A mean field model for the collective behaviour of interacting multi-species particles. Mathematical results and application to the inverse problem
The study of the normalized sum of random variables and its asymptotic behaviour has been and continues to be a central chapter in probability and statistical mechanics. When those variables are independent the central limit theorem ensures that the sum with square-root normalization converges toward a Gaussian distribution. The main topic of this thesis is the generalization of the central limit theorem for spin random variable whose interaction is described by a multi-species mean-field Hamiltonian. We found the conditions, in terms of the interaction, that lead in the thermodynamic limit to a Gaussian behaviour and those who lead to a higher order exponential distribution, under the assumption that the Hamiltonian is a convex function of the magnetizations and the first non vanishing partial derivatives of the pressure functional are all the same order (homogeneity hypothesis). The thesis handle other two problems concerning the multi-species mean-field model: the computation of the exact solution of the thermodynamic limit of the pressure and the solution of the inverse problem.