We introduce a no-risky-arbitrage price (NRAP) condition for asset market models allowing both unbounded short sales and externalities such as trading volume. We then demonstrate that the NRAP condition is sufficient for the existence of competitive equilibrium in the presence of externalities....

We provide a new proof of the non-emptiness of approximate cores of games with many players of a finite number of types. Earlier papers in the literature proceed by showing that, for games with many players, equal-treatment cores of their "balanced cover games", which are non-empty, can be...

We introduce a model of a local public goods economy with a continuum of agents and jurisdictions with finite, but unbounded populations, where the set of possible projects for each jurisdiction/club is unrestricted in size. Under boundedness of per capita payoffs, which simply ensures that...