Purification and Perturbations of Communication and Repeated Games (opens in new tab)

I prove that it is irrational for agents with even slightly private preferences to condition their strategy on private information that is payoff-irrelevant to them, contrary to powerful techniques for analyzing communication and repeated games. In repeated games with public+private monitoring, this means all pure equilibria are perfect public equilibria, and non-trivial belief free equilibria do not exist. In a wide class of communication g...