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On the existence of equilibria in economies with an infinite dimensional commodity space. (English) Zbl 0535.90020
This paper states an infinite dimensional extension of the Gale-Nikaido- Debreu lemma (or market equilibrium theorem) to locally convex topological vector spaces, in order to give, under standard assumptions, a proof of the existence of equilibria in an economy with infinitely many commodities which exactly parallels the proof of Debreu for the finite dimensional case.
The commodity space is a Banach space, conjugate to another Banach space, and ordered by a positive cone with a non-empty interior. The proof is given for a pure exchange economy but could be extended without any difficulty to a production economy. The idea of the argument is to use the duality between the commodity space and its predual and to truncate consumption sets to weak-star compact sets, in order to define excess demand correspondences when the consumers’ preferences satisfy a weak- star continuity assumption; Debreu’s argument is applied to the truncated economy and then a limit argument allows the truncation to go to infinity. $$L_{\infty}(M,{\mathcal M},\mu)$$ is of course a suitable commodity space.
The paper points out the assumptions which prevent from applying the approach to some Banach spaces as ca(K) and $$L_ p(M,{\mathcal M},\mu)$$, $$1\leq p<\infty$$ which have been found useful in practice to study some classical situations for economic theory: intertemporal equilibrium, uncertainty, differentiation of commodities. Subsequent results have proved that an extra assumption on preferences is then necessary for the existence of an equilibrium.

##### MSC:
 91B50 General equilibrium theory
Full Text:
##### References:
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