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EXPANDER GRAPHS AND SIEVING IN COMBINATORIAL STRUCTURES

Part of: Stochastic processes Graph theory

Published online by Cambridge University Press:  11 January 2018

FLORENT JOUVE  and
JEAN-SÉBASTIEN SERENI
FLORENT JOUVE*
Affiliation:
IMB, Université de Bordeaux, Talence, France email florent.jouve@math.u-bordeaux.fr
JEAN-SÉBASTIEN SERENI
Affiliation:
C.N.R.S. (LORIA), Vandœuvre-lès-Nancy, France email sereni@kam.mff.cuni.cz
*
✉ florent.jouve@math.u-bordeaux.fr
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Abstract

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We prove a general large-sieve statement in the context of random walks on subgraphs of a given graph. This can be seen as a generalization of previously known results where one performs a random walk on a group enjoying a strong spectral gap property. In such a context the point is to exhibit a strong uniform expansion property for a suitable family of Cayley graphs on quotients. In our combinatorial approach, this is replaced by a result of Alon–Roichman about expanding properties of random Cayley graphs. Applying the general setting we show, for instance, that with high probability (in a strong explicit sense) random coloured subsets of integers contain monochromatic (nonempty) subsets summing to  $0$ , and that a random colouring of the edges of a complete graph contains a monochromatic triangle.

Keywords

random walksgroupsgraphssieve

MSC classification

Primary: 60G50: Sums of independent random variables; random walks
Secondary: 05C25: Graphs and abstract algebra (groups, rings, fields, etc.)
Type
Research Article
Information
Journal of the Australian Mathematical Society , Volume 105 , Issue 1 , August 2018 , pp. 79 - 102
Copyright
© 2018 Australian Mathematical Publishing Association Inc. 

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