Walrasian Equilibrium with Few Buyers

We study the existence and the properties of Walrasian equilibrium (WEQ) in combinatorial auctions, under two natural classes of valuation functions. The first class is based on additive capacities or weights, and the second on the influence in a social network. While neither class holds the gross substitutes condition, we show that in both classes the existence of WEQ is guaranteed under certain restrictions, and in particular when there are only two competing buyers.

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