Goldner–Harary graph

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Goldner–Harary graph
Chromatic index
8
PropertiesPolyhedral
Planar
Chordal
Perfect
Treewidth 3
Table of graphs and parameters

In the

simplicial polyhedron by Branko Grünbaum in 1967.[4]

Properties

The Goldner–Harary graph is a

3-vertex-connected: the removal of any two of its vertices leaves a connected subgraph
.

The Goldner–Harary graph is also

non-Hamiltonian. The smallest possible number of vertices for a non-Hamiltonian polyhedral graph is 11. Therefore, the Goldner–Harary graph is a minimal example of graphs of this type. However, the Herschel graph
, another non-Hamiltonian polyhedron with 11 vertices, has fewer edges.

As a non-Hamiltonian maximal planar graph, the Goldner–Harary graph provides an example of a planar graph with book thickness greater than two.[5] Based on the existence of such examples, Bernhart and Kainen conjectured that the book thickness of planar graphs could be made arbitrarily large, but it was subsequently shown that all planar graphs have book thickness at most four.[6]

It has

diameter 2 and is a 3-edge-connected graph
.

It is also a 3-tree, and therefore it has treewidth 3. Like any k-tree, it is a chordal graph. As a planar 3-tree, it forms an example of an Apollonian network.

Geometry

By

skeleton
.

Geometric realization of the Goldner–Harary graph
Realization of the Goldner–Harary graph as the deltahedron obtained by attaching regular tetrahedra to the six faces of a triangular dipyramid.

Geometrically, a polyhedron representing the Goldner–Harary graph may be formed by gluing a tetrahedron onto each face of a

triangular dipyramid, similarly to the way a triakis octahedron is formed by gluing a tetrahedron onto each face of an octahedron. That is, it is the Kleetope of the triangular dipyramid.[4][7] The dual graph of the Goldner–Harary graph is represented geometrically by the truncation of the triangular prism
.

Algebraic properties

The

regular hexagon
, including both rotations and reflections.

The characteristic polynomial of the Goldner–Harary graph is : .

References

  1. ^ Goldner, A.; Harary, F. (1975), "Note on a smallest nonhamiltonian maximal planar graph", Bull. Malaysian Math. Soc., 6 (1): 41–42. See also the same journal 6(2):33 (1975) and 8:104-106 (1977). Reference from listing of Harary's publications.
  2. .
  3. ^ Read, R. C.; Wilson, R. J. (1998), An Atlas of Graphs, Oxford, England: Oxford University Press, p. 285.
  4. ^ .
  5. . See in particular Figure 9.
  6. .
  7. .

External links