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2410.21097

The Competitive Spectral Radius of Families of Nonexpansive Mappings

Marianne Akian, Stéphane Gaubert, Loïc Marchesini

correctmedium confidence
Category
Not specified
Journal tier
Specialist/Solid
Processed
Sep 28, 2025, 12:56 AM

Audit review

The paper proves the maximin characterization (Theorem 4) and existence of a uniform value, including a stationary optimal strategy for Max, under Assumption 8; it also proves a dual minimax characterization on distance-like functions D under a uniform almost-isometry hypothesis (Theorem 5). The candidate solution correctly reproduces the maximin side and strategy arguments, but its “dual side” proof is flawed: it uses S(sup_n w_n) ≤ sup_n S(w_n), which reverses the valid inequality for this Shapley operator, and it claims the minimax characterization on D without the almost-isometry assumption that the paper explicitly requires. Hence the model overstates the result and contains a key inequality error, whereas the paper’s claims and proofs are consistent with their stated assumptions. See Theorem 4 and Theorem 5, and the continuity/compactness properties in Assumption 8 and Proposition 10 for details .

Referee report (LaTeX)

\textbf{Recommendation:} no revision

\textbf{Journal Tier:} specialist/solid

\textbf{Justification:}

The paper introduces and solves a natural two-player generalization of escape rates for nonexpansive dynamics, providing maximin and (under a mild additional hypothesis) minimax Collatz–Wielandt-type characterizations, together with uniform value and strategy structure. The results connect several literatures (nonlinear spectral radii, repeated games, and nonexpansive dynamics) and are written clearly with careful operator-theoretic arguments (Assumption 8, continuity on Lip1). The claims are well supported by proofs, including compactness/Ascoli–Arzelà arguments and precise strategy constructions. I suggest only minor clarifications of presentation.