent. We establish this result by combining NP-reductions expressible as low-degree SOS derivations with the idea of relativizing CNF formulas in [Krajicek '04] and [Dantchev and Riis '03], and then applying a restriction argument as in [Atserias, Müller, and Oliva '13] and [Atserias, Lauria, and Nordstrom '14]. This yields a generic method of amplifying SOS degree lower bounds to size lower bounds, and also generalizes the approach in [ALN14] to obtain size lower bounds for the proof systems resolution, polynomial calculus, and Sherali-Adams from lower bounds on width, degree, and rank, respectively.

BibTeX - Entry

@InProceedings{lauria_et_al:LIPIcs:2015:5073,
  author =	{Massimo Lauria and Jakob Nordstr{\"o}m},
  title =	{{Tight Size-Degree Bounds for Sums-of-Squares Proofs}},
  booktitle =	{30th Conference on Computational Complexity (CCC 2015)},
  pages =	{448--466},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-81-1},
  ISSN =	{1868-8969},
  year =	{2015},
  volume =	{33},
  editor =	{David Zuckerman},
  publisher =	{Schloss Dagstuhl--Leibniz-Zentrum fuer Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{http://drops.dagstuhl.de/opus/volltexte/2015/5073},
  URN =		{urn:nbn:de:0030-drops-50736},
  doi =		{10.4230/LIPIcs.CCC.2015.448},
  annote =	{Keywords: Proof complexity, resolution, Lasserre, Positivstellensatz, sums-of-squares, SOS, semidefinite programming, size, degree, rank, clique, lower bound}
}

Keywords: Proof complexity, resolution, Lasserre, Positivstellensatz, sums-of-squares, SOS, semidefinite programming, size, degree, rank, clique, lower bound
Seminar: 30th Conference on Computational Complexity (CCC 2015)
Issue date: 2015
Date of publication: 2015


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