Occupancy fraction, fractional colouring, and triangle fraction

28 Dec 2018 Davies Ewan de Verclos Rémi de Joannis Kang Ross J. Pirot François

Given $\varepsilon>0$, there exists $f_0$ such that, if $f_0 \le f \le \Delta^2+1$, then for any graph $G$ on $n$ vertices of maximum degree $\Delta$ in which the neighbourhood of every vertex in $G$ spans at most $\Delta^2/f$ edges, (i) an independent set of $G$ drawn uniformly at random has at least $(1/2-\varepsilon)(n/\Delta)\log f$ vertices in expectation, and (ii) the fractional chromatic number of $G$ is at most $(2+\varepsilon)\Delta/\log f$. These bounds cannot in general be improved by more than a factor $2$ asymptotically... (read more)

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Categories


  • COMBINATORICS
  • DISCRETE MATHEMATICS
  • PROBABILITY