Matrix Energy as a Measure of Topological Complexity of a Graph
  The complexity of highly interconnected systems is rooted in the interwoven architecture defined by its connectivity structure. In this paper, we develop matrix energy of the underlying connectivity structure as a measure of topological complexity and highlight interpretations about certain global features of underlying system connectivity patterns. The proposed complexity metric is shown to satisfy the Weyuker criteria as a measure of its validity as a formal complexity metric. We also introduce the notion of P point in the graph density space. The P point acts as a boundary between multiple connectivity regimes for finite-size graphs. 
Kaushik Sinha and Olivier L. de Weck
physics.soc-ph cs.SI math.CO