A Note on Neighbour-Distinguishing Regular Graphs Total-Weighting

  • Jakub Przybyło


We investigate the following modification of a problem posed by Karoński, Łuczak and Thomason [J. Combin. Theory, Ser. B 91 (2004) 151–157]. Let us assign positive integers to the edges and vertices of a simple graph $G$. As a result we obtain a vertex-colouring of $G$ by sums of weights assigned to the vertex and its adjacent edges. Can we obtain a proper colouring using only weights 1 and 2 for an arbitrary $G$?

We know that the answer is yes if $G$ is a 3-colourable, complete or 4-regular graph. Moreover, it is enough to use weights from $1$ to $11$, as well as from $1$ to $\lfloor{\chi(G)\over2}\rfloor+1$, for an arbitrary graph $G$. Here we show that weights from $1$ to $7$ are enough for all regular graphs.

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