Genus, Skewness, Thickness and Coloring Theorems

A conjecture by Albertson states that if \( \chi(G) \geq n \), then \( cr(G) \geq cr(K_n) \), where \( \chi(G) \) is the chromatic number of \( G \) and \( cr(G) \) is the crossing number of \( G \). This conjecture is true for \( n \leq 16 \), but it remains open for \( n \geq 17 \).

In this paper, we consider the statements corresponding to this conjecture where the crossing number of \( G \) is replaced with:
– the genus \( \gamma(G) \) (the minimum genus of the orientable surface on which \( G \) is embeddable),
– the skewness \( \mu(G) \) (the minimum number of edges whose removal makes \( G \) planar), and
– the thickness \( \theta(G) \) (the minimum number of planar subgraphs of \( G \) whose union is \( G \)).