Lemma 3.2. If c2 + (diam(G)/(α(G) − 1))2 ≤ 1, then there is no c-realization of G.
Proof. Suppose that there is a c-realization φ of G. Consider the minimum axis-parallel rectangle that covers φ(v) for all
v ∈ V, and partition the rectangle into α(G) − 1 vertical blocks of the same horizontal length. By Observation 3.1, the
horizontal length of each block is at most diam(G)/(α(G) − 1). The vertical length of each block is at most c. Thus the diagonal
length of the blocks is at most
c2 + (diam(G)/(α(G) − 1))2 ≤ 1. Hence, any two points in a block are adjacent. On
the other hand, by the pigeonhole principle, there is a block containing two points associated with vertices in a maximum
independent set of G. This is a contradiction.