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2203.14129

Nash, Conley, and Computation: Impossibility and Incompleteness in Game Dynamics

Jason Milionis, Christos Papadimitriou, Georgios Piliouras, Kelly Spendlove

correctmedium confidence
Category
Not specified
Journal tier
Strong Field
Processed
Sep 28, 2025, 12:56 AM

Audit review

The paper proves (via Conley index and attractor–repeller duality) that the Kohlberg–Mertens 3×3 game admits no Type III dynamics (Theorem 5.1) and extends this to small-ε approximate equilibria and an open, positive-measure set of games (Theorem 6.2) . The candidate solution reaches the same conclusions but its core argument misapplies Lefschetz theory and attractor properties: (i) it incorrectly infers that CR(φ)=NE(g) implies NE(g) is a global attractor; the paper instead uses the attractor–repeller lattice and shows that a single chain-recurrent component must be the unique maximal attractor before deriving a contradiction via Conley index ; (ii) it asserts L(φ_T)=χ(NE(g)) for an attractor without establishing the required index localization and induced-map conditions; the paper avoids this by directly comparing Conley indices of the purported attractor and the whole space, invoking Corollary 4.6 to force a nonempty repeller . In Part B, the model further claims NE_ε(g) is an “annulus” (dimensionally incorrect in X=Δ^2×Δ^2) and relies on a non-justified Lipschitz neighborhood sandwich; the paper instead proves NE_ε(g) is homotopy equivalent to S^1 for sufficiently small ε by a careful polyhedral/BR-region analysis and then repeats the Conley-index obstruction, plus a clean positive-measure robustness argument .

Referee report (LaTeX)

\textbf{Recommendation:} minor revisions

\textbf{Journal Tier:} strong field

\textbf{Justification:}

The paper gives a compelling, dynamics-agnostic obstruction to convergence to (approximate) Nash equilibria using Conley index and attractor–repeller duality, and it situates the results well within both game theory and dynamical systems. The arguments are sound and the implications for the design of learning dynamics are important. A handful of minor clarifications (explicit statements of assumptions and thresholds) would improve accessibility and rigor without altering the substance.