Speaker: Prof. Giovani Vasconcelos Dept. of Physics Federal University of Pernambuco, Recife Brazil

Title: Multicanonical distribution: Statistical equilibrium of multiscale systems

Abstract: A multicanonical formalism is introduced to describe the statistical equilibrium of complex systems exhibiting a hierarchy of time and length scales, where the hierarchical structure is described as a set of nested ?internal heat reservoirs? with fluctuating ?temperatures.? The probability distribution of states at small scales is written as an appropriate averaging of the large-scale distribution (the Boltzmann-Gibbs distribution) over these effective internal degrees of freedom. For a large class of systems the multicanonical distribution is given explicitly in terms of generalized hypergeometric functions. As a concrete example, it is shown that generalized hypergeometric distributions describe remarkably well the statistics of acceleration measurements in Lagrangian turbulence.