Discussiones Mathematicae Graph Theory 25(1-2) (2005)
183-196
DOI: https://doi.org/10.7151/dmgt.1271
MEDIAN AND QUASI-MEDIAN DIRECT PRODUCTS OF GRAPHS
Bostjan Bresar
University of Maribor, FEECS |
Pranava K. Jha
Department of Computer Science |
Sandi Klavžar
Department of Mathematics and Computer Science, PEF |
Blaz Zmazek
University of Maribor, FME |
Abstract
Median graphs are characterized among direct products of graphs on at least three vertices. Beside some trivial cases, it is shown that one component of G×P3 is median if and only if G is a tree in that the distance between any two vertices of degree at least 3 is even. In addition, some partial results considering median graphs of the form G×K2 are proved, and it is shown that the only nonbipartite quasi-median direct product is K3×K3.Keywords: median graph, direct product, quasi-median graph, isometric embeddings, convexity.
2000 Mathematics Subject Classification: 05C75, 05C12.
References
[1] | G. Abay-Asmerom and R. Hammack, Centers of tensor products of graphs, Ars Combin., to appear. |
[2] | H.-J. Bandelt, Retracts of hypercubes, J. Graph Theory 8 (1984) 501-510, doi: 10.1002/jgt.3190080407. |
[3] | H.-J. Bandelt, G. Burosch and J.-M. Laborde, Cartesian products of trees and paths, J. Graph Theory 22 (1996) 347-356, doi: 10.1002/(SICI)1097-0118(199608)22:4<347::AID-JGT8>3.0.CO;2-L. |
[4] | H.-J. Bandelt, H.M. Mulder and E. Wilkeit, Quasi-median graphs and algebras, J. Graph Theory 18 (1994) 681-703, doi: 10.1002/jgt.3190180705. |
[5] | B. Bresar, W. Imrich and S. Klavžar, Tree-like isometric subgraphs of hypercubes, Discuss. Math. Graph Theory 23 (2003) 227-240, doi: 10.7151/dmgt.1199. |
[6] | B. Bresar, S. Klavžar and R. Skrekovski, Quasi-median graphs, their generalizations, and tree-like equalities, European J. Combin. 24 (2003) 557-572, doi: 10.1016/S0195-6698(03)00045-3. |
[7] | M. Deza and M. Laurent, Geometry of Cuts and Metrics (Springer-Verlag, Berlin, 1997). |
[8] | D. Djoković, Distance preserving subgraphs of hypercubes, J. Combin. Theory (B) 14 (1973) 263-267, doi: 10.1016/0095-8956(73)90010-5. |
[9] | J. Hagauer and S. Klavžar, Clique-gated graphs, Discrete Math. 161 (1996) 143-149, doi: 10.1016/0012-365X(95)00280-A. |
[10] | W. Imrich, Factoring cardinal product graphs in polynomial time, Discrete Math. 192 (1998) 119-144, doi: 10.1016/S0012-365X(98)00069-7. |
[11] | W. Imrich and S. Klavžar, Product Graphs: Structure and Recognition (Wiley, New York, 2000). |
[12] | P.K. Jha, S. Klavžar and B. Zmazek, Isomorphic components of Kronecker products of bipartite graphs, Discuss. Math. Graph Theory 17 (1997) 301-309, doi: 10.7151/dmgt.1057. |
[13] | S.-R. Kim, Centers of a tensor composite graph, in: Proceedings of the Twenty-second Southeastern Conference on Combinatorics, Graph Theory, and Computing (Baton Rouge, LA, 1991), Congr. Numer. 81 (1991) 193-203. |
[14] | S. Klavžar and H.M. Mulder, Median graphs: characterizations, location theory and related structures, J. Combin. Math. Combin. Comp. 30 (1999) 103-127. |
[15] | S. Klavžar and R. Skrekovski, On median graphs and median grid graphs, Discrete Math. 219 (2000) 287-293, doi: 10.1016/S0012-365X(00)00085-6. |
[16] | H.M. Mulder, The structure of median graphs, Discrete Math. 24 (1978) 197-204, doi: 10.1016/0012-365X(78)90199-1. |
[17] | H.M. Mulder, The Interval Function of a Graph (Mathematisch Centrum, Amsterdam, 1980). |
[18] | C. Tardif, On compact median graphs, J. Graph Theory 23 (1996) 325-336, doi: 10.1002/(SICI)1097-0118(199612)23:4<325::AID-JGT1>3.0.CO;2-T. |
[19] | P.M. Weichsel, The Kronecker product of graphs, Proc. Amer. Math. Soc. 13 (1962) 47-52, doi: 10.1090/S0002-9939-1962-0133816-6. |
[20] | P.M. Winkler, Isometric embedding in products of complete graphs, Discrete Appl. Math. 7 (1984) 221-225, doi: 10.1016/0166-218X(84)90069-6. |
Received 29 November 2003
Revised 1 September 2004
Close