ILLC-LIRa

illc-lira@list.uva.nl

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582 discussions

Next Thurdsay: LIRa session with Shane Steinert-Threlkeld
by LIRa Seminar 07 Oct '17

07 Oct '17

Dear all, on Thursday we will have our next LIRa session. Speaker: Shane Steinert-Threlkeld (ILLC, Amsterdam) Date and Time: Thursday, October 12th 2017, 16:00-17:30 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Expressivism for Epistemic Modals: Dynamics and Uniform Definability Abstract. Expressivists about a given fragment of language argue that the primary function of an assertion of a sentence from that fragment is not to state a fact but to express some other kind of attitude of the speaker. In this talk, I will discuss expressivism for epistemic modals like ‘might’ and investigate new logical problems that arise. For example: on the standard theory of assertion, an update operation like public announcement adequately models the evolution of the common ground. What is the corresponding dynamics for an expressivist? Answering this question requires showing that a certain disjunction is definable in terms of the other connectives. I will also show that this disjunction is not uniformly definable and discuss the implications of that result. Hope to see you there! The LIRa team

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Tuesday and Wednesday: Workshop on Topological Approaches in Epistemic Logic and PhD defense by Aybüke Özgün: Evidence in Epistemic Logic - A Topological Perspective
by LIRa Seminar 29 Sep '17

29 Sep '17

Dear all, On the occasion of the PhD defense by Aybüke Özgün there will be a *Workshop on Topological Approaches in Epistemic Logic* on Tuesday, October 3rd 2017 from 09:45 to 17:00 in the Nina van Leerzaal at the Allard Pierson Museum. All details can be found at https://sites.google.com/site/topologyandepistemiclogic/ Aybüke Özgün will defend her PhD thesis *Evidence in Epistemic Logic - A Topological Perspective* on Wednesday, October 4th, 2017. The ceremony will start at 16:00 sharp and take place in the Agnietenkapel. Hope to see you there! The LIRa team

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Monday: LIRa session with Aybüke Özgün and Ana Lucia Vargas Sandoval
by LIRa Seminar 01 Sep '17

01 Sep '17

Dear all, on Monday we will have our first LIRa session in the new semester. Speakers: Aybüke Özgün and Ana Lucia Vargas Sandoval (both ILLC, Amsterdam) Date and Time: Monday, September 4th 2017, 13:00-14:30 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Topo-Logic as a dynamic-epistemic logic (toward a logic for Learning Theory). Abstract. In this talk, we investigate a natural extension of Topo-Logic of Moss and Parikh (1992), obtained by adding to it dynamic modalities for ‘topological public announcements’ in the style of Bjorndahl (2017). In other words, we revisit Topo-Logic as a dynamic epistemic logic with public announcements. The resulting “Dynamic Topo-Logic” forms a logic of evidence-based knowledge, knowability, learning of new evidence, and stability (of some truth φ) under any further (true) evidence-acquisition. Moreover, we also talk about a topological arbitrary announcement modality studied by van Ditmarsch et al. (2015), and investigate its interplay with the effort modality. We therefore develop a formal, topological framework that clarifies the intuitively obvious, yet formally elusive connection between the dynamic notions effort and its seemingly special instances: public and arbitrary announcements. We give a complete axiomatization for this Dynamic Topo-Logic, which is — we argue — epistemically more intuitive and, in a sense, simpler than the standard axioms of Topo-Logic. Our completeness proof is also more direct, making use of a standard canonical model construction. Moreover, we study the relations between this extension and other known logical formalisms, showing in particular that it is co-expressive with the simpler and older logic of interior and global modality, which immediately provides an easy decidability proof both for the original Topo-Logic and for our extension. In turn, the effort modality also helps to simplify and streamline the axiomatization of the topological arbitrary announcement logic. If time permits, we also discuss a variant of the Dynamic Topo-Logic as a Dynamic Logic for Learning Theory, and use it to characterize various notions of knowledge, belief, and learning. The first part of the talk is joint work with Alexandru Baltag, and the second part is joint work with Alexandru Baltag, Nina Gierasimczuk, and Sonja Smets. Hope to see you there! The LIRa team

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Monday next week: LIRa session with Aybüke Özgün and Ana Lucia Vargas Sandoval
by LIRa Seminar 28 Aug '17

