DMTCS Proceedings, 2005 European Conference on Combinatorics, Graph Theory and Applications (EuroComb '05)

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DMTCS Conference vol AE (2005), pp. 25-30

DMTCS

2005 European Conference on Combinatorics, Graph Theory and Applications (EuroComb '05)

Stefan Felsner (ed.)

DMTCS Conference Volume AE (2005), pp. 25-30


author: Oleg Pikhurko, Joel Spencer and Oleg Verbitsky
title: Decomposable graphs and definitions with no quantifier alternation
keywords: descriptive complexity of graphs, first order logic, Ehrenfeucht game on graphs, graph decompositions
abstract: Let
D(G)
be the minimum quantifier depth of a first order sentence
Φ
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
Φ
. 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)≤2
log
*
n+O(1)
. On the other hand, we prove a lower bound
D
0
(G)≥
log
*
n-
log
*
log
*
n-O(1)
for all
G
. Here
log
*
n
is equal to the minimum number of iterations of the binary logarithm needed to bring
n
below 1.
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reference: Oleg Pikhurko and Joel Spencer and Oleg Verbitsky (2005), Decomposable graphs and definitions with no quantifier alternation, in 2005 European Conference on Combinatorics, Graph Theory and Applications (EuroComb '05), Stefan Felsner (ed.), Discrete Mathematics and Theoretical Computer Science Proceedings AE, pp. 25-30
bibtex: For a corresponding BibTeX entry, please consider our BibTeX-file.
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