Pre-hull Number of Cartesian and Strong Graph Products

Recently introduced invariants, copoint pre-hull number and convex pre-hull number, are both numerical measures of nonconvexity of a graph \( G \) that is a convex space. We consider in this work both the Cartesian and the strong product of graphs. Exact values in terms of invariants of the factors are presented for the first mentioned product. For the strong product, it is shown that such a result does not exist, but an exact result for trees is proved.