A combinatorial lemma and its applications

Abstract

Abstract In this paper, we present a generalization of a combinatorial lemma we stated and proved in a recent work. Then we apply the generalized lemma to prove: (1) a theorem on the existence of a zero for an excess demand mapping, (2) the existence of a continuum of zeros for a parameterized excess demand mapping, (3) Sperner’s lemma on labelings of triangulations. Proofs of these results are constructive: they contain algorithms (based on the combinatorial lemma) for the computation of objects of interest or, at least, of their approximations.

Keywords

• Browder fixed point theorem
• combinatorial methods
• continuum of zeros
• equilibrium
• fixed point
• Kakutani fixed point theorem