Logic List Mailing Archive

CfR: The Lindström Lectures 2025 - Jouko Väänänen, 17-18 November 2025, Hybrid: Gothenburg (Sweden) & Zoom

On 17-18 November 2025 the University of Gothenburg will host the 2025 edition of the annual Lindstrm Lectures. The Lindstrm Lectures is a distinguished lecture series initiated in 2013 celebrating the memory of Per (Pelle) Lindstrm, former (and first) professor in logic at the University of Gothenburg. For information about the Lindstrm lecture series see: https://www.gu.se/en/flov/the-lindstrom-lectures

We are proud to announce that the 2025 Lindstrm Lectures will be delivered by Jouko Vnnen, Professor of Mathematics at the University of Helsinki and the Institute for Logic, Language and Computation at the University of Amsterdam. Professor Vnnen will deliver a public lecture on Monday, 17 November 2025, 18.00-20.00 and a research lecture on Tuesday, 18 November at 10.00-12.00. Both lectures will be held at the University of Gothenburg. The public lecture will also be broadcast over Zoom. Title and abstracts are appended to this message.

A Zoom link for the public lecture will be distributed on the Nordic Online Logic Seminar mailing list (https://listserv.gu.se/sympa/subscribe/nordiclogic). Alternatively, contact Graham Leigh <graham.leigh@gu.se<mailto:graham.leigh@gu.se>> directly.

Best wishes,
Graham

Public Lindstrm Lecture
Monday, 17 November 2025 at 18:00 (UTC+1) at the Faculty of Humanities, University of Gothenburg and over Zoom
Jouko Vnnen (University of Helsinki and the Institute for Logic, Language and University of Amsterdam)
On the Logic of Dependence
Abstract: Dependence and independence concepts are ubiquitous in natural science, social science, humanities as well as in everyday life. The sentences "I park on this side of the road depending only on the day of the week" and "the time of descent is independent of the weight of the object" are examples of this. The question arises, do these concepts possess enough exactness for us to investigate their logic? There is currently a whole literature on this topic. It is the purpose of this talk to give a non-technical overview of this area of logic.

Research Lindstrm Lecture
Tuesday, 18 November 2025 at 10:00 (UTC+1) at the Faculty of Humanities, University of Gothenburg
Jouko Vnnen (University of Helsinki and the Institute for Logic, Language and University of Amsterdam)
In Search of New Lindstrm Theorems
Abstract: The combination of Lwenheim-Skolem Theorem and Compactness Theorem limits the expressive power of a logic to that of first order logic. This maximality principle is the famous Lindstrm Theorem for first order logic. It reveals that first order logic is at an optimal point of balance: by adding expressive power to it one necessarily loses model-theoretic properties. Soon after Lindstrm's result, the question was raised, whether there are other logics at a similar point of equilibrium. More precisely: are there strict strengthenings of first order logic satisfying a Lindstrm-type characterization? Despite the naturality of this question, it remained unanswered, until recently.

In 2012 Saharon Shelah offered a solution to this problem in the form of a new infinitary logic. It has a Lindstrm-type characterization in terms of model-theoretic properties combining weak forms of Compactness and a Lwenheim-Skolem type property. In all known cases, a proof of a Lindstrm-type characterization automatically gives a proof of Craig Interpolation. This is the case for Shelah's logic, too. There is, however, one aspect where Shelah's logic seems to be rather weak: the syntax. The logic is derived from a game, in the sense that a sentence is, by definition, a class of structures, closed under a certain Ehrenfeucht-Frass type of a game. This results in the absence of a syntax defined in such a way that the set of all formulas could be obtained by closing the set of atomic formulas under negation, conjunction, quantifiers, and possibly other logical operations. The lack of syntax complicates further study of it and logics in its neighborhood. In the present talk, we address the general question of deriving a syntax from a game, and the more localized question of finding a syntax for Shelah's logic. Partial answers are provided to both questions. This is joint work with Andres Villaveces and Siiri Kivimki.

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