A strong oriented k-coloring of an oriented graph G is a homomorphism from G to H having k vertices labelled by the k elements of an abelian additive group M, such that for any p...
The strong chromatic number, S(G), of an n-vertex graph G is the smallest number k such that after adding kn/k-n isolated vertices to G and considering any partition of the vertic...
The oriented chromatic number of an oriented graph G is the minimum order of an oriented graph H such that G admits a homomorphism to H. The oriented chromatic number of an undire...
We indicate strong non-approximability factors for central problems: N1/4 for Max Clique; N1/10 for Chromatic Number; and 66/65 for Max 3SAT. Underlying the Max Clique result is a...