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Conference Papers Discrete Mathematics and Theoretical Computer Science Year : 2005

Decomposable graphs and definitions with no quantifier alternation

Abstract

Let $D(G)$ be the minimum quantifier depth of a first order sentence $\Phi$ that defines a graph $G$ up to isomorphism in terms of the adjacency and the equality relations. Let $D_0(G)$ be a variant of $D(G)$ where we do not allow quantifier alternations in $\Phi$. Using large graphs decomposable in complement-connected components by a short sequence of serial and parallel decompositions, we show examples of $G$ on $n$ vertices with $D_0(G) \leq 2 \log^{\ast}n+O(1)$. On the other hand, we prove a lower bound $D_0(G) \geq \log^{\ast}n-\log^{\ast}\log^{\ast}n-O(1)$ for all $G$. Here $\log^{\ast}n$ is equal to the minimum number of iterations of the binary logarithm needed to bring $n$ below $1$.
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Dates and versions

hal-01184380 , version 1 (14-08-2015)

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Cite

Oleg Pikhurko, Joel Spencer, Oleg Verbitsky. Decomposable graphs and definitions with no quantifier alternation. 2005 European Conference on Combinatorics, Graph Theory and Applications (EuroComb '05), 2005, Berlin, Germany. pp.25-30, ⟨10.46298/dmtcs.3423⟩. ⟨hal-01184380⟩

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