Modal logic provides an effective language for expressing
properties of state-based systems. When equipped with operators
that can test for infinite behaviour like looping and
reachability, the logic becomes a powerful tool for specifying
correctness of nonterminating, reactive processes such as
communication protocols and control systems. An elegant example
of such a logic is the modal mu-calculus which extends basic
modal logic by two quantifiers for defining inductive and
co-inductive operators. As well as being highly expressive, this
logic enjoys good computational properties (decidability, finite
model property, …) that distinguish it as a central logic in
computer science. In this talk I will introduce the modal
mu-calculus, present some key properties and discuss recent
results regarding its proof theory.

This talk will compare two different conceptualisations of domain expansion in mathematics, as exemplified by Kenneth Manders and, among others, Richard Dedekind, respectively. After presenting how Manders’ ideas relate to the common model-theoretic notions of existentially closed models and model completeness of theories, we argue that the framework yields problematic assessments of some paradigmatic examples of domain expansion. We then move on to the question of how these examples are handled in Dedekind’s framework, and then use the results of this analysis to assess the merits of Manders’ proposal.

Everyone is invited for snacks and drinks in the common room after the talk!

In recent years there has been a renewed interest in the modal logic community toward Boolean algebras equipped with binary relations. The study of such relations and their representation theory has a long history, and is related to the study of point-free geometry, point-free topology, and region based theory of space. Our primary examples of Boolean algebras with relations will be de Vries algebras, which are dual to compact Hausdorff spaces. Our main goal is to use the methods of modal logic and universal algebra to investigate the logical calculi of Boolean algebras with binary relations. This will lead, via de Vries duality, to simple propositional calculi for compact Hausdorff spaces, Stone spaces, etc.

Need help making friends? Finding it hard to network? Or want to dive a bit into the theoretical bases of Facebook, and subsequently the methods of Cambridge Analytica? Then let this Cool Logic talk help you!

Explore a logical perspective on social group creation and preference change. We will go through a dynamic feature-based social-network change operator and a social-network-based feature change operator. Lastly, we will study these in tandem in the hope of creating a new operator, one that more accurately represents the oftentimes cruel reality of making friends. Afterwards, we will put our new found knowledge to the test, with drinks, snacks, and interesting conversations.

An elementary theory of concatenation, QT+, is introduced and used to establish mutual interpretability of Robinson arithmetic, Minimal Predicative Set Theory of Montagna and Mancini, quantifier-free part of Kirby’s finitary set theory, and Adjunctive Set Theory, with or without extensionality.

On the occasion of the PhD defense of Hein Duijf  on May 18th, there will be a workshop on May 17th 2018 in Utrecht. Speakers: John Horty (Maryland), Allard Tamminga (Groningen and Utrecht), Olivier Roy (Bayreuth), Natalie Gold (Oxford), Jan Broersen (Utrecht) and Hein Duijf  (Utrecht). Attendance is free, but registration is required.

Abstract:
Philosophers often distinguish between causal responsibility and moral responsibility, taking the latter to be an important mark of our distinctive humanity. But focusing exclusively on the attitudes and judgments we form toward people on the basis of their moral characters and behavior leads us to overly narrow conceptions both of responsibility and of humanity. As a corrective, this lecture considers the attitudes and judgments we make of artists on the basis of their artwork. By attending to the way in which artists may be aesthetically responsible for their creations, we can develop a richer understanding of responsibility and a more comprehensive idea of humanity.

This colloquium addresses the design and use of models to represent the beliefs and knowledge of agents as well as changes in the beliefs and knowledge of social communities.

The colloquium unites researchers who use a variety of formal tools to study the process of belief formation, belief revision and knowledge updating in social communities. We focus on multi-agent scenarios centered around topics such as belief merge, social-epistemic influence, group knowledge, and belief-polarisation.

Our approach will be interdisciplinary in nature and brings together insights originating from Logic, Game Theory, Belief Revision Theory, Formal Epistemology, Social Science, Network Theory, Cognitive Science and AI.