[Colloquium] [Staff] Jakob Nordstrom Talk

[Donna Brooms]

*PLEASE NOTE THE CORRECTION ON THE ROOM*



> *Theory Seminar Reminder*
>  Note non-standard day, day and time
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> Friday, May 9, 2014
> 10:30 a.m.
> Ryerson 277
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> Jakob Nordstrom
> Royal Institute of Tech., Stockholm
> www.csc.kth.se/~jakobn
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> Title: “Narrow Proofs May Be Maximally Long”
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> Abstract: We prove that there are 3-CNF formulas over n variables that can be refuted in resolution in width w but require resolution proofs of size n^Omega(w). This shows that the simple counting argument that any formula refutable in width w must have a proof in size n^O(w) is essentially tight. Moreover, our lower bounds can be generalized to polynomial calculus resolution (PCR) and Sherali-Adams, implying that the corresponding size upper bounds in terms of degree and rank are tight as well. Our results do not extend all the way to Lasserre, however---the formulas we study have Lasserre proofs of constant rank and size polynomial in both n and w.
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> Joint work with Albert Atserias and Massimo Lauria.
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> Host: Prof. Alexander Razborov
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