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Obstructions to some injective oriented colourings

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arxiv 2207.12523 v1 pith:LQT4O4UI submitted 2022-07-25 math.CO

Obstructions to some injective oriented colourings

classification math.CO
keywords orientedgraphinjectivecolouringhomomorphismmathcalproblemthere
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Each of several possible definitions of local injectivity for a homomorphism of an oriented graph $G$ to an oriented graph $H$ leads to an injective oriented colouring problem. For each case in which such a problem is solvable in polynomial time, we identify a set $\mathcal{F}$ of oriented graphs such that an oriented graph $G$ has an injective oriented colouring with the given number of colours if and only if there is no $F \in \mathcal{F}$ for which there is a locally-injective homomorphism of $F$ to $G$.

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