Generalised Mycielski Graphs as Topological Cliques
نویسندگان
چکیده
We prove that the coindex of the box complex B(H) of a graph H can be measured by the generalised Mycielski graphs which admit a homomorphism to it. As a consequence, we exhibit for every graph H a system of linear equations solvable in polynomial time, with the following properties: If the system has no solutions, then coind(B(H)) + 2 ≤ 3; if the system has solutions, then χ(H) ≥ 4.
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