28 Aug '17

Dear all, welcome back from the summer break. Please note that the regular time slot for LIRa this autumn will be Thursdays 16:00 – 17:30. However, we start with an exception next week on Monday at 13:00. For later events, see https://projects.illc.uva.nl/lgc/seminar/ Speakers: Aybüke Özgün and Ana Lucia Vargas Sandoval (both ILLC, Amsterdam) Date and Time: Monday, September 4th 2017, 13:00-14:30 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Topo-Logic as a dynamic-epistemic logic (toward a logic for Learning Theory). Abstract. In this talk, we investigate a natural extension of Topo-Logic of Moss and Parikh (1992), obtained by adding to it dynamic modalities for ‘topological public announcements’ in the style of Bjorndahl (2017). In other words, we revisit Topo-Logic as a dynamic epistemic logic with public announcements. The resulting “Dynamic Topo-Logic” forms a logic of evidence-based knowledge, knowability, learning of new evidence, and stability (of some truth φ) under any further (true) evidence-acquisition. Moreover, we also talk about a topological arbitrary announcement modality studied by van Ditmarsch et al. (2015), and investigate its interplay with the effort modality. We therefore develop a formal, topological framework that clarifies the intuitively obvious, yet formally elusive connection between the dynamic notions effort and its seemingly special instances: public and arbitrary announcements. We give a complete axiomatization for this Dynamic Topo-Logic, which is — we argue — epistemically more intuitive and, in a sense, simpler than the standard axioms of Topo-Logic. Our completeness proof is also more direct, making use of a standard canonical model construction. Moreover, we study the relations between this extension and other known logical formalisms, showing in particular that it is co-expressive with the simpler and older logic of interior and global modality, which immediately provides an easy decidability proof both for the original Topo-Logic and for our extension. In turn, the effort modality also helps to simplify and streamline the axiomatization of the topological arbitrary announcement logic. If time permits, we also discuss a variant of the Dynamic Topo-Logic as a Dynamic Logic for Learning Theory, and use it to characterize various notions of knowledge, belief, and learning. The first part of the talk is joint work with Alexandru Baltag, and the second part is joint work with Alexandru Baltag, Nina Gierasimczuk, and Sonja Smets. Hope to see you there! The LIRa team

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Tomorrow: PhD defense Giovanni Cinà: Categories for the working modal logician + Workshop: Interweaving Modal Logic and Category Theory
by LIRa Seminar 15 Jun '17

15 Jun '17

Dear all, tomorrow Giovanni Cinà will defend his PhD thesis *Categories for the working modal logician* The ceremony will start at 11:00 sharp and last till 12:30 in the Aula (Lutherse Kerk) of the University of Amsterdam, Spui, 1012 RM Amsterdam. Also tomorrow there will be a workshop associated to the defense *Interweaving Modal Logic and Category Theory* For more information, see https://interweavingblog.wordpress.com Thesis abstract We attempt to build a ladder connecting the heavens of Category Theory to the interests of modal logicians, in particular those concerned with modelling tasks and therefore involved with specific models and languages. The body of work presented in this theses witnesses two possible modes of interaction. The first is the study of hybrid models, namely structures that are on one hand significant from a category-theoretic perspective and on the other hand lend themselves to a treatment with modal languages. We show how presheaf models can be seen as particular relational structures and develop a hierarchy of modal languages to express their properties. To argue in favor of the flexibility of this framework we review several applications; we especially dive into the details of a modal logic for social choice functions. Furthermore, we highlight how in this setting some of the traditional issues of Modal Logic, e.g. completeness, expressivity and decidability, receive an original twist and can be resolved with alternative solutions. A second mode, more heuristic in nature, consists of regarding a given class of models as a category. The benefit of this stance is the baggage of questions that come with it. The right notion of morphism for these models, its closure under composition, the functoriality of some uniform constructions, these are some of the basic issues that get raised in this context. In the second half of the thesis we explicate how they can shape research in Modal Logic and how they are intertwined with existing problems. Hope to see you there! The LIRa team

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This Friday: PhD defense Giovanni Cinà: Categories for the working modal logician and Workshop: Interweaving Modal Logic and Category Theory
by LIRa Seminar 12 Jun '17

12 Jun '17

Dear all, Giovanni Cinà will defend his PhD thesis *Categories for the working modal logician* this Friday, June 16th, 2017. The ceremony will start at 11:00 sharp and last till 12:30 in the Aula (Lutherse Kerk) of the University of Amsterdam, Spui, 1012 RM Amsterdam. On the same day there will be a workshop associated to the defense: Interweaving Modal Logic and Category Theory. For more information, see https://interweavingblog.wordpress.com Thesis abstract We attempt to build a ladder connecting the heavens of Category Theory to the interests of modal logicians, in particular those concerned with modelling tasks and therefore involved with specific models and languages. The body of work presented in this theses witnesses two possible modes of interaction. The first is the study of hybrid models, namely structures that are on one hand significant from a category-theoretic perspective and on the other hand lend themselves to a treatment with modal languages. We show how presheaf models can be seen as particular relational structures and develop a hierarchy of modal languages to express their properties. To argue in favor of the flexibility of this framework we review several applications; we especially dive into the details of a modal logic for social choice functions. Furthermore, we highlight how in this setting some of the traditional issues of Modal Logic, e.g. completeness, expressivity and decidability, receive an original twist and can be resolved with alternative solutions. A second mode, more heuristic in nature, consists of regarding a given class of models as a category. The benefit of this stance is the baggage of questions that come with it. The right notion of morphism for these models, its closure under composition, the functoriality of some uniform constructions, these are some of the basic issues that get raised in this context. In the second half of the thesis we explicate how they can shape research in Modal Logic and how they are intertwined with existing problems. Hope to see you there! The LIRa team

