Topology of correlation based minimal spanning trees in real and model   markets
  We present here a topological characterization of the minimal spanning tree that can be obtained by considering the price return correlations of stocks traded in a financial market. We compare the minimal spanning tree obtained from a large group of stocks traded at the New York Stock Exchange during a 12-year trading period with the one obtained from surrogated data simulated by using simple market models. We find that the empirical tree has features of a complex network that cannot be reproduced, even as a first approximation, by a random market model and by the one-factor model. 
Giovanni Bonanno (1,2), Guido Caldarelli (1), Fabrizio Lillo (3)and   Rosario N. Mantegna (2,3) ((1) INFM UdR Roma1, (2) Dip...