Volume 2018
Article 1
Published by the Department of Computer Science, The University of Chicago.
On monotone circuits with local oracles and clique lower bounds
Jan Krajíček
Faculty of Mathematics and Physics
Charles University
Czech Republic
krajicek AT karlin DOT mff DOT cuni DOT cz
and
Igor C. Oliveira
Department of Computer Science
University of Oxford
UK
igor.carbonioliveira AT cs DOT ox DOT ac DOT uk
March 25, 2018
Abstract
We investigate monotone circuits with local oracles [Krajíček 2016]
i.e., circuits containing additional inputs $y_i = y_i(\vec{x})$ that can
perform unstructured computations on the input string $\vec{x}$.
Let $\mu \in [0,1]$ be the locality of the circuit, a parameter that bounds
the combined strength of the oracle functions $y_i(\vec{x})$, and
$U_{n,k}, V_{n,k} \subseteq \{0,1\}^m$ be the set of $k$-cliques and
the set of complete $(k-1)$-partite graphs, respectively (similarly to
[Razborov, 1985]).} Our results can be informally stated as follows.
- (i) For an appropriate extension of depth-$2$ monotone circuits with local
oracles, we show that the size of the smallest circuits separating
$U_{n,3}$ (triangles) and $V_{n,3}$ (complete bipartite graphs) undergoes
two phase transitions according to $\mu$.
- (ii) For $5 \leq k(n) \leq n^{1/4}$, arbitrary depth, and $\mu \leq 1/50$, we prove that the monotone circuit size complexity of separating the sets $U_{n,k}$ and $V_{n,k}$ is $n^{\Theta(\sqrt{k})}$, under a certain restrictive assumption on the local oracle gates.
The second result, which concerns monotone circuits with restricted oracles, extends and provides a matching upper bound for the exponential lower bounds on the monotone circuit size complexity of $k$-clique obtained in [Alon and Boppana, 1987].
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Submitted April 24, 2017, revised December 18, 2017,
published March 25, 2018.
Volume 2017, Article 2
Article 2
Volume 2018
Published articles