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Tomorrow: Workshop on Logic, Rationality and Common Sense, on the occasion of Jan van Eijck\'s retirement
by LIRa Seminar 01 Jun '17

01 Jun '17

Dear all, tomorrow there will be a workshop on the occasion of Jan van Eijck\'s retirement as researcher at CWI and as professor at ILLC. Date & Time: Friday, June 2nd 2017, 13:00-18:00 Location: Turing Room, Amsterdam Science Park Congress Centre, Science Park 105 (nextdoor to CWI), Amsterdam Reflections on the possibilities and the limitations of applications of logic to the analysis of human behaviour. The workshop is intended to create a space to talk about issues that are not often addressed in public in scientific circles. People who wish to attend the workshop are requested to fill out the following RSVP form: https://goo.gl/forms/s2KZryvHXSr5Bzw32. For more information, see http://homepages.cwi.nl/~jve/workshop Hope to see you there! The LIRa team

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Tomorrow: LIRa session with Gábor Hofer-Szabó
by LIRa Seminar 18 May '17

18 May '17

Dear all, tomorrow we will have our next LIRa session. Speaker: Gábor Hofer-Szabó (Hungarian Academy of Sciences) Date and Time: Friday, May 19th 2017, 15:30-17:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Three levels of Bell\'s inequalities. Abstract. Bell\'s inequalities can be discussed at three different levels: using classical probabilities, classical conditional probabilities, and quantum probabilities. In the talk I will show that the violation of Bell\'s inequalities have a clear meaning on the first two levels: on the first level it rules out the probabilistic interpretation of certain events; on the second level it rules out a common cause type explanation of certain correlations. However, the interpretation of Bell\'s inequalities applied in quantum field theories is not so obvious. Hope to see you there! The LIRa team

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This Friday: LIRa session with Gábor Hofer-Szabó
by LIRa Seminar 15 May '17

15 May '17

Dear all, this Friday we will have our next LIRa session. Speaker: Gábor Hofer-Szabó (Hungarian Academy of Sciences) Date and Time: Friday, May 19th 2017, 15:30-17:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Three levels of Bell\'s inequalities. Abstract. Bell\'s inequalities can be discussed at three different levels: using classical probabilities, classical conditional probabilities, and quantum probabilities. In the talk I will show that the violation of Bell\'s inequalities have a clear meaning on the first two levels: on the first level it rules out the probabilistic interpretation of certain events; on the second level it rules out a common cause type explanation of certain correlations. However, the interpretation of Bell\'s inequalities applied in quantum field theories is not so obvious. Hope to see you there! The LIRa team

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Tomorrow at 15:30: LIRa session with Sergio Rajsbaum
by LIRa Seminar 10 May '17

10 May '17

Dear all, tomorrow we will have our next LIRa session. Please note that we will start at 15:30 as usual. Our previous emails had the wrong time. Speaker: Sergio Rajsbaum (Instituto de Matemáticas, UNAM, Mexico City) Date and Time: Thursday, May 11th 2017, 15:30-17:00 Venue: KdVI Seminar Room F3.20, Science Park 107. Title: A simplicial complex model of dynamic epistemic logic for fault-tolerant distributed computing. Joint work with Eric Goubault (Ecole Polytechnique). Abstract. The usual epistemic S5 model for multi-agent systems is a Kripke graph, whose edges are labeled with the agents that do not distinguish between two states. We propose to uncover the higher dimensional information implicit in the Kripke graph, by using as a model its dual, a chromatic simplicial complex. For each state of the Kripke model there is a facet in the complex, with one vertex per agent. If an edge $(u,v)$ is labeled with a set of agents $latex S$, the facets corresponding to $u$ and $v$ intersect in a simplex consisting of one vertex for each agent of $S$. Then we use dynamic epistemic logic to study how the simplicial complex epistemic model changes after the agents communicate with each other. We show that there are topological invariants preserved from the initial epistemic complex to the epistemic complex after an action model is applied, that depend on how reliable the communication is. In turn, these topological properties determine the knowledge that the agents may gain after the communication happens. We choose distributed computing as a case study to work out in detail the dynamic epistemic simplicial complex theory. The reason is that distributed computability has been studied using combinatorial topology, where the set of all possible executions in a distributed system is represented by a simplicial complex. We establish a formal, categorical equivalence between Kripke models and simplicial complex epistemic models. In one direction, the connection provides a dynamic epistemic logic semantics to distributed computability, opening the possibility of reasoning about knowledge change in distributed computing. In the other direction, the connection allows to bring in the topological invariants known in distributed computing, to dynamic epistemic logic, and in particular show that knowledge gained after an epistemic action model is intimately related to higher dimensional topological properties. Hope to see you there! The LIRa team

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