Fractional clique decompositions of dense graphs and hypergraphs

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Colleges, School and Institutes

Abstract

Our main result is that every graph $G$ on $n\ge 10^4r^3$ vertices with minimum degree $\delta(G) \ge (1 - 1 / 10^4 r^{3/2} ) n$ has a fractional $K_r$-decomposition. Combining this result with recent work of Barber, K\"uhn, Lo and Osthus leads to the best known minimum degree thresholds for exact (non-fractional) $F$-decompositions for a wide class of graphs~$F$ (including large cliques).%as well as the best threshold in terms of $|F|$.For general $k$-uniform hypergraphs, we give a short argument which shows that there exists a constant $c_k>0$ such that every $k$-uniform hypergraph $G$ on $n$ vertices with minimum codegree at least $(1- c_k /r^{2k-1})  n $ has a fractional $K^{(k)}_r$-decomposition, where $K^{(k)}_r$ is the complete $k$-uniform hypergraph on $r$ vertices.(Related fractional decomposition results for triangles have been obtained by Dross and for hypergraph cliques by Dukes as well as Yuster.)All the above new results involve purely combinatorial arguments. In particular, this yields a combinatorial proof of Wilson's theorem that every large $F$-divisible complete graph has an $F$-decomposition.

Details

Original languageEnglish
Pages (from-to)148-186
JournalJournal of Combinatorial Theory. Series B
Volume127
Early online date2 Jun 2017
Publication statusPublished - Nov 2017

Keywords

  • Fractional decomposition, 05C70, 05C72, Minimum degree, Cliques