| Livingstone graph | |
| Vertices: | 266 |
| Edges: | 1463 |
| Automorphisms: | 175560 (J1) |
| Girth: | 5 |
| Radius: | 4 |
| Diameter: | 4 |
| Properties: | Symmetric Distance-transitive Primitive |
In the mathematical field of graph theory, the Livingstone graph is a distance-transitive graph with 266 vertices and 1463 edges. Its intersection array is .[1] It is the largest distance-transitive graph with degree 11.
The automorphism group of the Livingstone graph is the sporadic simple group J1, and the stabiliser of a point is PSL(2,11). As the stabiliser is maximal in J1, it acts primitively on the graph.
As the Livingstone graph is distance-transitive, PSL(2,11) acts transitively on the set of 11 vertices adjacent to a reference vertex v, and also on the set of 12 vertices at distance 4 from v. The second action is equivalent to the standard action of PSL(2,11) on the projective line over F11; the first is equivalent to an exceptional action on 11 points, related to the Paley biplane.