Tsinghua Logic Salon

Initiated by the center’s students and researchers in 2019, the Tsinghua Logic Salon has quickly grown into a lively platform for try-outs and exchanges of new ideas. Researchers in various fields of logic are invited to present their latest research, as well as the challenges that they see. Every participant is encouraged to engage in discussions and exchange of perspectives. Each session lasts for 1.5 hours in total, with 30 minutes of discussion included.

Organizing Committee (from September 2023): Junhua Yu, Chenwei Shi, Wei Wang, Jialiang Yan, Penghao Du.

■Schedule for 2023-2024 academic year

2024 FEB 29张俊 ZHANG Jun
2024 MAR 14 Byeong-uk Yi
2024 MAR 21贺飞 HE Fei
2024 MAR 28Wes Holliday
2024 Apr 18张长水 ZHANG Changshui
2024 MAY 09高速
2024 MAY 23徐源

■Current Events

2024 May 09 16:00-17:00 Su Gao (高速, Nankai University) Universal Structures in Continuous Logic

Continuous logic is a nonstandard multi-valued logic developed in recent years to study metric structures. In this talk we consider the question whether universal structures with the Urysohn property exist in continuous logic. It turns out that the answer depends on some particular properties of the continuous signatures. In this talk I will give conditions that will completely characterize the existence of Urysohn structures and some other related properties in continuous logic. This is joint work with Xuanzhi Ren.

2024 Apr 18 16:00-17:30 Changshui Zhang (Tsinghua University) 学习与推理


2024 Mar 28 16:00-17:30 Wesley H. Holliday (University of California, Berkeley) Preconditionals

Conditionals in their different flavors—material, strict, indicative, counterfactual, probabilistic, constructive, quantum, etc.—have long been of central interest in philosophical logic. In this talk, we will discuss our recent work on a new semantics for conditionals, covering a large class of what we call preconditionals. Familiar examples of bounded lattices equipped with a preconditional include Heyting algebras, ortholattices with the Sasaki hook, and Lewis-Stalnaker-style conditional algebras satisfying the so-called Flattening axiom. We have shown that every bounded lattice equipped with a preconditional can be represented using a relational structure (suitably topologized), yielding a single relational semantics for conditional logics normally treated by different semantics, as well as generalizing beyond those semantics. An associated paper is available at https://arxiv.org/abs/2402.02296.

2024 Mar 21 16:00-17:30 贺飞(清华大学) 面向并发程序的逻辑理论及其自动判定工具


2024 Mar 14 16:00-17.30 Byeong-Uk Yi (University of Toronto) Is Logic Axiomatizable?

I defend the negative answer to the question in the title, “Is logic aziomatizable?”, by considering sentences that involve plural constructions, such as the following:
[A] There are some things each of which admires one of them.
[B] There are some critics who admire only one another.
We can intuitively see that [A], for example, is logically implied by infinitely many sentences, such as the following:
[A1] c1 admires c2.
[A2] c2 admires c3.

[An] cn admires cn+1.

But [A] is not logically implied by any finite number of sentences among these. So the logic of languages that are rich enough to include [A] is non-compact. It follows from this that the logic of such languages is not axiomatizable. Similarly, we can see that [B], known as the Geach-Kaplan sentence, is logically implied by the following sentences (but not by any finite number of them):
[A1] c1 admires only c2, c1 is not c2, and c1 is a critic.
[A2] c2 admires only c3, c2 is not c3, and c2 is a critic.

[An] cn admires only cn+1, cn is not cn+1, and cn is a critic.

So we can conclude that the logic of languages that include [B] is not axiomatizable.

To put the argument in proper perspective, I shall discuss contemporary account of plural constructions and suggest that they fail to do justice to the logic of plural constructions because they are based on the traditional view of plural constructions as devices for abbreviating singular constructions. And I shall give a sketch of my account of the logic of plural constructions that are based on the view of plurals as substantial devices that complement their singular cousins.

2024 Feb 29 16:00-17.30 Jun Zhang (University of Michigan Ann Arbor & Shanghai Institute for Mathematics and Interdisciplinary Sciences) Cognitive Core of Mathematical Reasoning: Some Thoughts

My talk will explore a common foundation for mathematical reasoning and for their underlying cognitive processes. Starting from counting and spatial reasoning as two core developmental domains of mathematical cognition, I will discuss how the notion of object can be characterized by “concept lattice” (as in Formal Concept Analysis of Ganter and Wille 1999), and how the structure of knowledge can be captured by “knowledge space” (and its learning space, by Doignon and Falmagne 2015). Finally, motivated by the intertwined relations among lattice, logic, and topology, I will describe how the suite of topological operators, and hence topological semantics, can be generalized to general set systems (Lei and Zhang 2019), paving the way for using the latter as the common core for mathematical/formal cognitive systems.

■Past Events

Click HERE to check the past events.