Abstract
It is conjectured Zhang et al. (Appl Math Lett 15: 623–626, 2002) that if \(G\notin \{K_2,C_5\}\) is a connected graph, then there is a proper edge coloring of \(G\) using at most \(\Delta (G)+2\) colors that distinguishes vertices of \(G\) by means of their (naturally defined) color sets. In the paper several results concerning edge colorings of the direct product of two graphs are obtained that support the conjecture.
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Acknowledgments
The authors thank to anonymous referees for their remarks which helped to improve the presentation of results of the paper. They are especially grateful for the simple proof of Theorem 1.
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The work of the first author was supported by Science and Technology Assistance Agency under the contract No. APVV-0023-10 and by Grant VEGA 1/0652/12. The work of the remaining two authors was partially supported by MIUR (Ministero dell’Istruzione, dell’Università e della Ricerca).
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Horňák, M., Mazza, D. & Zagaglia Salvi, N. Edge Colorings of the Direct Product of Two Graphs. Graphs and Combinatorics 31, 975–992 (2015). https://doi.org/10.1007/s00373-014-1413-5
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DOI: https://doi.org/10.1007/s00373-014-1413-5
Keywords
- Edge coloring
- Chromatic index
- Color set
- Adjacent vertex distinguishing chromatic index
- Direct product of graphs