Origin and implications of zero degeneracy in networks spectra
  Spectra of real world networks exhibit properties which are different from the random networks. One such property is the existence of a very high degeneracy at zero eigenvalues. In this work, we provide possible reasons behind occurrence of the zero degeneracy in various networks spectra. Comparison of zero degeneracy in protein-protein interaction networks of six different species and in their corresponding model networks sheds light in understanding the evolution of complex biological systems. 
Alok Yadav and Sarika Jalan
cond-mat.dis-nn physics.soc-ph q-bio.MN