  We recently proposed a model coupling the evolution of the opinions of the
individual with the local network topology. The opinion dynamics is based on
the Bounded Confidence model. The social networks is based on a group concept
where each individual is totally connected to the members of its group and is
linked to the individuals of the other groups with a given probability. During
a time step, the individual has to decide between discussing with a member of
its own network and applying the opinion dynamics, or moving groups because it
has an opinion far from the average opinion of its own group. One of the main
results we obtained is that the group sizes, starting from an homogeneous
situation can be strongly heterogeneous at the equilibrium state. This kind of
heterogeneity can be identified in many real networks. In this paper we present
the complete set of behaviours that this complex model can exhibit, at group
level. In particular we will focus on the mechanisms that lead to the stability
of the groups and the appearance of heterogeneity in sizes.
