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Electronic Colloquium on Computational Complexity

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All reports by Author Jan Krajicek:

TR21-053 | 13th April 2021
Jan Krajicek

Information in propositional proofs and algorithmic proof search

We study from the proof complexity perspective the (informal) proof search problem:
Is there an optimal way to search for propositional proofs?
We note that for any fixed proof system there exists a time-optimal proof search algorithm. Using classical proof complexity results about reflection principles we prove that a time-optimal ... more >>>

TR19-077 | 30th May 2019
Jan Bydzovsky, Igor Carboni Oliveira, Jan Krajicek

Consistency of circuit lower bounds with bounded theories

Proving that there are problems in $P^{NP}$ that require boolean circuits of super-linear size is a major frontier in complexity theory. While such lower bounds are known for larger complexity classes, existing results only show that the corresponding problems are hard on infinitely many input lengths. For instance, proving almost-everywhere ... more >>>

TR16-071 | 1st May 2016
Jan Krajicek, Igor Carboni Oliveira

Unprovability of circuit upper bounds in Cook's theory PV

We establish unconditionally that for every integer $k \geq 1$ there is a language $L \in P$ such that it is consistent with Cook's theory PV that $L \notin SIZE(n^k)$. Our argument is non-constructive and does not provide an explicit description of this language.

more >>>

TR13-156 | 15th November 2013
Jan Krajicek

A reduction of proof complexity to computational complexity for $AC^0[p]$ Frege systems

Revisions: 2

We give a general reduction of lengths-of-proofs lower bounds for
constant depth Frege systems in DeMorgan language augmented by
a connective counting modulo a prime $p$
(the so called $AC^0[p]$ Frege systems)
to computational complexity
lower bounds for search tasks involving search trees branching upon
values of linear maps on ... more >>>

TR10-054 | 30th March 2010
Jan Krajicek

On the proof complexity of the Nisan-Wigderson generator based on a hard $NP \cap coNP$ function

Let $g$ be a map defined as the Nisan-Wigderson generator
but based on an $NP \cap coNP$-function $f$. Any string $b$ outside the range of
$g$ determines a propositional tautology $\tau(g)_b$ expressing this
fact. Razborov \cite{Raz03} has conjectured that if $f$ is hard on average for
P/poly then these ... more >>>

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