ILLC-LIRa May 2017

illc-lira@list.uva.nl

1 participants
6 discussions

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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Thursday: LIRa session with Sergio Rajsbaum
by LIRa Seminar 07 May '17

07 May '17

Dear all, on Thursday we will have our next LIRa session. Speaker: Sergio Rajsbaum (Instituto de Matemáticas, UNAM, Mexico City) Date and Time: Thursday, May 11th 2017, 15:00-17:00 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 $S$, 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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Correction! Room F3.20 tomorrow: LIRa session with Daniel Hoek
by LIRa Seminar 03 May '17

03 May '17

Dear all, unfortunately our last email contained the wrong room. We will meet tomorrow in the *KdVI Seminar Room F3.20*. Speaker: Daniel Hoek (New York University) Date and Time: Thursday, May 4th 2017, 15:30-17:00 Venue: KdVI Seminar Room F3.20, Science Park 107. Title: Logical Omniscience and the Epistemology of Phone Numbers. Abstract. There are two major schools of thought about the nature of belief. According to the first school, our beliefs are different aspects of a single, coherent picture we have of the world. This overall picture can be represented as a set of possible worlds. This account of belief has many theoretical virtues and meshes nicely with decision theory. But it is widely regarded as unrealistic, because it faces the so-called problem of logical omniscience. We can call this the map theory of belief, after Ramsey’s slogan for it: “belief is the map by which we steer”. Opposed to the map school is the belief box school, according to which our beliefs are separate entities that are to be represented as sentences or other syntactically structured objects such as Russellian propositions. While the belief box model is much more popular amongst philosophers, only the map model plays a role of any significance in economics and cognitive science. In this talk, I develop a proposal from Yalcin (2016) to show there is a third way. According to Yalcin’s theory, the objects of belief aren’t pieces of information or sentences. Rather, they are answers to specific questions. This allows us to form a conception of belief according to which our beliefs are connected insofar as their subject matters are related. On this theory, there are constitutive links holding all or most of our beliefs together into a single web, but the beliefs in the web need not add up to a single, coherent overall picture of the world. I will try to show that this third way marries the applicability of the map theory with some of the central advantages of the belief box theory. Hope to see you there! The LIRa team

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Tomorrow: LIRa session with Daniel Hoek
by LIRa Seminar 03 May '17

03 May '17

Dear all, tomorrow we will have our next LIRa session. Speaker: Daniel Hoek (New York University) Date and Time: Thursday, May 4th 2017, 15:30-17:00 Venue: ILLC Seminar Room F1.15, Science Park 107. Title: Logical Omniscience and the Epistemology of Phone Numbers. Abstract. There are two major schools of thought about the nature of belief. According to the first school, our beliefs are different aspects of a single, coherent picture we have of the world. This overall picture can be represented as a set of possible worlds. This account of belief has many theoretical virtues and meshes nicely with decision theory. But it is widely regarded as unrealistic, because it faces the so-called problem of logical omniscience. We can call this the map theory of belief, after Ramsey’s slogan for it: “belief is the map by which we steer”. Opposed to the map school is the belief box school, according to which our beliefs are separate entities that are to be represented as sentences or other syntactically structured objects such as Russellian propositions. While the belief box model is much more popular amongst philosophers, only the map model plays a role of any significance in economics and cognitive science. In this talk, I develop a proposal from Yalcin (2016) to show there is a third way. According to Yalcin’s theory, the objects of belief aren’t pieces of information or sentences. Rather, they are answers to specific questions. This allows us to form a conception of belief according to which our beliefs are connected insofar as their subject matters are related. On this theory, there are constitutive links holding all or most of our beliefs together into a single web, but the beliefs in the web need not add up to a single, coherent overall picture of the world. I will try to show that this third way marries the applicability of the map theory with some of the central advantages of the belief box theory. Hope to see you there! The LIRa team

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ILLC-LIRa May 2017