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Equitable two-colorings of uniform hypergraphs
European Journal of Combinatorics. 2015. Vol. 43. P. 185–203.
An equitable two-coloring of a hypergraph $H=(V,E)$ is a proper vertex two-coloring such that the cardinalities of color classes differ by at most one. In connection with the property B problem Radhakrishnan and Srinivasan proved that if $H$ is a $k$-uniform hypergraph with maximum vertex degree $\Delta(H)$ satisfying
$$
\Delta(H)\leqslant c\,\frac {2^{k-1}}{\sqrt{k\,\ln k}}
$$
for some absolute constant $c>0$, then $H$ is 2-colorable. By using the Lov\'asz Local Lemma for negatively correlated events and the random recoloring method we prove that if $H$ either is a simple hypergraph or has a lot of vertices, then under the same condition on the maximum vertex degree it has an equitable coloring with two colors. We also obtain a general result for equitable colorings of partial Steiner systems.
Research target:
Mathematics
Language:
English
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