visibility graph

Obstacle number of planar graphs

Author(s): Alpert; Koch; Laison

Does there exist a planar graph with obstacle number greater than 1? Is there some $k$ such that every planar graph has obstacle number at most $k$?

Keywords: graph drawing; obstacle number; planar graph; visibility graph

Point sets with no empty pentagon

Author(s): Wood

\begin{problem} Classify the point sets with no empty pentagon. \end{problem}

Keywords: combinatorial geometry; visibility graph

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