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arXiv · 1112.6172

Answer to a question of Alon and Lubetzky about the ultimate categorical independence ratio

Ágnes Tóth
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Abstract

Brown, Nowakowski and Rall defined the ultimate categorical independence ratio of a graph G as A(G)=\lim_{k\to \infty} i(G^{\times k}), where i(G)=\frac{α(G)}{|V(G)|} denotes the independence ratio of a graph G, and G^{\times k} is the k-th categorical power of G. Let a(G)=\max{\frac{|U|}{|U|+|N_G(U)|}: U is an independent set of G}}, where N_G(U) is the neighborhood of U in G. In this paper we answer a question of Alon and Lubetzky, namely we prove that if a(G)\le 1/2 then A(G)=a(G), and if a(G)>1/2 then A(G)=1. We also discuss some other open problems related to A(G) which are immediately settled by this result.

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Ágnes Tóth. 2011-12-28. Answer to a question of Alon and Lubetzky about the ultimate categorical independence ratio. https://arxiv.org/abs/1112.6172

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