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Entropy and equilibrium state of free market models
J.R. Iglesias1,2a and R.M.C. de Almeida1
Instituto de Física, UFRGS, and Instituto Nacional de Ciência e
Tecnologia de Sistemas Complexos, Caixa Postal 15051, 91501-970
Porto Alegre, RS, Brazil
2 Programa de Pós-Graduação em Economia Aplicada, UFRGS, Av. João Pessoa 52, 90040-000 Porto Alegre, RS, Brazil
a e-mail: firstname.lastname@example.org
Received in final form: 11 January 2012
Published online: 5 March 2012
Many recent models of trade dynamics use the simple idea of wealth exchanges among economic agents in order to obtain a stable or equilibrium distribution of wealth among the agents. In particular, a plain analogy compares the wealth in a society with the energy in a physical system, and the trade between agents to the energy exchange between molecules during collisions. In physical systems, the energy exchange among molecules leads to a state of equipartition of the energy and to an equilibrium situation where the entropy is a maximum. On the other hand, in a large class of exchange models, the system converges to a very unequal condensed state, where one or a few agents concentrate all the wealth of the society while the wide majority of agents shares zero or almost zero fraction of the wealth. So, in those economic systems a minimum entropy state is attained. We propose here an analytical model where we investigate the effects of a particular class of economic exchanges that minimize the entropy. By solving the model we discuss the conditions that can drive the system to a state of minimum entropy, as well as the mechanisms to recover a kind of equipartition of wealth.
Key words: Statistical and Nonlinear Physics
© EDP Sciences, Società Italiana di Fisica and Springer-Verlag, 2012