Goldner–Harary graph
| Goldner–Harary graph | |
|---|---|
 | |
| Named after | A. Goldner, Frank Harary |
| Vertices | 11 |
| Edges | 27 |
| Radius | 2 |
| Diameter | 2 |
| Girth | 3 |
| Automorphisms | 12 (D6) |
| Chromatic number | 4 |
| Chromatic index | 8 |
| Properties | Polyhedral Planar Chordal Perfect Treewidth 3 |
| Table of graphs and parameters | |
In the mathematical field of graph theory, the Goldner–Harary graph is a simple undirected graph with 11 vertices and 27 edges. It is named after Anita M. Goldner and Frank Harary, who proved in 1975 that it was the smallest non-Hamiltonian maximal planar graph.[1][2][3] The same graph had already been given as an example of a non-Hamiltonian simplicial polyhedron by Branko Grünbaum in 1967.[4]
Properties
[edit]The Goldner–Harary graph is a planar graph: it can be drawn in the plane with none of its edges crossing. When drawn on a plane, all its faces are triangular, making it a maximal planar graph.[5] As with every maximal planar graph, it is also 3-vertex-connected: the removal of any two of its vertices leaves a connected subgraph.
The Goldner–Harary graph is also non-Hamiltonian.[5] 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.[6]
As a non-Hamiltonian maximal planar graph, the Goldner–Harary graph provides an example of a planar graph with book thickness greater than two.[7] 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.[8]
It has book thickness 3, chromatic number 4, chromatic index 8, girth 3, radius 2, 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.[9]
The automorphism group of the Goldner–Harary graph is of order 12 and is isomorphic to the dihedral group D6, the group of symmetries of a regular hexagon, including both rotations and reflections.
The characteristic polynomial of the Goldner–Harary graph is : .
Polyhedron
[edit]
By Steinitz's theorem, the Goldner–Harary graph is a polyhedral graph: it is planar and 3-connected, so there exists a convex polyhedron having the Goldner–Harary graph as its skeleton.[10] Geometrically, the Goldner–Harary graph represents a simplicial polyhedron, formed by gluing tetrahedra onto each face of a triangular dipyramid. In other words, it is the Kleetope of the triangular dipyramid.[4][11] The dual graph of the Goldner–Harary graph is represented geometrically by the truncation of the triangular prism.
References
[edit]- ^ 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.
- ^ Dillencourt, M. B. (1996), "Polyhedra of small orders and their Hamiltonian properties", Journal of Combinatorial Theory, Series B, 66: 87–122, doi:10.1006/jctb.1996.0008.
- ^ Read, R. C.; Wilson, R. J. (1998), An Atlas of Graphs, Oxford, England: Oxford University Press, p. 285.
- ^ a b Grünbaum, Branko (1967), Convex Polytopes, Wiley Interscience, p. 357. Same page, 2nd ed., Graduate Texts in Mathematics 221, Springer-Verlag, 2003, ISBN 978-0-387-40409-7.
- ^ a b Tonyl, A. Robina; Tharani, A. Punitha (2018), "Triple Connected Line Domination Number for Some Standard and Special Graphs", International Journal of Advanced Scientific Research and Management, Volume 3 Issue 8, Aug 2018, ISSN 2455-6378
- ^ Barnette, David; Jucovič, Ernest (1970), "Hamiltonian circuits on 3-polytopes", Journal of Combinatorial Theory, 9 (1): 54–59, doi:10.1016/S0021-9800(70)80054-0.
- ^ Bernhart, Frank R.; Kainen, Paul C. (1979), "The book thickness of a graph", Journal of Combinatorial Theory, Series B, 27 (3): 320–331, doi:10.1016/0095-8956(79)90021-2. See in particular Figure 9.
- ^ Yannakakis, Mihalis (1986), "Four pages are necessary and sufficient for planar graphs", Proc. 18th ACM Symp. Theory of Computing (STOC), pp. 104–108, doi:10.1145/12130.12141, S2CID 5359519.
- ^ Knill, Oliver (June 17, 2018), Combinatorial manifolds are Hamiltonian, arXiv:1806.06436.
- ^ Yadav, Sanlosh Kumar (2023), Advanced Graph Theory, Springer, p. 100
- ^ Ewald, Günter (1973), "Hamiltonian circuits in simplicial complexes", Geometriae Dedicata, 2 (1): 115–125, doi:10.1007/BF00149287, S2CID 122755203.
External links
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