Energy of strongly connected digraphs whose underlying graph is a cycle
DOI:
https://doi.org/10.4067/S0716-09172016000400003Keywords:
Digraphs, energy, characteristic polynomial, strongly connected, directed cycles, dígrafos, energía, polinomiales, ciclos dirigidos, fuertemente conectadosAbstract
The energy of a digraph is defined as E (D) =∑₁n|Re (zk)|, where z1,..., znare the eigenvalues of the adjacency matrix of D. This is a generalization of the concept of energy introduced by I. Gutman in 1978 [3]. When the characteristic polynomial of a digraph D is of the form
where bo (D) = 1 and bk(D) ≥ 0 for all k, we show that
This expression for the energy has many applications in the study of extremal values of the energy in special classes of digraphs. In this paper we consider the set D* (Cn) of all strongly connected digraphs whose underlying graph is the cycle Cn, and characterize those whose characteristic polynomial is ofthe form (0.1). As a consequence, we find the extremal values ofthe energy based on (0.2).
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[7] J. Rada, I. Gutman, R. Cruz, The energy of directed hexagonal systems, Linear Alg. Appl. 439, pp. 1825—1833, (2013).
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