Transparent Rectangle Visibility Graphs

Abstract

A transparent rectangle visibility graph (TRVG) is a graph whose vertices can be represented by a collection of non-overlapping rectangles in the plane whose sides are parallel to the axes such that two vertices are adjacent if and only if there is a horizontal or vertical line intersecting the interiors of their rectangles. We show that every threshold graph, tree, cycle, rectangular grid graph, triangular grid graph and hexagonal grid graph is a TRVG. We also obtain a maximum number of edges of a bipartite TRVG and characterize complete bipartite TRVGs. More precisely, a bipartite TRVG with $n$ vertices has at most $2n-2$ edges. The complete bipartite graph $K_{p,q}$ is a TRVG if and only if $\min\{p,q\} \le 2$ or $(p,q) \in \{(3,3), (3,4)\}$. We prove similar results for the torus. Moreover, we study whether powers of cycles and their complements are TRVGs.