The Why of the Applicability of Statistical Physics to Economics
  We analyze the relationships between game theory and quantum mechanics and the extensions to statistical physics and information theory. We use certain quantization relationships to assign quantum states to the strategies of a player. These quantum states are contained in a density operator which describes the new quantum system. The system is also described through an entropy over its states, its evolution equation which is the quantum replicator dynamics and a criterion of equilibrium based on the Collective Welfare Principle. We show how the density operator and entropy are the bonds between game theories, quantum information theory and statistical physics. We propose the results of the study of these relationships like a reason of the applicability of physics in economics and the born of econophysics. 
Esteban Guevara Hidalgo