  Except for special classes of games, there is no systematic framework for
analyzing the dynamical properties of multi-agent strategic interactions.
Potential games are one such special but restrictive class of games that allow
for tractable dynamic analysis. Intuitively, games that are "close" to a
potential game should share similar properties. In this paper, we formalize and
develop this idea by quantifying to what extent the dynamic features of
potential games extend to "near-potential" games. We study convergence of three
commonly studied classes of adaptive dynamics: discrete-time better/best
response, logit response, and discrete-time fictitious play dynamics. For
better/best response dynamics, we focus on the evolution of the sequence of
pure strategy profiles and show that this sequence converges to a (pure)
approximate equilibrium set, whose size is a function of the "distance" from a
close potential game. We then study logit response dynamics and provide a
characterization of the stationary distribution of this update rule in terms of
the distance of the game from a close potential game and the corresponding
potential function. We further show that the stochastically stable strategy
profiles are pure approximate equilibria. Finally, we turn attention to
fictitious play, and establish that the sequence of empirical frequencies of
player actions converges to a neighborhood of (mixed) equilibria of the game,
where the size of the neighborhood increases with distance of the game to a
potential game. Thus, our results suggest that games that are close to a
potential game inherit the dynamical properties of potential games. Since a
close potential game to a given game can be found by solving a convex
optimization problem, our approach also provides a systematic framework for
studying convergence behavior of adaptive learning dynamics in arbitrary finite
strategic form games.
