Supporting weakly Pareto optimal allocations in infinite dimensional nonconvex economies

In this paper, we prove a new version of the Second Welfare Theorem for economies with a finite number of agents and an infinite number of commodities, when the preference correspondences are not convex-valued and/or when the total production set is not convex. For this kind of nonconvex economies, a recent result, obtained by one of the authors, introduces conditions which, when applied to the convex case, give for Banach commodity spaces the well-known result of decentralization by continuous prices of Pareto-optimal allocations under an interiority condition. In this paper, in order to prove a different version of the Second Welfare Theorem, we reinforce the conditions on the commodity space, assumed here to be a Banach lattice, and introduce a nonconvex version of the properness assumptions on preferences and the total production set. Applied to the convex case, our result becomes the usual Second Welfare Theorem when properness assumptions replace the interiority condition. The proof uses a Hahn-Banach Theorem generalization by Borwein and Jofré (in Joper Res Appl Math 48:169–180, 1997) which allows to separate nonconvex sets in general Banach spacesThis work was partially supported by Nucleo Complex Engineering System. The successive versions of the paper were partly prepared during visits of Alejandro Jofré to CERMSEM and of Monique Florenzano and Pascal Gourdel to the Centro de Modelamiento Matematico. The hospitality of both institutions and the support of the french Coopération régionale Cone Sud are gratefully aknowledged. The authors thank Ali Khan for stimulating exchange of ideas and literature, Roko Aliprantis, Jean-Marc Bonnisseau, Alain Chateauneuf, Roger Guesnerie, Filipe Martins Da Rocha, Moncef Meddeb, B. Mordukovich, Lionel Thibault and Rabee Tourky for valuable discussions