alle ore 14,30 presso l'aula 2 del Dipartimento di Matematica e Informatica "U. DINI"
I Proff. DANIELA BUBBOLONI e MICHELE GORI
(Università di Firenze)
terrà una conferenza dal titolo:
"Symmetric majority rules"
abstract:
Committees are often required to provide a strict ranking of a given family of alternatives. It is possible to design many procedures to aggregate committee members’ preferences on alternatives into a strict ranking of alternatives. Among them, we are interested to analyse those satisfying certain principles usually invoked by social choice theorists. The first principle is the requirement that the identities of individuals are not used to determine the social outcome so that every individual opinion equally influences the collective decision. The second one is instead the requirement that any two alternatives are equally treated. These two principles, called anonymity and neutrality respectively, simply say that individual and alternative names are immaterial. We also consider the reversal symmetry principle which states that if everybody in the society completely changes her mind about her own ranking of alternatives, then a complete change in the social outcome occurs. Finally, we assume that the decision process also obeys a majority principle, that is, each time a precisely specified and large enough amount of committee members ranks an alternative over another,
that ranking has to be maintained in the final decision. The paper investigates under which conditions such special collective decision procedures can be really designed using, as main tool, group theory.