Abstract
The complex adjacency matrix \({A_{\!\mathbb {C}}}(G)\) for a multidigraph G is introduced in Barik and Sahoo (AKCE Int J Graphs Comb 17(1):466–479, 2020). We study the rank of multidigraphs corresponding to the complex adjacency matrix and call it \({A_{\!\mathbb {C}}}\)-rank. It is known that a connected graph G has rank 2 if and only if G is a complete bipartite graph, and has rank 3 if and only if it is a complete tripartite graph (Cheng in Electron J Linear Algebra 16:60–67, 2007). We observe that these results hold as special cases for multidigraphs but are not sufficient. In this article, we characterize all multidigraphs with \({A_{\!\mathbb {C}}}\)-rank 2 and 3, respectively.
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References
Bapat, R.B., Kalita, D., Pati, S.: On weighted directed graphs. Linear Algebra Appl. 436, 99–111 (2012)
Barik, S., Sahoo, G.: A new matrix representation of multidigraphs. AKCE Int. J. Graphs Comb. 17(1), 466–479 (2020)
Chang, G., Huang, L., Yeh, H.: A characterization of graphs with rank 4. Linear Algebra Appl. 434, 1793–1798 (2011)
Chang, G., Huang, L., Yeh, H.: A characterization of graphs with rank 5. Linear Algebra Appl. 436, 4241–4250 (2012)
Cheng, B., Liu, B.: On the nullity of graphs. Electron. J. Linear Algebra 16, 60–67 (2007)
Cvetković, D.M., Doob, M., Sachs, H.: Spectra of Graphs: Theory and Applications. Academic press, Cambridge (1980)
Fan, Y., Wang, Y., Wang, Y.: A note on the nullity of unicyclic signed graphs. Linear Algebra Appl. 438, 1193–1200 (2013)
Gong, S., Fan, Y., Yin, Z.: On the nullity of graphs with pendant trees. Linear Algebra Appl. 433, 1374–1380 (2010)
Guo, K., Mohar, B.: Hermitian adjacency matrix of digraphs and mixed graphs. J. Graph Theory 85(1), 217–248 (2017)
Haicheng, M., Gao, S., Li, D.: Graphs with pendant pertices and r(G)\(\le \)7. J. Appl. Math. Phys. 8, 240–246 (2020)
Haicheng, M., Yanga, W., Li, S.: Positive and negative inertia index of a graph. Linear Algebra Appl. 438, 331–341 (2013)
Horn, R.A., Johnson, C.R.: Matrix Analysis. Cambridge University Press, Cambridge (2012)
Koh, K.M., Tay, E.G.: On optimal orientations of G vertex-multiplications. Discrete Math. 219, 153–171 (2000)
Li, S.: On the nullity of graphs with pendent vertices. Linear Algebra Appl. 429, 1619–1628 (2018)
Reff, N.: Spectral properties of complex unit gain graphs. Linear Algebra Appl. 436, 3165–3176 (2012)
Reff, N.: Oriented gain graphs, line graphs and eigenvalues. Linear Algebra Appl. 506, 316–328 (2016)
Tian, Y.: Equalities and inequalities for inertias of Hermitian matrices with applications. Linear Algebra Appl. 433, 263–296 (2010)
Tian, F., Wang, D., Zhu, M.: A characterization of signed planar graphs with rank at most 4. Linear Multilinear Algebra 64, 807–817 (2016)
Xu, F., Zhou, Q., Wong, D., Tian, F.L.: Complex unit gain graphs of rank 2. Linear Algebra Appl. 597, 155–169 (2020)
Yu, G.H., Qu, H., Tu, J.H.: Inertia of complex unit gain graphs. Appl. Math. Comput. 265, 619–629 (2015)
Yu, G.H., Zhang, X.D., Feng, L.H.: The inertia of weighted unicyclic graphs. Linear Algebra Appl. 448, 130–152 (2014)
Zhang, W.J., Yu, A.M.: On the rank of weighted graphs. Linear and Multilinear Algebra 65(3), 635–652 (2017)
Acknowledgements
The first author acknowledges SERB, DST, Government of India for the financial support (Project No.-MTR/2017/000080). The second author acknowledges the financial support from UGC, Government of India.
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Barik, S., Reddy, S.U. On the \({A_{\!\mathbb {C}}}\)-rank of multidigraphs. Aequat. Math. 98, 189–213 (2024). https://doi.org/10.1007/s00010-023-01020-6
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DOI: https://doi.org/10.1007/s00010-023-01020-6