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2026 Oct 08 16:00-17:30 Bruno Bentzen (Zhejiang University) Systems of intuitionistic logic with actuality
The system of intuitionistic logic with actuality recently proposed by Niki and Omori is arguably better suited to capture classical actuality within an intuitionistic background logic, as it proves a number of classically-flavored principles, including @φ ∨ ¬@φ, ¬¬@φ → @φ, ((@φ → ψ) → @φ) → @φ, or (@φ → ψ) ∨ (@ψ → φ). In this paper, I firstly develop an alternative system that justifies the actuality operator intuitionistically by means of an extension of the BHK explanation developed by Bentzen and Fassio to reason with actuality…
2026 Oct 08 14:00-15:30 Wei Wang (Tsinghua University) Effectivity Functions Without Superadditivity: Representation Theorem and Logic
In multi-player games, where agents form coalitions to reach collective goals, a natural notion is coalitional power: what a coalition can achieve regardless of any other agents’ actions. Coalitional power can be captured both abstractly by effectivity functions and concretely by strategic game forms, thanks to the representation theorem of truly playable effectivity functions by strategic game forms (see [1]). This representation theorem has empowered a host of logics for reasoning about coalitional power, such as those based on Coalition Logic (CL). However, the theorem only applies to effectivity functions satisfying superadditivity, which precludes dependence between different coalitions’ powers or actions. Given the ubiquity of such dependence, it is natural to study effectivity functions without superadditivity…
[1] Valentin Goranko, Wojciech Jamroga, and Paolo Turrini. Strategic games and truly playable effectivity functions. Autonomous Agents and Multi-Agent Systems, 26:288–314, 2013.
2026 May 7 14:00-15:30 Xin Li (李鑫, Tsinghua University) Blok-Esakia定理
本期进阶读书会将于 2026年5月7日（周四）14:00-15:30 在清华大学逻辑学中心举行，由清华大学李鑫同学报告 F. Wolter, M. Zakharyaschev 的文章 On the Blok-Esakia Theorem，介绍 Blok-Esakia 定理，展示 Blok 提出的代数证明；如有时间，还会介绍该定理在直觉主义模态逻辑中的扩展。More>>
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