发表机构
Toulouse School of Economics, University of Toulouse Capitole（图卢兹经济学院，图卢兹第一大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文证明，在货币攻击模型中，防御者的隐藏干预可破坏全局博弈的唯一临界值选择，导致多重均衡，并给出多重性存在的条件。
AI 中文摘要
当参与者的激励随私人信息单调变化时，全局博弈会选择唯一的临界值。我们证明，当拥有私人信息的参与者可以采取一项代价高昂、同时进行且不可观察的行动来捍卫现状时，这一逻辑可能失效。在货币攻击模型中，防御者仅在中间信号区间采取行动。沿着交易者的临界值方程，这种区间响应产生了一个内生的防御损失项，该项在激活分量的端点处消失，但在中间区间可能主导递减的基准收益差。我们建立了一个原始区域，在该区域内防御不活跃且唯一性得以保留，并给出了一个有限累积分布函数超调条件，在该条件下，两个活跃防御临界值根与不活跃基准根共存。由于边际无差异不一定意味着全局激励，我们还给出了真正的单调临界值最优响应的充分条件。最后，向外圆整的区间算术证明，一个适当先验参数向量恰好具有三个对称的单调临界值均衡，并且该拓扑在局部持续存在。这一结果分离了全局博弈选择的基于收益的边界：隐藏干预可以在没有公共信号或信息层级扰动的情况下恢复多重性。
英文摘要
Global games select a unique cutoff when a player's incentive moves monotonically with private information. We show that this logic can fail when a privately informed participant can take a costly, simultaneous, and unobserved action that defends the status quo. In a currency-attack model, the defender acts only at intermediate signals. Along the traders' cutoff equation, this interval response creates an endogenous defense-loss term that vanishes at the endpoints of an activation component but can dominate the decreasing benchmark payoff margin in between. We establish a primitive region in which defense is inactive and uniqueness survives, and a finite-CDF overshoot condition under which two active-defense cutoff roots coexist with the inactive benchmark root. Because marginal indifference need not imply global incentives, we also give sufficient conditions for a genuine monotone cutoff best response. Finally, outward-rounded interval arithmetic proves that a proper-prior parameter vector has exactly three symmetric monotone-cutoff equilibria and that this topology persists locally. The result isolates a payoff-based boundary of global-game selection: hidden intervention can restore multiplicity without public signalling or a perturbation of the information hierarchy.
