Semi-algebraic sets and equilibria of binary games
  Any nonempty, compact, semi-algebraic set in [0, 1] n is the projection of the set of mixed equilibria of a finite game with 2 actions per player on its first n coordinates. A similar result follows for sets of equilibrium payoffs. The proofs are constructive and elementary. 
Guillaume Vigeral (CEREMADE), Yannick Viossat (CEREMADE)
math.OC