Ordering of bicyclic signed digraphs by energy

Abstract

Let Sn be the class of bicyclic signed digraphs with n vertices whose two signed directed even cycles are vertex-disjoint. In this paper, we characterize the ordering of bicyclic signed digraphs in Sn by energy with two positive or negative directed even cycles (resp., one positive directed even cycle and one negative directed even cycle). Furthermore, we determine extremal energy in Sn by the two orderings.