  This paper studies the evolution of the distribution of opinions in a
population of individuals in which there exist two distinct subgroups of
highly-committed, well-connected opinion leaders endowed with a strong
convincing power. Each individual, located at a vertex of a directed graph, is
characterized by her name, the list of people she is interacting with, her
level of awareness, and her opinion. Various temporal evolutions according to
different local rules are compared in order to find under which conditions the
formation of strongly polarized subgroups, each adopting the opinion of one of
the two groups of opinion leaders, is favored.
