On Cournot oligopolies with a biconcave price function

The power of a recent result for Nash equilibria of sum-aggregative games is illustrated by providing a variant of Ewerhart's equilibrium uniqueness theorem for Cournot oligopolies with a biconcave essential price function. This variant, contrary to the original result, allows for industry revenue that is discontinuous at 0 and can be considered a major generalization of the classical uniqueness result of Szidarovszky and Okuguchi for rent-seeking games. It assumes that the elasticity of the price function has a limit when its argument tends to zero.