Author:
Ayyaswamy Singaraj,Balachandran Selvaraj,Gutman Ivan
Abstract
The energy of a digraph D is defined as E(D) = ?n,i=1 ?Re(zi)?, where z1, z2,
..., zn are the (possibly complex) eigenvalues of D . We show that if D
is a strongly connected digraph on n vertices, a arcs, and c2 closed walks
of length two, such that Re(z1) ? (a + c2)=(2n) ? 1 , then E(D) ? n(1 +
?n)=2. Equality holds if and only if D is a directed strongly regular graph
with parameters (n, n+?n/2, 3n+2?n/8, n+2?n/8, n+2?n/8). This bound
extends to digraphs an earlier result [J. H. Koolen, V. Moulton:, Maximal
energy graphs. Adv. Appl. Math., 26 (2001), 47-52], obtained for simple
graphs.
Publisher
National Library of Serbia
Subject
Applied Mathematics,Discrete Mathematics and Combinatorics,Analysis
Cited by
18 articles.
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