On some collusive and signaling equilibria in ascending auctions for multiple objects

We consider two ascending auctions for multiple objects: the SEAMO (simultaneous English auction for multiple objects) and the the JAMO (Japanese auction for multiple objects). We first derive a (competitive) Perfect Bayesian Equilibrium of the JAMO by exploiting the strategic equivalence between the JAMO and the Survival Auction which consists of a finite sequence of sealed-bid auctions. Then, we prove that many of the (unwanted) collusive or signaling equilibria studied in the literature in the framework of the SEAMO do not have a counterpart in the JAMO. However, it is shown that certain collusive equilibria based on retaliatory strategies do exist in both auctions.