Let X be a non-empty, compact, convex set in Rn and 0 an upper semi-continuous mapping from X to the collection of non-empty, compact, convex subsets of Rn. It is well known that such a mapping has a stationary point on X, i.e. there exists a point in X satisfying that its image under 0 has a non-empty intersection with the normal cone of X at the point. In case for every point in X it holds that the intersection of the image under 0 with the normal cone of X at the point is either empty orcontains the origin 0n , then 0 must have a zero point on X, i.e. there exists a point in X satisfying that 0n lies in the image of the point. Another well-known condition for the existence of a zero point follows from Ky Fan's coincidence theorem, which says that if for every point the intersection of the image with the tangent cone of X at the point is non-empty, the mapping must have a zero point. In this paper we extend all these existence results by giving a general zero point existence theorem, of which the two results are obtained as special cases. We also discuss what kind of solutions may exist when no further conditions are stated on the mapping 0. Finally, we show how our results can be used to establish several new intersection results on a compact, convex set.
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Paper provided by Tilburg University, Center for Economic Research in its series Discussion Paper with number
107.
Herings,P. Jean-Jacques & Koshevoy,Gleb A. & Talman,Dolf & Yang,Zaifu, 2002.
"A General Existence Theorem of Zero Points,"
Research Memoranda
055, Maastricht : METEOR, Maastricht Research School of Economics of Technology and Organization.
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Find related papers by JEL classification: C62 - Mathematical and Quantitative Methods - - Mathematical Methods and Programming - - - Existence and Stability Conditions of Equilibrium
References listed on IDEAS Please report citation or reference errors to , or , if you are the registered author of the cited work, log in to your RePEc Author Service profile, click on "citations" and make appropriate adjustments.:
Herings, P.J.J. & Laan, G. van der & Talman, D., 2001.
"Quantity constrained equilibria,"
Discussion Paper
93, Tilburg University, Center for Economic Research.
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Other versions:
Talman,Dolf & Laan,Gerard,van der & Herings,P. Jean-Jacques, 2001.
"Quantity Constrained Equilibria,"
Research Memoranda
012, Maastricht : METEOR, Maastricht Research School of Economics of Technology and Organization.
[Downloadable!]