JOSÉ HELENO FARO
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Artigo Científico Alpha-maxmin as an aggregation of two selve(2024) Chateauneuf, Alain; JOSÉ HELENO FARO; Tallon, Jean-Marc; Vergopoulos, VassiliThis paper offers a novel perspective on the -maxmin model, taking its components as originating from distinct selves within the decision maker. Drawing from the notion of multiple selves prevalent in inter-temporal decision-making contexts, we present an aggregation approach where each self possesses its own preference relation. Contrary to existing interpretations, these selves are not merely a means to interpret the decision maker’s overall utility function but are considered as primitives. Through consistency requirements, we derive an -maxmin representation as an outcome of a convex combination of the preferences of two distinct selves. We first explore a setting involving objective information and then move on to a fully subjective derivation.Artigo Científico Independence and variational bewley preferences: a note(2020) Bastianello, Lorenzo; JOSÉ HELENO FARO; Teles, FláviaThis note studies some alternatives and weak versions of the Independence axiom in a decision theoretic framework under uncertainty. We propose a characterization of this axiom using a property called Weight Independence. Moreover we study how the Independence axiom is related with the Variational Bewley model of Faro [2015]. We show that Variational Bewley preferences satisfy a weaker form of independence called Independence for Constant Weights. This topic gives us the opportunity to discuss the pioneeristic contributions of David Schmeidler on the weakening of the Independence axiom.Artigo Científico Dynamically consistent objective and subjective rationality(2022) Bastianello, Lorenzo; JOSÉ HELENO FARO; Santos, AnaA group of experts, for instance climate scientists, is to advise a decision maker about the choice between two policies f and g. Consider the following decision rule. If all experts agree that the expected utility of f is higher than the expected utility of g, the unanimity rule applies, and f is chosen. Otherwise, the precautionary principle is implemented and the policy yielding the highest minimal expected utility is chosen. This decision rule may lead to time inconsistencies when adding an intermediate period of partial resolution of uncertainty. We show how to coherently reassess the initial set of experts’ beliefs so that precautionary choices become dynamically consistent: new beliefs should be added until one obtains the smallest “rectangular set” that contains the original one. Our analysis offers a novel behavioral characterization of rectangularity and a prescriptive way to aggregate opinions in order to avoid sure regret.Artigo Científico Ambiguity aversion in the long run: “To disagree, we must also agree”(2016) Araujo, Aloisio; Silva, Pietro da; JOSÉ HELENO FAROArtigo Científico On the confidence preferences model(2012) Chateauneuf, Alain; JOSÉ HELENO FAROIn this paper we study the model of decision under uncertainty consistent with confidence preferences. In that model, a decision maker held beliefs represented by a fuzzy set of priors and tastes captured by a standard affine utility index on consequences. First, we find some interesting properties concerning the well-known maxmin expected utility model, taking into account the point of view of the confidence preferences model. Further, we provide new examples of preferences that capture ambiguity-averse attitudes weaker than ambiguity attitudes featured by maxmin expected utility theory. Finally, we discuss the axiomatic foundations for the confidence preferences model with optimistic behavior.Artigo Científico Financial market structures revealed by pricing rules: Efficient complete markets are prevalent(2018) Araujo, Aloisio; Chateauneuf, Alain; JOSÉ HELENO FAROArtigo Científico Variational bewley preferences(2015) JOSÉ HELENO FAROArtigo Científico Pricing rules and arrow – debreu ambiguous valuation(2012) Araujo, Aloisio; Chateauneuf, Alain; JOSÉ HELENO FAROThis paper considers pricing rules of single-period securities markets with finitely many states. Our main result characterizes those pricing rules C that are super-replication prices of a frictionless and arbitrage-free incomplete asset structure with a bond. This characterization relies on the equivalence between the sets of frictionless securities and securities priced by C. The former captures securities without bid-ask spreads, while the second captures the class of securities where, if some of its delivers is replaced by a higher payoff, then the resulting security is characterized by a higher value priced by C. We also analyze the special case of pricing rules associated with securities markets admitting a structure of basic assets paying one in some event and nothing otherwise. In this case, we show that the pricing rule can be characterized in terms of capacities. This Arrow–Debreu ambiguous state price can be viewed as a generalization for incomplete markets of Arrow–Debreu state price valuation. Also, some interesting cases are given by pricing rules determined by an integral w.r.t. a risk-neutral capacity. For instance, incomplete markets of Arrow securities and a bond are revealed by a Choquet integral w.r.t. a special risk-neutral capacity.Artigo Científico Updating variational (Bewley) preferences(2021) JOSÉ HELENO FARO; Santos, AnaArtigo Científico Ambiguity through confidence functions(2009) Chateauneuf, Alain; JOSÉ HELENO FAROWe characterize preference relations over bounded below Anscombe and Aumann’s acts and give necessary and sufficient conditions that guarantee the existence of a utility function u on consequences, a confidence function ϕ on the set of all probabilities over states of nature, and a positive threshold level of confidence ˛0 such that our preference relation has a functional representation J, where given an act f J(f) = min p ∈ L˛0 ϕ 1 ϕ(p) S u(f) dp. The level set L˛0ϕ := {p : ϕ(p) ≥ ˛0} reflects the priors held by the decision maker and the valueϕ(p) captures the relevance of prior p for his decision. The combination ofϕ and˛0 may describe the decision maker’s subjective assessment of available information. An important feature of our representation is the characterization of the maximal confidence function which allows us to obtain results on comparative ambiguity aversion and on special cases, namely the subjective expected utility, the Choquet expected utility with convex capacity, and the maxmin expected utilit