# circular coloring

## Circular colouring the orthogonality graph ★★

Author(s): DeVos; Ghebleh; Goddyn; Mohar; Naserasr

Let denote the graph with vertex set consisting of all lines through the origin in and two vertices adjacent in if they are perpendicular.

**Problem**Is ?

Keywords: circular coloring; geometric graph; orthogonality

## Circular coloring triangle-free subcubic planar graphs ★★

**Problem**Does every triangle-free planar graph of maximum degree three have circular chromatic number at most ?

Keywords: circular coloring; planar graph; triangle free